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• MySQL won't start, reinstall fails on Ubuntu 12.04

  - by Evils

  My problem started yesterday night when I tried to change the my.cnf config on my ubuntu 12.04 x64 System. I simply tried to changed the bind-address parameter from 127.0.0.1 to 0.0.0.0. A simple restart after a reboot gave this error: stop: Unknown instance: start: Job failed to start I tried to start mysql then by using 'mysqld' which outputs this: 130701 11:05:59 [Note] Plugin 'FEDERATED' is disabled. mysqld: Table 'mysql.plugin' doesn't exist 130701 11:05:59 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it. 130701 11:05:59 InnoDB: The InnoDB memory heap is disabled 130701 11:05:59 InnoDB: Mutexes and rw_locks use GCC atomic builtins 130701 11:05:59 InnoDB: Compressed tables use zlib 1.2.3.4 130701 11:05:59 InnoDB: Initializing buffer pool, size = 128.0M 130701 11:05:59 InnoDB: Completed initialization of buffer pool 130701 11:05:59 InnoDB: highest supported file format is Barracuda. 130701 11:05:59 InnoDB: Waiting for the background threads to start 130701 11:06:00 InnoDB: 5.5.31 started; log sequence number 1595675 130701 11:06:00 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306 130701 11:06:00 [Note] - '127.0.0.1' resolves to '127.0.0.1'; 130701 11:06:00 [Note] Server socket created on IP: '127.0.0.1'. 130701 11:06:00 [ERROR] Can't start server : Bind on unix socket: Permission denied 130701 11:06:00 [ERROR] Do you already have another mysqld server running on socket: /var/run/mysqld/mysqld.sock ? 130701 11:06:00 [ERROR] Aborting 130701 11:06:00 InnoDB: Starting shutdown... 130701 11:06:00 InnoDB: Shutdown completed; log sequence number 1595675 130701 11:06:00 [Note] mysqld: Shutdown complete Meanwhile I already tried to reinstall and purge the complete mysql package which results in another error which says that dpkg cant change the admins password. While this error appeared another error came with it. When trying to install something new with apt, it always says 'fopen: permission denied' right after it tries to update my man-db. This is my dmesg output: [ 6879.687998] type=1400 audit(1372669683.397:36): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/mysqld" pid=9336 comm="apparmor_parser" [ 6881.323215] init: mysql main process (9340) terminated with status 1 [ 6881.323316] init: mysql respawning too fast, stopped Any help will be appreciated as this is a productive server which renders useless without mysql.

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• How should we serve files in a small bioinformatics cluster?

  - by cespinoza

  We have a small cluster of six ubuntu servers. We run bioinformatics analyses on these clusters. Each analysis takes about 24 hours to complete, each core i7 server can handle 2 at a time, takes as input about 5GB data and outputs about 10-25GB of data. We run dozens of these a week. The software is a hodgepodge of custom perl scripts and 3rd party sequence alignment software written in C/C++. Currently, files are served from two of the compute nodes (yes, we're using compute nodes as file servers)-- each node has 5 1TB sata drives mounted separately (no raid) and is pooled via glusterfs 2.0.1. They each have as 3 bonded intel ethernet pci gigabit ethernet cards, attached to a d-link DGS-1224T switch ($300 24 port consumer-level). We are not currently using jumbo frames (not sure why, actually). The two file-serving compute nodes are then mirrored via glusterfs. Each of the four other nodes mounts the files via glusterfs. The files are all large (4gb+), and are stored as bare files (no database/etc) if that matters. As you can imagine, this is a bit of a mess that grew organically without forethought and we want to improve it now that we're running out of space. Our analyses are I/O intensive and it is a bottle neck-- we're only getting 140mB/sec between the two fileservers, maybe 50mb/sec from the clients (which only have single NICs). We have a flexible budget which I can probably get up $5k or so. How should we spend our budget? We need at least 10TB of storage fast enough to serve all nodes. How fast/big does the cpu/memory of such a file server have to be? Should we use NFS, ATA over Ethernet, iSCSI, Glusterfs, or something else? Should we buy two or more servers and create some sort of storage cluster, or is 1 server enough for such a small number of nodes? Should we invest in faster NICs (say, PCI-express cards with multiple connectors)? The switch? Should we use raid, if so, hardware or software? and which raid (5, 6, 10, etc)? Any ideas appreciated. We're biologists, not IT gurus.

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• Can not get sound over hdmi in kubuntu 9.10

  - by user32509

  I have used a hdmi cable to connect my lcd (which is connected with my speakers) with my nvida 275 gtx grafic card. I can not get the sound output to work. The hardware itself is working probably - I tested it under windows. Currently I am running Kubuntu 9.10 64 with Nvidia 190.53. The sound output worked fine before I installed the hdmi connection. (German output - i can change it, if you tell me how :)) aplay -l **** Liste von PLAYBACK Geräten **** Karte 0: Intel [HDA Intel], Gerät 0: ALC889A Analog [ALC889A Analog] Untergeordnete Geräte: 1/1 Untergeordnetes Gerät '0: subdevice #0 Karte 0: Intel [HDA Intel], Gerät 1: ALC889A Digital [ALC889A Digital] Untergeordnete Geräte: 1/1 Untergeordnetes Gerät '0: subdevice #0 aplay -L front:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog Front speakers surround40:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 4.0 Surround output to Front and Rear speakers surround41:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 4.1 Surround output to Front, Rear and Subwoofer speakers surround50:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 5.0 Surround output to Front, Center and Rear speakers surround51:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 5.1 Surround output to Front, Center, Rear and Subwoofer speakers surround71:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 7.1 Surround output to Front, Center, Side, Rear and Woofer speakers iec958:CARD=Intel,DEV=0 HDA Intel, ALC889A Digital IEC958 (S/PDIF) Digital Audio Output null Discard all samples (playback) or generate zero samples (capture) pulse Playback/recording through the PulseAudio sound server And i disabled mute in kmix an all channels :) Edit: lspci -v ... 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 02) Subsystem: Giga-byte Technology Device a022 Flags: bus master, fast devsel, latency 0, IRQ 22 Memory at ea400000 (64-bit, non-prefetchable) [size=16K] Capabilities: [50] Power Management version 2 Capabilities: [60] Message Signalled Interrupts: Mask- 64bit+ Queue=0/0 Enable- Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00 Capabilities: [100] Virtual Channel <?> Capabilities: [130] Root Complex Link <?> Kernel driver in use: HDA Intel Kernel modules: snd-hda-intel ... cat /proc/asound/version Advanced Linux Sound Architecture Driver Version 1.0.20. lsmod | grep snd_hda_intel snd_hda_intel 31880 2 snd_hda_codec 87584 2 snd_hda_codec_realtek,snd_hda_intel snd_pcm 93160 3 snd_hda_intel,snd_hda_codec,snd_pcm_oss snd 77096 16 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device snd_page_alloc 10928 2 snd_hda_intel,snd_pcm I think I am missing the something-hdmi module? Is there such a thing?

