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  • Cross-forest universal groups on Windows Server?

    - by DotGeorge
    I would like to create a Universal Group whose members are a mix of cross-forests users and groups. In the following example, two forests are mentioned (US and UK) and two domains in each forest (GeneralStaff and Java): For example, the universalDevelopers group may comprise of members from UK.Java.Developers and US.Java.Developers. Then, for example, there may be a group of universalSales which contains the users UK.GeneralStaff.John and US.GeneralStaff.Dave. In UK forest at the minute, I can freely add members and groups from the UK. But there is no way to add members from the US forest, despite having a two-way trust in place... e.g. I can login with US members into UK and vice-versa. A further complication is that, with a Universal group in the UK (which contains three domains), I can only add two of the three. It can't see the third. Could people please provide some thoughts on why cross-forest groups can't be created and ways of 'seeing' all domains within a forest. EDIT: This is on a combination of Windows 2003 and 2008 server. Answers can be regarding either. Thanks!

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  • VMWare Setup with 2 Servers and a DAS (DELL MD3220)

    - by Kumala
    I am planning to use a VMWare based setup consisting of two VMWare servers (2 CPU, 256GB Memory) and a DAS (DELL MD3220 with 24x900GB disks). The virtual machines will be half running MS SQL databases (Application, Sharepoint, BI) and the other half of the VM will be file services, IIS. To enhance the capacity of the storage, we'll be adding a MD1220 enclosure with another 24x900GB to the MD3220. Both DAS will have 2 controllers. Our current measured IOPS is 1000 IOPS average, 7000 IOPS peak (those happen maybe twice per hour). We are in the planning phase now and are looking at the proper setup of the disks. The intention is to setup up both DAS one of the DAS with RAID 10 only and the other DAS with RAID 5. That will allow us to put the applications on the DAS that supports the application performance needs best. Question is how best to partition the two DASs to get best possible IOPS/MBps, each DAS will have to have 2 hot spares? For the RAID 5 Setup: Generally speaking, would it be better to have one single disk group across all 22 disks (24 - 2 hot spares) with both controllers assigned to the one disk group or is it better to have 2 disk groups each 11 disks, assigned to one of the two controllers? Same question for the RAID 10 setup: The plan is: 2 disks for logs (Raid 1), 2 Hotspare and 20 disks for RAID 10. Option 1: 5 * 4 disks (RAID 10), with two groups assigned to 1 controller and 3 groups to the other controller Option 2: One large RAID 10 across all the disks and have both controllers assigned to the same group? I would assume that there is no right or wrong, but it all depends very much on the specific application behaviour, so I am looking for some general ideas what the pros and cons are of the different options. IF there are other meaningful options, feel free to propose them.

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  • How far should we take the N+N redundancy craziness ?

    - by Brann
    The industry standard when it comes from redundancy is quite high, to say the least. To illustrate my point, here is my current setup (I'm running a financial service). Each server has a RAID array in case something goes wrong on one hard drive .... and in case something goes wrong on the server, it's mirrored by another spare identical server ... and both server cannot go down at the same time, because I've got redundant power, and redundant network connectivity, etc ... and my hosting center itself has dual electricity connections to two different energy providers, and redundant network connectivity, and redundant toilets in case the two security guards (sorry, four) needs to use it at the same time ... and in case something goes wrong anyway (a nuclear nuke? can't think of anything else), I've got another identical hosting facility in another country with the exact same setup. Cost of reputational damage if down = very high Probability of a hardware failure with my setup : <<1% Probability of a hardware failure with a less paranoiac setup : <<1% ASWELL Probability of a software failure in our application code : 1% (if your software is never down because of bugs, then I suggest you doublecheck your reporting/monitoring system is not down. Even SQLServer - which is arguably developed and tested by clever people with a strong methodology - is sometimes down) In other words, I feel like I could host a cheap laptop in my mother's flat, and the human/software problems would still be my higher risk. Of course, there are other things to take into consideration such as : scalability data security the clients expectations that you meet the industry standard But still, hosting two servers in two different data centers (without extra spare servers, nor doubled network equipment apart from the one provided by my hosting facility) would provide me with the scalability and the physical security I need. I feel like we're reaching a point where redundancy is just a communcation tool. Honestly, what's the difference between a 99.999% uptime and a 99.9999% uptime when you know you'll be down 1% of the time because of software bugs ? How far do you push your redundancy crazyness ?

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  • Any program to help me check whether an ethernet channel can support full-length VLAN packet?

    - by Jimm Chen
    Sometimes, I have to face such a situation that I need to quickly and explicitly know whether a full length VLAN packet can traverse between two RJ45 ports. Yes, I mean 802.1Q ethernet frame with Etype=81 00 (diagram below). What I can do now is: Get two Windows PCs, for each PC, intall Intel Gigabit NIC and Intel specific driver to create a virtual NIC, with VLAN ID=3 assigned. Then connect the two PCs to each of the two RJ45 port. Finally execute ping to generate a full-length ethernet packet. ping -f -l 1472 <dest-IP> This way, I can be sure that the sent packet has the maximum "IP data payload" of 1500 bytes(8 bytes of ICMP header and 1472 bytes of ICMP data). If the ping gets reply, I know that the ethernet channel support full-length VLAN packet. From my experiment, some home switch or broad band routers(e.g. Linksys WRT54G) does not support full-length VLAN packet switching, so only ping -f -l 1468 succeeds. You see, I have to use an expensive Intel NIC to carry on that test, quite inconvenient. You know, for most laptop today, they do not equip an Intel NIC, and, even it is an Intel NIC, Intel VLAN driver, Intel has limitations on the models on which VLAN driver can be installed. So, my question is: Is there a small program that can let me send a full-length VLAN packet without installing a dedicated VLAN driver? Or better, the program has a stock feature that does the very job for my situation. Windows programs preferred, Linux solution welcome. Simpler the program, the better. Thank you.

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  • Running multiple copies of openssh-server (sshd) on Ubuntu

    - by cecilkorik
    I may be attacking this problem the wrong way, if so let me know. I have a server which is available through SSH from both the public internet and the local LAN. I would like to have two very different security policies for each, by running two copies of sshd with two different sshd_config files each on a different port. Some of the things I'd like to change is to allow password or public-key authentication on the LAN, but public-key only from the internet. All (real) users could login from the LAN side, but only certain authorized users would be individually whitelisted to login through the internet. As far as I can tell this requires having two different SSH daemons running on different ports with different sshd_configs. I am fine with the different ports part, I can easily forward port 22 to any port I want through my firewall. So my question is what is the best way to actually START the second sshd under Ubuntu 10.04 LTS. Is there a recommended way to do something like this? Surely I am not the first person with this sort of need. I have a bit of experience with upstart, and I can manually hack the second sshd into /etc/init/ssh.conf I suppose but I'm not sure if that will get overwritten by the package. However I do it, It's important to ensure both sshd processes always get restarted after any automatic or manual upgrade of the openssh-server package. Thanks in advance.

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  • Downmix surround to Dolby Pro-Logic at the OS/driver level in Windows 7?

    - by davr
    First off, I'm talking about Dolby Pro-Logic, a really old tech for encoding 4 audio channels (L/R/C/SR) into two analog outputs, and then extracting them again. It was used in surround sound systems in the last century. I have a modern PC that can output 5.1 analog audio (Three outputs on the back carry six channels of audio). But I have a really old surround sound reciever that only has a two-channel, L/R input, which it extracts 4 channels of audio from, and outputs to 5.1 speakers. What I want is some way for the OS, Windows 7, to act as if I really had 5.1 audio channels available, so applications produce surround audio, but before outputting it out of the back of my PC, apply Dolby Pro-Logic matrix encoding so that it outputs over only two channels. These two channels would then get sent to my receiver via a RCA cable, which would decode it again and drive the surround speakers. Is anything like this possible? I'm pretty sure I could do it at an application / codec level, but I'm looking for something that I just have to set once.

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  • Is 2 GB of RAM better than 2.5 GB?

