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• Problem upgrading kernel on debian 3.1

  - by exhuma

  Hi, I have a quite old box in a remote server farm. So I have no direct access. Only remote SSH (and via SSH to a serial console). I haven't updated this box in ages. Now, whenever I want to install a new package, a dependency to glibc appears. Unfortunately, the install of glibc depends on a 2.6 kernel and I am running a venerable 2.4 kernel (one more reason to upgrade). The problem is, that the install of a new kernel has an indirect (over locales) dependency to glibc. So, to install glibc, I need a new kernel. For a new kernel, I need to upgrade glibc. Essentially I am blocked. What's the best way to proceed considering I have no "hardware" access? Here's a quick transcript of the upgrade process: [green:~]% sudo aptitude install linux-image-686 Reading Package Lists... Done Building Dependency Tree Reading extended state information Initializing package states... Done Reading task descriptions... Done The following packages are unused and will be REMOVED: gcc-4.3-base The following NEW packages will be automatically installed: dash libc6-i686 libparse-recdescent-perl linux-image-2.6-686 linux-image-2.6.18-6-686 module-init-tools yaird The following packages have been kept back: adduser apache2 apache2-mpm-prefork apache2-utils apache2.2-common apt apt-utils aptitude autoconf autotools-dev awstats base-files base-passwd [...snip...] util-linux vacation vim vim-common wamerican wbritish wget whiptail whois wwwconfig-common zlib1g The following NEW packages will be installed: dash libc6-i686 libparse-recdescent-perl linux-image-2.6-686 linux-image-2.6.18-6-686 linux-image-686 module-init-tools yaird The following packages will be upgraded: hotplug libc6 2 packages upgraded, 8 newly installed, 1 to remove and 277 not upgraded. Need to get 0B/22.7MB of archives. After unpacking 52.1MB will be used. Do you want to continue? [Y/n/?] Writing extended state information... Done Preconfiguring packages ... (Reading database ... 34065 files and directories currently installed.) Preparing to replace libc6 2.3.6.ds1-13 (using .../libc6_2.7-18lenny2_i386.deb) ... Checking for services that may need to be restarted... Checking init scripts... WARNING: init script for postgresql not found. [ --- libc6 config screen appears here --- ] WARNING: POSIX threads library NPTL requires kernel version 2.6.8 or later. If you use a kernel 2.4, please upgrade it before installing glibc. The installation of a 2.6 kernel _could_ ask you to install a new libc first, this is NOT a bug, and should *NOT* be reported. In that case, please add etch sources to your /etc/apt/sources.list and run: apt-get install -t etch linux-image-2.6 Then reboot into this new kernel, and proceed with your upgrade dpkg: error processing /var/cache/apt/archives/libc6_2.7-18lenny2_i386.deb (--unpack): subprocess pre-installation script returned error exit status 1 Errors were encountered while processing: /var/cache/apt/archives/libc6_2.7-18lenny2_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1) Ack! Something bad happened while installing packages. Trying to recover: dpkg: dependency problems prevent configuration of locales: locales depends on glibc-2.7-1; however: Package glibc-2.7-1 is not installed. dpkg: error processing locales (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: locales Reading Package Lists... Done Building Dependency Tree Reading extended state information Initializing package states... Done Reading task descriptions... Done Now, if I follow the instrunctions as promted I get the following. Note that I am using aptitude instead of apt-get to benefit from the better dependency tracking. I did try with apt-get first. But that let me to the same problem. [green:~]% sudo aptitude install -t etch linux-image-2.6.26-2-686 Reading Package Lists... Done Building Dependency Tree Reading extended state information Initializing package states... Done Reading task descriptions... Done E: Unable to correct problems, you have held broken packages. E: Unable to correct dependencies, some packages cannot be installed E: Unable to resolve some dependencies! Some packages had unmet dependencies. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following packages have unmet dependencies: linux-image-2.6.26-2-686: Depends: initramfs-tools (>= 0.55) but it is not installable or yaird (>= 0.0.13) but it is not installable or linux-initramfs-tool which is a virtual package. Any ideas?

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• Choice and setup of version control

  - by Peter M

  I am about to set up an new laptop and in the process transition to a new version control system as part of a general cleanup. Currently I use a centralized version control system (yes it is VSS, and yes I know all the pro's and con's of that system, but as a single user system it works well for me). I have very little requirements for a new system and I am free to choose among any of the current mainstream players, but cost constraints will push me towards oss. Some of my requirements are: Runs on a single machine (ie the laptop in question) under windows I am not sharing things with other developers or workers - this is more for my own historical benefits. I want to version source code, documentation and binary files I have a large hierarchy of projects that are unrelated (see below) I have files within the hierarchy that don't need to be controlled (but could be) Some projects use Visual Studio, so some integration there could be nice. There could be some sharing of files between jobs. I generally only need a small about of branching in code files The directory hierarchy that I have at the moment is somewhat like: Root | |--Customer #1 | | | |--Job #1 | | | | | |--Data files received from Customer for Job (not controlled) | | |--Documentation files (controlled) | | |--Project information files (not controlled - but could be) | | |--Software Project Files (controlled) | | |--Scratch dir for job (not controlled) | | | |--Job #2 | | (same structure as above) | |--Customer #2 | |.. | |--Cusmtomer #n |.. Currently I have about 22 customers with differing numbers of projects underneath them. At the moment I have a single VSS repository based at the root of the directory structure. If I kept with a centralized system (ie SVN) I believe that I should keep the same approach and continue with a single repository based from the root dir. Is this a valid approach? However if I move to a distributed tool then I am unsure of how I should handle the situation. My initial guess is that I should not have a repository based on the root of my entire directory structure - but that is a guess so I really don't know how valid it is. Should I pitch a distributed approach at the Root, Customer, Job or sub-Job directory level? Also what I am not clear on with distributed tools (and perhaps with SVN as well), is if I can branch parts of a repository. For example, I can see branching source code in software projects as being useful, but branching my documentation as not being useful. So if I pitch a repository at the Job level, can I just branch the Software Project Files? Or would all files in that Job be branched? Every time I look at distributed tools I get a nagging feeling that they are not suited to my style of setup. I am uncomfortable with idea of having to manually set up something like 50 to 80 separate repositories (if I pitch at the Job level, or 20+ if at the Customer level) within my directory hierarchy. This feeling also extends to having all those repositories scattered around as well - however I do have a backup strategy that I trust, so this latter feeling is pretty well unfounded. So what advice can you all give me? Thanks in advance!

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• Hardware recommendations / parts list for a modern, quiet ZFS NAS box - 2011-Feb edition [closed]

  - by dandv

  I want to build some really reliable storage for my data, and it seems that ZFS is the only filesystem at the moment that does live checksumming. That rules out DroboPro, so I'm looking to building a quiet ZFS NAS that would start with 4 2TB or larger hard drives. I'd like this system to be very reliable and relatively future-proof for 2-3 years, so I'm willing to invest some $$$ and buy higher end components. I did see questions here and on other forums about low-cost servers, but I'm not looking for those. I'd be super happy to go for an off-the-shelf solution, but I haven't found one that's quiet. I started doing the research (summarized on my wiki), but I realized that it just gets too complicated for what I know as a software dude, and I'm entering the analysis paralysis area. At this point, I'm basically looking for a parts list for a configuration that will work (and is modern), and I know there are folks around here who are way more competent than me. I've built computers and am comfortable assembling one and messing with *nix; I can follow guides; I just want to end the decision process for the hardware and software configuration. What I've researched so far (not that these are very modern components): Case: I think I've settled on the Antec Twelve Hundred case because it cools well, is quiet, and simply has 12 bays that allow elastic mounting. The SilverStone Raven is its counter-candidate, but I find its construction quite odd. For the PSU, I'm torn between Antec CP-850 and Nexus RX-8500, but I did this research more than a year ago. The Nexus has a very uniform power profile, and I'd rather not have the Antec spin up and down based on load. On the other hand, I'm not sure how often my file server will draw more than 400W under use. For the hard drives, I've read that WD Black drives are actually WD RE3 with a software setting changed. I'd also like to buy different drive types, not just 4 WDs. Recommendations? Right now I have a 2TB Hitachi Deskstar 7K300. For the motherboard, CPU and RAM I have no idea, other than the RAM must be ECC. I already asked a question here about ECC RAM, but I was misguided and was looking for a motherboard that would support USB 3.0 as well. I've learned to go with eSATA, or worry about USB later. Then there's the (liquid) cooling, Wi-Fi card, and FreeBSD vs. OpenSolaris Express. Lastly, I'm wondering if I can make this PC into a media server by adding a Blu-ray drive and a good sound card. But support for Blu-Ray is spotty on Linux, and I don't know if Windows 7 on VirtualBox would get sufficient hardware access to output HDMI or SPDIFF signals. (Running OpenSolaris virtualized is not an option because of the reliability risk.) Then there are HDCP concerns. Suggestions on that would be appreciated as well, but I don't want us to get sidetracked. A specific shopping list on the core components would be great, so I can start ordering, and in the meantime educate myself with regards to the other issues. Finally, I think this could become a great FAQ for those technically inclined to build their own ZFS server, but confused by the dizzying array of options out there, and I promise to compile the results and share my experience building and benchmarking the server.

