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• MySQL ODBC + SSL with only the SSL Cipher option?

  - by sdek

  Does anybody know how I can have an SSL encrypted connection over MySQL ODBC without the cert options? So I asked my web host to setup a MySQL+SSL connection so that we can access our website's database via ODBC or MySQL Query Browser (or the likes). I am able to get an encrypted connection with the standard mysql client and MySQL Query Browser, but I can't get the ODBC connection to work. Looking for a little help... The way they set it up is a little different from the way I have read about on the interweb. The host didn't setup a cert, or at least I don't think so - I don't need to specify any cert options in my connection. I just need to specify the ssl cipher. Here is how I connect with the mysql client: mysql -h myhost.com -u myuser --ssl-cipher=3DES -p That works to get an encrypted connection. At least I am pretty sure it works because when I run mysql> \s I get SSL: Cipher in use is EDH-RSA-DES-CBC3-SHA Also, when I put EDH-RSA-DES-CBC3-SHA into the SSL Cipher field of MySQL Query Browser (without specifying any other SSL options) it connects just fine. But then when I try to do the same thing with my MySQL ODBC 3.5.1 and 5.1 I get a generic error. Here is the error from the 5.1 Driver. Connection Failed: [HY000] [MySQL][ODBC 5.1 Driver]SSL connection error

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• Catastrophic Failure opening ODBC via Citrix

  - by Joshdan

  We recently had our Citrix server crash unexpectedly. When it came back up, there was a new issue -- every ODBC connection fails with "Catastrophic Failure" (0x8000FFFF). The issue is limited to Citrix / ICA connections; logging in as the same user via RDP works as usual. The following code is my minimal test case (for wscript): ''// test_odbc.vbs strConn = "Driver={Microsoft Text Driver (*.txt; *.csv)};Dbq=c:\files\;" Set rs = CreateObject("ADODB.recordset") strSQL = "SELECT * FROM myFile.csv" wscript.echo "Press OK to Test" ''// This line breaks over Citrix, but not over Terminal Services ''// ---------------------- rs.open strSQL, strConn, 3,3 ''// ---------------------- wscript.echo rs("a") Any insight would be greatly appreciated. Windows Server 2003 SP1, Citrix MetaFrame Presentation Server 4.0. Clients include at least versions 10.2-11 running on 2000-Vista, OS X. ODBC error happens whether a DSN is used or not, on at least Access, MS-SQL, and CSV. Connections both through the SSL Gateway and directly. There have been a few users actually able to log in without trouble, but I can't pin down anything special about them.

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• How can something relevant to graphics completely kill a motherboard?

  - by leladax

  I was coding something in OpenGL and after a bug there was an 'OS slowed down' situation. After a few seconds the screen went blank and the laptop shutdown. Now not even a led turns on battery or not. It doesn't appear to be the AC or the battery since there was some battery when it died and when it's connected to the AC the laptop produces near the AC connection a very slight 'clicking' noise (very faint, one has to be very careful to notice it, I don't know if it was there forever tbh). I suspect the motherboard died, as in something from the point it gets AC or battery power and the point it actually feeds itself. But I can't figure out how that effect was produced by the OpenGL bug or graphics overheating. If the graphics died alone, it should at least give some indication that the laptop is barely alive, at least a led, a sound, anything, the laptop is instead completely dead (other than faint 'clicking' I mentioned). Does anyone have expert advice on this? I'm especially interested in any ideas connected to "graphics overheated/bugged ---- they killed motherboard". I have a very lengthy experience in that stuff as a hobbyist and it really puzzles me. It's not just a "AC died" situation I can easily google.

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• How to configure a large mtu (linux)

  - by Somejan

  I have a gigabit ethernet connection from my laptop to my router, and a working ipv6 connection to the internet. I can receive very large packets from sites on the internet, with sizes up to at least 10000 bytes (according to wireshark). (edit: turns out to be linux's 'generic receive offload') However, when trying to send anything, my local computer fragments at just below 1500 bytes for ipv6. (On ipv4, I can send tcp packets to the internet of at least 1514 bytes, I can ping with packets up to the configured mtu of 6128 but they are blackholed.) I'm on ubuntu 12.04. I have configured an mtu for my eth0 of 6128 (the maximum it accepts), both using ip link set dev eth0 mtu 6128 and in the NetworkManager applet gui, and restarted the connection. ip link show eth0 shows the 6128 mtu is indeed set. ip -6 route shows that none of the paths the kernel knows about have an mtu set. I can ping over ipv4 with packets up to 6128 bytes (though I don't get responses), but when I do ping6 myrouter -c3 -s1500 -Mdo I get error replies from my own computer saying that the packets are too large and the mtu is 1480. I have confirmed with Wireshark that nothing is put on the wire, and the replies are indeed generated by my own computer. So, how do I get my computer to use the larger mtu?

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• Internet Troubles - PPPoE vs PPPoA?

  - by AkkA

  I have been having some internet troubles at home (ADSL2+ connection in Australia). We get random drop-outs from the authentication connection. It will keep the connection to the DSL service, but we lose authentication and either have to restart the router/modem (its combined, a Belkin one, not sure on model number) or unplug the phone cable, wait about 30 seconds and plug it in again. I've called the ISP (Telstra) a few times, but they only offer limited support when we dont use their supported hardware. Apparently something had happened on their side, they checked the box again (at least it sounded that simple), and told me it would be fine. It wasnt. I've replaced all the filters around the house, but that didnt help either. We do live a little bit away from the exchange (get a sync speed of about 3000/900), so I thought it could be due to line noise but that hasnt helped. Telstra allow both PPPoE and PPPoA connections (which I'm configuring through my router, dont have software on the PC side). I've been running PPPoA the whole time, would it make any difference changing it to PPPoE? If not, are there any other theories as to why we would be experiencing these drop-outs? It has been fine for at least 12 months, then suddenly started about 2 months ago.

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• WAMP starts Apache or Mysql, but not both?

  - by ladenedge

  When I install WAMP, the Apache and Mysql services are set to run as the LocalService user and all works well. However, because I need to access remote UNC paths in my PHP code, I need to run at least Apache as a user that exists on both the local host and the remote host - I'll call him WampUser. When both Apache and Mysql are set to start as WampUser, I cannot start both at the same time. If both are stopped, I can start either successfully. When I attempt to start the other, I get Error 1053: The service did not respond to the start or control request in a timely fashion. This error appears immediately - there is no timeout. When at least one of the services is set to start as LocalService, both start fine. I can, therefore, solve my problem by setting Apache to WampUser and Mysql to LocalService, but I'm more interested in why this is happening in the first place. I'm especially curious because this situation does not occur on other servers - something I've done to this server has made these two services exclusive when running as the same user. Here are some miscellaneous data points: I am using Windows Server 2003. I've provided recursive Full Control to the C:\wamp directory for WampUser. Nothing appears in the event log after the service fails. No log entries appear in either the Mysql log or the Apache error log. Neither application appears in the process list when the appropriate service is stopped. Any ideas?