    - by pibboater
    My laptop has two slots for RAM, and currently has two 512 MB chips, for 1 GB. Windows XP is running terribly slow on it, so I want to upgrade the RAM. I could buy two 1 GB chips to replace both of the current 512 MB chips, to give me 2 GB of RAM. Or, the price is the same to buy one 2 GB chip, to replace just one of the 512 MB chips, and give me 2.5 GB total. The RAM it takes is PC2-4200 533MHz DDR2. What do you think would be better: buying two 1 GB chips so it can take advantage of dual-channel operation, or buying one 2 GB chip to end up with more total RAM but not dual-channel operation? Like I said, price is the same, so performance is the only consideration. I'm not doing anything especially intensive like video or photo editing -- just having multiple Office programs open, playing music, browsers, etc., but currently even opening the first application takes forever. If it matters, the laptop is a Toshiba Qosmio G25-AV513 running Windows XP Media Center SP3. Thanks! Kevin

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  • Need Help Scoping a Server to use for study (MCITP Ent Admin + SharePoint 2010)

    - by AVFamily76
    i need to study for mcitp, but i also need to study for sharepoint 2010 i have a poweredge 1850 with two single-core CPUs + two 73G drives - it kills me on electricity, so don't want to use it, and it won't do VT, but it could be one of three boxes for a lab that's cheap, but will cost a lot on electricity i was thinking . . . OPTION #1 Opteron 4170 HE (50 watt chip), 6-core, only two-bills ($200), but the board's are $250, so that's an $800 box, then get another box to dual-boot Win7/Hyper-V on the cheap...? OPTION #2 Used Quad - but how many VM's that are really banging away could it run at same time? (Server 2008r2, SQL 2008r2, Search Server) OPTION #3 Study from books and just get one box that can run two VM's at same time, even if slowly. the last time i had and used a home lab was five years ago when i had a DC, SQL, Exchange and business app box, that's where i got my server skills was just banging on it for four years, but didn't read any books, so now i have to get certified and know the material, and just am not sure how much attention i should pay to the box i use versus the studying time and reading. sorry it's a subjective question, and am obviously open to all sorts of abuse here, but hope you can tell me also how many VM's i can run at the same time given what they'll be doing (SQL and SharePoint FAST search server are resource hungry) thanks!

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  • Does using a hexacore CPU make sense?

    - by Exa
    I'm currently planning to upgrade my computer system and I want to exchange CPU, board and RAM. I already had a look at some hexacore-CPUs from AMD and would like to know if it makes any sense to use such a CPU with six cores. Is there any software which really uses six cores? Especially in gaming? I'm using this PC mostly for gaming and from time to time for developing. I know that on the dual-core system (2 x 3GHz) I currently use, Visual Studio creates two instances of the compiler, one for each core. Would there be six instances of the compiler on a hexacore system for super fast compiling? Is there any software that uses six cores? Would running two applications cause the usage of more CPUs? (For example two CPUs for a game you're playing while two other CPUs are used for compiling at the same time) I hope someone can point out the benefits of a hexacore system. The OS would be Windows 7 64 Bit and I use the PC for gaming most of the time. (Crysis 2, CoD, stuff like that)

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  • Is 1GB + 1GB RAM better than 2GB +0.5GB?

    - by pibboater
    My laptop has two slots for RAM, and currently has two 512 MB chips, for 1 GB. Windows XP is running terribly slow on it, so I want to upgrade the RAM. I could buy two 1 GB chips to replace both of the current 512 MB chips, to give me 2 GB of RAM. Or, the price is the same to buy one 2 GB chip, to replace just one of the 512 MB chips, and give me 2.5 GB total. The RAM it takes is PC2-4200 533MHz DDR2. What do you think would be better: buying two 1 GB chips so it can take advantage of dual-channel operation, or buying one 2 GB chip to end up with more total RAM but not dual-channel operation? Like I said, price is the same, so performance is the only consideration. I'm not doing anything especially intensive like video or photo editing -- just having multiple Office programs open, playing music, browsers, etc., but currently even opening the first application takes forever. If it matters, the laptop is a Toshiba Qosmio G25-AV513 running Windows XP Media Center SP3. Thanks! Kevin

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  • Configure linux machine as bridge/switch and end device

    - by leemes
    At my home, I have two desktop PCs in two rooms. The router / DSL modem is in one of these rooms. Now I want to configure a home server (having 2 LAN ports, running 24/7) in the corridor between the two rooms, using only one LAN cable at each door. This gives me the following physical configuration: (door) (door) .----/-/----. .-----/-/----------._ FritzBox | | | .----´´ DSL Router PC1 Server | PC2 As just said, the server has 2 network interfaces and is running Ubuntu. What I need now is a network configuration which enables both the server and PC1 to connect to the router. I think the server needs to serve as a bridge or switch. Currently, all computers are configured having static IP addresses. If I'm understanding it correctly, a bridge / switch doesn't have its own IP address, but as the server needs to be configured as an own end device, it needs to have one. My first question is, do I have to configure both interfaces separately, giving both the same static IP address? My next question is, how do I bridge the two physical networks into one? I have basic understanding (but am always confused again and again) of bridges and switches, but I don't know how to configure it in software. I only know that it's possible to do so :) The third question is: Is it possible to configure this in a way that network packets from/to PC1 to/from the router only go through hardware or only consume low CPU in the server? Can you help me? Thanks in advance!

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  • How to delete removed devices from a mdadm RAID1?

    - by Kabuto
    I had to replace two hard drives in my RAID1. After adding the two new partitions the old ones are still showing up as removed while the new ones are only added as spare. I've had no luck removing the partitions marked as removed. Here's the RAID in question. Note the two devices (0 and 1) with state removed. $ mdadm --detail /dev/md1 mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. /dev/md1: Version : 00.90 Creation Time : Thu May 20 12:32:25 2010 Raid Level : raid1 Array Size : 1454645504 (1387.26 GiB 1489.56 GB) Used Dev Size : 1454645504 (1387.26 GiB 1489.56 GB) Raid Devices : 3 Total Devices : 3 Preferred Minor : 1 Persistence : Superblock is persistent Update Time : Tue Nov 12 21:30:39 2013 State : clean, degraded Active Devices : 1 Working Devices : 3 Failed Devices : 0 Spare Devices : 2 UUID : 10d7d9be:a8a50b8e:788182fa:2238f1e4 Events : 0.8717546 Number Major Minor RaidDevice State 0 0 0 0 removed 1 0 0 1 removed 2 8 34 2 active sync /dev/sdc2 3 8 18 - spare /dev/sdb2 4 8 2 - spare /dev/sda2 How do I get rid of these devices and add the new partitions as active RAID devices? Update I seem to have gotten rid of them. My RAID is resyncing, but the two drives are still marked as spares and are number 3 and 4, which looks wrong. I'll have to wait for the resync to finish. All I did was to fix the metadata error by editing my mdadm.conf and rebooting. I tried rebooting before, but this time it worked for whatever reason. Number Major Minor RaidDevice State 3 8 2 0 spare rebuilding /dev/sda2 4 8 18 1 spare rebuilding /dev/sdb2 2 8 34 2 active sync /dev/sdc2

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  • What method of MySQL mirroring should I use for this?

    - by user45745
    I'm running an web application hosting service (basically hosting forums for free), and I have two remote servers at my disposal. The code for the application is stored on both servers and isn't a problem, but I'm wondering how to deal with the databases. When someone goes onto a site *.example-host.com, they are sent to one of the two servers and both must be capable of loading the forums from a database. The database must also have write access, for when new members register or post topics etc. The main requirement is speed, but uptime is also important (if a server goes out, the site should still work). I have a few options, but I'm inexperienced and not sure which to go with: 1) [PHP] Split the forum records 50:50 between the two servers. If a server does not have the record for a forum requested, it can request it from the other by remote MySQL and load it. This idea sounded okay, until I realised that 50% of the time, users would be waiting significantly longer for pages to load. I also realised that if one of the servers went down, half the forums would be inaccessible and registrations would have to be disabled. 2) [MySQL] Dual master replication. This would attempt to mirror the two databases and sounds perfect, but I've heard that it can be very problematic. I don't know how fast this is. 3) [MySQL] Use a standard replication, distribute read only queries on both nodes and read/write queries to the master. This sounds like a good option, but again, I'm not sure on speed. I also don't know what would happen if the master server went down. If you have any other suggestions, please post them :)

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  • Rsync root files between systems without specifying password

    - by xpt
    This seems very tricky to me. I've set up my two systems so that I can rsync files between them as me, without specifying password. Now the the problem is to rsync files that belong to root. On both of my systems, there are no root passwords. The only way to become root is via sudo. So I can neither give a password for sudo rsyn local root@remote:, no use my ssh-agent to supply pass phrase. I don't want to set up a root password on any systems; and I do need the files to be owned by root on both systems. EDIT: Using the files that belong to root is just an example, I need a way for my unprivileged account to read/write system (including root-owned) files easily. One example is to copy my configured /root environment into the freshly-installed system. The two systems are actually two VMs under a single host, so it's not a big concern for me to copy root-owned files between them. EDIT 2: If I only want to copy my configured /root environment into the freshly-installed system, I can use tar: sudo tar cvzf - /root | ssh me@remote sudo tar xvzf - -C / But I do need rsync to update from time to time. Any easy way to make it happen? EDIT 3: Formally formulate the question Alright, it all began with the question, how to rsync files that belong to root between two systems as a normal unprivileged user, without specifying password, under the condition that, The root account is locked on both of systems. I.e., there are no root passwords. The only way to become root is via sudo (recommended security practice, see http://help.ubuntu.com/community/RootSudo) I don't want a completely passwordless sudo but don’t want to be typing passwords all the time either. The normal unprivileged user has entered their ssh pass phrase into the ssh agent. Thanks

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  • Monitoring Between EC2 Regions

    - by ABrown
    I'm working on a small EC2 project that involves a handful of servers in two different regions (US East and EU West). My first task is to implement a Nagios monitoring solution. Monitoring within a region is simple - I just use the private domain names/IPs, but I'm a little unsure of the best way to handle monitoring the second region without setting up a second Nagios install. The environment is fairly static, so I'm not going to be scripting the configuration with the EC2 tools just yet. As I see it, I have two options. Two Nagios installations (which is over-kill for the small number of servers I'm dealing with). Pros: I don't have to alter the group permissions nor do I have to pay for the traffic, redundancy in the monitoring solution - I could monitor the Nagios servers. Cons: two installations to deal with and I'd need to run another server instance. Have the single installation monitor both regions. Pros: one installation to deal with. Cons: slightly reduced security - security group will have to have NRPE (5666) opened for one source IP and also paying for a small amount of bandwidth at the Internet rate for data transfer between the regions. I guess my question is - how have others handled this problem and what are your recommendations? Thanks!