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• Choice of an OS for a home ZFS NAS

  - by OlafM

  I am preparing a home NAS with an old Athlon 64 X2 3800+, 4 GB ECC RAM, Asus M2V MX motherboard, and a single 3 TB WDC Green (another one as mirror may be installed in the future). It's the cheapest solution I found that includes ECC memory and the higher energy consumption is offset by the lower (zero) cost of acquisition. The system will be used for: music storage and stream to other desktop computers; storage of the scanned dia slides (3-4k slides, 180 MB TIFF each one plus reduced quality JPEG version); stream of these photos to a local iPad 2 (maybe Plex App? not yet sure); (one additional) remote backup via rsync/ssh or ZFS send/receive. It will be controlled via remote ssh, maybe VNC, no monitor attached. Absolute requirement is a reliable ZFS solution, plus the ability to easily install packets/software/virtual machines and to update remotely (I will be the admin and I don't live near the NAS). I have mainly three options: NAS4free/FreeNAS OpenIndiana Solaris Express 11 (yeah yeah I know the license requirements, I will write a perl script on it to count it as development machine). Problems: NAS4free/FreeNAS (I tested only NAS4free) required embedded installation for remote upgrading, but full install for easy addition of software packets. Since I need at least AirVideo Server (linux/win) and Plex App (win/linux) to stream the photos and some videos to iPad (they both require virtualbox), but I cannot be there to install updates, NAS4free/FreeNAS are excluded. http://www.nas4free.org/general_information.html explains the issue: embedded can be remotely updated, full cannot. Solaris has also another advantage: Crashplan client supports Solaris and I'm already using it for other backups. I would like to leave the option open, even if I will be doing backups probably through zfs send/receive. NexentaStor was left out because zfs send/receive are not included in the free version. The question is now Solaris 11 Express over OpenIndiana. To ease the management, I will be using http://www.napp-it.org Which one would you suggest and why? I found lots of informations and it's difficult for me to decide. I think (from the napp-it manual) that Solaris has some additional options for SMB shares, but are they really needed at home? I think I won't even use ACLs, since normal unix-style permissions are enough. OpenIndiana has maybe more frequent updates (Solaris offers only security updates between releases), but again, do I need them? I don't think so. Moreover, this is a NAS that has to work and nothing else, I cannot risk having problems that require me to access the server. Isn't OpenIndiana a bit more... cutting edge (in the Solaris world)? I'm just asking, no need to focus on this for the answer :-) I would limit myself to these two options (SE11.1/OI) also because I will be making a NAS for me in the future (where high performances with Mac shares are also required) and Solaris has kernel support for AFP. I will use this server to gather experience as well. After this long question, thanks in advance! If you need additional info, let me know and I will update this post.

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• Determining the required depth and specifications for a server cabinet

  - by Bingu Bingme

  I'm trying to understand the considerations ("why") that go into determining the specifications ("what") for a rackmount server cabinet, in order to determine what sort of rack I should purchase for my home use. Since this is for home use, I won't be following certain best practices (eg. hot/cold aisle, not even air conditioning) and may be willing to sacrifice in various areas in order to reduce cost and footprint - but please advise if there are safety concerns or other considerations to note. The most basic specs for a server cabinet are the dimensions (external width x external depth x usable height). Width: commonly 600mm or 800mm (if the use case requires extra clearance around the sides, such as if there is lots of cabling). In my case and most common cases, I'm going to stick with 600mm. Height: Select a sufficiently tall rack to fit my equipment. But how much may I stuff into it? Eg, if there is a 15U rack, can I really populate it with 15U of servers, or should I leave 1U at top and bottom for air circulation? Depth: Racks commonly have external depth of 600mm (network equipment), 800mm, 1000mm, or even longer. I'm trying to see how to fit into the 800mm depth. With reference to http://www.server-racks.com/rack-mount-depth.html, I'm hoping to have the front and rear posts mounted ~ 28.5" (72cm) apart, which would leave only 8cm for front space and rear space. How much rear space (from rear posts to back of rack) do I really need? I won't use cable management arms, so can I mount a 72cm depth server since the power, KVM, network cables won't take up much depth? My most important equipment are all < 60cm depth (4U chassis) and should comfortably fit within the 800mm cabinet. The rest of the equipment are very old 1U servers that range from 65-72cm depth. I might still want to make further use of them, or I might discard them since they are so old. Even if the 72cm servers cannot be powered on in an 800mm rack, I should be able to use them as 1U shelves. But, what server depth can I expect to be able to operate? Or am I forced to upgrade to 1000mm depth racks in order to use any servers deeper than 60cm? With reference to best practices for HP racks, some other specs and installation considerations: There aren't any minimum recommendations for clearance on the sides of the rack. It is recommended to leave 48" front clearance. The 48" front clearance is based on 32" chassis depth, 13" to extend the rack rails and mate the inner/outer rails, and 3" for movement. If I don't use such rails (eg, use shelves instead), it should be sufficient to leave front clearance of chassis depth + 3". It is recommended to leave 30" rear clearance "to provide space for servicing the rack". I'm planning to back the rack into a corner of the room, and wheel it slightly out when I need to access the rear. If the wheeling plan is ok, I still need to know how much rear clearance is required for air circulation and ventilation purposes. Castor wheels and stabilising feet. Since I'm backing the rack into a corner of the room, I'll only be able to set the stabilising feet on the front corners. Thoughts on safety? The rack that I'm considering has front glass doors with side ventilation slits and fully perforated rear doors. I'm hoping this will be a good balance between temperature and noise (only ventilation slits facing out the front, while the rear is facing the walls). Or is the sound of high-rpm fans going to escape through the front slits anyway and destroy my sanity?

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• Dell Latitude E6430 Docking Station + Dual Monitor + Laptop Screen Tri-Monitor setup

  - by Larry

  I have a company issued laptop and docking station as well as two monitors The specifications of the hardware are as follows; Laptop: Latitude E6430 BIOS: A02.00 Processor: i7-3720QM CPU @ 2.60 (8 CPUs) Memory: 4096MB RAM Page file: 1825MB used, 4793MB available DirectX 11 Display Driver/Chip: MVIDIA NVS 5200M DAC: Integrated RAMDAC Aprox Total Memory: 2376 (Above 3 details same for both displays) Current Display Mode (Display 1): 1600x900 Current Display Mode (Display 2): 1440x900 the docking station is a Dell Latitude E6420 Docking Station PR03X Port Replicator and I don't think the monitor model is particularly relevant to resolving this issue but they are both Acer V193Ws The story goes like this; the laptop works fine if I VGA one monitor into the laptop through the vga port on the back of the lefthand side of the laptop I can achieve dual monitor display fine (laptop screen + monitor) if I plug the laptop into the docking station and use the vga port in the back of the docking station I can dual monitor fine (laptop screen + monitor) if I plug the laptop into the docking station, the laptop's lefthand side VGA port no longer seems to function at all I've spoken to internal IT about this issue and they're going to get me some kind of VGA splitter or a DVI-VGA adapter to use with the docking station for the second Acer Monitor, but that isn't going to happen for a few days. So I guess what I'm wondering is; is there any way to continue to use the side VGA port on my laptop while using the docking station VGA port? and as a secondary 'followup' pending resolution of the initial issue with getting both monitors up and running (at the moment I have both monitors on my desk but am just using my laptop screen as one of my dual monitor display with one of the monitors [the one connected to dock]), is there any way to CONTINUE to use my laptop monitor to in effect have a triple monitor display (2 monitors + docked laptop)? I am wondering this because internal IT told me that they were aware of some issues with the particular display drivers in my box and triple monitor displays but weren't really going to look TOO much in-depth into that (which is perfectly understandable) since getting the adapter for the dual monitors up and running was the greater priority within their purview. So this is a two parter; Can I dual monitor using two vga cables with 1 docking station vga port and one laptop vga port? is there a setting that can be tweaked somewhere? because plugging the box into the station seems to make the side port stop working and... Is there any reasonably simple and cost-effective work around (e.g. I am find with shelling out maybe a few dollars out of my own pocket for some hardware or software to make my company box tri-display capable) but if this requires some extensive rebuild or new OSs or doing stuff to the BIOS I'd rather have a straight answer about this being untenable as a slight modification to a (once again) company laptop and stop wasting time looking into it Thanks! and please let me know if you guys need any more details (tech specs or something) to answer this question [EDIT] 2/10/2014 Just an update; turned out it really was just a hardware limitation issue. The old laptop just couldn't hack it. Got a new laptop with a better video card and different monitors from my company and am successfully using a triple display currently (2 monitors + laptop screen)

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• DDNS Not Creating Journal (Dhcpd and Named)