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• Good Enough Failover Strategy for DNS / MySQL / Email

  - by IMB

  I've asked and read a lot questions regarding DNS failover but the more I read the more complicated it becomes, some people say it's good enough some say it isn't. No clear answers from what I read. I was wondering if we can set it straight once and for all, at least for the requirements of most websites out there. Right now let's assume the following: We don't need really need load-balancing, what we need is a failover solution. We are running a website based on LAMP on a VPS. We need to make sure that the Web Server, MySQL, Email are always accessible if not 99%. Basically here's my idea and questions about it: Web Server: We need at least one failover server (another VPS on a separate data center). Is DNS Failover via Round Robin good, if not, what's the best? And how do you exactly implement it? How do you make the files you upload/delete on Server A is also on Server B? MySQL: I've only read a brief intro to MySQL replication and I assume that I can replicate Server A to Server B and vice versa on the fly right? So just it case Server A fails and Server B is now running, it will continue to work and replicate to Server A when it becomes available. So in essence Server B is now the primary server, and will later on failover to Server A, should a failure happen again. Email: If we are gonna use DNS Failover, using webmail or relying on emails stored on the server is probably not a good idea right? Since some emails might be on Server A while some might be on Server B? I assume a basic email forwarder to a 3rdparty is good enough (like Gmail for example) to ensure all emails are kept in one place. Here's a basic diagram for a better picture: http://i.stack.imgur.com/KWSIi.png

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• What is going on when I can't access an SMB server share (not accessible error) until I run cmdkey to delete the credential?

  - by Warren P

  I have a network connection share issue. The first connection works, and seems to stay connected for at least a few hours. However, after each time my windows 7 PC reboots, it can no longer form a network connection to the shared folder, nor browse to it, until I not only unmap and remap the mapped drive, but also, I have to use cmdkey to delete the stored credentials like this: cmdkey /delete:Domain:target=HOSTNAME My work PC is on a domain, and I am not the IT administrator, but I'm curious if there is anything I can do to investigate this issue. Any settings in registry or group policy that I could examine to see why the first connection works, but each subsequent attempt (once a stored credential exists) to browse or use the connection, fails with a connection error saying it is "not accessible", like this: I do not even get any error until at least several minutes go by. THe first thing I see is a window frozen and empty, and then I get this error: This has happened when connecting to a share on a DROBO device, and on a share which is not on the domain, but which was a Microsoft Home Server. I wonder if there's something broken in WIndows 7 professional with regards to connecting to non-domain shares when an active directory domain controller exists, and a particular workstation is joined to a domain? The problem only occurs if I click "remember credentials". It is not fixed by any amount of working with net use. Usingcmdkey to delete all stored credentials for the host is the only way to get back in, and it affects all non-domain shared folders. Update I'm hoping there are some registry locations I could check that could be misconfigured in some way that might explain why SMB/CIFS stored credentials for non-domain systems seem to be auto-invalidated in this weird way. Knowing how whacko Microsoft Windows domain and security handling is sometimes, this could be some kind of stupid "feature".

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• central apache log analysis of many hosts

  - by Jason Antman

  We have 30+ apache httpd servers, and are looking to perform analysis on the logs both for historical trending and near "real time" monitoring/alerting. I'm mainly interested in things like error rates (4xx/5xx), response time, overall request rate, etc. but it would also be very useful to pull out more compute-intensive statistics like unique client IPs and user agents per unit of time. I'm leaning towards building this as a centralized collector/server/storage, and am also considering the possibility of storing non-apache logs (i.e. general syslog, firewall logs, etc.) in the same system. Obviously a large part of this will probably have to be custom (at least the connection between pieces and the parsing/analysis we do), but I haven't been able to find much information on people who have done stuff like this, at least at shops smaller than Google/Facebook/etc. who can throw their log data into a hundred-node compute cluster and run Map/Reduce on it. The main things I'm looking for are: - All open source - Some way of collecting logs from apache machines that isn't too resource-intensive, and transports them relatively quickly over the network - Some way of storing them (NoSQL? key-value store?) on the backend, for a given amount of time (and then rolling them up into historical averages) - In the middle of this, a way of graphing in near-real-time (probably also with some statistical analysis on it) and hopefully alerting off of those graphs. Any suggestions/pointers/ideas, to either "products"/projects or descriptions of how other people do this would be greatly helpful. Unfortunately, we're not exactly a new-age-y devops shop, lots of old stuff, homogeneous infrastructure, and strained boxes.

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• Copying files between linux machines with strong authentication but without encryption

  - by Zizzencs

  I'm looking for a suitable program to copy files from one linux machine to another one. The program should be able to do authentication but it should not do encryption. The reason behind the latter is the lack of CPU power to do the encryption. I copy backups from ~70 machines to a single backup server simultaneously. The single server is an HP Proliant DL360 G7, with 10 Gbps ethernet connection and an FC storage backend that can do 4 Gbps. Through FTP I can write ~400MB/sec to the storage (that's about what I want) but through ssh with arcfour I can only do ~100MB/sec while having 100% CPU usage. That's why I want file transfers not to be encrypted. The alternatives that I found not really suitable: rcp: no authentication, forget it FTP: making the authentication "secure" (at least preventing plain-text password exchange) is possible but not really easy and I haven't found a method to force any FTP daemon to encrypt the control channel (for the authentication) and not to encrypt the data channel (for data transfers) SCP/SFTP: in farely recent ssh(d) implementations you can't turn off encryption. The best you can do is to use the arcfour cypher for the encryption but it sill uses too much CPU power for my needs. rsync over ssh: same problems as with SCP/SFTP. plain rsync: from the documentation of rsyncd: "The authentication protocol used in rsync is a 128 bit MD4 based challenge response system. This is fairly weak protection, though (with at least one brute-force hash-finding algorithm publicly available), so if you want really top-quality security, then I recommend that you run rsync over ssh." It's a no-go. Is there a protocol/program that can do exactly what I want? (A big plus would be if it could work on windows as well and/or if it would support rsync-stlye copying/synchronization (e.g. copy only the differences).)