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  • Quick guide to Oracle IRM 11g: Configuring SSL

    - by Simon Thorpe
    Quick guide to Oracle IRM 11g index So far in this guide we have an IRM Server up and running, however I skipped over SSL configuration in the previous article because I wanted to focus in more detail now. You can, if you wish, not bother with setting up SSL, but considering this is a security technology it is worthwhile doing. Contents Setting up a one way, self signed SSL certificate in WebLogic Setting up an official SSL certificate in Apache 2.x Configuring Apache to proxy traffic to the IRM server There are two common scenarios in which an Oracle IRM server is configured. For a development or evaluation system, people usually communicate directly to the WebLogic Server running the IRM service. However in a production environment and for some proof of concept evaluations that require a setup reflecting a production system, the traffic to the IRM server travels via a web server proxy, commonly Apache. In this guide we are building an Oracle Enterprise Linux based IRM service and this article will go over the configuration of SSL in WebLogic and also in Apache. Like in the past articles, we are going to use two host names in the configuration below,irm.company.com will refer to the public Apache server irm.company.internal will refer to the internal WebLogic IRM server Setting up a one way, self signed SSL certificate in WebLogic First lets look at creating just a simple self signed SSL certificate to be used in WebLogic. This is a quick and easy way to get SSL working in your environment, however the downside is that no browsers are going to trust this certificate you create and you'll need to manually install the certificate onto any machine's communicating with the server. This is fine for development or when you have only a few users evaluating the system, but for any significant use it's usually better to have a fully trusted certificate in use and I explain that in the next section. But for now lets go through creating, installing and testing a self signed certificate. We use a library in Java to create the certificates, open a console and running the following commands. Note you should choose your own secure passwords whenever you see password below. [oracle@irm /] source /oracle/middleware/wlserver_10.3/server/bin/setWLSEnv.sh [oracle@irm /] cd /oracle/middleware/user_projects/domains/irm_domain/config/fmwconfig/ [oracle@irm /] java utils.CertGen -selfsigned -certfile MyOwnSelfCA.cer -keyfile MyOwnSelfKey.key -keyfilepass password -cn "irm.oracle.demo" [oracle@irm /] java utils.ImportPrivateKey -keystore MyOwnIdentityStore.jks -storepass password -keypass password -alias trustself -certfile MyOwnSelfCA.cer.pem -keyfile MyOwnSelfKey.key.pem -keyfilepass password [oracle@irm /] keytool -import -trustcacerts -alias trustself -keystore TrustMyOwnSelf.jks -file MyOwnSelfCA.cer.der -keyalg RSA We now have two Java Key Stores, MyOwnIdentityStore.jks and TrustMyOwnSelf.jks. These contain keys and certificates which we will use in WebLogic Server. Now we need to tell the IRM server to use these stores when setting up SSL connections for incoming requests. Make sure the Admin server is running and login into the WebLogic Console at http://irm.company.intranet:7001/console and do the following; In the menu on the left, select the + next to Environment to expose the submenu, then click on Servers. You will see two servers in the list, AdminServer(admin) and IRM_server1. If the IRM server is running, shut it down either by hitting CONTROL + C in the console window it was started from, or you can switch to the CONTROL tab, select IRM_server1 and then select the Shutdown menu and then Force Shutdown Now. In the Configuration tab select IRM_server1 and switch to the Keystores tab. By default WebLogic Server uses it's own demo identity and trust. We are now going to switch to the self signed one's we've just created. So select the Change button and switch to Custom Identity and Custom Trust and hit save. Now we have to complete the resulting fields, the setting's i've used in my evaluation server are below. IdentityCustom Identity Keystore: /oracle/middleware/user_projects/domains/irm_domain/config/fmwconfig/MyOwnIdentityStore.jks Custom Identity Keystore Type: JKS Custom Identity Keystore Passphrase: password Confirm Custom Identity Keystore Passphrase: password TrustCustom Trust Keystore: /oracle/middleware/user_projects/domains/irm_domain/config/fmwconfig/TrustMyOwnSelf.jks Custom Trust Keystore Type: JKS Custom Trust Keystore Passphrase: password Confirm Custom Trust Keystore Passphrase: password Now click on the SSL tab for the IRM_server1 and enter in the alias and passphrase, in my demo here the details are; IdentityPrivate Key Alias: trustself Private Key Passphrase: password Confirm Private Key Passphrase: password And hit save. Now lets test a connection to the IRM server over HTTPS using SSL. Go back to a console window and start the IRM server, a quick reminder on how to do this is... [oracle@irm /] cd /oracle/middleware/user_projects/domains/irm_domain/bin [oracle@irm /] ./startManagedWeblogic IRM_server1 Once running, open a browser and head to the SSL port of the server. By default the IRM server will be listening on the URL https://irm.company.intranet:16101/irm_rights. Note in the example image on the right the port is 7002 because it's a system that has the IRM services installed on the Admin server, this isn't typical (or advisable). Your system is going to have a separate managed server which will be listening on port 16101. Once you open this address you will notice that your browser is going to complain that the server certificate is untrusted. The images on the right show how Firefox displays this error. You are going to be prompted every time you create a new SSL session with the server, both from the browser and more annoyingly from the IRM Desktop. If you plan on always using a self signed certificate, it is worth adding it to the Windows certificate store so that when you are accessing sealed content you do not keep being informed this certificate is not trusted. Follow these instructions (which are for Internet Explorer 8, they may vary for your version of IE.) Start Internet Explorer and open the URL to your IRM server over SSL, e.g. https://irm.company.intranet:16101/irm_rights. IE will complain that about the certificate, click on Continue to this website (not recommended). From the IE Tools menu select Internet Options and from the resulting dialog select Security and then click on Trusted Sites and then the Sites button. Add to the list of trusted sites a URL which mates the server you are accessing, e.g. https://irm.company.intranet/ and select OK. Now refresh the page you were accessing and next to the URL you should see a red cross and the words Certificate Error. Click on this button and select View Certificates. You will now see a dialog with the details of the self signed certificate and the Install Certificate... button should be enabled. Click on this to start the wizard. Click next and you'll be asked where you should install the certificate. Change the option to Place all certificates in the following store. Select browse and choose the Trusted Root Certification Authorities location and hit OK. You'll then be prompted to install the certificate and answer yes. You also need to import the root signed certificate into the same location, so once again select the red Certificate Error option and this time when viewing the certificate, switch to the Certification Path tab and you should see a CertGenCAB certificate. Select this and then click on View Certificate and go through the same process as above to import the certificate into the store. Finally close all instances of the IE browser and re-access the IRM server URL again, this time you should not receive any errors. Setting up an official SSL certificate in Apache 2.x At this point we now have an IRM server that you can communicate with over SSL. However this certificate isn't trusted by any browser because it's path of trust doesn't end in a recognized certificate