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• Removing file with strange characters in filename in OS X

  - by SiggyF

  After a memory error in my program, I am stuck with a file with a strange filename. It's proving quite resistant to all normal methods to remove files with strange names. The filename is: %8BUȅ҉%95d%F8%FF%FF\x0f%8E%8F%FD%FF%FF%8B%B5T%F8%FF%FF%8B%85\%F8%FF%FF\x03%85x%F8%FF%FF%8B%95D%F8%FF%FF%8B%BD%9C%F8%FF%FF%8D\x04%86%8B%B5@%F8%FF%FF%89%85%90%F8%FF%FF%8B%85X%F8%FF%FF\x03%85%9C%F8%FF%FF%C1%E7\x02%8B%8Dx I tried the following: rm * - "No such file or directory" rm -- filename - "No such file or directory" rm "filename" - "No such file or directory" ls -i to get the inode number - "No such file or directory" stat filename - "No such file or directory" zip the directory where the file is in - error occured while adding "" to the archive. delete directory in finder - error -43 in python: os.unlink(os.listdir(u'.')[0]) - OSError No such file or directory find . -type f -exec rm {} \; - "No such file or directory" checked for locks on the file with lsof - no locks All these attempts result in a file (long filename here) not found error, or error -43. Even the ls -i. I couldn't find anymore options, so before reformatting or repairing my filesystem (fsck might help) I thought maybe there is something I missed. I wrote this small c program to get the inode: #include <stdio.h> #include <stddef.h> #include <sys/types.h> int main(void) { DIR *dp; struct dirent *ep; dp = opendir ("./"); if (dp != NULL) { while (ep = readdir (dp)) { printf("d_ino=%ld, ", (unsigned long) ep->d_ino); printf("d_name=%s.\n", ep->d_name); } (void) closedir (dp); } else perror ("Couldn't open the directory"); return 0; } That works. I now have the inode, but the normal find -inum inode -exec rm '{}' \; doesn't work. I think I have to use the clri now.

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• Network unreachable on Ubuntu guest after trying to set up a host only network on Virtualbox

  - by gkb0986

  I have a Mac OS X host and a bunch of guests including Ubuntu and Arch Linux. I was trying to set up a host-only network at eth1 to let me ssh into the system. But now eth0 isn't working properly either. Ubuntu can no longer connect to remote hosts or browse the internet. It tells me that the network is unreachable. What's gone wrong here? I've included some diagnostics below. $ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:10968 errors:0 dropped:0 overruns:0 frame:0 TX packets:10968 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:897264 (897.2 KB) TX bytes:897264 (897.2 KB) Other diagnostic commands and the output: $sudo lspci -n 00:00.0 0600: 8086:1237 (rev 02) 00:01.0 0601: 8086:7000 00:01.1 0101: 8086:7111 (rev 01) 00:02.0 0300: 80ee:beef 00:03.0 0200: 8086:100e (rev 02) 00:04.0 0880: 80ee:cafe 00:05.0 0401: 8086:2415 (rev 01) 00:06.0 0C03: 106B:003F 00:07.0 0680: 8086:7113 (REV 08) 00:0D.0 0106: 8086:2829 (REV 02) $sudo lshw -c network *-network DISABLED description: Ethernet interface product: 82540EM Gigabit Ethernet Controller vendor: Intel Corporation physical id: 3 bus info: pci@0000:00:03.0 logical name: eth0 version: 02 serial: 08:00:27:7d:22:df size: 1Gbit/s capacity: 1Gbit/s width: 32 bits clock: 66MHz capabilities: pm pcix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=e1000 driverversion=7.3.21-k8-NAPI duplex=full firmware=N/A latency=64 link=no mingnt=255 multicast=yes port=twisted pair speed=1Gbit/s resources: irq:19 memory:f0000000-f001ffff ioport:d010(size=8) $lsmod Module Size Used by nls_utf8 12557 1 isofs 40257 1 vboxsf 43743 2 vesafb 13844 1 snd_intel8x0 38570 2 snd_ac97_codec 134869 1 snd_intel8x0 ac97_bus 12730 1 snd_ac97_codec snd_pcm 97275 2 snd_intel8x0,snd_ac97_codec snd_seq_midi 13324 0 snd_rawmidi 30748 1 snd_seq_midi snd_seq_midi_event 14899 1 snd_seq_midi rfcomm 47604 0 snd_seq 61929 2 snd_seq_midi,snd_seq_midi_event bnep 18281 2 bluetooth 180113 10 rfcomm,bnep ppdev 17113 0 psmouse 97519 0 snd_timer 29990 2 snd_pcm,snd_seq joydev 17693 0 snd_seq_device 14540 3 snd_seq_midi,snd_rawmidi,snd_seq vboxvideo 12622 1 serio_raw 13211 0 snd 79041 11 snd_intel8x0,snd_ac97_codec,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device soundcore 15091 1 snd vboxguest 235498 7 vboxsf parport_pc 32866 0 drm 241971 2 vboxvideo i2c_piix4 13301 0 snd_page_alloc 18529 2 snd_intel8x0,snd_pcm mac_hid 13253 0 lp 17799 0 parport 46562 3 ppdev,parport_pc,lp usbhid 47238 0 hid 99636 1 usbhid e1000 108589 0

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• On ESXi, guest machines hang for significant intervals compared to real machines. How can I fix this?

  - by Tarbox

  This is ESXi version 5.0.0. We plan on upgrading to 5.5 eventually. I have four code profiles, two taken on a real, unvirtualized machine, two taken on a virtual machine. Ordering the list of subroutines by time spent in each one, the two real profiles are practically identical. The two virtual profiles are different from each other and from the real profiles: a subset of subroutines are taking a lot more time on the virtual machines, and the subset is different for each run. The two virtual profiles take a similar amount of time, which is 3 times the amount of time the real profiles take. This gross "how long does it take?" result is consistent after hundreds of tests across three different virtual machines on two different host machines -- the virtual machine is just slower. I've only the code profiling on the four, however. Here's the most guilty set of lines: This is the real machine: 8µs $text = '' unless defined $text; 1.48ms foreach ( split( "\n", $text ) ) { This is the first run on the virtual machine: 20.1ms $text = '' unless defined $text; 1.49ms foreach ( split( "\n", $text ) ) { This is the second run on the virtual machine: 6µs $text = '' unless defined $text; 21.9ms foreach ( split( "\n", $text ) ) { My WAG is that the VM is swapping out the thread and then swapping it back in, destroying some level of cache in the process, but these code profiles were taken when the vm in question was the only active vm on the host, so... what? What does that mean? The guest itself is under light load, this is a latency problem for my users rather than throughput. The host is also under a light load, if I knew what resources to assign where, I could do it without worrying about the cost. I've attempted to lock memory, reserve cpu, assign a restrictive affinity, and disable hyperthread sharing. They don't help, it still takes the VM 2-4x the amount of time to do the same thing as the real machine. The host the tests were run on is 6x2.50GHz, Intel Xeon E5-26400 w/ 16gigs of ram. The guest exhibits the same performance under a wide combination of settings. The real machine is 4x2.13GHz, Xeon E5506 w/ 2 gigs of ram. Thank you for all advice.