  - by user130094

  * EDIT 1 * After monkeying with additional debug logging I see some log entries of interest. 27-Jul-2012 23:45:26.537 general: error: zone example.lan/IN/internal: journal rollforward failed: no more 27-Jul-2012 23:45:26.537 general: error: zone example.lan/IN/internal: not loaded due to errors. ^^^ If I can remedy the above messages I think I'll be good to go ^^^ * EDIT 2 * Grasping at straws I touched a forward and a reverse zone journal file and restarted named. Boom! Works. Despite documentation stating the files are created automatically and what I have seen before... dunno why but that did the trick. Also re-checked perms on the dir the files live in. As certain as I was, they were correct with named having rw. CentOS 6 (final) dhcpd 4.1.1-P1 named BIND 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 Basic DHCP and DNS functionality are in place on 192.168.111.2. Clients are assigned addresses as intended and can resolve local DNS names as well as Internet names. My problem is that named's zone journal files are not created. chroot: /var/named/chroot I tried placing the zone files in various directories (/var/named/data, /var/named, /var/named/dynamic - no matter which dir with named owning and wide open perms I now get nowhere). Along the way I, at one point, got a permission denied when named tried to create the journal. Resolved the issue by: chown --recursive named:named /var/named chmod --recursive 777 /var/named The journal was then created and here's where things fell apart. I attempted to tame permissions to something more sane and broke it. Once changed and having restarted named it threw an error indicating the journal was out of sync (or something to that affect)... didn't matter since this is a new setup so I deleted it and now it is not recreated. Now though I see no errors in /var/log/messages, my chrooted /var/log/named.log, or chrooted /var/log/named.debug. I increased the debug level with 'rndc trace' - no love. Increased trace to 10, still nothing. SELinux is disabled... [root@server temp]# sestatus SELinux status: disabled dhcpd.conf... allow client-updates; ddns-update-style interim; subnet 192.168.111.0 netmask 255.255.255.224 { ... key dhcpudpate { algorithm hmac-md5; secret LDJMdPdEZED+/nN/AGO9ZA==; } zone example.lan. { primary 192.168.111.2; key dhcpudpate; } } named.conf... key dhcpudpate { algorithm hmac-md5; secret "LDJMdPdEZED+/nN/AGO9ZA=="; }; zone "example.lan" { type master; file "/var/named/dynamic/example.lan.db"; allow-transfer { none; }; allow-update { key dhcpudpate; }; notify false; check-names ignore; }; The following shows /var/log/named.log output of named starting up - no errors. 27-Jul-2012 21:33:39.349 general: info: zone 111.168.192.in-addr.arpa/IN/internal: loaded serial 2012072601 27-Jul-2012 21:33:39.349 general: info: zone example.lan/IN/internal: loaded serial 2012072501 27-Jul-2012 21:33:39.350 general: info: zone example2.lan/IN/internal: loaded serial 2012072501 27-Jul-2012 21:33:39.350 general: info: zone example3.lan/IN/internal: loaded serial 2012072601 27-Jul-2012 21:33:39.350 general: info: zone example4.lan/IN/internal: loaded serial 2012072501 27-Jul-2012 21:33:39.351 general: info: zone example5.lan/IN/internal: loaded serial 2012072501 27-Jul-2012 21:33:39.351 general: info: managed-keys-zone ./IN/internal: loaded serial 0 27-Jul-2012 21:33:39.351 general: info: zone example.lan/IN/external: loaded serial 2012072501 27-Jul-2012 21:33:39.352 general: info: zone example1.lan/IN/external: loaded serial 2012072501 27-Jul-2012 21:33:39.352 general: info: zone example2.lan/IN/external: loaded serial 2012072501 27-Jul-2012 21:33:39.352 general: info: zone example3.lan/IN/external: loaded serial 2012072501 27-Jul-2012 21:33:39.353 general: info: managed-keys-zone ./IN/external: loaded serial 0 27-Jul-2012 21:33:39.353 general: notice: running 27-Jul-2012 21:34:03.825 general: info: received control channel command 'trace 10' 27-Jul-2012 21:34:03.825 general: info: debug level is now 10 ...and /var/log/messages for a named start... Jul 27 23:02:04 server named[9124]: ---------------------------------------------------- Jul 27 23:02:04 server named[9124]: BIND 9 is maintained by Internet Systems Consortium, Jul 27 23:02:04 server named[9124]: Inc. (ISC), a non-profit 501(c)(3) public-benefit Jul 27 23:02:04 server named[9124]: corporation. Support and training for BIND 9 are Jul 27 23:02:04 server named[9124]: available at https://www.isc.org/support Jul 27 23:02:04 server named[9124]: ---------------------------------------------------- Jul 27 23:02:04 server named[9124]: adjusted limit on open files from 4096 to 1048576 Jul 27 23:02:04 server named[9124]: found 2 CPUs, using 2 worker threads Jul 27 23:02:04 server named[9124]: using up to 4096 sockets Jul 27 23:02:04 server named[9124]: loading configuration from '/etc/named.conf' Jul 27 23:02:04 server named[9124]: using default UDP/IPv4 port range: [1024, 65535] Jul 27 23:02:04 server named[9124]: using default UDP/IPv6 port range: [1024, 65535] Jul 27 23:02:04 server named[9124]: listening on IPv4 interface eth0, 192.168.111.2#53 Jul 27 23:02:04 server named[9124]: generating session key for dynamic DNS Jul 27 23:02:04 server named[9124]: sizing zone task pool based on 12 zones Jul 27 23:02:04 server named[9124]: set up managed keys zone for view internal, file 'dynamic/3bed2cb3a3acf7b6a8ef408420cc682d5520e26976d354254f528c965612054f.mkeys' Jul 27 23:02:04 server named[9124]: set up managed keys zone for view external, file 'dynamic/3c4623849a49a53911c4a3e48d8cead8a1858960bccdea7a1b978d73ec2f06d7.mkeys' Jul 27 23:02:04 server named[9124]: command channel listening on 127.0.0.1#953 What can I do to troubleshoot this further? It almost seems as though dhcpd is not triggering the update. Maybe I should troubleshoot here and, if so, how? Many thanks.

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• VMware vSphere cluster design for site redundancy

  - by Stefan Radovanovici

  I have a question about the best design for site redudancy when using vSphere clusters. A bit of background info about our situation first though. We are a medium-sized company with two main offices, located in different countries. Our networks are linked by a Layer2 150Mbps leased line which is currently underused. We have a variety of services running for internal use within the company, some on physycal servers and some on existing vSphere clusters. In our department we also run several services (almost all running under various forms of Linux) like NTP, Syslog, jump servers, monitoring servers and so on. We have now the requirement that those servers need to be redundant within each location (which they are not at the moment) and also site redudant (which they are to some extent, the servers are duplicated in the 2nd location with configurations kept in sync via various methods at the application layer). There is no SAN available for us, at least not something that we can use at the moment. Cost is also an issue. While we do have some budget available for this, we can't afford to buy SANs for both locations for example. I looked at the VSA feature and it seems that this could be something for us but I am unsure how to solve the site-redudancy requirement. At the moment for testing purposes I am setting up in a lab a vSphere 5 with VSA on two ESXi hosts. I am currently using the Essentials Plus kit with VSA license, which allows me to build a VSA cluster on up to 3 hosts, together with a vCenter license to manage them. The hosts each have two dual-port network cards and two 600GB drives, running in Raid1. Hardware-wise this will be enough for us to run the all the services we need as VMs and will provide redundandcy within the site. At the moment I see only two option to have site redundancy: build an identical VSA cluter in the second location and keep the various services sync'ed at application layer (database sync, rsync and so on). simply move one of the hosts from the existing cluster to the second location, basically having the VSA cluster span the 150Mbps link between the sites. I would very much prefer the second option but I am unsure how well it'll work, if it can work at all. Technically it should, we can span the needed VLANs across the leased line and have them available in the second location. The advantage would be that we don't need to worry at all about sync'ing databases and the like. But I have the feeling that the bandwidth will not be enough, I have no way of knowing how much traffic will the VSA cluster generate between the hosts. I realize that this will most likely depend on the individual usage of the VMs but still, I have no idea how VSA replicates data between the ESXi hosts. Are these my only options or can my goals be achieved in some other way ? Is there perhaps a way to have some sort of "cold stand by" cluster in the second location where the VMs would be sync'ed once per night from the main location ? The idea is that in case the first site becomes unavailable, we would be able to bring all those VMs online there. We would be ok with the data being 1 day old. Any answers are appreciated. Best regards, Stefan

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• Choice of an OS for a home ZFS NAS