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• Cisco IOS ACL: Don't permit incoming connections just because they are from port 80

  - by cjavapro

  I am going much based on my memory and I may not be correct on all of this. On a Cisco 851 (IOS) that uses a BVI or a bridge-route (the servers on the inside are configured with static and public IP addresses). I would apply two access lists (both end with deny ip any any log) on FastEthernet4 (the WAN port). There would be one for FA4 in and another for FA4 out. FA4 out would have a line like access-list 110 permit 98.76.54.0 0.0.0.255 gt 1023 any eq http I think this means from 98.76.54.* with a from port of at least 1024 can connect to any other machine with a destination port 80. So, then I have to allow the response to the HTTP connection. FA4 in would have a line like access-list 120 permit any eq http 98.76.54.0 0.0.0.255 gt 1023 Now the problem with that is that anybody on the outside can set their from port to port 80 and then connect to any inside port that is at least 1024. How do we prevent this and require the incoming data to be a response to the outgoing data.

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• Is It Possible To Self-Teach PHP, Wordpress, CentOS (Linux), Apache, Nginx etc?

  - by Aahan

  consider me a total noob, who uses a Windows PC and has never touched Linux. But I want to administer, manage and take responsibility of my server, at least at some point, if not now. But since I am a full-time blogger I am unable to find time to study at an institute. So, here is my question — - Is It Possible To Self-Teach HTML, CSS, PHP, JavaScript, Wordpress, CentOS (or for that matter any Linux distro), Apache, Nginx, and Varnish? Yes, beginning with HTML, absolutely all of them. I might seem overly ambitious and foolish, but I just want to do it. Aren't there any self-taught server admins? (1) Please help me out with the names of good books, links and whatever you can. (2) How long would it take me to get there (approximately)? 3 years? 5 years? (I have good touch with HTML & Wordpress.) This is a great community, I hope at least some of you will shoot some suggestions at me.

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• What can I do to determine the root cause of a Windows server hanging/freezing?

  - by Aaronaught

  We set up a new server here a few weeks ago that I am informally responsible for managing. Almost everything works perfectly except for one thing: Every so often it hangs without warning. To clarify: When I say hangs, I mean completely. None of the services respond and I'm unable to even get onto a local console - the display acts as though there's no VGA signal. One time, the server actually responded to pings, another time I got the "destination host unreachable" response, but most of the time the pings just time out, as one would expect for a hung server. Event logs don't show anything after a reboot. I don't mean that they don't show anything interesting, I mean that they don't show anything at all from before the failure occurs to after the reboot. And there are never any performance problems, strange errors, or other obvious signs of impending doom before it happens. I don't expect any easy answers here. What I'd like to know his I can methodically determine the root cause of this problem, be it a misbehaving service, defective hardware, or something else. Is there any kind of logging I can set up that will help me get to the bottom of this? Any hardware diagnostics or remote monitoring? Anything else I can do to help me discover what's actually happening, or at least be able to eliminate what isn't wrong? Just to reiterate, I really don't want to start speculating about possible causes and take a trial-and-error approach, because it's going to be at least several days at a time before I would have conclusive results. I'm looking for solutions to reliably trace the problem to its source.

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• KVM Hosting: How to efficiently replicate guests

  - by javano

  I have three KVM servers each with 1 guest VM, running directly on it's local storage, (so they are essentially getting a dedicated box worth of computing power each). In the event of a host failure I would like the guests replicated to at least one of the other hosts so I can spin it up there, until the failing host is fixed. I am curious about KVM cloning. I can clone a VM live or when it's suspended/shutdown. Obivously suspended VMs will naturally be quicker to clone but these three VMs comprise three parts of a single solution, so I don't want to ever have any one of them shutdown. How can I efficiently clone these VMs between servers? I have had a couple of ideas, but are these insane or, is there a better method I have missed for my scenario? Set up a DRDB partition between box 1 and 2 where VM 1 runs from, and so is replicated between box1 and box 2, repeat between box 2 & 3, and box 3 & 1 (This could be insane, I have never used DRDB only read about it) Just use standard KVM CLI clone options to perform live clones (I'm dubious about this because I don't know how long it will take and what the performance impact will be during) Run a copy of each VM on at least one other host, and have the guest on one host export it's data to the matching guest on another host where it can import that data, scripting this on the guest) Some of other way? Ideas welcome! Side Note These servers have 4x15k SAS drives in a RAID 10 so they aren't rocketing fast, and as I mentioned, each VM runs from the host's local storage, no NAS or SAN etc. So that is why I am asking this question about guest replication. Also, this isn't about disaster recovery. Guests will be exporting their data to a NAS over a VPN, so I am looking at how I can have them quickly spun up in a host failure situation.

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• Storing Windows Updates for reuse

  - by Saiyine

  At work we update lots of computers using Windows Update. Windows XP and 7 all day long, rarely some Vista. We do it through a corporate proxy, as connecting them to a domain to build a Wsus server is out of the question, so we download about two gigabytes a day of the very same updates everyday. I've tried WSUS Offline. It's pretty complete but when it finishes it's common to be still missing hundreds of megabytes of updates, because its intention is not to fully update a system but to install the critical updates, as the developers explain in the forums. Now I'm trying with Autoupdater. It's far worse, with poor capabilities for non-English Windows XP, but at least it gives the option to install non critical updates in Windows 7. It still misses hundres of megabytes of updates after fully updating the system. And finally, both doesn't install the driver related updates of Windows 7, so they at most save us a couple of hundreds of megabytes and a reboot (with the associated login to the computer and to the proxy) out of three or four. So, is it possible to somewhat extract the installed updates in a Windows 7 system and not having to download the same updates again and again at least with machines with the same hardware? Or even better, a generic package with all the updates?

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• Rescue system running TFS that BSODs, into vmware esxi

  - by 3molo

  Hi, After moving to new facilities, one of our old Dell servers running Windows Server 2003 R2 on PowerEdge 2650 HW BSODs with 0x8e. The server runs Team Foundation Server, so we have a few guys dependent on it. No one here knows TFS, so we have no idea how difficult it would be to setup from scratch. We have the MSSQL database(s) backed up, recent and fresh copy. Tried removing/refitting memory modules, but with no success. The system boots into safe mode but hangs occasionally. I booted a linux livecd and did a dd of both c: and d:, so I have all the data in compressed images on a vmware machine. For the guest, I created a 38G (actually it became 40GB) partition to act as C:, and booted a live cd. I then uncompressed the compressed disk image of c: and dd'd it to the new c: using 'gunzip -dc c.img.gz | dd of=/dev/sda1 bs=1M'. The operation ran for about 1000 seconds, and completed successfully. I assumed it would at least try to boot windows (but most likely BSOD due to not having correct drivers), but the Vmware ESXi guest does not seem to recognize it as a bootable disk. We don't have the vmware enterprise license, so the vmware converter cold cloning is not an option. Did I do something wrong in my dd's etc with the ISOs, or why would it not (try to) boot? Am I wasting my time? What other approach is there? Will continue to try to remove services and drivers to make the physical machine at least work reasonably well in safe mode. What do you suggest? 1. Continue to get the dd'd images to the virtual disk and get it to boot. 2. Install a new windows server, get team foundation server and restore from backup. 3. Focus on the old problematic hardware Any help appreciated

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• New router, slower internet connection?