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• vmdk to live cd - VMware vmxnet virtual NIC driver Kernel panic

  - by ronalchn

  Task I am trying to convert a virtual machine to a live CD. Specifically, the virtual machine I am trying to convert is the IOI 2013 Competition Environment. In this task, I am aided by a guide Converting a virtual disk image: VDI or VMDK to an ISO you can distribute. Symptoms However, after getting through all the instructions, the live CD causes a kernel panic on boot on bare metal. In particular, the screen shows: [0.737348] cdrom: Uniform CD-ROM driver Revision: 3.20 [0.737503] sr 3:0:0:0: >Attached scsi CD-ROM sr0 [0.737638] sr 3:0:0:0: >Attached scsi generic sg2 type 5 [0.737771] Freeing unused kernel memory: 756k freed [0.738093] Write protecting the kernel text: 5960k [0.738155] Write protecting the kernel read-only data: 2424k [0.738224] NX-protecting the kernel data: 4280k Loading, please wait... [0.752252] udevd[100]: starting version 175 [0.768708] VMware vmxnet3 virtual NIC driver - version 1.1.29.0-k-NAPI [0.781204] VMware PVSCSI driver - version 1.0.2.0-k [0.789555] VMware vmxnet virtual NIC driver [0.799356] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000200 [0.799356] [0.799472] Pid: 1, comm: init Tainted: G 0 3.5.0-17-generic #28-Ubuntu [0.799549] Call Trace: [0.799603] [<c15bf0ec>] panic+0x81/0x17b [0.799654] [<c104a6a5>] do_exit+0x745/0x7a0 [0.799707] [<c104a9a4>] do_group_exit+0x34/0xa0 [0.799760] [<c104aa28>] sys_exit_group+0x18/0x20 [0.799813] [<c15cff5f>] sysenter_do_call+0x12/0x28 Possible problem I suspect that the problem is the VMware vmxnet virtual NIC driver - however, I do not know how I can uninstall it, and possibly install one for a bare metal machine. If anyone knows which packages needs installing/uninstalling at the .rootfs/ chroot directory stage, please let me know. Details on procedure Do note that after importing the .ova file into Virtualbox, the virtual machine is stored as a .vmdk file already, and not a .vdi file. I would like to point out some results of the procedure followed in case of any questions. This is after extracting the filesystem from the .raw file to the .rootfs/ directory mentioned in the blog. I changed the filesystem table as mentioned in the blog, then looked at the possible "kernel optimized for virtualization". However, I found that linux-image-generic was already installed. Also, when running the command dpkg-query --showformat='${Package}\n' -W 'vmware-tools*' (or dpkg-query --showformat='${Package}\n' -W '*-virtual'), no packages were found. Thus, I did not find any virtualization specific packages. I proceeded to generate the iso following the steps in the blog, and burned it to a DVD.

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• QNAP (469L) with Debian: can't connect to router

  - by agtoever

  I've been running my QNAP 469L with Debian (Wheezy deb7u3) for a few months. Yesterday I upgraded the memory to 4 GB. The system boots fine, but since the upgrade, I'm not able to connect the server to my router (a TP-Link WR941ND). My configuration: The router runs a DHCP server (192.168.67.100 and up), with a preconfigured ip address for the QNAP (192.168.67.10). The router is on 192.168.67.1. As said, Debian is installed on the QNAP (which can be regarded as a normal computer). Networking hardware on the QNAP: Intel PRO/1000 Network Connection using the e1000e kernel module. This is what I have tried so far: Replace the network cable (tried 3 different cables on different router ports). Check for messages from the kernel: dmesg | grep eth. Besides the normal hardware messages I get a ADDRCONF(NETDEV_UP): eth0: link is not ready for each call to ifup. Manually restart the network sudo server networking restart Check sudo ifconfig (eth0 is up, but no ip addresses). Check the /etc/network/interfaces which has (besides the loopback device) an allow-hotplug eth0 and iface eth0 inet dhcp, which is afaik the default Debian configuration. Since the server has two ethernet ports, I checked if I'm using the right port (checked the hardware address that ifconfig reports for eth0 is the same as the hardware address that is in the preconfigured ip address for the server in the router. Do a manual sudo ifdown eth0 && sudo ifup eth0 with no results (but an extra ADDRCONF(NETDEV_UP): eth0: link is not ready in the kernel log) Do a dhcp request dhclient -v eth0: for about a minute requests are send (according to the terminal) and at the end I get a No DHCPOFFERS received. No working leases in persistent database - sleeping.. Check the router system log if DHCP requests are received. I see them for some devices (my Mac, my iPhone) but not from the QNAP. The log entry looks like: DHCPS:Recv REQUEST from 84:85:06:07:75:6A and then a DHCPS:Send ACK to 192.168.67.101. There are no records from the QNAP's hardware address. So the two error messages that I do get are: ADDRCONF(NETDEV_UP): eth0: link is not ready for every ifup and No DHCPOFFERS received. No working leases in persistent database - sleeping. for every DHCP call.

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• Why is my concurrency capacity so low for my web app on a LAMP EC2 instance?