  - by OlafM

  I am preparing a home NAS with an old Athlon 64 X2 3800+, 4 GB ECC RAM, Asus M2V MX motherboard, and a single 3 TB WDC Green (another one as mirror may be installed in the future). It's the cheapest solution I found that includes ECC memory and the higher energy consumption is offset by the lower (zero) cost of acquisition. The system will be used for: music storage and stream to other desktop computers; storage of the scanned dia slides (3-4k slides, 180 MB TIFF each one plus reduced quality JPEG version); stream of these photos to a local iPad 2 (maybe Plex App? not yet sure); (one additional) remote backup via rsync/ssh or ZFS send/receive. It will be controlled via remote ssh, maybe VNC, no monitor attached. Absolute requirement is a reliable ZFS solution, plus the ability to easily install packets/software/virtual machines and to update remotely (I will be the admin and I don't live near the NAS). I have mainly three options: NAS4free/FreeNAS OpenIndiana Solaris Express 11 (yeah yeah I know the license requirements, I will write a perl script on it to count it as development machine). Problems: NAS4free/FreeNAS (I tested only NAS4free) required embedded installation for remote upgrading, but full install for easy addition of software packets. Since I need at least AirVideo Server (linux/win) and Plex App (win/linux) to stream the photos and some videos to iPad (they both require virtualbox), but I cannot be there to install updates, NAS4free/FreeNAS are excluded. http://www.nas4free.org/general_information.html explains the issue: embedded can be remotely updated, full cannot. Solaris has also another advantage: Crashplan client supports Solaris and I'm already using it for other backups. I would like to leave the option open, even if I will be doing backups probably through zfs send/receive. NexentaStor was left out because zfs send/receive are not included in the free version. The question is now Solaris 11 Express over OpenIndiana. To ease the management, I will be using http://www.napp-it.org Which one would you suggest and why? I found lots of informations and it's difficult for me to decide. I think (from the napp-it manual) that Solaris has some additional options for SMB shares, but are they really needed at home? I think I won't even use ACLs, since normal unix-style permissions are enough. OpenIndiana has maybe more frequent updates (Solaris offers only security updates between releases), but again, do I need them? I don't think so. Moreover, this is a NAS that has to work and nothing else, I cannot risk having problems that require me to access the server. Isn't OpenIndiana a bit more... cutting edge (in the Solaris world)? I'm just asking, no need to focus on this for the answer :-) I would limit myself to these two options (SE11.1/OI) also because I will be making a NAS for me in the future (where high performances with Mac shares are also required) and Solaris has kernel support for AFP. I will use this server to gather experience as well. After this long question, thanks in advance! If you need additional info, let me know and I will update this post. UPDATES Given the first answers, I will strongly suggest the person paying the hardware to insert a second HD. Better 2x2TB than 1x3TB (3 TB is oversized anyway). I was trying to keep the initial costs down to spread them over a longer period, but better having something good from the beginning.

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• How does the Cloud compare to Colocation? And development too

  - by David

  Currently I/we run a SaaS web application where each subscriber has their own physical instance of the application in addition to their own database. The setup has each web application instance deployed on two different IIS boxes both for load-balancing and redundancy (the machines have their Windows Update install times 12 hours apart, for example). Databases are mirrored on two different SQL Server 2012 machines with AlwaysOn for uptime. I don't make use of SQL Server clustering (as it doesn't provide storage-level failover: we don't have a shared storage box). Because it's a Windows setup it means there are two Domain Controllers (we cheat: they're both Mac Minis, 17W each, which keeps our colo power costs low). Finally there's also an Exchange server (Mailbox, Hub Transport and Client Access). One of the SQL Servers also doubles-up as an Exchange Hub Transport. Running costs are about $700 a month for our quarter-rack colocation (which includes power and peering/transfer), then there's about $150 a month for SPLA licensing, so $850 a month in total. Then there's the hard-to-quantify cost of administration, but I reckon I spend a couple of hours a week checking-in on the servers: reviewing event logs, etc. I keep getting bombarded by ads and manufactured news stories about how great "the cloud" is. Back in 2008 when the cloud was taking off I was reading up about the proper "cloud" services like Google AppEngine, where you write in Python against Google's API and that's how they scale your application across servers and also use their database provider for scaling storage. Simple enough to understand. Then came along Amazon, and I understand how Amazon Storage works, but I'm not sure how Amazon Compute works: web application pages don't take much CPU time to compute, how do you even quantify usage anyway? Finally, RackSpace gets in the act and now I'm really confused. RackSpace advertise "Cloud" SQL Server 2012 available for about "$0.70 per hour", going by how they advertise it I thought the "hour" meant the sum of CPU time, IO blocking time, maybe time spent transferring data, so for a low-intensity application that works out pretty cheap then? Nope. I went on to a Sales Chat window and spoke to one of their advisors. They told me the $0.70/hour was actually for every hour the SQL Server is running... but who wants a SQL Server for only a few hours? You're going to need it available 24 hours a day for months on end. $0.70 * 24 * 31 works out at $520 a month, which is rediculously expensive for SQL Server. An SPLA license for SQL Server is only $50 a month or so. That $520 a month does not include "fanatical support", and you also need to stack on top the costs of the host Windows server instance too. From what I can tell, Rackspace's "Cloud" products seem like like an cynical rebranding of an overpriced VPS service, but priced by the hour. I have the same confusion about Windows Azure which uses similar terms to describe the products available, but I think that's because Azure offers both traditional shared webhosting in addition to their own APIs you can target for scalable applications.

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• Fixing predicated NSFetchedResultsController/NSFetchRequest performance with SQLite backend?

  - by Jaanus

  I have a series of NSFetchedResultsControllers powering some table views, and their performance on device was abysmal, on the order of seconds. Since it all runs on main thread, it's blocking my app at startup, which is not great. I investigated and turns out the predicate is the problem: NSPredicate *somePredicate = [NSPredicate predicateWithFormat:@"ANY somethings == %@", something]; [fetchRequest setPredicate:somePredicate]; I.e the fetch entity, call it "things", has a many-to-many relation with entity "something". This predicate is a filter that limits the results to only things that have a relation with a particular "something". When I removed the predicate for testing, fetch time (the initial performFetch: call) dropped (for some extreme cases) from 4 seconds to around 100ms or less, which is acceptable. I am troubled by this, though, as it negates a lot of the benefit I was hoping to gain with Core Data and NSFRC, which otherwise seems like a powerful tool. So, my question is, how can I optimize this performance? Am I using the predicate wrong? Should I modify the model/schema somehow? And what other ways there are to fix this? Is this kind of degraded performance to be expected? (There are on the order of hundreds of <1KB objects.) EDIT WITH DETAILS: Here's the code: [fetchRequest setFetchLimit:200]; NSLog(@"before fetch"); BOOL success = [frc performFetch:&error]; if (!success) { NSLog(@"Fetch request error: %@", error); } NSLog(@"after fetch"); Updated logs (previously, I had some application inefficiencies degrading the performance here. These are the updated logs that should be as close to optimal as you can get under my current environment): 2010-02-05 12:45:22.138 Special Ppl[429:207] before fetch 2010-02-05 12:45:22.144 Special Ppl[429:207] CoreData: sql: SELECT DISTINCT 0, t0.Z_PK, t0.Z_OPT, <model fields> FROM ZTHING t0 LEFT OUTER JOIN Z_1THINGS t1 ON t0.Z_PK = t1.Z_2THINGS WHERE t1.Z_1SOMETHINGS = ? ORDER BY t0.ZID DESC LIMIT 200 2010-02-05 12:45:22.663 Special Ppl[429:207] CoreData: annotation: sql connection fetch time: 0.5094s 2010-02-05 12:45:22.668 Special Ppl[429:207] CoreData: annotation: total fetch execution time: 0.5240s for 198 rows. 2010-02-05 12:45:22.706 Special Ppl[429:207] after fetch If I do the same fetch without predicate (by commenting out the two lines in the beginning of the question): 2010-02-05 12:44:10.398 Special Ppl[414:207] before fetch 2010-02-05 12:44:10.405 Special Ppl[414:207] CoreData: sql: SELECT 0, t0.Z_PK, t0.Z_OPT, <model fields> FROM ZTHING t0 ORDER BY t0.ZID DESC LIMIT 200 2010-02-05 12:44:10.426 Special Ppl[414:207] CoreData: annotation: sql connection fetch time: 0.0125s 2010-02-05 12:44:10.431 Special Ppl[414:207] CoreData: annotation: total fetch execution time: 0.0262s for 200 rows. 2010-02-05 12:44:10.457 Special Ppl[414:207] after fetch 20-fold difference in times. 500ms is not that great, and there does not seem to be a way to do it in background thread or otherwise optimize that I can think of. (Apart from going to a binary store where this becomes a non-issue, so I might do that. Binary store performance is consistently ~100ms for the above 200-object predicated query.) (I nested another question here previously, which I now moved away).