  - by qwerty

  So, we just bought a new router a few hours ago, and it does work. However, for some reason the speed is just ridiculously slow (compared to before, at least)! If i run a test on speedtest.net i get the following results: http://i.imgur.com/68JyH.png which are pretty good. But for some reason it's like the connection just "hangs" for a second when i navigate to a site through the browser (have tried different browsers). It's not on all sites, it kind of happens randomly. I think the browser cache might be speeding some sites up, because if i visit a site that i HAVEN'T visited before (since i cleared my cache), it takes like two seconds (if not more) to open the site. If i have visited it, it opens directly (it barely loads). Not sure what to do, really. Any suggestions on what might speed it up? Any settings i can play with in the router settings? The router is of the brand Belkin. I'm not sure about the model though, it says "Belkin, Play Max Wireless Router" on the box? Thanks in advance! EDIT: Alright, it takes a lot more than two seconds. At least 3-4 depending on the site. Any suggestions?

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• disable mystery programs running at startup

  - by pstanton

  Hi and sorry for the ambiguous title... I have a few programs that should run at startup which are 'properly' configured to do so via adding shortcuts to the startup directory: C:\Users\[me]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup However I have (at least) 4 programs which are also starting up, which I can't find where they are configured or how to disable them. I have tried to find them in the above folder, as well as in the 'startup' section of 'msconfig'. The programs include: Skype (for which I have disabled 'start when windows starts' in its options) Thunderbird (for which I cannot find any option to run-at-startup) Task manager (as above) and some anonymous call to javaw (can't find any more details but it fails anyway) The other strange thing is that it seems like these (at least skype and thunderbird) are running 'as administrator' ... i have deduced this because I am unable to use the file-drag-and-drop feature in both (which is a known problem when running 'as administrator'). If someone could guide me to where these extra programs are configured to run-at-startup I would be very greatful! ps. my user account has the administrator role. EDIT: preferrably without another 3rd party tool...

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• Microsoft Word 2008 on the Mac sometimes "Disappears" documents, really.

  - by Ross Charette

  This happens in a computer lab environment, has happened at least 3 times. We are running Microsoft Office 2008 for mac on Leopard, everything is updated. Our user's home directories are on a network drive, but the /Library/Cache folder is running locally. Typically a student will have a Word file that they have been working on, it's been saved before they even logged onto the computer that day. They log on, open the document, click the save icon (not go to File Save), sometimes even save multiple times, then close Word. The document is now gone. It's not hidden, there are no autosaves or anything in the Cache folder. Definitely not in the trash or trashes folder. It can't find it when you click on it in 'recent documents'. Searching meticulously though every folder in their home drive turns up nothing. They look using Finder, I look ssh'd as root into their home using ls -la. I look for similar files in case they renamed it by mistake. It's gone. Disappeared. Vaporized. It's happened to at least 3 different users in the past year. Much whining. Any idea?

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• Windows XP VM on VMWare ESXi 4.1 "pausing" / blocked occasionally

  - by FelixD

  We have an issue with Windows XP SP3 VMs on VMWare ESXi 4.1.0 (the free version): They sometimes seem to "pause" for several minutes. This happens rarely (maybe once a month per VM, at least noticed only that often), but still is an issue for us. It happens for three different but similar VMs on three pretty different hosts (different hardware). I have the feeling that the "pausing" is not actually the CPU blocking, but probably the harddisks, but not 100% sure. The servers have one IDE disk (C:) and one SCSI (D:) and it might be either of the two. I have seen scheduled tasks simply not starting for up to 9 minutes and then running normally again with normal speed. They were totally blocked. This is not a load issue, the VMWare hosts have average load and the VMs in question already have reserved CPU resources plus high priorities for CPU and disk. The Windows boxes run mainly MySQL, Tomcat, FileZilla server, Cygwin stuff, Java + R applications, VMWare client, Elusiva Terminal Server pro, Nagios client. Not sure if this might be related with any of that software (e.g. Elusiva). Trying to debug this, there was nothing visible in Windows Event log, other logs in C:\Windows, VMWare events etc. Unfortunately the vmware.log file ends with "Log throttled". We found that we ran into 2 VMWare bugs there: The VMWare client writes lots on bogus messages in the vmware.log, which we now disabled (log level error setting) plus the bug that VMWare does not unthrottle the log (at least so far despite VM reboots). I know there is not much guidance and that may also be the reason why I so far didn't find anything related on the web or on ServerFault, but maybe some of this rings a bell with someone? Or please direct me to what more info to post. I hope that the vmware.logs get unthrottled eventually (can't easily restart the hosts at the moment). Thanks for any input!

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• Working with an external button box

  - by Scott

  I tried this question on Stack Overflow, but I was pointed here, so here goes: For a new project for myself, I am looking for a way to be able to (for example) open a pop-up window on my laptop, by pressing a button on an external device (to be build by myself, or at least bought) connected with USB. Basically I would be looking at something like a Arduino or Raspberry (IF I am looking in the right direction) with buttons on it, and as soon as I hit a button on the external box with physical buttons, a command activates on my laptop and for example opens a popup window in which I can input tekst. Does anyone know: 1) if it is possible to do this at all. 2) What equipment is needed for the external box, what programming is needed. I preffer .net (dot net) but maybe it can only be done with software from the external box. If anyone can point me in the right direction, like make/model of the external box or websites I would be very happy. I have knowledge of Visual Studio/.net but I am willing to learn other languages if .net is not an option for this project. Thanks in advance Scott PS: If anyone knows of some better tags, or at least knows what I mean and needs me to edit the question, please do tell me... I am new on Stack Overflow/Superuser.

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• What should I use to ping multiple IPs and get notified of time outs?

  - by HumanVirus

  I've been using MultiPing to ping hundreds of IPs (from access points and such) and check their performance (packet loss, latency) and uptime. The program is very easy to use, but I was wondering if someone could recommend me something that would work better and that would also work in Linux. The features I'm looking for are: Notification Types: At least desktop notifications and SMS, but it would be great if it also had e-mail, IM, or other types of notifications. (MultiPing has some of these, but they don't work too well.) Being notified about the root problem only: Since some devices are dependent on others, I'd like to be notified only about the root problem. E.g. Let's say I have A[x.x.x.222]B[x.x.x.33C[x.x.x.44]D[x.x.x.55], and B goes down, therefore C and D will also be down. Is it possible to get a notification only about B being down? Light on resources. Ideally multiplatform or at least available for both Linux and Windows. I've heard about Nagios and Shinken being used for monitoring. Would you recommend that I use something of the sort or would that be too much for my needs? If using Nagios, Shinken, or similar software is recommended, can anyone tell me what sites I should go to or what books I should get that would be good for someone who is totally new at this? I'd appreciate any suggestions.