  - by AMF

  I come from a web developer background and have been humming along building my PHP app, using the CakePHP framework. The problem arose when I began the ab (Apache Bench) testing on the Amazon EC2 instance in which the app resides. I'm getting pretty horrendous average page load times, even though I'm running a c1.medium instance (2 cores, 2GB RAM), and I think I'm doing everything right. I would run: ab -n 200 -c 20 http://localhost/heavy-but-view-cached-page.php Here are the results: Concurrency Level: 20 Time taken for tests: 48.197 seconds Complete requests: 200 Failed requests: 0 Write errors: 0 Total transferred: 392111200 bytes HTML transferred: 392047600 bytes Requests per second: 4.15 [#/sec] (mean) Time per request: 4819.723 [ms] (mean) Time per request: 240.986 [ms] (mean, across all concurrent requests) Transfer rate: 7944.88 [Kbytes/sec] received While the ab test is running, I run VMStat, which shows that Swap stays at 0, CPU is constantly at 80-100% (although I'm not sure I can trust this on a VM), RAM utilization ramps up to about 1.6G (leaving 400M free). Load goes up to about 8 and site slows to a crawl. Here's what I think I'm doing right on the code side: In Chrome browser uncached pages typically load in 800-1000ms, and cached pages load in 300-500ms. Not stunning, but not terrible either. Thanks to view caching, there might be at most one DB query per page-load to write session data. So we can rule out a DB bottleneck. I have APC on. I am using Memcached to serve the view cache and other site caches. xhprof code profiler shows that cached pages take up 10MB-40MB in memory and 100ms - 1000ms in wall time. Pages that would be the worst offenders would look something like this in xhprof: Total Incl. Wall Time (microsec): 330,143 microsecs Total Incl. CPU (microsecs): 320,019 microsecs Total Incl. MemUse (bytes): 36,786,192 bytes Total Incl. PeakMemUse (bytes): 46,667,008 bytes Number of Function Calls: 5,195 My Apache config: KeepAlive On MaxKeepAliveRequests 100 KeepAliveTimeout 3 <IfModule mpm_prefork_module> StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 120 MaxRequestsPerChild 1000 </IfModule> Is there something wrong with the server? Some gotcha with the EC2? Or is it my code? Some obvious setting I should look into? Too many DNS lookups? What am I missing? I really want to get to 1,000 concurrency capacity, but at this rate, it ain't gonna happen.

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• BlueScreens on my ThinkPad with Windows 7 64 Bit and a SSD (CRITICAL_OBJECT_TERMINATION, ntoskernel.exe)

  - by pvorb

  I'm getting BlueScreens about every five days for more than three months. Here's an example: A problem has been detected and Windows has been shut down to prevent damage to your computer. The problem seems to be caused by the following file: ntoskrnl.exe CRITICAL_OBJECT_TERMINATION If this is the first time you've seen this stop error screen, restart your computer. If this screen appears again, follow these steps: Check to make sure any new hardware or software is properly installed. If this is a new installation, ask your hardware or software manufacturer for any Windows updates you might need. If problems continue, disable or remove any newly installed hardware or software. Disable BIOS memory options such as caching or shadowing. If you need to use safe mode to remove or disable components, restart your computer, press F8 to select Advanced Startup Options, and then select Safe Mode. Technical Information: *** STOP: 0x000000f4 (0x0000000000000003, 0xfffffa80065f2b30, 0xfffffa80065f2e10, 0xfffff80002f9bf40) *** ntoskrnl.exe - Address 0xfffff80002c98d00 base at 0xfffff80002c19000 DateStamp 0x4d9fdd5b It's has always been the same BlueScreen message showing CRITICAL_OBJECT_TERMINATION, 0x000000f4, and ntoskrnl.exe. Of course the addresses change. My computer is a ThinkPad T400 (about 2 years old) with a SSD in it. I'm also running Windows 7 Professional 64 bit. When I bought my computer, it had a 250GByte SeaGate HDD in it, which I replaced by a 500GByte HDD by Western Digital. Last september I bought a Corsair F120 SSD and replaced the HDD by this SSD. Then I bought a LEICKE HDD adapter for the UltraBay II where I plugged in my 500GByte HDD. This configuration ran about half a year without any errors. After re-installing Windows this spring, I am getting regular BlueScreens. Sometimes my system runs for about 2 weeks without a BSOD, sometimes I get several BlueScreens a day. The only thing that I noticed is, that I'm always running Google Chrome when it happens. Is there anyone who has made his/her own bad experiences whith some of my components or is there anybody who can tell me if it would be helpful to send my notebook to Lenovo? Thank you very much for your help on my issue! Regards, Paul

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• Architectural advice - web camera remote access

  - by Alan Hollis

  I'm looking for architectural advice. I have a client who I've built a website for which essentially allows users to view their web cameras remotely. The current flow of data is as follows: User opens page to view web camera image. Javascript script polls url on server ( appended with unique timestamp ) every 1000ms Ftp connection is enabled for the cameras ftp user. Web camera opens ftp connection to server. Web camera begins taking photos. Web camera sends photo to ftp server. On image url request: Server reads latest image on hard drive uploaded via ftp for camera. Server deleted any older images from the server. This is working okay at the moment for a small amount of users/cameras ( about 10 users and around the same amount of cameras), but we're starting to worrying about the scalability of this approach. My original plan was instead of having the files read from the server, the web server would open up an ftp connection to the web server and read the latest images directly from there meaning we should have been able to scale horizontally fairly easily. But ftp connection establishment times were too slow ( mainly due to the fact that PHP out of the ox is unable to persist ftp connections ) and so we abandoned this approach and went straight for reading from the hard drive. The firmware provider for the cameras state they're able to build a http client which instead of using ftp to upload the image could post the image to a web server. This seems plausible enough to me, but I'm looking for some architectural advice. My current thought is a simple Nginx/PHP/Redis stack. Web camera issues post requests of latest image to Nginx/PHP and the latest image for that camera is stored in Redis. The clients can then pull the latest image from Redis which should be extremely quick as the images will always be stored in memory. The data flow would then become: User opens page to view web camera image. Javascript script polls url on server ( appended with unique timestamp ) every 1000ms Camera is sent an http request to start posting images to a provided url Web camera begins taking photos. Web camera sends post requests to server as fast as it can On image url request: Server reads latest image from redis Server tells redis to delete later image My questions are: Are there any greater overheads of transferring images via HTTP instead of FTP? Is there a simple way to calculate how many potential cameras we could have streaming at once? Is there any way to prevent potentially DOS'ing our own servers due to web camera requests? Is Redis a good solution to this problem? Should I abandon PHP/Ngix combination and go for something else? Is this proposed solution actually any good? Will adding HTTPs to the mix cause posting the image to become too slow? Thanks in advance Alan

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• debugging JBoss 100% CPU usage

  - by Nate

  We are using JBoss to run two of our WARs. One is our web app, the other is our web service. The web app accesses a database on another machine and makes requests to the web service. The web service makes JMS requests to other machines, aggregates the data, and returns it. At our biggest client, about once a month the JBoss Java process takes 100% of all CPUs. The machine running JBoss has 8 CPUs. Our web app is still accessible during this time, however pages take about 3 minutes to load. Restarting JBoss restores everything to normal. The database machine and all the other machines are fine, only the machine running JBoss is affected. Memory usage is normal. Network utilization is normal. There are no suspect error messages in the JBoss logs. I have set up a test environment as close as possible to the client's production environment and I've done load testing with as much as 2x the number of concurrent users. I have not gotten my test environment to replicate the problem. Where do we go from here? How can we narrow down the problem? Currently the only plan we have is to wait until the problem occurs in production on its own, then do some debugging to determine the cause. So far people have just restarted JBoss when the problem occurred to minimize down time. Next time it happens they will get a developer to take a look. The question is, next time it happens, what can be done to determine the cause? We could setup a separate JBoss instance on the same box and install the web app separately from the web service. This way when the problem next occurs we will know which WAR has the problem (assuming it is our code). This doesn't narrow it down much though. Should I enable JMX remote? This way the next time the problem occurs I can connect with VisualVM and see which threads are taking the CPU and what the hell they are doing. However, is there a significant down side to enabling JMX remote in a production environment? Is there another way to see what threads are eating the CPU and to get a stacktrace to see what they are doing? Any other ideas? Thanks!