authority (CA). Also you are communicating directly to the WebLogic Server over a non standard SSL port, 16101. In a production environment it is common to have another device handle the initial public internet traffic and then proxy this to the WebLogic server. The diagram below shows a very simplified view of this type of deployment. What i'm going to walk through next is configuring Apache to proxy traffic to a WebLogic server and also to use a real SSL certificate from an official CA. First step is to configure Apache to handle incoming requests over SSL. In this guide I am configuring the IRM service in Oracle Enterprise Linux 5 update 3 and Apache 2.2.3 which came with OpenSSL and mod_ssl components. Before I purchase an SSL certificate, I need to generate a certificate request from the server. Oracle.com uses Verisign and for my own personal needs I use cheaper certificates from GoDaddy. The following instructions are specific to Apache, but there are many references out there for other web servers. For Apache I have OpenSSL and the commands are; [oracle@irm /] cd /usr/bin [oracle@irm bin] openssl genrsa -des3 -out irm-apache-server.key 2048 Generating RSA private key, 2048 bit long modulus ............................+++ .........+++ e is 65537 (0x10001) Enter pass phrase for irm-apache-server.key: Verifying - Enter pass phrase for irm-apache-server.key: [oracle@irm bin] openssl req -new -key irm-apache-server.key -out irm-apache-server.csr Enter pass phrase for irm-apache-server.key: You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [GB]:US State or Province Name (full name) [Berkshire]:CA Locality Name (eg, city) [Newbury]:San Francisco Organization Name (eg, company) [My Company Ltd]:Oracle Organizational Unit Name (eg, section) []:Security Common Name (eg, your name or your server's hostname) []:irm.company.com Email Address []:[email protected] Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []:testing An optional company name []: You must make sure to remember the pass phrase you used in the initial key generation, you will need this when later configuring Apache. In the /usr/bin directory there are now two new files. The irm-apache-server.csr contains our certificate request and is what you cut and paste, or upload, to your certificate authority when you purchase and validate your SSL certificate. In response you will typically get two files. Your server certificate and another certificate file that will likely contain a set of certificates from your CA which validate your certificate's trust. Next we need to configure Apache to use these files. Typically there is an ssl.conf file which is where all the SSL configuration is done. On my Oracle Enterprise Linux server this file is located in /etc/httpd/conf.d/ssl.conf and i've added the following lines. <VirtualHost irm.company.com> # Setup SSL for irm.company.com ServerName irm.company.com SSLEngine On SSLCertificateFile /oracle/secure/irm.company.com.crt SSLCertificateKeyFile /oracle/secure/irm.company.com.key SSLCertificateChainFile /oracle/secure/gd_bundle.crt </VirtualHost> Restarting Apache (apachectl restart) and I can now attempt to connect to the Apache server in a web browser, https://irm.company.com/. If all is configured correctly I should now see an Apache test page delivered to me over HTTPS. Configuring Apache to proxy traffic to the IRM server Final piece in setting up SSL is to have Apache proxy requests for the IRM server but do so securely. So the requests to Apache will be over HTTPS using a legitimate certificate, but we can also configure Apache to proxy these requests internally across to the IRM server using SSL with the self signed certificate we generated at the start of this article. To do this proxying we use the WebLogic Web Server plugin for Apache which you can download here from Oracle. Download the zip file and extract onto the server. The file extraction reveals a set of zip files, each one specific to a supported web server. In my instance I am using Apache 2.2 32bit on an Oracle Enterprise Linux, 64 bit server. If you are not sure what version your Apache server is, run the command /usr/sbin/httpd -V and you'll see version and it its 32 or 64 bit. Mine is a 32bit server so I need to extract the file WLSPlugin1.1-Apache2.2-linux32-x86.zip. The from the resulting lib folder copy the file mod_wl.so into /usr/lib/httpd/modules/. First we want to test that the plug in will work for regular HTTP traffic. Edit the httpd.conf for Apache and add the following section at the bottom. LoadModule weblogic_module modules/mod_wl.so <IfModule mod_weblogic.c>    WebLogicHost irm.company.internal    WebLogicPort 16100    WLLogFile /tmp/wl-proxy.log </IfModule> <Location /irm_rights>    SetHandler weblogic-handler </Location> <Location /irm_desktop>    SetHandler weblogic-handler </Location> <Location /irm_sealing>    SetHandler weblogic-handler </Location> <Location /irm_services>    SetHandler weblogic-handler </Location> Now restart Apache again (apachectl restart) and now open a browser to http://irm.company.com/irm_rights. Apache will proxy the HTTP traffic from the port 80 of your Apache server to the IRM service listening on port 16100 of the WebLogic Managed server. Note above I have included all four of the Locations you might wish to proxy. http://irm.company.internalirm_rights is the URL to the management website, /irm_desktop is the URL used for the IRM Desktop to communicate. irm_sealing is for web services based document sealing and irm_services is for IRM server web services. The last two are typically only used when you have the IRM server integrated with another application and it is unlikely you'd be accessing these resources from the public facing Apache server. However, just in case, i've mentioned them above. Now let's enable SSL communication from Apache to WebLogic. In the ZIP file we extracted were some more modules we need to copy into the Apache folder. Looking back in the lib that we extracted, there are some more files. Copy the following into the /usr/lib/httpd/modules/ folder. libwlssl.so libnnz11.so libclntsh.so.11.1 Now the documentation states that should only need to do this, but I found that I also needed to create an environment variable called LD_LIBRARY_PATH and point this to the folder /usr/lib/httpd/modules/. If I didn't do this, starting Apache with the WebLogic module configured to SSL would throw the error. [crit] (20014)Internal error: WL SSL Init failed for server: (null) on 0 So I had to edit the file /etc/profile and add the following lines at the bottom. You may already have the LD_LIBRARY_PATH variable defined, therefore simply add this path to it. LD_LIBRARY_PATH=/usr/lib/httpd/modules/ export LD_LIBRARY_PATH Now the WebLogic plug in uses an Oracle Wallet to store the required certificates.You'll need to copy the self signed certificate from the IRM server over to the Apache server. Copy over the MyOwnSelfCA.cer.der into the same folder where you are storing your public certificates, in my example this is /oracle/secure. It's worth mentioning these files should ONLY be readable by root (the user Apache runs as). Now lets create an Oracle Wallet and import the self signed certificate from the IRM server. The file orapki was included in the bin folder of the Apache 1.1 plugin zip you extracted. orapki wallet create -wallet /oracle/secure/my-wallet -auto_login_only orapki wallet add -wallet /oracle/secure/my-wallet -trusted_cert -cert MyOwnSelfCA.cer.der -auto_login_only Finally change the httpd.conf to reflect that we want the WebLogic Apache plug-in to use HTTPS/SSL and not just plain HTTP. <IfModule mod_weblogic.c>    WebLogicHost irm.company.internal    WebLogicPort 16101    SecureProxy ON    WLSSLWallet /oracle/secure/my-wallet    WLLogFile /tmp/wl-proxy.log </IfModule> Then restart Apache once more and you can go back to the browser to test the communication. Opening the URL https://irm.company.com/irm_rights will proxy your request to the WebLogic server at https://irm.company.internal:16101/irm_rights. At this point you have a fully functional Oracle IRM service, the next step is to create a sealed document and test the entire system.