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• Team Foundation Server Setup/Access

  - by Angel Brighteyes

  What I need: A TFS 2010 Setup that allows 2 application developers to access the TFS from remote locations. How it is setup: Server 2008 Standard 2g Ram 300g HD space SharePoint Server 2007, using SQL Server 2005 SQL Server 2008 Standard Team Foundation Server 2010 IIS 7 Sharepoint Bindings: TFS.DynAccount.Me:80; TFS:80 TFS Bindings: TFS.DynAccount.Me:8080; TFS:8080 Using DynDNS service to account for the dynamic ip address being used, this is a requirement for the moment until I can get a better isp package. Access using Local Accounts Server is not setup on a domain, or as a domain. Consequently I did not setup AD services. Problem: When logged into TFS using my credentials TFS\AdminUser through the DynDNS account TFS.DynAccount.Me I recieve the 'Red X of Death' on the Documents and Reports folder. When logged into the TFS through the local peer to peer network using the same credentials TFS\AdminUser I do not receive the 'Red X of Death' problem. Further Troubleshooting: When users 'Right Click' the 'TeamProject1' Click 'Show Project Portal' it tries to take them to http://TFS:8080 instead of http://TFS.DynAccount.Me:8080, which doing further research I am assuming that it is because team foundation server was setup with a local name of TFS instead of 'TFS.DynAccount.Me' as specified here in Visual Studio Magazines: The Red X of Death. Users can Access the Team Portal for SharePoint via http://TFS.DynAccount.Me/TeamCollection/TeamProject so it is not like we are dead in the water or anything. However, as most employees/staff are prone to do, they have expressed a great distaste for having to do it this way and just be patient until the current project is finished since we are under a very strict deadline. Is there a way to set this up differently, or change some settings someplace, reinstall it, point a CName record for our domain website to the DynAccount (e.g. TFS.OurDomain.com points to TFS.DynAccount.Me, which consequently does allow access to the http site without issues), or something. I really don't feel like after all the time and effort I have spent into, first the cost, second the bloody install, third learning SharePoint well enough, fourth the hours into days spent on this, fifth more troubleshooting, sixth employee headaches to just let it lay where it is at. I figure in my spare/off time I would keep trying to get this to work. So I really appreciate any help any one can give me. I know this is probably something really stupid simple that I will 'Face Palm' over, but at the moment the stress and frustration just has me beat. Thank you again, this community has always been a great help.

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• Architecture for a business objects / database access layer

  - by gregmac

  For various reasons, we are writing a new business objects/data storage library. One of the requirements of this layer is to separate the logic of the business rules, and the actual data storage layer. It is possible to have multiple data storage layers that implement access to the same object - for example, a main "database" data storage source that implements most objects, and another "ldap" source that implements a User object. In this scenario, User can optionally come from an LDAP source, perhaps with slightly different functionality (eg, not possible to save/update the User object), but otherwise it is used by the application the same way. Another data storage type might be a web service, or an external database. There are two main ways we are looking at implementing this, and me and a co-worker disagree on a fundamental level which is correct. I'd like some advice on which one is the best to use. I'll try to keep my descriptions of each as neutral as possible, as I'm looking for some objective view points here. Business objects are base classes, and data storage objects inherit business objects. Client code deals with data storage objects. In this case, common business rules are inherited by each data storage object, and it is the data storage objects that are directly used by the client code. This has the implication that client code determines which data storage method to use for a given object, because it has to explicitly declare an instance to that type of object. Client code needs to explicitly know connection information for each data storage type it is using. If a data storage layer implements different functionality for a given object, client code explicitly knows about it at compile time because the object looks different. If the data storage method is changed, client code has to be updated. Business objects encapsulate data storage objects. In this case, business objects are directly used by client application. Client application passes along base connection information to business layer. Decision about which data storage method a given object uses is made by business object code. Connection information would be a chunk of data taken from a config file (client app does not really know/care about details of it), which may be a single connection string for a database, or several pieces connection strings for various data storage types. Additional data storage connection types could also be read from another spot - eg, a configuration table in a database that specifies URLs to various web services. The benefit here is that if a new data storage method is added to an existing object, a configuration setting can be set at runtime to determine which method to use, and it is completely transparent to the client applications. Client apps do not need to be modified if data storage method for a given object changes. Business objects are base classes, data source objects inherit from business objects. Client code deals primarily with base classes. This is similar to the first method, but client code declares variables of the base business object types, and Load()/Create()/etc static methods on the business objects return the appropriate data source-typed objects. The architecture of this solution is similar to the first method, but the main difference is the decision about which data storage object to use for a given business object is made by the business layer, not the client code. I know there are already existing ORM libraries that provide some of this functionality, but please discount those for now (there is the possibility that a data storage layer is implemented with one of these ORM libraries) - also note I'm deliberately not telling you what language is being used here, other than that it is strongly typed. I'm looking for some general advice here on which method is better to use (or feel free to suggest something else), and why.

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• Why not .NET-style delegates rather than closures in Java?

  - by h2g2java

  OK, this is going to be my beating a dying horse for the 3rd time. However, this question is different from my earlier two about closures/delegates, which asks about plans for delegates and what are the projected specs and implementation for closures. This question is about - why is the Java community struggling to define 3 different types of closures when we could simply steal the whole concept of delegates lock, stock and barrel from our beloved and friendly neighbour - Microsoft. There are two non-technical conclusions I would be very tempted to jump into: The Java community should hold up its pride, at the cost of needing to go thro convoluted efforts, by not succumbing to borrowing any Microsoft concepts or otherwise vindicate Microsoft's brilliance. Delegates is a Microsoft patented technology. Alright, besides the above two possibilities, Q1. Is there any weakness or inadequacy in msft-styled delegates that the three (or more) forms of closures would be addressing? Q2. I am asking this while shifting between java and c# and it intrigues me that c# delegates does exactly what I needed. Are there features that would be implemented in closures that are not currently available in C# delegates? If so what are they because I cannot see what I need more than what C# delegates has adequately provided me? Q3. I know that one of the concerns about implementing closures/delegates in java is the reduction of orthogonality of the language, where more than one way is exposed to perform a particular task. Is it worth the level convolution and time spent to avoid delegates just to ensure java retains its level of orthogonality? In SQL, we know that it is advisable to break orthogonality by frequently adequately satisfying only the 2nd normal form. Why can't java be subjected to reduction of orthogonality and OO-ness for the sake of simplicity? Q4. The architecture of JVM is technically constrained from implementing .NET-styled delegates. If this reason WERE (subjunctive to emphasize unlikelihood) true, then why can't the three closures proposals be hidden behind a simple delegate keyword or annotation: if we don't like to use @delegate, we could use @method. I cannot see how delegate statement format is more complex than the three closure proposals.

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• .NET 4.0 Dynamic object used statically?

  - by Kevin Won

  I've gotten quite sick of XML configuration files in .NET and want to replace them with a format that is more sane. Therefore, I'm writing a config file parser for C# applications that will take a custom config file format, parse it, and create a Python source string that I can then execute in C# and use as a static object (yes that's right--I want a static (not the static type dyanamic) object in the end). Here's an example of what my config file looks like: // my custom config file format GlobalName: ExampleApp Properties { ExternalServiceTimeout: "120" } Python { // this allows for straight python code to be added to handle custom config def MyCustomPython: return "cool" } Using ANTLR I've created a Lexer/Parser that will convert this format to a Python script. So assume I have that all right and can take the .config above and run my Lexer/Parser on it to get a Python script out the back (this has the added benefit of giving me a validation tool for my config). By running the resultant script in C# // simplified example of getting the dynamic python object in C# // (not how I really do it) ScriptRuntime py = Python.CreateRuntime(); dynamic conf = py.UseFile("conftest.py"); dynamic t = conf.GetConfTest("test"); I can get a dynamic object that has my configuration settings. I can now get my config file settings in C# by invoking a dynamic method on that object: //C# calling a method on the dynamic python object var timeout = t.GetProperty("ExternalServiceTimeout"); //the config also allows for straight Python scripting (via the Python block) var special = t.MyCustonPython(); of course, I have no type safety here and no intellisense support. I have a dynamic representation of my config file, but I want a static one. I know what my Python object's type is--it is actually newing up in instance of a C# class. But since it's happening in python, it's type is not the C# type, but dynamic instead. What I want to do is then cast the object back to the C# type that I know the object is: // doesn't work--can't cast a dynamic to a static type (nulls out) IConfigSettings staticTypeConfig = t as IConfigSettings Is there any way to figure out how to cast the object to the static type? I'm rather doubtful that there is... so doubtful that I took another approach of which I'm not entirely sure about. I'm wondering if someone has a better way... So here's my current tactic: since I know the type of the python object, I am creating a C# wrapper class: public class ConfigSettings : IConfigSettings that takes in a dynamic object in the ctor: public ConfigSettings(dynamic settings) { this.DynamicProxy = settings; } public dynamic DynamicProxy { get; private set; } Now I have a reference to the Python dynamic object of which I know the type. So I can then just put wrappers around the Python methods that I know are there: // wrapper access to the underlying dynamic object // this makes my dynamic object appear 'static' public string GetSetting(string key) { return this.DynamicProxy.GetProperty(key).ToString(); } Now the dynamic object is accessed through this static proxy and thus can obviously be passed around in the static C# world via interface, etc: // dependency inject the dynamic object around IBusinessLogic logic = new BusinessLogic(IConfigSettings config); This solution has the benefits of all the static typing stuff we know and love while at the same time giving me the option of 'bailing out' to dynamic too: // the DynamicProxy property give direct access to the dynamic object var result = config.DynamicProxy.MyCustomPython(); but, man, this seems rather convoluted way of getting to an object that is a static type in the first place! Since the whole dynamic/static interaction world is new to me, I'm really questioning if my solution is optimal or if I'm missing something (i.e. some way of casting that dynamic object to a known static type) about how to bridge the chasm between these two universes.