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• Nginx common configuration that I might have missed

  - by ApPeL

  I recently moved from Apache Mod_wsgi to Nginx, and I have seen a major improvement on speed a lowering on memory usage and I am generally very happy with the it. I am not a server expert, so please be gentle. I am wondering if there are any small configuration that I might have missed, that will cause me some issues in the long run... Please see my nginx.conf file user nginx nginx; worker_processes 4; error_log /var/log/nginx/error_log info; events { worker_connections 1024; use epoll; } http { include /etc/nginx/mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] ' '"$request" $status $bytes_sent ' '"$http_referer" "$http_user_agent" ' '"$gzip_ratio"'; client_header_timeout 10m; client_body_timeout 10m; send_timeout 10m; connection_pool_size 256; client_header_buffer_size 1k; large_client_header_buffers 4 2k; request_pool_size 4k; gzip on; gzip_min_length 1100; gzip_buffers 4 8k; gzip_types text/plain; output_buffers 1 32k; postpone_output 1460; sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 75 20; ignore_invalid_headers on; index index.html; server { listen 80; server_name localhost; location /media/ { root /www/django_test1/myapp; # Notice this is the /media folder that we create above } location /mediaadmin/ { alias /opt/python2.6/lib/python2.6/site-packages/django/contrib/admin/media/; # Notice this is the /media folder that we create above } location / { # host and port to fastcgi server fastcgi_pass 127.0.0.1:8080; fastcgi_param SERVER_ADDR $server_addr; fastcgi_param SERVER_PORT $server_port; fastcgi_param SERVER_NAME $server_name; fastcgi_param SERVER_PROTOCOL $server_protocol; fastcgi_param PATH_INFO $fastcgi_script_name; fastcgi_param REQUEST_METHOD $request_method; fastcgi_param QUERY_STRING $query_string; fastcgi_param CONTENT_TYPE $content_type; fastcgi_param CONTENT_LENGTH $content_length; fastcgi_pass_header Authorization; fastcgi_intercept_errors off; client_max_body_size 100M; } access_log /var/log/nginx/localhost.access_log main; error_log /var/log/nginx/localhost.error_log; } }

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• Computer randomly reboots during "intensive activity".

  - by Reznor

  My friend has been playing games on his new build for some time now. However, lately, his computer will randomly reboot out of nowhere, so far only happening in game, and presumably only to happen in game as it happens nowhere else. This can happen in game during play or even in the options. Note, it isn't a crash or blue screen. It's just a normal reboot. This started today, I believe, and has only occured in two games: Dead Space and Stalker: Shadow of Chernobyl. He has played a handful of games before these, for about a week or so, without this problem. We theorized on two possibilities: Maybe something is overheating? Maybe the power supply is inadequate? These two were quickly dismissed, as all his components were operating at normal temperatures when he got back to his desktop from the reboot, and we all know these parts don't exactly cool down quickly, especially if they get hot enough to trigger a reboot. Besides, I know at-least my motherboard reports processor overheating at start-up, and requests I press f1 to continue into boot. The PSU one was dismissed too. He has an 850w power supply on a rig that was estimated to take only 720 some watts, that's with some overcompensating to be safe. He opened up his case to make sure nothing was seated wrong or in the way. All was fine, but he did notice a sticker on his video card. It had a giant barcode on it and some numbers. Now, I'm used to seeing these stickers, they're the warranty stickers, right, and removal voids the warranty? Yeah, well, we find it odd because this sticker is slapped right over the circuits of the video card, not on a block or anything. Is this normal? Should he remove it? Right now, I am concerned with the memory. Could that be at fault? Here are his specs: Windows 7 Home Premium, 64-Bit Intel i7 950 EVGA GeForce 570 GTX 4 GB DDR3 PC10666 dual-channel Corsair RAM Corsair 850w PSU Gigabyte GA-X58A-UD3R Western Digital 1 TB WD1001FALS

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• How can I minimize the amount my router slows down my Internet connection speed?

  - by Lord Torgamus

  Background I'm working with what I assume is a pretty common Internet setup: a cable modem, a wireless router and a few Internet-connected devices. Lately, I've started being more demanding on my Internet connection, and noticed that using my router slows down my download speeds considerably. I just kind of dealt with it until Zune Marketplace on the Xbox 360 told me that a movie was going to take well over ten hours to download, and I just didn't want to wait that long. Good little scientist that I am, I tried to reduce the problem down to one variable. The test As a control, I turned off all the devices in the house that use wireless Internet, and unplugged all the wired devices except for the Xbox. I also power-cycled both the modem and the router. I then tried to download the movie again, and was told that it would still take over ten hours. Next, I unplugged the router, and connected the Xbox directly to the modem. The movie downloaded in just over one hour. As far as I can tell, this means that my ISP, other cable users near me, the remote servers, anything wireless-related and my machines' disk speeds can't be at fault. A similar experiment that replaced the Xbox with a wired laptop produced similar results. To me, this says "the router is responsible for things taking around ten times longer to download." My question I'd still prefer to use the router for a few reasons: it's a pain to connect and disconnect everything every time there's a big file to download direct connection to the modem isn't good for security only one machine can be connected directly to the modem at a time What can I do to have fast connection speeds while still using the router? I don't mind turning other machines off, as long as I don't have to mess with power and ethernet cables. EDIT : After asking this followup question and then this one, I installed dd-wrt on my router, and I seem to be getting higher and more consistent speeds. Perhaps more importantly, my memory use is fairly constant. I know this isn't an answer — which is why I'm not posting it as an answer — but it is how I resolved the situation, and hopefully it'll be helpful for someone.

