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  • UDP traffic effect on network performance

    - by user314536
    well, i have network that each proxy (lets assume we have 200 proxies), send UDP packages every constant amount of time. (let assume 10 seconds) to constant amount of hosts (lets assume 10) my question is how will 6 * 10 seconds * 200 proxies * 10 target hosts = 120,000 UDP roundtrip communication per minute will affect my network, in terms of available connections, speed, stability, UDP package loss rate etc... can anyone please refer me to some links on this issue ? thanks

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  • What can cause EXC_BAD_INSTRUCTION in dyldbootstrap?

    - by Georg Fritzsche
    Porting a bigger project to iPhone i have it running in the simulator, but trying to run it on a iPad device results in a EXC_BAD_INSTRUCTIONin dyld code with the following backtrace: #0 0x2fe01088 in __dyld__ZN13dyldbootstrapL30randomizeExecutableLoadAddressEPK12macho_headerPPKcPm () #1 0x2fe06a72 in __dyld__ZN4dyld5_mainEPK12macho_headermiPPKcS5_S5_ () #2 0x2fe06d3c in __dyld__ZN9__gnu_cxx13new_allocatorIPFPKc17dyld_image_statesjPK15dyld_image_infoEE8allocateEmPKv () #3 0x2fe0b398 in __dyld__ZN9__gnu_cxx13new_allocatorISt13_Rb_tree_nodeIPK11ImageLoaderEE8allocateEmPKv () #4 0x2fe05fa6 in __dyld__ZN4dyld11removeImageEP11ImageLoader () #5 0x2fe06506 in __dyld__ZN4dyld5_mainEPK12macho_headermiPPKcS5_S5_ () #6 0x2fe0128c in __dyld__ZN13dyldbootstrapL30randomizeExecutableLoadAddressEPK12macho_headerPPKcPm () #7 0x2fe01060 in __dyld_branch_to_lookupDyldFunction () This is building for iPhone Device 3.2 with the architectures armv6 armv7 and happens before main() is ever entered. I am currently at a loss for how to find the cause of this, any ideas?

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  • Implicit conversion while using += operator?

    - by bdhar
    Conside the following code: int main() { signed char a = 10; a += a; // Line 5 a = a + a; return 0; } I am getting this warning at Line 5: d:\codes\operator cast\operator cast\test.cpp(5) : warning C4244: '+=' : conversion from 'int' to 'signed char', possible loss of data Does this mean that += operator makes an implicit cast of the right hand operator to int? P.S: I am using Visual studio 2005

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  • Linqbuilder Query with an OrderBy

    - by Renshai
    I have a 1 : M relationship. I built a dynamic query based on input from users to return the listing of parents entities along with their children (using predicate builder: (done successfully new TDataContext().Ps.Where(predicate) )... but need to order the results by a field found only on the child entities. I'm at a loss: new TDataContext().Ps.Where(predicate).OrderBy(p = p.Cs. ??) where Ps = parents collection relationship with Cs = child entities any help appreciated.

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  • MAC OS X: How to determine if filesystem is case sensitive?

    - by trojanfoe
    I have used the statfs(2) system call to get many characteristics of a Mac OS X filesystem, but it doesn't tell me if the filesystem is case-sensitive or not. I need this information as the application I am developing will be moving many files around and I want to detect potential loss of data due to files being moved from a case-sensitive filesystem to a case-insensitive filesystem. Can anyone suggest a way of detecting this?

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  • Sum Values in Multidimensional Array

    - by lemonpole
    Hello all. I'm experimenting with arrays in PHP and I am setting up a fake environment where a "team's" record is held in arrays. $t1 = array ( "basicInfo" => array ( "The Sineps", "December 25, 2010", "lemonpole" ), "overallRecord" => array ( 0, 0, 0, 0 ), "overallSeasons" => array ( "season1.cs" => array (0, 0, 0), "season2.cs" => array (0, 0, 0) ), "matches" => array ( "season1.cs" => array ( "week1" => array ("12", "3", "1"), "week2" => array ("8", "8" ,"0"), "week3" => array ("8", "8" ,"0") ), "season2.cs" => array ( "week1" => array ("9", "2", "5"), "week2" => array ("12", "2" ,"2") ) ) ); What I am trying to achieve is to add all the wins, loss, and draws, from each season's week to their respective week. So for example, the sum of all the weeks in $t1["matches"]["season1.cs"] will be added to $t1["overallSeasons"]["season1.cs"]. The result would leave: "overallSeasons" => array ( "season1.cs" => array (28, 19, 1), "season2.cs" => array (21, 4, 7) ), I tried to work this out on my own for the past hour and all I have gotten is a little more knowledge of for-loops and foreach-loops :o... so I think I now have the basics down such as using foreach loops and so on; however, I am still fairly new to this so bear with me! I can get the loop to point to $t1["matches"] key and go through each season but I can't seem to figure out how to add all of the wins, loss, and draw, for each individual week. For now, I'm only looking for answers concerning the overall seasons sum since I can work from there once I figure out how to achieve this. Any help will be much appreciated but please, try and keep it simple for me... or comment the code accordingly please! Thanks!