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  • Q1 2010 New Feature: Paging with RadGridView for Silverlight and WPF

    We are glad to announce that the Q1 2010 Release has added another weapon to RadGridViews growing arsenal of features. This is the brand new RadDataPager control which provides the user interface for paging through a collection of data. The good news is that RadDataPager can be used to page any collection. It does not depend on RadGridView in any way, so you will be free to use it with the rest of your ItemsControls if you chose to do so. Before you read on, you might want to download the samples solution that I have attached. It contains a sample project for every scenario that I will discuss later on. Looking at the code while reading will make things much easier for you. There is something for everyone among the 10 Visual Studio projects that are included in the solution. So go and grab it. I. Paging essentials The single most important piece of software concerning paging in Silverlight is the System.ComponentModel.IPagedCollectionView interface. Those of you who are on the WPF front need not worry though. As you might already know, Teleriks Silverlight and WPF controls is share the same code-base. Since WPF does not contain a similar interface, Telerik has provided its own Telerik.Windows.Data.IPagedCollectionView. The IPagedCollectionView interface contains several important members which are used by RadGridView to perform the actual paging. Silverlight provides a default implementation of this interface which, naturally, is called PagedCollectionView. You should definitely take a look at its source code in case you are interested in what is going on under the hood. But this is not a prerequisite for our discussion. The WPF default implementation of the interface is Teleriks QueryableCollectionView which, among many other interfaces, implements IPagedCollectionView. II. No Paging In order to gradually build up my case, I will start with a very simple example that lacks paging whatsoever. It might sound stupid, but this will help us build on top of this paging-devoid example. Let us imagine that we have the simplest possible scenario. That is a simple IEnumerable and an ItemsControl that shows its contents. This will look like this: No Paging IEnumerable itemsSource = Enumerable.Range(0, 1000); this.itemsControl.ItemsSource = itemsSource; XAML <Border Grid.Row="0" BorderBrush="Black" BorderThickness="1" Margin="5">     <ListBox Name="itemsControl"/> </Border> <Border Grid.Row="1" BorderBrush="Black" BorderThickness="1" Margin="5">     <TextBlock Text="No Paging"/> </Border> Nothing special for now. Just some data displayed in a ListBox. The two sample projects in the solution that I have attached are: NoPaging_WPF NoPaging_SL3 With every next sample those two project will evolve in some way or another. III. Paging simple collections The single most important property of RadDataPager is its Source property. This is where you pass in your collection of data for paging. More often than not your collection will not be an IPagedCollectionView. It will either be a simple List<T>, or an ObservableCollection<T>, or anything that is simply IEnumerable. Unless you had paging in mind when you designed your project, it is almost certain that your data source will not be pageable out of the box. So what are the options? III. 1. Wrapping the simple collection in an IPagedCollectionView If you look at the constructors of PagedCollectionView and QueryableCollectionView you will notice that you can pass in a simple IEnumerable as a parameter. Those two classes will wrap it and provide paging capabilities over your original data. In fact, this is what RadGridView does internally. It wraps your original collection in an QueryableCollectionView in order to easily perform many useful tasks such as filtering, sorting, and others, but in our case the most important one is paging. So let us start our series of examples with the most simplistic one. Imagine that you have a simple IEnumerable which is the source for an ItemsControl. Here is how to wrap it in order to enable paging: Silverlight IEnumerable itemsSource = Enumerable.Range(0, 1000); var pagedSource = new PagedCollectionView(itemsSource); this.radDataPager.Source = pagedSource; this.itemsControl.ItemsSource = pagedSource; WPF IEnumerable itemsSource = Enumerable.Range(0, 1000); var pagedSource = new QueryableCollectionView(itemsSource); this.radDataPager.Source = pagedSource; this.itemsControl.ItemsSource = pagedSource; XAML <Border Grid.Row="0"         BorderBrush="Black"         BorderThickness="1"         Margin="5">     <ListBox Name="itemsControl"/> </Border> <Border Grid.Row="1"         BorderBrush="Black"         BorderThickness="1"         Margin="5">     <telerikGrid:RadDataPager Name="radDataPager"                               PageSize="10"                              IsTotalItemCountFixed="True"                              DisplayMode="All"/> This will do the trick. It is quite simple, isnt it? The two sample projects in the solution that I have attached are: PagingSimpleCollectionWithWrapping_WPF PagingSimpleCollectionWithWrapping_SL3 III. 2. Binding to RadDataPager.PagedSource In case you do not like this approach there is a better one. When you assign an IEnumerable as the Source of a RadDataPager it will automatically wrap it in a QueryableCollectionView and expose it through its PagedSource property. From then on, you can attach any number of ItemsControls to the PagedSource and they will be automatically paged. Here is how to do this entirely in XAML: Using RadDataPager.PagedSource <Border Grid.Row="0"         BorderBrush="Black"         BorderThickness="1" Margin="5">     <ListBox Name="itemsControl"              ItemsSource="{Binding PagedSource, ElementName=radDataPager}"/> </Border> <Border Grid.Row="1"         BorderBrush="Black"         BorderThickness="1"         Margin="5">     <telerikGrid:RadDataPager Name="radDataPager"                               Source="{Binding ItemsSource}"                              PageSize="10"                              IsTotalItemCountFixed="True"                              DisplayMode="All"/> The two sample projects in the solution that I have attached are: PagingSimpleCollectionWithPagedSource_WPF PagingSimpleCollectionWithPagedSource_SL3 IV. Paging collections implementing IPagedCollectionView Those of you who are using WCF RIA Services should feel very lucky. After a quick look with Reflector or the debugger we can see that the DomainDataSource.Data property is in fact an instance of the DomainDataSourceView class. This class implements a handful of useful interfaces: ICollectionView IEnumerable INotifyCollectionChanged IEditableCollectionView IPagedCollectionView INotifyPropertyChanged Luckily, IPagedCollectionView is among them which lets you do the whole paging in the server. So lets do this. We will add a DomainDataSource control to our page/window and connect the items control and the pager to it. Here is how to do this: MainPage <riaControls:DomainDataSource x:Name="invoicesDataSource"                               AutoLoad="True"                               QueryName="GetInvoicesQuery">     <riaControls:DomainDataSource.DomainContext>         <services:ChinookDomainContext/>     </riaControls:DomainDataSource.DomainContext> </riaControls:DomainDataSource> <Border Grid.Row="0"         BorderBrush="Black"         BorderThickness="1"         Margin="5">     <ListBox Name="itemsControl"              ItemsSource="{Binding Data, ElementName=invoicesDataSource}"/> </Border> <Border Grid.Row="1"         BorderBrush="Black"         BorderThickness="1"         Margin="5">     <telerikGrid:RadDataPager Name="radDataPager"                               Source="{Binding Data, ElementName=invoicesDataSource}"                              PageSize="10"                              IsTotalItemCountFixed="True"                              DisplayMode="All"/> By the way, you can replace the ListBox from the above code snippet with any other ItemsControl. It can be RadGridView, it can be the MS DataGrid, you name it. Essentially, RadDataPager is sending paging commands to the the DomainDataSource.Data. It does not care who, what, or how many different controls are bound to this same Data property of the DomainDataSource control. So if you would like to experiment with this, you can throw in any number of other ItemsControls next to the ListBox, bind them in the same manner, and all of them will be paged by our single RadDataPager. Furthermore, you can throw in any number of RadDataPagers and bind them to the same property. Then when you page with any one of them will automatically update all of the rest. The whole picture is simply beautiful and we can do all of this thanks to WCF RIA Services. The two sample projects (Silverlight only) in the solution that I have attached are: PagingIPagedCollectionView PagingIPagedCollectionView.Web IV. Paging RadGridView While you can replace the ListBox in any of the above examples with a RadGridView, RadGridView offers something extra. Similar to the DomainDataSource.Data property, the RadGridView.Items collection implements the IPagedCollectionView interface. So you are already thinking: Then why not bind the Source property of RadDataPager to RadGridView.Items? Well thats exactly what you can do and you will start paging RadGridView out-of-the-box. It is as simple as that, no code-behind is involved: MainPage <Border Grid.Row="0"         BorderBrush="Black"         BorderThickness="1" Margin="5">     <telerikGrid:RadGridView Name="radGridView"                              ItemsSource="{Binding ItemsSource}"/> </Border> <Border Grid.Row="1"         BorderBrush="Black"         BorderThickness="1"         Margin="5">     <telerikGrid:RadDataPager Name="radDataPager"                               Source="{Binding Items, ElementName=radGridView}"                              PageSize="10"                              IsTotalItemCountFixed="True"                              DisplayMode="All"/> The two sample projects in the solution that I have attached are: PagingRadGridView_SL3 PagingRadGridView_WPF With this last example I think I have covered every possible paging combination. In case you would like to see an example of something that I have not covered, please let me know. Also, make sure you check out those great online examples: WCF RIA Services with DomainDataSource Paging Configurator Endless Paging Paging Any Collection Paging RadGridView Happy Paging! Download Full Source Code Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Parallelism in .NET – Part 1, Decomposition

    - by Reed
    The first step in designing any parallelized system is Decomposition.  Decomposition is nothing more than taking a problem space and breaking it into discrete parts.  When we want to work in parallel, we need to have at least two separate things that we are trying to run.  We do this by taking our problem and decomposing it into parts. There are two common abstractions that are useful when discussing parallel decomposition: Data Decomposition and Task Decomposition.  These two abstractions allow us to think about our problem in a way that helps leads us to correct decision making in terms of the algorithms we’ll use to parallelize our routine. To start, I will make a couple of minor points. I’d like to stress that Decomposition has nothing to do with specific algorithms or techniques.  It’s about how you approach and think about the problem, not how you solve the problem using a specific tool, technique, or library.  Decomposing the problem is about constructing the appropriate mental model: once this is done, you can choose the appropriate design and tools, which is a subject for future posts. Decomposition, being unrelated to tools or specific techniques, is not specific to .NET in any way.  This should be the first step to parallelizing a problem, and is valid using any framework, language, or toolset.  However, this gives us a starting point – without a proper understanding of decomposition, it is difficult to understand the proper usage of specific classes and tools within the .NET framework. Data Decomposition is often the simpler abstraction to use when trying to parallelize a routine.  In order to decompose our problem domain by data, we take our entire set of data and break it into smaller, discrete portions, or chunks.  We then work on each chunk in the data set in parallel. This is particularly useful if we can process each element of data independently of the rest of the data.  In a situation like this, there are some wonderfully simple techniques we can use to take advantage of our data.  By decomposing our domain by data, we can very simply parallelize our routines.  In general, we, as developers, should be always searching for data that can be decomposed. Finding data to decompose if fairly simple, in many instances.  Data decomposition is typically used with collections of data.  Any time you have a collection of items, and you’re going to perform work on or with each of the items, you potentially have a situation where parallelism can be exploited.  This is fairly easy to do in practice: look for iteration statements in your code, such as for and foreach. Granted, every for loop is not a candidate to be parallelized.  If the collection is being modified as it’s iterated, or the processing of elements depends on other elements, the iteration block may need to be processed in serial.  However, if this is not the case, data decomposition may be possible. Let’s look at one example of how we might use data decomposition.  Suppose we were working with an image, and we were applying a simple contrast stretching filter.  When we go to apply the filter, once we know the minimum and maximum values, we can apply this to each pixel independently of the other pixels.  This means that we can easily decompose this problem based off data – we will do the same operation, in parallel, on individual chunks of data (each pixel). Task Decomposition, on the other hand, is focused on the individual tasks that need to be performed instead of focusing on the data.  In order to decompose our problem domain by tasks, we need to think about our algorithm in terms of discrete operations, or tasks, which can then later be parallelized. Task decomposition, in practice, can be a bit more tricky than data decomposition.  Here, we need to look at what our algorithm actually does, and how it performs its actions.  Once we have all of the basic steps taken into account, we can try to analyze them and determine whether there are any constraints in terms of shared data or ordering.  There are no simple things to look for in terms of finding tasks we can decompose for parallelism; every algorithm is unique in terms of its tasks, so every algorithm will have unique opportunities for task decomposition. For example, say we want our software to perform some customized actions on startup, prior to showing our main screen.  Perhaps we want to check for proper licensing, notify the user if the license is not valid, and also check for updates to the program.  Once we verify the license, and that there are no updates, we’ll start normally.  In this case, we can decompose this problem into tasks – we have a few tasks, but there are at least two discrete, independent tasks (check licensing, check for updates) which we can perform in parallel.  Once those are completed, we will continue on with our other tasks. One final note – Data Decomposition and Task Decomposition are not mutually exclusive.  Often, you’ll mix the two approaches while trying to parallelize a single routine.  It’s possible to decompose your problem based off data, then further decompose the processing of each element of data based on tasks.  This just provides a framework for thinking about our algorithms, and for discussing the problem.