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• jqGrid multi-checkbox custom edittype solution

  - by gsiler

  For those of you trying to understand jqGrid custom edit types ... I created a multi-checkbox form element, and thought I'd share. This was built using version 3.6.4. If anyone has a more efficient solution, please pass it on. Within the colModel, the appropriate edit fields look like this: edittype:'custom' editoptions:{ custom_element:MultiCheckElem, custom_value:MultiCheckVal, list:'Check1,Check2,Check3,Check4' } Here are the javascript functions (BTW, It also works – with some modifications – when the list of checkboxes is in a DIV block): //———————————————————— // Description: // MultiCheckElem is the "custom_element" function that builds the custom multiple check box input // element. From what I have gathered, jqGrid calls this the first time the form is launched. After // that, only the "custom_value" function is called. // // The full list of checkboxes is in the jqGrid "editoptions" section "list" tag (in the options // parameter). //———————————————————— function MultiCheckElem( value, options ) { //———- // for each checkbox in the list // build the input element // set the initial "checked" status // endfor //———- var ctl = ''; var ckboxAry = options.list.split(','); for ( var i in ckboxAry ) { var item = ckboxAry[i]; ctl += '<input type="checkbox" '; if ( value.indexOf(item + '|') != -1 ) ctl += 'checked="checked" '; ctl += 'value="' + item + '"> ' + item + '</input><br />&nbsp;'; } ctl = ctl.replace( /<br />&nbsp;$/, '' ); return ctl; } //———————————————————— // Description: // MultiCheckVal is the "custom_value" function for the custom multiple check box input element. It // appears that jqGrid invokes this function the first time the form is submitted and, the rest of // the time, when the form is launched (action = set) and when it is submitted (action = 'get'). //———————————————————— function MultiCheckVal(elem, action, val) { var items = ''; if (action == 'get') // the form has been submitted { //———- // for each input element // if it's checked, add it to the list of items // endfor //———- for (var i in elem) { if (elem[i].tagName == 'INPUT' && elem[i].checked ) items += elem[i].value + ','; } // items contains a comma delimited list that is returned as the result of the element items = items.replace(/,$/, ''); } else // the form is launched { //———- // for each input element // based on the input value, set the checked status // endfor //———- for (var i in elem) { if (elem[i].tagName == 'INPUT') { if (val.indexOf(elem[i].value + '|') == -1) elem[i].checked = false; else elem[i].checked = true; } } // endfor } return items; }

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• Computer science undergraduate project ideas

  - by Mehrdad Afshari

  Hopefully, I'm going to finish my undergraduate studies next semester and I'm thinking about the topic of my final project. And yes, I've read the questions with duplicate title. I'm asking this from a bit different viewpoint, so it's not an exact dupe. I've spent at least half of my life coding stuff in different languages and frameworks so I'm not looking at this project as a way to learn much about coding and preparing for real world apps or such. I've done lots of those already. But since I have to do it to complete my degree, I felt I should spend my time doing something useful instead of throwing the whole thing out. I'm planning to make it an open source project or a hosted Web app (depending on the type) if I can make a high quality thing out of it, so I decided to ask StackOverflow what could make a useful project. Situation I've plenty of freedom about the topic. They also require 30-40 pages of text describing the project. I have the following points in mind (the more satisfied, the better): Something useful for software development Something that benefits the community Having academic value is great Shouldn't take more than a month of development (I know I'm lazy). Shouldn't be related to advanced theoretical stuff (soft computing, fuzzy logic, neural networks, ...). I've been a business-oriented software developer. It should be software oriented. While I love hacking microcontrollers and other fun embedded electronic things, I'm not really good at soldering and things like that. I'm leaning toward a Web application (think StackOverflow, PasteBin, NerdDinner, things like those). Technology It's probably going to be done in .NET (C#, F#) and Windows platform. If I really like the project (cool low level hacking), I might actually slip to C/C++. But really, C# is what I'm efficient at. Ideas Programming language, parsing and compiler related stuff: Designing a domain specific programming language and compiler Templating language compiled to C# or IL Database tools and related code generation stuff Web related technologies: ASP.NET MVC View engine doing something cool (don't know what exactly...) Specific-purpose, small, fast ASP.NET-based Web framework Applications: Visual Studio plugin to integrate with Bazaar (it's too much work, I think). ASP.NET based, jQuery-powered issue tracker (and possibly, project lifecycle management as a whole - poor man's TFS) Others: Something related to GPGPU Looking forward for great ideas! Unfortunately, I can't help on a currently existing project. I need to start my own to prevent further problems (as it's an undergrad project, nevertheless).

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• Delete Nodes + attributes that match Xpath except specific attributes

  - by Ryan Ternier

  I'm trying to find the best (efficient) way of doing this. I have a medium sized XML document. Depending on specific settings certain portions of it need to be filtered out for security reasons. I'll be doing this in XSLT as it's configurable and no code should need changing. I've looked around, but not getting much luck on it. For example: I have the following XPath: //*[@root='2.16.840.1.113883.3.51.1.1.6.1'] Whicrooth gives me all nodes with a root attribute equal to a specific OID. In these nodes I want to have all attributes except for a few (ex. foo and bar) erased, and then having another attribute added (ex. reason) I also need to have multiple XPath expressions that can be ran to zero down on a specific node and clear it's contents out in a similar fashion, with respect to nodes with specific attributes. I'm playing around with information from: XPath expression to select all XML child nodes except a specific list? and XSLT Remove Elements and/or Attributes by Name per XSL Parameters Will update shortly when I can have access what what I"ve done so far. Example: XML Before Transformation <root> <childNode> <innerChild root="2.16.840.1.113883.3.51.1.1.6.1" a="b" b="c" type="innerChildness"/> <innerChildSibling/> </childNode> <animals> <cat> <name>bob</name> </cat> </animals> <tree/> <water root="2.16.840.1.113883.3.51.1.1.6.1" z="zed" l="ell" type="liquidLIke"/> </root> After <root> <childNode> <innerChild root="2.16.840.1.113883.3.51.1.1.6.1" flavor="MSK"/> <!-- filtered --> <innerChildSibling/> </childNode> <animals> <cat flavor="MSK" /> <!-- cat was filtered --> </animals> <tree/> <water root="2.16.840.1.113883.3.51.1.1.6.1" flavor="MSK"/> <!-- filtered --> </root>

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• Append indexed input fields with attached datepicker widget

  - by Micor

  I am looking for the most efficient way to add a set of fields with datepicker widget attached on click event. So here I have a set of indexed events being generated on a page: <div id="events"> <div class="event"> <input type="text" id="event_0_startDate" name="event[0].startDate" class="date"/> <input type="hidden" id="event_0_startDate_day" name="event[0].startDate_day" /> <input type="hidden" id="event_0_startDate_month" name="event[0].startDate_month" /> <input type="hidden" id="event_0_startDate_year" name="event[0].startDate_year"/> </div> <div class="event"> <input type="text" id="event_1_startDate" name="event[1].startDate" class="date"/> <input type="hidden" id="event_1_startDate_day" name="event[1].startDate_day" /> <input type="hidden" id="event_1_startDate_month" name="event[1].startDate_month" /> <input type="hidden" id="event_1_startDate_year" name="event[1].startDate_year" /> </div> .... more event divs .... </div> <a href="#" id="add_event">Add event</a> .. with datepicker widget attached: $(".date").datepicker({ onClose: function(dateText,picker) { var prefix = $(this).attr('id'); $('#' + prefix + '_month').val( dateText.split(/\//)[0] ); $('#' + prefix + '_day').val( dateText.split(/\//)[1] ); $('#' + prefix + '_year').val( dateText.split(/\//)[2] ); } }); I need a function that will add inside div id="events" after the last div class="event" another div class="event" where N is the next index and attach datepicker widget above to the new input field with class="date" like: <div class="event"> <input type="text" id="event_N_startDate" name="event[N].startDate" class="date"/> <input type="hidden" id="event_N_startDate_day" name="event[N].startDate_day"/> <input type="hidden" id="event_N_startDate_month" name="event[N].startDate_month" /> <input type="hidden" id="event_N_startDate_year" name="event[N].startDate_year" /> </div> Thank you.