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• Why should you choose Oracle WebLogic 12c instead of JBoss EAP 6?

  - by Ricardo Ferreira

  In this post, I will cover some technical differences between Oracle WebLogic 12c and JBoss EAP 6, which was released a couple days ago from Red Hat. This article claims to help you in the evaluation of key points that you should consider when choosing for an Java EE application server. In the following sections, I will present to you some important aspects that most customers ask us when they are seriously evaluating for an middleware infrastructure, specially if you are considering JBoss for some reason. I would suggest that you keep the following question in mind while you are reading the points: "Why should I choose JBoss instead of WebLogic?" 1) Multi Datacenter Deployment and Clustering - D/R ("Disaster & Recovery") architecture support is embedded on the WebLogic Server 12c product. JBoss EAP 6 on the other hand has no direct D/R support included, Red Hat relies on third-part tools with higher prices. When you consider a middleware solution to host your business critical application, you should worry with every architectural aspect that are related with the solution. Fail-over support is one little aspect of a truly reliable solution. If you do not worry about D/R, your solution will not be reliable. Having said that, with Red Hat and JBoss EAP 6, you have this extra cost that will increase considerably the total cost of ownership of the solution. As we commonly hear from analysts, open-source are not so cheaper when you start seeing the big picture. - WebLogic Server 12c supports advanced LAN clustering, detection of death servers and have a common alert framework. JBoss EAP 6 on the other hand has limited LAN clustering support with no server death detection. They do not generate any alerts when servers goes down (only if you buy JBoss ON which is a separated technology, but until now does not support JBoss EAP 6) and manual intervention are required when servers goes down. In most cases, admin people must rely on "kill -9", "tail -f someFile.log" and "ps ax | grep java" commands to manage failures and clustering anomalies. - WebLogic Server 12c supports the concept of Node Manager, which is a separated process that runs on the physical | virtual servers that allows extend the administration of the cluster to WebLogic managed servers that are often distributed across multiple machines and geographic locations. JBoss EAP 6 on the other hand has no equivalent technology. Whole server instances must be managed individually. - WebLogic Server 12c Node Manager supports Coherence to boost performance when managing servers. JBoss EAP 6 on the other hand has no similar technology. There is no way to coordinate JBoss and infiniband instances provided by JBoss using high throughput and low latency protocols like InfiniBand. The Node Manager feature also allows another very important feature that JBoss EAP lacks: secure the administration. When using WebLogic Node Manager, all the administration tasks are sent to the managed servers in a secure tunel protected by a certificate, which means that the transport layer that separates the WebLogic administration console from the managed servers are secured by SSL. - WebLogic Server 12c are now integrated with OTD ("Oracle Traffic Director") which is a web server technology derived from the former Sun iPlanet Web Server. This software complements the web server support offered by OHS ("Oracle HTTP Server"). Using OTD, WebLogic instances are load-balanced by a high powerful software that knows how to handle SDP ("Socket Direct Protocol") over InfiniBand, which boost performance when used with engineered systems technologies like Oracle Exalogic Elastic Cloud. JBoss EAP 6 on the other hand only offers support to Apache Web Server with custom modules created to deal with JBoss clusters, but only across standard TCP/IP networks.  2) Application and Runtime Diagnostics - WebLogic Server 12c have diagnostics capabilities embedded on the server called WLDF ("WebLogic Diagnostic Framework") so there is no need to rely on third-part tools. JBoss EAP 6 on the other hand has no diagnostics capabilities. Their only diagnostics tool is the log generated by the application server. Admin people are encouraged to analyse thousands of log lines to find out what is going on. - WebLogic Server 12c complement WLDF with JRockit MC ("Mission Control"), which provides to administrators and developers a complete insight about the JVM performance, behavior and possible bottlenecks. WebLogic Server 12c also have an classloader analysis tool embedded, and even a log analyzer tool that enables administrators and developers to view logs of multiple servers at the same time. JBoss EAP 6 on the other hand relies on third-part tools to do something similar. Again, only log searching are offered to find out whats going on. - WebLogic Server 12c offers end-to-end traceability and monitoring available through Oracle EM ("Enterprise Manager"), including monitoring of business transactions that flows through web servers, ESBs, application servers and database servers, all of this with high deep JVM analysis and diagnostics. JBoss EAP 6 on the other hand, even using JBoss ON ("Operations Network"), which is a separated technology, does not support those features. Red Hat relies on third-part tools to provide direct Oracle database traceability across JVMs. One of those tools are Oracle EM for non-Oracle middleware that manage JBoss, Tomcat, Websphere and IIS transparently. - WebLogic Server 12c with their JRockit support offers a tool called JRockit Flight Recorder, which can give developers a complete visibility of a certain period of application production monitoring with zero extra overhead. This automatic recording allows you to deep analyse threads latency, memory leaks, thread contention, resource utilization, stack overflow damages and GC ("Garbage Collection") cycles, to observe in real time stop-the-world phenomenons, generational, reference count and parallel collects and mutator threads analysis. JBoss EAP 6 don't even dream to support something similar, even because they don't have their own JVM. 3) Application Server Administration - WebLogic Server 12c offers a complete administration console complemented with scripting and macro-like recording capabilities. A single WebLogic console can managed up to hundreds of WebLogic servers belonging to the same domain. JBoss EAP 6 on the other hand has a limited console and provides a XML centric administration. JBoss, after ten years, started the development of a rudimentary centralized administration that still leave a lot of administration tasks aside, so admin people and developers must touch scripts and XML configuration files for most advanced and even simple administration tasks. This lead applications to error prone and risky deployments. Even using JBoss ON, JBoss EAP are not able to offer decent administration features for admin people which must be high skilled in JBoss internal architecture and its managing capabilities. - Oracle EM is available to manage multiple domains, databases, application servers, operating systems and virtualization, with a complete end-to-end visibility. JBoss ON does not provide management capabilities across the complete architecture, only basic monitoring. Even deployment must be done aside JBoss ON which does no integrate well with others softwares than JBoss. Until now, JBoss ON does not supports JBoss EAP 6, so even their minimal support for JBoss are not available for JBoss EAP 6 leaving customers uncovered and subject to high skilled JBoss admin people. - WebLogic Server 12c has the same administration model whatever is the topology selected by the customer. JBoss EAP 6 on the other hand differentiates between two operational models: standalone-mode and domain-mode, that are not consistent with each other. Depending on the mode used, the administration skill is different. - WebLogic Server 12c has no point-of-failures processes, and it does not need to define any specialized server. Domain model in WebLogic is available for years (at least ten years or more) and is production proven. JBoss EAP 6 on the other hand needs special processes to garantee JBoss integrity, the PC ("Process-Controller") and the HC ("Host-Controller"). Different from WebLogic, the domain model in JBoss is quite new (one year at tops) of maturity, and need to mature considerably until start doing things like WebLogic domain model does. - WebLogic Server 12c supports parallel deployment model which enables some artifacts being deployed at the same time. JBoss EAP 6 on the other hand does not have any similar feature. Every deployment are done atomically in the containers. This means that if you have a huge EAR (an EAR of 120 MB of size for instance) and deploy onto JBoss EAP 6, this EAR will take some minutes in order to starting accept thread requests. The same EAR deployed onto WebLogic Server 12c will reduce the deployment time at least in 2X compared to JBoss. 