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  • Partition Wise Joins

    - by jean-pierre.dijcks
    Some say they are the holy grail of parallel computing and PWJ is the basis for a shared nothing system and the only join method that is available on a shared nothing system (yes this is oversimplified!). The magic in Oracle is of course that is one of many ways to join data. And yes, this is the old flexibility vs. simplicity discussion all over, so I won't go there... the point is that what you must do in a shared nothing system, you can do in Oracle with the same speed and methods. The Theory A partition wise join is a join between (for simplicity) two tables that are partitioned on the same column with the same partitioning scheme. In shared nothing this is effectively hard partitioning locating data on a specific node / storage combo. In Oracle is is logical partitioning. If you now join the two tables on that partitioned column you can break up the join in smaller joins exactly along the partitions in the data. Since they are partitioned (grouped) into the same buckets, all values required to do the join live in the equivalent bucket on either sides. No need to talk to anyone else, no need to redistribute data to anyone else... in short, the optimal join method for parallel processing of two large data sets. PWJ's in Oracle Since we do not hard partition the data across nodes in Oracle we use the Partitioning option to the database to create the buckets, then set the Degree of Parallelism (or run Auto DOP - see here) and get our PWJs. The main questions always asked are: How many partitions should I create? What should my DOP be? In a shared nothing system the answer is of course, as many partitions as there are nodes which will be your DOP. In Oracle we do want you to look at the workload and concurrency, and once you know that to understand the following rules of thumb. Within Oracle we have more ways of joining of data, so it is important to understand some of the PWJ ideas and what it means if you have an uneven distribution across processes. Assume we have a simple scenario where we partition the data on a hash key resulting in 4 hash partitions (H1 -H4). We have 2 parallel processes that have been tasked with reading these partitions (P1 - P2). The work is evenly divided assuming the partitions are the same size and we can scan this in time t1 as shown below. Now assume that we have changed the system and have a 5th partition but still have our 2 workers P1 and P2. The time it takes is actually 50% more assuming the 5th partition has the same size as the original H1 - H4 partitions. In other words to scan these 5 partitions, the time t2 it takes is not 1/5th more expensive, it is a lot more expensive and some other join plans may now start to look exciting to the optimizer. Just to post the disclaimer, it is not as simple as I state it here, but you get the idea on how much more expensive this plan may now look... Based on this little example there are a few rules of thumb to follow to get the partition wise joins. First, choose a DOP that is a factor of two (2). So always choose something like 2, 4, 8, 16, 32 and so on... Second, choose a number of partitions that is larger or equal to 2* DOP. Third, make sure the number of partitions is divisible through 2 without orphans. This is also known as an even number... Fourth, choose a stable partition count strategy, which is typically hash, which can be a sub partitioning strategy rather than the main strategy (range - hash is a popular one). Fifth, make sure you do this on the join key between the two large tables you want to join (and this should be the obvious one...). Translating this into an example: DOP = 8 (determined based on concurrency or by using Auto DOP with a cap due to concurrency) says that the number of partitions >= 16. Number of hash (sub) partitions = 32, which gives each process four partitions to work on. This number is somewhat arbitrary and depends on your data and system. In this case my main reasoning is that if you get more room on the box you can easily move the DOP for the query to 16 without repartitioning... and of course it makes for no leftovers on the table... And yes, we recommend up-to-date statistics. And before you start complaining, do read this post on a cool way to do stats in 11.

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  • Independence Day for Software Components &ndash; Loosening Coupling by Reducing Connascence

    - by Brian Schroer
    Today is Independence Day in the USA, which got me thinking about loosely-coupled “independent” software components. I was reminded of a video I bookmarked quite a while ago of Jim Weirich’s “Grand Unified Theory of Software Design” talk at MountainWest RubyConf 2009. I finally watched that video this morning. I highly recommend it. In the video, Jim talks about software connascence. The dictionary definition of connascence (con-NAY-sense) is: 1. The common birth of two or more at the same time 2. That which is born or produced with another. 3. The act of growing together. The brief Wikipedia page about Connascent Software Components says that: Two software components are connascent if a change in one would require the other to be modified in order to maintain the overall correctness of the system. Connascence is a way to characterize and reason about certain types of complexity in software systems. The term was introduced to the software world in Meilir Page-Jones’ 1996 book “What Every Programmer Should Know About Object-Oriented Design”. The middle third of that book is the author’s proposed graphical notation for describing OO designs. UML became the standard about a year later, so a revised version of the book was published in 1999 as “Fundamentals of Object-Oriented Design in UML”. Weirich says that the third part of the book, in which Page-Jones introduces the concept of connascence “is worth the price of the entire book”. (The price of the entire book, by the way, is not much – I just bought a used copy on Amazon for $1.36, so that was a pretty low-risk investment. I’m looking forward to getting the book and learning about connascence from the original source.) Meanwhile, here’s my summary of Weirich’s summary of Page-Jones writings about connascence: The stronger the form of connascence, the more difficult and costly it is to change the elements in the relationship. Some of the connascence types, ordered from weak to strong are: Connascence of Name Connascence of name is when multiple components must agree on the name of an entity. If you change the name of a method or property, then you need to change all references to that method or property. Duh. Connascence of name is unavoidable, assuming your objects are actually used. My main takeaway about connascence of name is that it emphasizes the importance of giving things good names so you don’t need to go changing them later. Connascence of Type Connascence of type is when multiple components must agree on the type of an entity. I assume this is more of a problem for languages without compilers (especially when used in apps without tests). I know it’s an issue with evil JavaScript type coercion. Connascence of Meaning Connascence of meaning is when multiple components must agree on the meaning of particular values, e.g that “1” means normal customer and “2” means preferred customer. The solution to this is to use constants or enums instead of “magic” strings or numbers, which reduces the coupling by changing the connascence form from “meaning” to “name”. Connascence of Position Connascence of positions is when multiple components must agree on the order of values. This refers to methods with multiple parameters, e.g.: eMailer.Send("[email protected]", "[email protected]", "Your order is complete", "Order completion notification"); The more parameters there are, the stronger the connascence of position is between the component and its callers. In the example above, it’s not immediately clear when reading the code which email addresses are sender and receiver, and which of the final two strings are subject vs. body. Connascence of position could be improved to connascence of type by replacing the parameter list with a struct or class. This “introduce parameter object” refactoring might be overkill for a method with 2 parameters, but would definitely be an improvement for a method with 10 parameters. This points out two “rules” of connascence:  The Rule of Degree: The acceptability of connascence is related to the degree of its occurrence. The Rule of Locality: Stronger forms of connascence are more acceptable if the elements involved are closely related. For example, positional arguments in private methods are less problematic than in public methods. Connascence of Algorithm Connascence of algorithm is when multiple components must agree on a particular algorithm. Be DRY – Don’t Repeat Yourself. If you have “cloned” code in multiple locations, refactor it into a common function.   Those are the “static” forms of connascence. There are also “dynamic” forms, including… Connascence of Execution Connascence of execution is when the order of execution of multiple components is important. Consumers of your class shouldn’t have to know that they have to call an .Initialize method before it’s safe to call a .DoSomething method. Connascence of Timing Connascence of timing is when the timing of the execution of multiple components is important. I’ll have to read up on this one when I get the book, but assume it’s largely about threading. Connascence of Identity Connascence of identity is when multiple components must reference the entity. The example Weirich gives is when you have two instances of the “Bob” Employee class and you call the .RaiseSalary method on one and then the .Pay method on the other does the payment use the updated salary?   Again, this is my summary of a summary, so please be forgiving if I misunderstood anything. Once I get/read the book, I’ll make corrections if necessary and share any other useful information I might learn.   See Also: Gregory Brown: Ruby Best Practices Issue #24: Connascence as a Software Design Metric (That link is failing at the time I write this, so I had to go to the Google cache of the page.)