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• Need help implementing simple socket server using GIOService (GLib, Glib-GIO)

  - by Mark Renouf

  I'm learning the basics of writing a simple, efficient socket server using GLib. I'm experimenting with GSocketService. So far I can only seem to accept connections but then they are immediately closed. From the docs I can't figure out what step I am missing. I'm hoping someone can shed some light on this for me. When running the following: # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. Output from the server: # ./server New Connection from 127.0.0.1:36962 New Connection from 127.0.0.1:36963 New Connection from 127.0.0.1:36965 Current code: /* * server.c * * Created on: Mar 10, 2010 * Author: mark */ #include <glib.h> #include <gio/gio.h> gchar *buffer; gboolean network_read(GIOChannel *source, GIOCondition cond, gpointer data) { GString *s = g_string_new(NULL); GError *error; GIOStatus ret = g_io_channel_read_line_string(source, s, NULL, &error); if (ret == G_IO_STATUS_ERROR) g_error ("Error reading: %s\n", error->message); else g_print("Got: %s\n", s->str); } gboolean new_connection(GSocketService *service, GSocketConnection *connection, GObject *source_object, gpointer user_data) { GSocketAddress *sockaddr = g_socket_connection_get_remote_address(connection, NULL); GInetAddress *addr = g_inet_socket_address_get_address(G_INET_SOCKET_ADDRESS(sockaddr)); guint16 port = g_inet_socket_address_get_port(G_INET_SOCKET_ADDRESS(sockaddr)); g_print("New Connection from %s:%d\n", g_inet_address_to_string(addr), port); GSocket *socket = g_socket_connection_get_socket(connection); gint fd = g_socket_get_fd(socket); GIOChannel *channel = g_io_channel_unix_new(fd); g_io_add_watch(channel, G_IO_IN, (GIOFunc) network_read, NULL); return TRUE; } int main(int argc, char **argv) { g_type_init(); GSocketService *service = g_socket_service_new(); GInetAddress *address = g_inet_address_new_from_string("127.0.0.1"); GSocketAddress *socket_address = g_inet_socket_address_new(address, 4000); g_socket_listener_add_address(G_SOCKET_LISTENER(service), socket_address, G_SOCKET_TYPE_STREAM, G_SOCKET_PROTOCOL_TCP, NULL, NULL, NULL); g_object_unref(socket_address); g_object_unref(address); g_socket_service_start(service); g_signal_connect(service, "incoming", G_CALLBACK(new_connection), NULL); GMainLoop *loop = g_main_loop_new(NULL, FALSE); g_main_loop_run(loop); }

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• Overriding LINQ extension methods

  - by Ruben Vermeersch

  Is there a way to override extension methods (provide a better implementation), without explicitly having to cast to them? I'm implementing a data type that is able to handle certain operations more efficiently than the default extension methods, but I'd like to keep the generality of IEnumerable. That way any IEnumerable can be passed, but when my class is passed in, it should be more efficient. As a toy example, consider the following: // Compile: dmcs -out:test.exe test.cs using System; namespace Test { public interface IBoat { void Float (); } public class NiceBoat : IBoat { public void Float () { Console.WriteLine ("NiceBoat floating!"); } } public class NicerBoat : IBoat { public void Float () { Console.WriteLine ("NicerBoat floating!"); } public void BlowHorn () { Console.WriteLine ("NicerBoat: TOOOOOT!"); } } public static class BoatExtensions { public static void BlowHorn (this IBoat boat) { Console.WriteLine ("Patched on horn for {0}: TWEET", boat.GetType().Name); } } public class TestApp { static void Main (string [] args) { IBoat niceboat = new NiceBoat (); IBoat nicerboat = new NicerBoat (); Console.WriteLine ("## Both should float:"); niceboat.Float (); nicerboat.Float (); // Output: // NiceBoat floating! // NicerBoat floating! Console.WriteLine (); Console.WriteLine ("## One has an awesome horn:"); niceboat.BlowHorn (); nicerboat.BlowHorn (); // Output: // Patched on horn for NiceBoat: TWEET // Patched on horn for NicerBoat: TWEET Console.WriteLine (); Console.WriteLine ("## That didn't work, but it does when we cast:"); (niceboat as NiceBoat).BlowHorn (); (nicerboat as NicerBoat).BlowHorn (); // Output: // Patched on horn for NiceBoat: TWEET // NicerBoat: TOOOOOT! Console.WriteLine (); Console.WriteLine ("## Problem is: I don't always know the type of the objects."); Console.WriteLine ("## How can I make it use the class objects when the are"); Console.WriteLine ("## implemented and extension methods when they are not,"); Console.WriteLine ("## without having to explicitely cast?"); } } } Is there a way to get the behavior from the second case, without explict casting? Can this problem be avoided?

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• Best way to handle multiple tables to replace one big table in Rails? (e.g. 'Books1', 'Books2', etc.

  - by mikep

  Hello, I've decided to use multiple tables for an entity (e.g. Books1, Books2, Books3, etc.), instead of just one main table which could end up having a lot of rows (e.g. just Books). I'm doing this to try and to avoid a potential future performance drop that could come with having too many rows in one table. With that, I'm looking for a good way to handle this in Rails, mainly by trying to avoid loading a bunch of unused associations. (I know that I could use a partition for this, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. I'm going to split the adds across the tables. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end class Books3 < ActiveRecord::Base belongs_to :user end I'm assuming that the main performance hit would come in terms of memory and possibly some method call overhead for each User object, since it has to load all of those associations, which in turn creates all of those nice, dynamic model accessor methods like User.find_by_. But for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. For example, with a user.id of 2, I'd only need books3.find_by_author('Author'), but the way I'm thinking of setting this up, I'd still have access to Books1..n. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. So, a few questions: 1) Is there's some sort of special Ruby/Rails methodology that could be applied to this 'multiple tables to represent one entity' scheme? Are there any 'best practices' for this? 2) Is it really bad to have so many unused has_many associations for each object? Is there a better way to do this? 3) Does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class? For example, so I can call books.find_by_author('Author') instead of books3.find_by_author('Author'). Thank you!