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• Passing integer lists in a sql query, best practices

  - by Artiom Chilaru

  I'm currently looking at ways to pass lists of integers in a SQL query, and try to decide which of them is best in which situation, what are the benefots of each, and what are the pitfalls, what should be avoided :) Right now I know of 3 ways that we currently use in our application. 1) Table valued parameter: Create a new Table Valued Parameter in sql server: CREATE TYPE [dbo].[TVP_INT] AS TABLE( [ID] [int] NOT NULL ) Then run the query against it: using (var conn = new SqlConnection(DataContext.GetDefaultConnectionString)) { var comm = conn.CreateCommand(); comm.CommandType = CommandType.Text; comm.CommandText = @" UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN @values IDs ON DA.ID = IDs.ID"; comm.Parameters.Add(new SqlParameter("values", downloadResults.Select(d => d.ID).ToDataTable()) { TypeName = "TVP_INT" }); conn.Open(); comm.ExecuteScalar(); } The major disadvantages of this method is the fact that Linq doesn't support table valued params (if you create an SP with a TVP param, linq won't be able to run it) :( 2) Convert the list to Binary and use it in Linq! This is a bit better.. Create an SP, and you can run it within linq :) To do this, the SP will have an IMAGE parameter, and we'll be using a user defined function (udf) to convert this to a table.. We currently have implementations of this function written in C++ and in assembly, both have pretty much the same performance :) Basically, each integer is represented by 4 bytes, and passed to the SP. In .NET we have an extension method that convers an IEnumerable to a byte array The extension method: public static Byte[] ToBinary(this IEnumerable intList) { return ToBinaryEnum(intList).ToArray(); } private static IEnumerable<Byte> ToBinaryEnum(IEnumerable<Int32> intList) { IEnumerator<Int32> marker = intList.GetEnumerator(); while (marker.MoveNext()) { Byte[] result = BitConverter.GetBytes(marker.Current); Array.Reverse(result); foreach (byte b in result) yield return b; } } The SP: CREATE PROCEDURE [Accounts-UpdateImportAttempts] @values IMAGE AS BEGIN UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN dbo.udfIntegerArray(@values, 4) IDs ON DA.ID = IDs.Value4 END And we can use it by running the SP directly, or in any linq query we need using (var db = new DataContext()) { db.Accounts_UpdateImportAttempts(downloadResults.Select(d => d.ID).ToBinary()); // or var accounts = db.Accounts .Where(a => db.udfIntegerArray(downloadResults.Select(d => d.ID).ToBinary(), 4) .Select(i => i.Value4) .Contains(a.ID)); } This method has the benefit of using compiled queries in linq (which will have the same sql definition, and query plan, so will also be cached), and can be used in SPs as well. Both these methods are theoretically unlimited, so you can pass millions of ints at a time :) 3) The simple linq .Contains() It's a more simple approach, and is perfect in simple scenarios. But is of course limited by this. using (var db = new DataContext()) { var accounts = db.Accounts .Where(a => downloadResults.Select(d => d.ID).Contains(a.ID)); } The biggest drawback of this method is that each integer in the downloadResults variable will be passed as a separate int.. In this case, the query is limited by sql (max allowed parameters in a sql query, which is a couple of thousand, if I remember right). So I'd like to ask.. What do you think is the best of these, and what other methods and approaches have I missed?

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• How to avoid using duplicate savepoint names in nested transactions in nested stored procs?

  - by Gary McGill

  I have a pattern that I almost always follow, where if I need to wrap up an operation in a transaction, I do this: BEGIN TRANSACTION SAVE TRANSACTION TX -- Stuff IF @error <> 0 ROLLBACK TRANSACTION TX COMMIT TRANSACTION That's served me well enough in the past, but after years of using this pattern (and copy-pasting the above code), I've suddenly discovered a flaw which comes as a complete shock. Quite often, I'll have a stored procedure calling other stored procedures, all of which use this same pattern. What I've discovered (to my cost) is that because I'm using the same savepoint name everywhere, I can get into a situation where my outer transaction is partially committed - precisely the opposite of the atomicity that I'm trying to achieve. I've put together an example that exhibits the problem. This is a single batch (no nested stored procs), and so it looks a little odd in that you probably wouldn't use the same savepoint name twice in the same batch, but my real-world scenario would be too confusing to post. CREATE TABLE Test (test INTEGER NOT NULL) BEGIN TRAN SAVE TRAN TX BEGIN TRAN SAVE TRAN TX INSERT INTO Test(test) VALUES (1) COMMIT TRAN TX BEGIN TRAN SAVE TRAN TX INSERT INTO Test(test) VALUES (2) COMMIT TRAN TX DELETE FROM Test ROLLBACK TRAN TX COMMIT TRAN TX SELECT * FROM Test DROP TABLE Test When I execute this, it lists one record, with value "1". In other words, even though I rolled back my outer transaction, a record was added to the table. What's happening is that the ROLLBACK TRANSACTION TX at the outer level is rolling back as far as the last SAVE TRANSACTION TX at the inner level. Now that I write this all out, I can see the logic behind it: the server is looking back through the log file, treating it as a linear stream of transactions; it doesn't understand the nesting/hierarchy implied by either the nesting of the transactions (or, in my real-world scenario, by the calls to other stored procedures). So, clearly, I need to start using unique savepoint names instead of blindly using "TX" everywhere. But - and this is where I finally get to the point - is there a way to do this in a copy-pastable way so that I can still use the same code everywhere? Can I auto-generate the savepoint name on the fly somehow? Is there a convention or best-practice for doing this sort of thing? It's not exactly hard to come up with a unique name every time you start a transaction (could base it off the SP name, or somesuch), but I do worry that eventually there would be a conflict - and you wouldn't know about it because rather than causing an error it just silently destroys your data... :-(

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• AppDomain dependencies across directories

  - by strager

  I am creating a plugin system and I am creating one AppDomain per plugin. Each plugin has its own directory with its main assemblies and references. The main assemblies will be loaded by my plugin loader, in addition to my interface assemblies (so the plugin can interact with the application). Creating the AppDomain: this.appDomain = AppDomain.CreateDomain("AppDomain", null, new AppDomainSetup { ApplicationBase = pluginPath, PrivateBinPath = pluginPath, }); Loading the assemblies: this.appDomain.Load(myInterfaceAssembly.GetName(true)); var assemblies = new List<Assembly>(); foreach (var assemblyName in this.assemblyNames) { assemblies.Add(this.appDomain.Load(assemblyName)); } The format of assemblyName is the assembly's filename without ".dll". The problem is that AppDomain.Load(assemblyName) throws an exception: Could not load file or assembly '[[assemblyName]], Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified. All of the dependencies of [[assemblyName]] are: Inside the directory pluginPath, The myInterfaceAssembly which is already loaded, or In the GAC (e.g. mscorelib). Clearly I'm not doing something right. I have tried: Creating an object using this.appDomain.CreateInstanceAndUnwrap inheriting from MarshalByRefObject with a LoadAssembly method to load the assembly. I get an exception saying that the current assembly (containing the proxy class) could not be loaded (file not found, as above), even if I manually call this.appDomain.Load(Assembly.GetExecutingAssembly().GetName(true)). Attaching an AssemblyResolve handler to this.appDomain. I'm met with the same exception as in (1), and manually loading doesn't help. Recursively loading assemblies by loading their dependencies into this.appDomain first. This doesn't work, but I doubt my code is correct: private static void LoadAssemblyInto(AssemblyName assemblyName, AppDomain appDomain) { var assembly = Assembly.Load(assemblyName); foreach (var referenceName in assembly.GetReferencedAssemblies()) { if (!referenceName.FullName.StartsWith("MyProject")) { continue; } var loadedAssemblies = appDomain.GetAssemblies(); if (loadedAssemblies.Any((asm) => asm.FullName == referenceName.FullName)) { continue; } LoadAssemblyInto(referenceName, appDomain); } appDomain.Load(assembly.GetName(true)); } How can I load my plugin assembly with its dependencies in that plugin's directory while also loading some assemblies in the current directory? Note: The assemblies a plugin may (probably will) reference are already loaded in the current domain. This can be shared across domains (performance benefit? simplicity?) if required. Fusion log: *** Assembly Binder Log Entry (12/24/2010 @ 10:46:40 AM) *** The operation failed. Bind result: hr = 0x80070002. The system cannot find the file specified. Assembly manager loaded from: C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll Running under executable C:\MyProject\bin\Debug\MyProject.vshost.exe --- A detailed error log follows. LOG: Start binding of native image vshost32, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=x86. WRN: No matching native image found. LOG: Bind to native image assembly did not succeed. Use IL image. LOG: IL assembly loaded from C:\MyProject\bin\Debug\MyProject.vshost.exe

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• How to fix width of DIV that contains floated elements?