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  • Class Loading Deadlocks

    - by tomas.nilsson
    Mattis follows up on his previous post with one more expose on Class Loading Deadlocks As I wrote in a previous post, the class loading mechanism in Java is very powerful. There are many advanced techniques you can use, and when used wrongly you can get into all sorts of trouble. But one of the sneakiest deadlocks you can run into when it comes to class loading doesn't require any home made class loaders or anything. All you need is classes depending on each other, and some bad luck. First of all, here are some basic facts about class loading: 1) If a thread needs to use a class that is not yet loaded, it will try to load that class 2) If another thread is already loading the class, the first thread will wait for the other thread to finish the loading 3) During the loading of a class, one thing that happens is that the <clinit method of a class is being run 4) The <clinit method initializes all static fields, and runs any static blocks in the class. Take the following class for example: class Foo { static Bar bar = new Bar(); static { System.out.println("Loading Foo"); } } The first time a thread needs to use the Foo class, the class will be initialized. The <clinit method will run, creating a new Bar object and printing "Loading Foo" But what happens if the Bar object has never been used before either? Well, then we will need to load that class as well, calling the Bar <clinit method as we go. Can you start to see the potential problem here? A hint is in fact #2 above. What if another thread is currently loading class Bar? The thread loading class Foo will have to wait for that thread to finish loading. But what happens if the <clinit method of class Bar tries to initialize a Foo object? That thread will have to wait for the first thread, and there we have the deadlock. Thread one is waiting for thread two to initialize class Bar, thread two is waiting for thread one to initialize class Foo. All that is needed for a class loading deadlock is static cross dependencies between two classes (and a multi threaded environment): class Foo { static Bar b = new Bar(); } class Bar { static Foo f = new Foo(); } If two threads cause these classes to be loaded at exactly the same time, we will have a deadlock. So, how do you avoid this? Well, one way is of course to not have these circular (static) dependencies. On the other hand, it can be very hard to detect these, and sometimes your design may depend on it. What you can do in that case is to make sure that the classes are first loaded single threadedly, for example during an initialization phase of your application. The following program shows this kind of deadlock. To help bad luck on the way, I added a one second sleep in the static block of the classes to trigger the unlucky timing. Notice that if you uncomment the "//Foo f = new Foo();" line in the main method, the class will be loaded single threadedly, and the program will terminate as it should. public class ClassLoadingDeadlock { // Start two threads. The first will instansiate a Foo object, // the second one will instansiate a Bar object. public static void main(String[] arg) { // Uncomment next line to stop the deadlock // Foo f = new Foo(); new Thread(new FooUser()).start(); new Thread(new BarUser()).start(); } } class FooUser implements Runnable { public void run() { System.out.println("FooUser causing class Foo to be loaded"); Foo f = new Foo(); System.out.println("FooUser done"); } } class BarUser implements Runnable { public void run() { System.out.println("BarUser causing class Bar to be loaded"); Bar b = new Bar(); System.out.println("BarUser done"); } } class Foo { static { // We are deadlock prone even without this sleep... // The sleep just makes us more deterministic try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Bar b = new Bar(); } class Bar { static { try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Foo f = new Foo(); }

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  • Use Drive Mirroring for Instant Backup in Windows 7

    - by Trevor Bekolay
    Even with the best backup solution, a hard drive crash means you’ll lose a few hours of work. By enabling drive mirroring in Windows 7, you’ll always have an up-to-date copy of your data. Windows 7’s mirroring – which is only available in Professional, Enterprise, and Ultimate editions – is a software implementation of RAID 1, which means that two or more disks are holding the exact same data. The files are constantly kept in sync, so that if one of the disks fails, you won’t lose any data. Note that mirroring is not technically a backup solution, because if you accidentally delete a file, it’s gone from both hard disks (though you may be able to recover the file). As an additional caveat, having mirrored disks requires changing them to “dynamic disks,” which can only be read within modern versions of Windows (you may have problems working with a dynamic disk in other operating systems or in older versions of Windows). See this Wikipedia page for more information. You will need at least one empty disk to set up disk mirroring. We’ll show you how to mirror an existing disk (of equal or lesser size) without losing any data on the mirrored drive, and how to set up two empty disks as mirrored copies from the get-go. Mirroring an Existing Drive Click on the start button and type partitions in the search box. Click on the Create and format hard disk partitions entry that shows up. Alternatively, if you’ve disabled the search box, press Win+R to open the Run window and type in: diskmgmt.msc The Disk Management window will appear. We’ve got a small disk, labeled OldData, that we want to mirror in a second disk of the same size. Note: The disk that you will use to mirror the existing disk must be unallocated. If it is not, then right-click on it and select Delete Volume… to mark it as unallocated. This will destroy any data on that drive. Right-click on the existing disk that you want to mirror. Select Add Mirror…. Select the disk that you want to use to mirror the existing disk’s data and press Add Mirror. You will be warned that this process will change the existing disk from basic to dynamic. Note that this process will not delete any data on the disk! The new disk will be marked as a mirror, and it will starting copying data from the existing drive to the new one. Eventually the drives will be synced up (it can take a while), and any data added to the E: drive will exist on both physical hard drives. Setting Up Two New Drives as Mirrored If you have two new equal-sized drives, you can format them to be mirrored copies of each other from the get-go. Open the Disk Management window as described above. Make sure that the drives are unallocated. If they’re not, and you don’t need the data on either of them, right-click and select Delete volume…. Right-click on one of the unallocated drives and select New Mirrored Volume…. A wizard will pop up. Click Next. Click on the drives you want to hold the mirrored data and click Add. Note that you can add any number of drives. Click Next. Assign it a drive letter that makes sense, and then click Next. You’re limited to using the NTFS file system for mirrored drives, so enter a volume label, enable compression if you want, and then click Next. Click Finish to start formatting the drives. You will be warned that the new drives will be converted to dynamic disks. And that’s it! You now have two mirrored drives. Any files added to E: will reside on both physical disks, in case something happens to one of them. Conclusion While the switch from basic to dynamic disks can be a problem for people who dual-boot into another operating system, setting up drive mirroring is an easy way to make sure that your data can be recovered in case of a hard drive crash. Of course, even with drive mirroring, we advocate regular backups to external drives or online backup services. Similar Articles Productive Geek Tips Rebit Backup Software [Review]Disabling Instant Search in Outlook 2007Restore Files from Backups on Windows Home ServerSecond Copy 7 [Review]Backup Windows Home Server Folders to an External Hard Drive TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips CloudBerry Online Backup 1.5 for Windows Home Server Snagit 10 VMware Workstation 7 Acronis Online Backup Windows Firewall with Advanced Security – How To Guides Sculptris 1.0, 3D Drawing app AceStock, a Tiny Desktop Quote Monitor Gmail Button Addon (Firefox) Hyperwords addon (Firefox) Backup Outlook 2010

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  • SQL SERVER – Not Possible – Delete From Multiple Table – Update Multiple Table in Single Statement

    - by pinaldave
    There are two questions which I get every single day multiple times. In my gmail, I have created standard canned reply for them. Let us see the questions here. I want to delete from multiple table in a single statement how will I do it? I want to update multiple table in a single statement how will I do it? The answer is – No, You cannot and you should not. SQL Server does not support deleting or updating from two tables in a single update. If you want to delete or update two different tables – you may want to write two different delete or update statements for it. This method has many issues – from the consistency of the data to SQL syntax. Now here is the real reason for this blog post – yesterday I was asked this question again and I replied my canned answer saying it is not possible and it should not be any way implemented that day. In the response to my reply I was pointed out to my own blog post where user suggested that I had previously mentioned this is possible and with demo example. Let us go over my conversation – you may find it interesting. Let us call the user DJ. DJ: Pinal, can we delete multiple table in a single statement or with single delete statement? Pinal: No, you cannot and you should not. DJ: Oh okey, if that is the case, why do you suggest to do that? Pinal: (baffled) I am not suggesting that. I am rather suggesting that it is not possible and it should not be possible. DJ: Hmm… but in that case why did you blog about it earlier? Pinal: (What?) No, I did not. I am pretty confident. DJ: Well, I am confident as well. You did. Pinal: In that case, it is my word against your word. Isn’t it? DJ: I have proof. Do you want to see it that you suggest it is possible? Pinal: Yes, I will be delighted too. (After 10 Minutes) DJ: Here are not one but two of your blog posts which talks about it - SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2 Pinal: Oh! DJ: I know I was correct. Pinal: Well, oh man, I did not mean there what you mean here. DJ: I did not understand can you explain it further. Pinal: Here we go. The example in the other blog is the example of the cascading delete or cascading update. I think you may want to understand the concept of the foreign keys and cascading update/delete. The concept of cascading exists to maintain data integrity. If there primary keys get deleted the update or delete reflects on the foreign key table to maintain the key integrity and data consistency. SQL Server follows ANSI Entry SQL with regard to referential integrity between PrimaryKey and ForeignKey columns which requires the inserting, updating, and deleting of data in related tables to be restricted to values that preserve the integrity. This is all together different concept than deleting multiple values in a single statement. When I hear that someone wants to delete or update multiple table in a single statement what I assume is something very similar to following. DELETE/UPDATE Table 1 (cols) Table 2 (cols) VALUES … which is not valid statement/syntax as well it is not ASNI standards as well. I guess, after this discussion with DJ, I realize I need to do a blog post so I can add the link to this blog post in my canned answer. Well, it was a fun conversation with DJ and I hope it the message is very clear now. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Joins, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • How to Save Hundreds or Thousands of Dollars on Cell Phone Service