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• Fulltext search for django : Mysql not so bad ? (vs sphinx, xapian)

  - by Eric

  I am studying fulltext search engines for django. It must be simple to install, fast indexing, fast index update, not blocking while indexing, fast search. After reading many web pages, I put in short list : Mysql MYISAM fulltext, djapian/python-xapian, and django-sphinx I did not choose lucene because it seems complex, nor haystack as it has less features than djapian/django-sphinx (like fields weighting). Then I made some benchmarks, to do so, I collected many free books on the net to generate a database table with 1 485 000 records (id,title,body), each record is about 600 bytes long. From the database, I also generated a list of 100 000 existing words and shuffled them to create a search list. For the tests, I made 2 runs on my laptop (4Go RAM, Dual core 2.0Ghz): the first one, just after a server reboot to clear all caches, the second is done juste after in order to test how good are cached results. Here are the "home made" benchmark results : 1485000 records with Title (150 bytes) and body (450 bytes) Mysql 5.0.75/Ubuntu 9.04 Fulltext : ========================================================================== Full indexing : 7m14.146s 1 thread, 1000 searchs with single word randomly taken from database : First run : 0:01:11.553524 next run : 0:00:00.168508 Mysql 5.5.4 m3/Ubuntu 9.04 Fulltext : ========================================================================== Full indexing : 6m08.154s 1 thread, 1000 searchs with single word randomly taken from database : First run : 0:01:11.553524 next run : 0:00:00.168508 1 thread, 100000 searchs with single word randomly taken from database : First run : 9m09s next run : 5m38s 1 thread, 10000 random strings (random strings should not be found in database) : just after the 100000 search test : 0:00:15.007353 1 thread, boolean search : 1000 x (+word1 +word2) First run : 0:00:21.205404 next run : 0:00:00.145098 Djapian Fulltext : ========================================================================== Full indexing : 84m7.601s 1 thread, 1000 searchs with single word randomly taken from database with prefetch : First run : 0:02:28.085680 next run : 0:00:14.300236 python-xapian Fulltext : ========================================================================== 1 thread, 1000 searchs with single word randomly taken from database : First run : 0:01:26.402084 next run : 0:00:00.695092 django-sphinx Fulltext : ========================================================================== Full indexing : 1m25.957s 1 thread, 1000 searchs with single word randomly taken from database : First run : 0:01:30.073001 next run : 0:00:05.203294 1 thread, 100000 searchs with single word randomly taken from database : First run : 12m48s next run : 9m45s 1 thread, 10000 random strings (random strings should not be found in database) : just after the 100000 search test : 0:00:23.535319 1 thread, boolean search : 1000 x (word1 word2) First run : 0:00:20.856486 next run : 0:00:03.005416 As you can see, Mysql is not so bad at all for fulltext search. In addition, its query cache is very efficient. Mysql seems to me a good choice as there is nothing to install (I need just to write a small script to synchronize an Innodb production table to a MyISAM search table) and as I do not really need advanced search feature like stemming etc... Here is the question : What do you think about Mysql fulltext search engine vs sphinx and xapian ?

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• How to optimize Core Data query for full text search

  - by dk

  Can I optimize a Core Data query when searching for matching words in a text? (This question also pertains to the wisdom of custom SQL versus Core Data on an iPhone.) I'm working on a new (iPhone) app that is a handheld reference tool for a scientific database. The main interface is a standard searchable table view and I want as-you-type response as the user types new words. Words matches must be prefixes of words in the text. The text is composed of 100,000s of words. In my prototype I coded SQL directly. I created a separate "words" table containing every word in the text fields of the main entity. I indexed words and performed searches along the lines of SELECT id, * FROM textTable JOIN (SELECT DISTINCT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) ON id=textTableId LIMIT 50 This runs very fast. Using an IN would probably work just as well, i.e. SELECT * FROM textTable WHERE id IN (SELECT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) LIMIT 50 The LIMIT is crucial and allows me to display results quickly. I notify the user that there are too many to display if the limit is reached. This is kludgy. I've spent the last several days pondering the advantages of moving to Core Data, but I worry about the lack of control in the schema, indexing, and querying for an important query. Theoretically an NSPredicate of textField MATCHES '.*\bfoo.*' would just work, but I'm sure it will be slow. This sort of text search seems so common that I wonder what is the usual attack? Would you create a words entity as I did above and use a predicate of "word BEGINSWITH 'foo'"? Will that work as fast as my prototype? Will Core Data automatically create the right indexes? I can't find any explicit means of advising the persistent store about indexes. I see some nice advantages of Core Data in my iPhone app. The faulting and other memory considerations allow for efficient database retrievals for tableview queries without setting arbitrary limits. The object graph management allows me to easily traverse entities without writing lots of SQL. Migration features will be nice in the future. On the other hand, in a limited resource environment (iPhone) I worry that an automatically generated database will be bloated with metadata, unnecessary inverse relationships, inefficient attribute datatypes, etc. Should I dive in or proceed with caution?

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• "Wrapping" a BindingList<T> propertry with a List<T> property for serialization.

  - by Eric

  I'm writing an app that allows users search and browse catalogs of widgets. My WidgetCatalog class is serialized and deserialized to and from XML files using DataContractSerializer. My app is working now but I think I can make the code a lot more efficient if I started taking advantage of data binding rather then doing everything manually. Here's a stripped down version of my current WidgetCatalog class. [DataContract(Name = "WidgetCatalog")] class WidgetCatalog { [DataContract(Name = "Name")] public string Name { get; set; } [DataContract(Name = "Widgets")] public List<Widget> Widgets { get; set; } } I had to write a lot of extra code to keep my UI in sync when widgets are added or removed from a catalog, or their internal properties change. I'm pretty inexperienced with data-binding, but I think I want a BindingList<Widget> rather than a plain old List<Widget>. Is this right? In the past when I had similar needs I found that BindingList<T> does not serialize very well. Or at least the Event Handers between the items and the list are not serialized. I was using XmlSerializer though, and DataContractSerializer may work better. So I'm thinking of doing something like the code below. [DataContract(Name = "WidgetCatalog")] class WidgetCatalog { [DataMember(Name = "Name")] public string Name { get; set; } [DataMember(Name = "Widgets")] private List<Widget> WidgetSerializationList { get { return this._widgetBindingList.ToList<Widget>(); } set { this._widgetBindingList = new BindingList<Widget>(value); } } //these do not get serialized private BindingList<Widget> _widgetBindingList; public BindingList<Widget> WidgetBindingList { get { return this._widgetBindingList; } } public WidgetCatalog() { this.WidgetSerializationList = new List<Widget>(); } } So I'm serializing a private List<Widget> property, but the GET and SET accessors of the property are reading from, and writing to theBindingList<Widget> property. Will this even work? It seems like there should be a better way to do this.

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