4) Support and Upgrades - WebLogic Server 12c has patch management available. JBoss EAP 6 on the other hand has no patch management available, each JBoss EAP instance should be patched manually. To achieve such feature, you need to buy a separated technology called JBoss ON ("Operations Network") that manage this type of stuff. But until now, JBoss ON does not support JBoss EAP 6 so, in practice, JBoss EAP 6 does not have this feature. - WebLogic Server 12c supports previuous WebLogic domains without any reconfiguration since its kernel is robust and mature since its creation in 1995. JBoss EAP 6 on the other hand has a proven lack of supportability between JBoss AS 4, 5, 6 and 7. Different kernels and messaging engines were implemented in JBoss stack in the last five years reveling their incapacity to create a well architected and proven middleware technology. - WebLogic Server 12c has patch prescription based on customer configuration. JBoss EAP 6 on the other hand has no such capability. People need to create ticket supports and have their installations revised by Red Hat support guys to gain some patch prescription from them. - Oracle WebLogic Server independent of the version has 8 years of support of new patches and has lifetime release of existing patches beyond that. JBoss EAP 6 on the other hand provides patches for a specific application server version up to 5 years after the release date. JBoss EAP 4 and previous versions had only 4 years. A good question that Red Hat will argue to answer is: "what happens when you find issues after year 5"?  5) RAC ("Real Application Clusters") Support - WebLogic Server 12c ships with a specific JDBC driver to leverage Oracle RAC clustering capabilities (Fast-Application-Notification, Transaction Affinity, Fast-Connection-Failover, etc). Oracle JDBC thin driver are also available. JBoss EAP 6 on the other hand ships only the standard Oracle JDBC thin driver. Load balancing with Oracle RAC are not supported. Manual intervention in case of planned or unplanned RAC downtime are necessary. In JBoss EAP 6, situation does not reestablish automatically after downtime. - WebLogic Server 12c has a feature called Active GridLink for Oracle RAC which provides up to 3X performance on OLTP applications. This seamless integration between WebLogic and Oracle database enable more value added to critical business applications leveraging their investments in Oracle database technology and Oracle middleware. JBoss EAP 6 on the other hand has no performance gains at all, even when admin people implement some kind of connection-pooling tuning. - WebLogic Server 12c also supports transaction and web session affinity to the Oracle RAC, which provides aditional gains of performance. This is particularly interesting if you are creating a reliable solution that are distributed not only in an LAN cluster, but into a different data center. JBoss EAP 6 on the other hand has no such support. 6) Standards and Technology Support - WebLogic Server 12c is fully Java EE 6 compatible and production ready since december of 2011. JBoss EAP 6 on the other hand became fully compatible with Java EE 6 only in the community version after three months, and production ready only in a few days considering that this article was written in June of 2012. Red Hat says that they are the masters of innovation and technology proliferation, but compared with Oracle and even other proprietary vendors like IBM, they historically speaking are lazy to deliver the most newest technologies and standards adherence. - Oracle is the steward of Java, driving innovation into the platform from commercial and open-source vendors. Red Hat on the other hand does not have its own JVM and relies on third-part JVMs to complete their application server offer. 95% of Red Hat customers are using Oracle HotSpot as JVM, which means that without Oracle involvement, their support are limited exclusively to the application server layer and we all know that most problems are happens in the JVM layer. - WebLogic Server 12c supports natively JDK 7, which empower developers to explore the maximum of the Java platform productivity when writing code. This feature differentiate WebLogic from others application servers (except GlassFish that are also managed by Oracle) because the usage of JDK 7 introduce such remarkable productivity features like the "try-with-resources" enhancement, catching multiple exceptions with one try block, Strings in the switch statements, JVM improvements in terms of JDBC, I/O, networking, security, concurrency and of course, the most important feature of Java 7: native support for multiple non-Java languages. More features regarding JDK 7 can be found here. JBoss EAP 6 on the other hand does not support JDK 7 officially, they comment in their community version that "Java SE 7 can be used with JBoss 7" which does not gives you any guarantees of enterprise support for JDK 7. - Oracle WebLogic Server 12c supports integration with Spring framework allowing Spring applications to use WebLogic special transaction manager, exposing bean interfaces to WebLogic MBeans to take advantage of all WebLogic monitoring and administration advantages. JBoss EAP 6 on the other hand has no special integration with Spring. In fact, Red Hat offers a suspicious package called "JBoss Web Platform" that in theory supports Spring, but in practice this package does not offers any special integration. It is just a facility for Red Hat customers to have support from both JBoss and Spring technology using the same customer support. 7) Lightweight Development - Oracle WebLogic Server 12c and Oracle GlassFish are completely integrated and can share applications without any modifications. Starting with the 12c version, WebLogic now understands natively GlassFish deployment descriptors and specific configurations in order to offer you a truly and reliable migration path from a community Java EE application server to a enterprise middleware product like WebLogic. JBoss EAP 6 on the other hand has no support to natively reuse an existing (or still in development) application from JBoss AS community server. Users of JBoss suffer of critical issues during deployment time that includes: changing the libraries and dependencies of the application, patching the DTD or XSD deployment descriptors, refactoring of the application layers due classloading issues and anomalies, rebuilding of persistence, business and web layers due issues with "usage of the certified version of an certain dependency" or "frameworks that Red Hat potentially does not recommend" etc. If you have the culture or enterprise IT directive of developing Java EE applications using community middleware to in a certain future, transition to enterprise (supported by a vendor) middleware, Oracle WebLogic plus Oracle GlassFish offers you a more sustainable solution. - WebLogic Server 12c has a very light ZIP distribution (less than 165 MB). JBoss EAP 6 ZIP size is around 130 MB, together with JBoss ON you have more 100 MB resulting in a higher download footprint. This is particularly interesting if you plan to use automated setup of application server instances (for example, to rapidly setup a development or staging environment) using Maven or Hudson. - WebLogic Server 12c has a complete integration with Maven allowing developers to setup WebLogic domains with few commands. Tasks like downloading WebLogic, installation, domain creation, data sources deployment are completely integrated. JBoss EAP 6 on the other hand has a limited offer integration with those tools.  - WebLogic Server 12c has a startup mode called WLX that turns-off EJB, JMS and JCA containers leaving enabled only the web container with Java EE 6 web profile. JBoss EAP 6 on the other hand has no such feature, you need to disable manually the containers that you do not want to use. - WebLogic Server 12c supports fastswap, which enables you to change classes without redeployment. This is particularly interesting if you are developing patches for the application that is already deployed and you do not want to redeploy the entire application. This is the same behavior that most application servers offers to JSP pages, but with WebLogic Server 12c, you have the same feature for Java classes in general. JBoss EAP 6 on the other hand has no such support. Even JBoss EAP 5 does not support this until now. 8) JMS and Messaging - WebLogic Server 12c has a proven and high scalable JMS implementation since its initial release in 1995. JBoss EAP 6 on the other hand has a still immature technology called HornetQ, which was introduced in JBoss EAP 5 replacing everything that was implemented in the previous versions. Red Hat loves to introduce new technologies across JBoss versions, playing around with customers and their investments. And when they are asked about why they have changed the implementation and caused such a mess, their answer is always: "the previous implementation was inadequate and not aligned with the community strategy so we are creating a new a improved one". This Red Hat practice leads to uncomfortable investments that in a near future (sometimes less than a year) will be affected in someway. - WebLogic Server 12c has troubleshooting and monitoring features included on the WebLogic console and WLDF. JBoss EAP 6 on the other hand has no direct monitoring on the console, activity is reflected only on the logs, no debug logs available in case of JMS issues. - WebLogic Server 12c has extremely good performance and scalability. JBoss EAP 6 on the other hand has a JMS storage mechanism relying on Oracle database or MySQL. This means that if an issue in production happens and Red Hat affirms that an performance issue is happening due to database problems, they will not support you on the performance issue. They will orient you to call Oracle instead. - WebLogic Server 12c supports messaging enterprise features like SAF ("Store and Forward"), Distributed Queues/Topics and Foreign JMS providers support that leverage JMS implementations without compromise developer code making things completely transparent. JBoss EAP 6 on the other hand do not even dream to support such features. 