    - by Chris Hoffman
    Cell phone contracts are bad. You get a seemingly cheap phone up front, but you more than pay for the cost of the phone over two years. Prepaid phone plans are surging in North America for a reason. Prepaid phone plans will be cheaper and more flexible than traditional contracts with big carriers for many people. However much you use your phone, there’s a good chance you can save money with a prepaid service. No More Contracts Here’s how cell phone service typically works in North America: You get a subsidized phone for “free”, $99, or $199. You sign up for a two-year contract and more than pay back the cost of that phone over the length of the contract. This is similar to leasing something or purchasing it on a credit card and paying it back over two years — you spend less up front, but you’re paying more in the long run. But this isn’t the only option. You could opt for a cheaper prepaid service that doesn’t lock you into a contract. If you don’t use your phone much, you could just pay for what you use and avoid the hefty cell phone bills. If you use your phone a lot, you could get a cheaper plan, too. Now, this certainly isn’t for everyone. If you want the latest iPhone or Galaxy smartphone every two years and require a 4G data connection, prepaid services may not be for you. On the other hand, if you don’t need the latest phone, you can save money here. You can also save a huge amount of money if you don’t use your phone much. Phone Options When you choose your prepaid or contract-free service, you’ll often be able to purchase a phone from them. You’ll generally be able to find dirt-cheap dumbphones and the cheapest, slowest Android phones for not very much money. If you are able to buy a top-of-the-line smartphone, you’ll have to pay the full, unsubsidized price. That’s $649 for either an iPhone 5S or Samsung Galaxy S4. Whatever phones the service provider offers, you could always buy a phone elsewhere — for example, you could buy an unsubsidized iPhone direct from Apple and then take it to your cell phone service of choice. Most services will allow you to get a SIM card and pop it into your existing phone rather than purchasing a phone. If you can get a hand-me-down smartphone, you can often save quite a bit of money. For example, you may have a family member upgrading from an iPhone 4S to an iPhone 5S. You could take their phone to a prepaid carrier and have a nicer phone on a cheap cell phone plan. If you brought an old smartphone to a big carrier like AT&T or Verizon, they wouldn’t give you a discount on your monthly plan. You’d have to pay the same amount of money every month as if you had gotten a subsidized phone. Google’s Nexus phones are also great options for people looking to buy smartphones and pay up-front. Google’s Nexus 4 offered a modern, almost top-of-the-line Android smartphone experience at $299 or $349 when it came out last year. Google will soon be releasing the Nexus 5 and it’s expected to be priced at $349. That’s certainly a lot more than a cheap phone, but it’s a fairly high-end smartphone at almost half the price of an iPhone 5S or Galaxy S4. Nexus phones can be purchased online from Google’s Play Store. Service Options When choosing a service, you need to consider what you actually use. If you’re someone who only uses your phone rarely, you can get plans that will allow you to pay as little as a few dollars per month. If you’re someone who’s usually in range of Wi-Fi, you may not need much data at all. If you want a plan with unlimited talk, texting, and data usage, you can get it for much cheaper than you’d pay on a major carrier like AT&T. The options here range from pay-as-you-go plans, like the ones offered by T-Mobile, which allow you to put a certain amount of money in and only drain that balance when you actually use minutes, texts, or data. If you only make a few calls and send a few texts per month, you’d only pay a few bucks. On the other end, Walmart’s Straight Talk service is a popular option that offers unlimited talk, texting, and data at $45 per month. Which service is right for you depends on a lot of things, including your usage and what each network’s coverage is like in your area. You’ll want to do some research of your own before choosing a service. Prepaid services also offer you even more flexibility after you choose one. If you’re not happy or a better deal comes along, you can switch — you’re not locked into your service for two years and you won’t pay an early termination fee. Image Credit: Intel Free Press on Flickr, Jon Fingas on Flickr, John Karakatsanis on Flickr, kendalkinggroup on Flickr     

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  • Coherence Data Guarantees for Data Reads - Basic Terminology

    - by jpurdy
    When integrating Coherence into applications, each application has its own set of requirements with respect to data integrity guarantees. Developers often describe these requirements using expressions like "avoiding dirty reads" or "making sure that updates are transactional", but we often find that even in a small group of people, there may be a wide range of opinions as to what these terms mean. This may simply be due to a lack of familiarity, but given that Coherence sits at an intersection of several (mostly) unrelated fields, it may be a matter of conflicting vocabularies (e.g. "consistency" is similar but different in transaction processing versus multi-threaded programming). Since almost all data read consistency issues are related to the concept of concurrency, it is helpful to start with a definition of that, or rather what it means for two operations to be concurrent. Rather than implying that they occur "at the same time", concurrency is a slightly weaker statement -- it simply means that it can't be proven that one event precedes (or follows) the other. As an example, in a Coherence application, if two client members mutate two different cache entries sitting on two different cache servers at roughly the same time, it is likely that one update will precede the other by a significant amount of time (say 0.1ms). However, since there is no guarantee that all four members have their clocks perfectly synchronized, and there is no way to precisely measure the time it takes to send a given message between any two members (that have differing clocks), we consider these to be concurrent operations since we can not (easily) prove otherwise. So this leads to a question that we hear quite frequently: "Are the contents of the near cache always synchronized with the underlying distributed cache?". It's easy to see that if an update on a cache server results in a message being sent to each near cache, and then that near cache being updated that there is a window where the contents are different. However, this is irrelevant, since even if the application reads directly from the distributed cache, another thread update the cache before the read is returned to the application. Even if no other member modifies a cache entry prior to the local near cache entry being updated (and subsequently read), the purpose of reading a cache entry is to do something with the result, usually either displaying for consumption by a human, or by updating the entry based on the current state of the entry. In the former case, it's clear that if the data is updated faster than a human can perceive, then there is no problem (and in many cases this can be relaxed even further). For the latter case, the application must assume that the value might potentially be updated before it has a chance to update it. This almost aways the case with read-only caches, and the solution is the traditional optimistic transaction pattern, which requires the application to explicitly state what assumptions it made about the old value of the cache entry. If the application doesn't want to bother stating those assumptions, it is free to lock the cache entry prior to reading it, ensuring that no other threads will mutate the entry, a pessimistic approach. The optimistic approach relies on what is sometimes called a "fuzzy read". In other words, the application assumes that the read should be correct, but it also acknowledges that it might not be. (I use the qualifier "sometimes" because in some writings, "fuzzy read" indicates the situation where the application actually sees an original value and then later sees an updated value within the same transaction -- however, both definitions are roughly equivalent from an application design perspective). If the read is not correct it is called a "stale read". Going back to the definition of concurrency, it may seem difficult to precisely define a stale read, but the practical way of detecting a stale read is that is will cause the encompassing transaction to roll back if it tries to update that value. The pessimistic approach relies on a "coherent read", a guarantee that the value returned is not only the same as the primary copy of that value, but also that it will remain that way. In most cases this can be used interchangeably with "repeatable read" (though that term has additional implications when used in the context of a database system). In none of cases above is it possible for the application to perform a "dirty read". A dirty read occurs when the application reads a piece of data that was never committed. In practice the only way this can occur is with multi-phase updates such as transactions, where a value may be temporarily update but then withdrawn when a transaction is rolled back. If another thread sees that value prior to the rollback, it is a dirty read. If an application uses optimistic transactions, dirty reads will merely result in a lack of forward progress (this is actually one of the main risks of dirty reads -- they can be chained and potentially cause cascading rollbacks). The concepts of dirty reads, fuzzy reads, stale reads and coherent reads are able to describe the vast majority of requirements that we see in the field. However, the important thing is to define the terms used to define requirements. A quick web search for each of the terms in this article will show multiple meanings, so I've selected what are generally the most common variations, but it never hurts to state each definition explicitly if they are critical to the success of a project (many applications have sufficiently loose requirements that precise terminology can be avoided).

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