  - by joe

  I have a DIV container with several inner DIVs layed out by floating them all left. The inner DIVs may change width on certain events, and the containing DIV adjusts accordingly. I use float:left in the container to keep it shrunk to the width of the inner divs. I use float:left in the inner divs so the layout is clean even when their contents change. The catch is that I want the DIV container width and height to remain constant, UNLESS a particular event causes a change to the inner widths. Conceptually I want to use float on the inners for the layout benefit, but then I want to "fix" them so they don't float around. So if the container is 700px wide, I want it to remain so even if the user narrows the browser window. I'd like the container, and it's internal DIVs to just be clipped by the browser window. I sense this can all be done nicely in CSS, I just can't quite figure out how. I'm not averse to adding another container if necessary... Since the only desired layout changes are event-based, I am also willing to use a bit of JS. But is this necessary? (And I'm still not sure I know what to modify: container dimensions? inner floatiness? other?) <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <style type="text/css"> #canvas { overflow:auto; /* for clearing floats */ } #container { float:left; /* so container shrinks around contained divs */ border:thin solid blue; } .inner { float:left; /* so inner elems line up nicely w/o saying fixed coords */ padding-top:8px; padding-bottom:4px; padding-left:80px; padding-right:80px; } #inner1 { background-color:#ffdddd; } #inner2 { background-color:#ddffdd; } #inner3 { background-color:#ddddff; } </style> </head> <body> <div id="canvas"> <div id="container"> <div id="inner1" class="inner"> inner 1 </div> <div id="inner2" class="inner"> inner 2 </div> <div id="inner3" class="inner"> inner 3 </div> </div> </div> cleared element </body> </html>

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• Efficiency of Java "Double Brace Initialization"?

  - by Jim Ferrans

  In Hidden Features of Java the top answer mentions Double Brace Initialization, with a very enticing syntax: Set<String> flavors = new HashSet<String>() {{ add("vanilla"); add("strawberry"); add("chocolate"); add("butter pecan"); }}; This idiom creates an anonymous inner class with just an instance initializer in it, which "can use any [...] methods in the containing scope". Main question: Is this as inefficient as it sounds? Should its use be limited to one-off initializations? (And of course showing off!) Second question: The new HashSet must be the "this" used in the instance initializer ... can anyone shed light on the mechanism? Third question: Is this idiom too obscure to use in production code? Summary: Very, very nice answers, thanks everyone. On question (3), people felt the syntax should be clear (though I'd recommend an occasional comment, especially if your code will pass on to developers who may not be familiar with it). On question (1), The generated code should run quickly. The extra .class files do cause jar file clutter, and slow program startup slightly (thanks to coobird for measuring that). Thilo pointed out that garbage collection can be affected, and the memory cost for the extra loaded classes may be a factor in some cases. Question (2) turned out to be most interesting to me. If I understand the answers, what's happening in DBI is that the anonymous inner class extends the class of the object being constructed by the new operator, and hence has a "this" value referencing the instance being constructed. Very neat. Overall, DBI strikes me as something of an intellectual curiousity. Coobird and others point out you can achieve the same effect with Arrays.asList, varargs methods, Google Collections, and the proposed Java 7 Collection literals. Newer JVM languages like Scala, JRuby, and Groovy also offer concise notations for list construction, and interoperate well with Java. Given that DBI clutters up the classpath, slows down class loading a bit, and makes the code a tad more obscure, I'd probably shy away from it. However, I plan to spring this on a friend who's just gotten his SCJP and loves good natured jousts about Java semantics! ;-) Thanks everyone!

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• Google App Engine - Secure Cookies

  - by tponthieux

  I'd been searching for a way to do cookie based authentication/sessions in Google App Engine because I don't like the idea of memcache based sessions, and I also don't like the idea of forcing users to create google accounts just to use a website. I stumbled across someone's posting that mentioned some signed cookie functions from the Tornado framework and it looks like what I need. What I have in mind is storing a user's id in a tamper proof cookie, and maybe using a decorator for the request handlers to test the authentication status of the user, and as a side benefit the user id will be available to the request handler for datastore work and such. The concept would be similar to forms authentication in ASP.NET. This code comes from the web.py module of the Tornado framework. According to the docstrings, it "Signs and timestamps a cookie so it cannot be forged" and "Returns the given signed cookie if it validates, or None." I've tried to use it in an App Engine Project, but I don't understand the nuances of trying to get these methods to work in the context of the request handler. Can someone show me the right way to do this without losing the functionality that the FriendFeed developers put into it? The set_secure_cookie, and get_secure_cookie portions are the most important, but it would be nice to be able to use the other methods as well. #!/usr/bin/env python import Cookie import base64 import time import hashlib import hmac import datetime import re import calendar import email.utils import logging def _utf8(s): if isinstance(s, unicode): return s.encode("utf-8") assert isinstance(s, str) return s def _unicode(s): if isinstance(s, str): try: return s.decode("utf-8") except UnicodeDecodeError: raise HTTPError(400, "Non-utf8 argument") assert isinstance(s, unicode) return s def _time_independent_equals(a, b): if len(a) != len(b): return False result = 0 for x, y in zip(a, b): result |= ord(x) ^ ord(y) return result == 0 def cookies(self): """A dictionary of Cookie.Morsel objects.""" if not hasattr(self,"_cookies"): self._cookies = Cookie.BaseCookie() if "Cookie" in self.request.headers: try: self._cookies.load(self.request.headers["Cookie"]) except: self.clear_all_cookies() return self._cookies def _cookie_signature(self,*parts): self.require_setting("cookie_secret","secure cookies") hash = hmac.new(self.application.settings["cookie_secret"], digestmod=hashlib.sha1) for part in parts:hash.update(part) return hash.hexdigest() def get_cookie(self,name,default=None): """Gets the value of the cookie with the given name,else default.""" if name in self.cookies: return self.cookies[name].value return default def set_cookie(self,name,value,domain=None,expires=None,path="/", expires_days=None): """Sets the given cookie name/value with the given options.""" name = _utf8(name) value = _utf8(value) if re.search(r"[\x00-\x20]",name + value): # Don't let us accidentally inject bad stuff raise ValueError("Invalid cookie %r:%r" % (name,value)) if not hasattr(self,"_new_cookies"): self._new_cookies = [] new_cookie = Cookie.BaseCookie() self._new_cookies.append(new_cookie) new_cookie[name] = value if domain: new_cookie[name]["domain"] = domain if expires_days is not None and not expires: expires = datetime.datetime.utcnow() + datetime.timedelta( days=expires_days) if expires: timestamp = calendar.timegm(expires.utctimetuple()) new_cookie[name]["expires"] = email.utils.formatdate( timestamp,localtime=False,usegmt=True) if path: new_cookie[name]["path"] = path def clear_cookie(self,name,path="/",domain=None): """Deletes the cookie with the given name.""" expires = datetime.datetime.utcnow() - datetime.timedelta(days=365) self.set_cookie(name,value="",path=path,expires=expires, domain=domain) def clear_all_cookies(self): """Deletes all the cookies the user sent with this request.""" for name in self.cookies.iterkeys(): self.clear_cookie(name) def set_secure_cookie(self,name,value,expires_days=30,**kwargs): """Signs and timestamps a cookie so it cannot be forged""" timestamp = str(int(time.time())) value = base64.b64encode(value) signature = self._cookie_signature(name,value,timestamp) value = "|".join([value,timestamp,signature]) self.set_cookie(name,value,expires_days=expires_days,**kwargs) def get_secure_cookie(self,name,include_name=True,value=None): """Returns the given signed cookie if it validates,or None""" if value is None:value = self.get_cookie(name) if not value:return None parts = value.split("|") if len(parts) != 3:return None if include_name: signature = self._cookie_signature(name,parts[0],parts[1]) else: signature = self._cookie_signature(parts[0],parts[1]) if not _time_independent_equals(parts[2],signature): logging.warning("Invalid cookie signature %r",value) return None timestamp = int(parts[1]) if timestamp < time.time() - 31 * 86400: logging.warning("Expired cookie %r",value) return None try: return base64.b64decode(parts[0]) except: return None uid=1234|1234567890|d32b9e9c67274fa062e2599fd659cc14 Parts: 1. uid is the name of the key 2. 1234 is your value in clear 3. 1234567890 is the timestamp 4. d32b9e9c67274fa062e2599fd659cc14 is the signature made from the value and the timestamp

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• Problems related to showing MessageBox from non-GUI threads

  - by Hans Løken

  I'm working on a heavily data-bound Win.Forms application where I've found some strange behavior. The app has separate I/O threads receiving updates through asynchronous web-requests which it then sends to the main/GUI thread for processing and updating of application-wide data-stores (which in turn may be data-bound to various GUI-elements, etc.). The server at the other end of the web-requests requires periodic requests or the session times out. I've gone through several attempted solutions of dealing with thread-issues etc. and I've observed the following behavior: If I use Control.Invoke for sending updates from I/O-thread(s) to main-thread and this update causes a MessageBox to be shown the main form's message pump stops until the user clicks the ok-button. This also blocks the I/O-thread from continuing eventually leading to timeouts on the server. If I use Control.BeginInvoke for sending updates from I/O-thread(s) to main-thread the main form's message pump does not stop, but if the processing of an update leads to a messagebox being shown, the processing of the rest of that update is halted until the user clicks ok. Since the I/O-threads keep running and the message pump keeps processing messages several BeginInvoke's for updates may be called before the one with the message box is finished. This leads to out-of-sequence updates which is unacceptable. I/O-threads add updates to a blocking queue (very similar to http://stackoverflow.com/questions/530211/creating-a-blocking-queuet-in-net/530228#530228). GUI-thread uses a Forms.Timer that periodically applies all updates in the blocking queue. This solution solves both the problem of blocking I/O threads and sequentiality of updates i.e. next update will be never be started until previous is finished. However, there is a small performance cost as well as introducing a latency in showing updates that is unacceptable in the long run. I would like update-processing in the main-thread to be event-driven rather than polling. So to my question. How should I do this to: avoid blocking the I/O-threads guarantee that updates are finished in-sequence keep the main message pump running while showing a message box as a result of an update.