9) Caching and Grid - Coherence, which is the leading and most mature data grid technology from Oracle, is available since early 2000 and was integrated with WebLogic in 2009. Coherence and WebLogic clusters can be both managed from WebLogic administrative console. Even Node Manager supports Coherence. JBoss on the other hand discontinued JBoss Cache, which was their caching implementation just like they did with the messaging implementation (JBossMQ) which was a issue for long term customers. JBoss EAP 6 ships InfiniSpan version 1.0 which is immature and lack a proven record of successful cases and reliability. - WebLogic Server 12c has a feature called ActiveCache which uses Coherence to, without any code changes, replicate HTTP sessions from both WebLogic and other application servers like JBoss, Tomcat, Websphere, GlassFish and even Microsoft IIS. JBoss EAP 6 on the other hand does have such support and even when they do in the future, they probably will support only their own application server. - Coherence can be used to manage both L1 and L2 cache levels, providing support to Oracle TopLink and others JPA compliant implementations, even Hibernate. JBoss EAP 6 and Infinispan on the other hand supports only Hibernate. And most important of all: Infinispan does not have any successful case of L1 or L2 caching level support using Hibernate, which lead us to reflect about its viability. 10) Performance - WebLogic Server 12c is certified with Oracle Exalogic Elastic Cloud and can run unchanged applications at this engineered system. This approach can benefit customers from Exalogic optimization's of both kernel and JVM layers to boost performance in terms of 10X for web, OLTP, JMS and grid applications. JBoss EAP 6 on the other hand has no investment on engineered systems: customers do not have the choice to deploy on a Java ultra fast system if their project becomes relevant and performance issues are detected. - WebLogic Server 12c maintains a performance gain across each new release: starting on WebLogic 5.1, the overall performance gain has been close to 4X, which close to a 20% gain release by release. JBoss on the other hand does not provide SPECJAppServer or SPECJEnterprise performance benchmarks. Their so called "performance gains" remains hidden in their customer environments, which lead us to think if it is true or not since we will never get access to those environments. - WebLogic Server 12c has industry performance benchmarks with submissions across platforms and configurations leading SPECJ. Oracle WebLogic leads SPECJAppServer performance in multiple categories, fitting all customer topologies like: dual-node, single-node, multi-node and multi-node with RAC. JBoss... again, does not provide any SPECJAppServer performance benchmarks. - WebLogic Server 12c has a feature called work manager which allows your application to embrace new performance levels based on critical resource utilization of the CPUs usage. Work managers prioritizes work and allocates threads based on an execution model that takes into account administrator-defined parameters and actual run-time performance and throughput. JBoss EAP 6 on the other hand has no compared feature and probably they never will. Not supporting such feature like work managers, JBoss EAP 6 forces admin people and specially developers to uncover performance gains in a intrusive way, rewriting the code and doing performance refactorings. 11) Professional Services Support - WebLogic Server 12c and any other technology sold by Oracle give customers the possibility of hire OCS ("Oracle Consulting Services") to manage critical scenarios, deployment assistance of new applications, high skilled consultancy of architecture, best practices and people allocation together with customer teams. All OCS services are available without any restrictions, having the customer bought software from Oracle or just starting their implementation before any acquisition. JBoss EAP 6 or Red Hat to be more specifically, only offers professional services if you buy subscriptions from them. If you are developing a new critical application for your business and need the help of Red Hat for a serious issue or architecture decision, they will probably say: "OK... I can help you but after you buy subscriptions from me". Red Hat also does not allows their professional services consultants to manage environments that uses community based software. They will probably force you to first buy a subscription, download their "enterprise" version and them, optionally hire their consultants. - Oracle provides you our university to educate your team into our technologies, including of course specialized trainings of WebLogic application server. At any time and location, you can hire Oracle to train your team so you get trustful knowledge according to your specific needs. Certifications for the products are also available if your technical people desire to differentiate themselves as professionals. Red Hat on the other hand have a limited pool of resources to train your team in their technologies. Basically they are selling training and certification for RHEL ("Red Hat Enterprise Linux") but if you demand more specialized training in JBoss middleware, they will probably connect you to some "certified" partner localized training since they are apparently discontinuing their education center, at least here in Brazil. They were not able to reproduce their success with RHEL education to their middleware division since they need first sell the subscriptions to after gives you specialized training. And again, they only offer you specialized training based on their enterprise version (EAP in the case of JBoss) which means that the courses will be a quite outdated. There are reports of developers that took official training's from Red Hat at this year (2012) and in a certain JBoss advanced course, Red Hat supposedly covered JBossMQ as the messaging subsystem, and even the printed material provided was based on JBossMQ since the training was created for JBoss EAP 4.3. 12) Encouraging Transparency without Ulterior Motives - WebLogic Server 12c like any other software from Oracle can be downloaded any time from anywhere, you should only possess an OTN ("Oracle Technology Network") credential and you can download any enterprise software how many times you want. And is not some kind of "trial" version. It is the official binaries that will be running for ever in your data center. Oracle does not encourages the usage of "specific versions" of our software. The binaries you buy from Oracle are the same binaries anyone in the world could download and use for testing and personal education. JBoss EAP 6 on the other hand are not available for download unless you buy a subscription and get access to the Red Hat enterprise repositories. If you need to test, learn or just start creating your application using Red Hat's middleware software, you should download it from the community website. You are not allowed to download the enterprise version that, according to Red Hat are more secure, reliable and robust. But no one of us want to start the development of a software with an unsecured, unreliable and not scalable middleware right? So what you do? You are "invited" by Red Hat to buy subscriptions from them to get access to the "cool" version of the software. - WebLogic Server 12c prices are publicly available in the Oracle website. If you want to know right now how much WebLogic will cost to your organization, just click here and get access to our price list. In the case of WebLogic, check out the "US Oracle Technology Commercial Price List". Oracle also encourages you to get in touch with a sales representative to discuss discounts that would make possible the investment into our technology. But you are not required to do this, only if you are interested in buying our technology or maybe you want to discuss some discount scenarios. JBoss EAP 6 on the other hand does not have its cost publicly available in Red Hat's website or in any other media, at least is not so easy to get such information. The only link you will possibly find in their website is a "Contact a Sales Representative" link. This is not a very good relationship between an customer and an vendor. This is not an example of transparency, mainly when the software are sold as open. In this situations, customers expects to see the software prices publicly available, so they can have the chance to decide, based on the existing features of the software, if the cost is fair or not. Conclusion Oracle WebLogic is the most mature, secure, reliable and scalable Java EE application server of the market, and have a proven record of success around the globe to prove it's majority. Don't lose the chance to discover today how WebLogic could fit your needs and sustain your global IT middleware strategy, no matter if your strategy are completely based on the Cloud or not.

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• JavaScript in different browsers

  - by PointsToShare

  Adventures with JavaScript rendered in IE 8, Chrome 15, and Firefox 8.0 I have written a little monogram about the advantages of Math and wrote a few JavaScript applications to demonstrate them. I was a bit careless and used elements on the page in my JavaScript without using any of the GetElementsByXXXX methods to identify them.  Say I had a text box named tbSeqNum into which I entered a number to be used in a computation. In my code I simply referred to its value by using it directly. Like here: Function Blah() {                 return tbSeqNum.value; } This ran fine in IE8. In IE, the elements are available as global variables. This is not the case in either Firefox or Chrome. In there one has to create the variable and only then use it. Assuming I also used tbSeqNum as the element’s ID, this works: Function Blah() {                 return GetElementById(“tbSeqNum”).value; } Naturally this corrected function also works in IE, so be warned. Also, coming from windows programming (I am long in the tooth and programmed long before the internet), I have a habit of putting an “Exit” button on my pages and setting their onclick to: onclick=”window.close()”. Again, this works fine in IE. In Firefox and chrome, it does not! There you can only close a window that you opened in the code. A window that was opened by navigation to a URL will not close.  Before I deployed mu code to my website, I painfully removed all my Exit buttons. But my greatest surprise came when I tested my pages in the various browsers. In my code I do a comparison on the performance of two algorithms used to solve the same problem. One is brute force, the other uses a mathematical formula. The compare functions runs each many times and displays the time it took for each and also the ratio. Chrome runs JavaScript between 5 and 10 times faster than Firefox and between 50 and 100 times faster that IE. Wow!!! This difference is especially remarkable when the code uses iteration. I suspect that the JS engines in Chrome and Firefox simply cache the result of a function and if it is called again with the same parameters, it returns the cached result. To see it in action play run the “How Many Squares” page in www.mgsltns.com/games.htm The host is running on Unix, so the link is case sensitive. Last Note: IE9 runs JS a bit faster, but still lags behind almost as badly. That’s All Folks!

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• Infinite detail inside Perlin noise procedural mapping

  - by Dave Jellison

  I am very new to game development but I was able to scour the internet to figure out Perlin noise enough to implement a very simple 2D tile infinite procedural world. Here's the question and it's more conceptual than code-based in answer, I think. I understand the concept of "I plug in (x, y) and get back from Perlin noise p" (I'll call it p). P will always be the same value for the same (x, y) (as long as the Perlin algorithm parameters haven't changed, like altering number of octaves, et cetera). What I want to do is be able to zoom into a square and be able to generate smaller squares inside of the already generated overhead tile of terrain. Let's say I have a jungle tile for overhead terrain but I want to zoom in and maybe see a small river tile that would only be a creek and not large enough to be a full "big tile" of water in the overhead. Of course, I want the same net effect as a Perlin equation inside a Perlin equation if that makes sense? (aka. I want two people playing the game with the same settings to get the same terrain and details every time). I can conceptually wrap my head around the large tile being based on an "zoomed out" coordinate leaving enough room to drill into but this approach doesn't make sense in my head (maybe I'm wrong). I'm guessing with this approach my overhead terrain would lose all of the cohesiveness delivered by the Perlin. Imagine I calculate (0, 0) as overhead tile 1 and then to the east of that I plug in (50, 0). OK, great, I now have 49 pixels of detail I could then "drill down" into. The issue I have in my head with this approach (without attempting it) is that there's no guarantee from my Perlin noise that (0,0) would be a good neighbor to (50,0) as they could have wildly different "elevations" or p/resultant values returning from the Perlin equation when I generate the overhead map. I think I can conceive of using the Perlin noise for the overhead tile to then reuse the p value as a seed for the "detail" level of noise once I zoom in. That would ensure my detail Perlin is always the same configuration for (0,0), (1,0), etc. ad nauseam but I'm not sure if there are better approaches out there or if this is a sound approach at all.

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