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• Servlet/JSP Flow Control: Enums, Exceptions, or Something Else?

  - by Christopher Parker

  I recently inherited an application developed with bare servlets and JSPs (i.e.: no frameworks). I've been tasked with cleaning up the error-handling workflow. Currently, each <form> in the workflow submits to a servlet, and based on the result of the form submission, the servlet does one of two things: If everything is OK, the servlet either forwards or redirects to the next page in the workflow. If there's a problem, such as an invalid username or password, the servlet forwards to a page specific to the problem condition. For example, there are pages such as AccountDisabled.jsp, AccountExpired.jsp, AuthenticationFailed.jsp, SecurityQuestionIncorrect.jsp, etc. I need to redesign this system to centralize how problem conditions are handled. So far, I've considered two possible solutions: Exceptions Create an exception class specific to my needs, such as AuthException. Inherit from this class to be more specific when necessary (e.g.: InvalidUsernameException, InvalidPasswordException, AccountDisabledException, etc.). Whenever there's a problem condition, throw an exception specific to the condition. Catch all exceptions via web.xml and route them to the appropriate page(s) with the <error-page> tag. enums Adopt an error code approach, with an enum keeping track of the error code and description. The descriptions can be read from a resource bundle in the finished product. I'm leaning more toward the enum approach, as an authentication failure isn't really an "exceptional condition" and I don't see any benefit in adding clutter to the server logs. Plus, I'd just be replacing one maintenance headache with another. Instead of separate JSPs to maintain, I'd have separate Exception classes. I'm planning on implementing "error" handling in a servlet that I'm writing specifically for this purpose. I'm also going to eliminate all of the separate error pages, instead setting an error request attribute with the error message to display to the user and forwarding back to the referrer. Each target servlet (Logon, ChangePassword, AnswerProfileQuestions, etc.) would add an error code to the request and redirect to my new servlet in the event of a problem. My new servlet would look something like this: public enum Error { INVALID_PASSWORD(5000, "You have entered an invalid password."), ACCOUNT_DISABLED(5002, "Your account has been disabled."), SESSION_EXPIRED(5003, "Your session has expired. Please log in again."), INVALID_SECURITY_QUESTION(5004, "You have answered a security question incorrectly."); private final int code; private final String description; Error(int code, String description) { this.code = code; this.description = description; } public int getCode() { return code; } public String getDescription() { return description; } }; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String sendTo = "UnknownError.jsp"; String message = "An unknown error has occurred."; int errorCode = Integer.parseInt((String)request.getAttribute("errorCode"), 10); Error errors[] = Error.values(); Error error = null; for (int i = 0; error == null && i < errors.length; i++) { if (errors[i].getCode() == errorCode) { error = errors[i]; } } if (error != null) { sendTo = request.getHeader("referer"); message = error.getDescription(); } request.setAttribute("error", message); request.getRequestDispatcher(sendTo).forward(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } Being fairly inexperienced with Java EE (this is my first real exposure to JSPs and servlets), I'm sure there's something I'm missing, or my approach is suboptimal. Am I on the right track, or do I need to rethink my strategy?

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• 3D game engine for networked world simulation / AI sandbox

  - by Martin

  More than 5 years ago I was playing with DirectSound and Direct3D and I found it really exciting although it took much time to get some good results with C++. I was a college student then. Now I have mostly enterprise development experience in C# and PHP, and I do it for living. There is really no chance to earn money with serious game development in our country. Each day more and more I find that I miss something. So I decided to spend an hour or so each day to do programming for fun. So my idea is to build a world simulation. I would like to begin with something simple - some human-like creatures that live their life - like Sims 3 but much more simple, just basic needs, basic animations, minimum graphic assets - I guess it won't be a city but just a large house for a start. The idea is to have some kind of a server application which stores the world data in MySQL database, and some client applications - body-less AI bots which simulate movement and some interactions with the world and each other. But it wouldn't be fun without 3D. So there are also 3D clients - I can enter that virtual world and see the AI bots living. When the bot enters visible area, it becomes material - loads a mesh and animations, so I can see it. When I leave, the bots lose their 3d mesh bodies again, but their virtual life still continues. With time I hope to make it like some expandable scriptable sandbox to experiment with various AI algorithms and so on. But I am not intended to create a full-blown MMORPG :D I have looked for many possible things I would need (free and open source) and now I have to make a choice: OGRE3D + enet (or RakNet). Old good C++. But won't it slow me down so much that I won't have fun any more? CrystalSpace. Formally not a game engine but very close to that. C++ again. MOgre (OGRE3D wrapper for .NET) + lidgren (networking library which is already used in some gaming projects). Good - I like C#, it is good for fast programming and also can be used for scripting. XNA seems just a framework, not an engine, so really have doubts, should I even look at XNA Game Studio :( Panda3D - full game engine with positive feedback. I really like idea to have all the toolset in one package, it has good reviews as a beginner-friendly engine...if you know Python. On the C++ side, Panda3D has almost non-existent documentation. I have 0 experience with Python, but I've heard it is easy to learn. And if it will be fun and challenging then I guess I would benefit from experience in one more programming language. Which of those would you suggest, not because of advanced features or good platform support but mostly for fun, easy workflow and expandability, and so I can create and integrate all the components I need - the server with the database, AI bots and a 3D client application?

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• Search engine solution for Django that actually works?

  - by prometheus

  The story so far: Decided to go with Xapian as search backend because it has all search-engine features I was looking for, knows about Unicode, stemming, has few dependencies and requires no bloated app-server installation on top of it. Tried Django and Haystack (plus xapian-haystack, the backend glue code to tie Haystack to Xapian) because it was advertised on quite some blogs as "working". Did not work. Neither django-haystack nor the xapian-haystack project provide a version combination that actually works together. MASTER from both projects yields an error from Xapian, so it's not stable at all. Haystack 1.0.1 and xapian-haystack 1.0.x/1.1.0 are not API-compatible. Plus, in a minimally working installation of Haystack 1.0.1 and xapian-haystack MASTER, any complex query yields zero results due to errors in either django-haystack or xapian-haystack (I double-verified this), maybe because the unit-tests actually test very simple cases, and no edge-cases at all. Tried Djapian. The source-code is riddled with spelling errors (mind you, in variable names, not comments), documentation is also riddled with ambiguities and outdated information that will never lead to a working installation. Not surprisingly, users rarely ask for features but how to get it working in the first place. Next on the plate: exploring Solr (installing a Java environment plus Tomcat gives me headaches, the machine is RAM- and CPU-constrained), or Lucene (slightly less headaches, but still). Before I proceed spending more time with a solution that might or might not work as advertised, I'd like to know: Did anyone ever get an actual, real-world search solution working in Django? I'm serious. I find it really frustrating reading about "large problems mostly solved", and then realizing that you will never get a working installation from the source-code because, actually, all bloggers dealing with those "mostly solved problems" never went past basic installation and copy-pasting the official tutorials. So here are the requirements: must be able to search for 10-100 terms in one query must handle + (term must be present) and - (term must not be present), AND/OR must handle arbitrary grouping (i.e. parentheses around AND/OR) must allow for Django-ORM filtering before or after fulltext-search (i.e. pre-/post-processing of results with the full set of filters that Django knows about) alternatively, there must be a facility to bulk-fetch the result set and transform it into a QuerySet should be light on the machine, so preferably no humongous JVM and Java-based app-server installation Is there anything out there that does this? I'm not interested in anecdotal evidence, or references to some blog posts that claim it should be working. I'd like to hear from someone who actually has a fully-functional setup working in the real world, under real conditions, with real queries. EDIT: Let me repeat again that I'm not so much interested in anecdotal evidence that someone, somewhere has a somewhat running installation working with unspecified properties. I already went there, I read all the blog posts, mailing lists, I contacted the authors, but when it came to actual implementation of real-world scenarios, nothing ever worked as advertised. Also, and a user below brought that point up as well, considering the TCO of any project, I'm definitely not interested in hearing that someone, somewhere was able to pull it off once a vendor parachuted in an unknown number of specialists to monkey-patch the whole installation with specific domain-knowledge that's documented nowhere. So, please, if you claim you have a working installation that actually satisfies minimum requirements for a full-fledged search (see requirements above), please provide the following so that we can all benefit from a search solution for Django that actually solves the problem: exact Linux distribution, release version, exact release version of Haystack (or equivalent) and release version of search backend, exact release version of the search engine publicly (!) available documentation how to set up all components exactly in the way that your installation was set up such that the minimal requirements above are met. Thank you.

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