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  • JavaScript: Container with draggable. Constrain draggable to a circle shape, in container.

    - by ritsuke
    Hey guys, I'm looking for a simple solution to place a draggable element inside of a box container. When the user begins to interact with the draggable, the draggable element should remain constrained to a circular shape, within the container. At a complete loss as to how I should accomplish this. Thank you! :-) Additional: Box container would be 100 pixels wide and tall Draggable would be 20 pixels wide and tall http://tool-man.org/examples/dragging.html This is on the TODO list, but of course this site is no longer maintained

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  • How do I bring a processes window to the foreground on X Windows? (C++)

    - by Lorenz03Tx
    I have the PID for the process (and the name), I want to bring it to the front on linux (ubuntu). On mac I would simply do SetFrontProcess(pid), on windows I'd enumerate the windows pick out the one I wanted and call SetWindowPos(hwnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE); but I'm at a loss of what to do on linux. I've looked at X Lib a bit, but most/all of those functions seem to operate on windows inside your process. Thanks in advanced.

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  • How to check if internet connection is present in java?

    - by Chris
    How do you check if you can connect to the internet via java? One way would be: final URL url = new URL("http://www.google.com"); final URLConnection conn = url.openConnection(); ... if we got here, we should have net ... But is there something more appropriate to perform that task, especially if you need to do consecutive checks very often and a loss of internet connection is highly probable?

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  • disk-to-disk backup without costly backup redundancy?

    - by AaronLS
    A good backup strategy involves a combination of 1) disconnected backups/snapshots that will not be affected by bugs, viruses, and/or security breaches 2) geographically distributed backups to protect against local disasters 3) testing backups to ensure that they can be restored as needed Generally I take an onsite backup daily, and an offsite backup weekly, and do test restores periodically. In the rare circumstance that I need to restore files, I do some from the local backup. Should a catastrophic event destroy the servers and local backups, then the offsite weekly tape backup would be used to restore the files. I don't need multiple offsite backups with redundancy. I ALREADY HAVE REDUNDANCY THROUGH THE USE OF BOTH LOCAL AND REMOTE BACKUPS. I have recovery blocks and par files with the backups, so I already have protection against a small percentage of corrupt bits. I perform test restores to ensure the backups function properly. Should the remote backups experience a dataloss, I can replace them with one of the local backups. There are historical offsite backups as well, so if a dataloss was not noticed for a few weeks(such as a bug/security breach/virus), the data could be restored from an older backup. By doing this, the only scenario that poses a risk to complete data loss would be one where both the local, remote, and servers all experienced a data loss in the same time period. I'm willing to risk that happening since the odds of that trifecta negligibly small, and the data isn't THAT valuable to me. So I hope I have emphasized that I don't need redundancy in my offsite backups because I have covered all the bases. I know this exact technique is employed by numerous businesses. Of course there are some that take multiple offsite backups, because the data is so incredibly valuable that they don't even want to risk that trifecta disaster, but in the majority of cases the trifecta disaster is an accepted risk. I HAD TO COVER ALL THIS BECAUSE SOME PEOPLE DON'T READ!!! I think I have justified my backup strategy and the majority of businesses who use offsite tape backups do not have any additional redundancy beyond what is mentioned above(recovery blocks, par files, historical snapshots). Now I would like to eliminate the use of tapes for offsite backups, and instead use a backup service. Most however are extremely costly for $/gb/month storage. I don't mind paying for transfer bandwidth, but the cost of storage is way to high. All of them advertise that they maintain backups of the data, and I imagine they use RAID as well. Obviously if you were using them to host servers this would all be necessary, but for my scenario, I am simply replacing my offsite backups with such a service. So there is no need for RAID, and absolutely no value in another layer of backups of backups. My one and only question: "Are there online data-storage/backup services that do not use redundancy or offer backups(backups of my backups) as part of their packages, and thus are more reasonably priced?" NOT my question: "Is this a flawed strategy?" I don't care if you think this is a good strategy or not. I know it pretty standard. Very few people make an extra copy of their offsite backups. They already have local backups that they can use to replace the remote backups if something catastrophic happens at the remote site. Please limit your responses to the question posed. Sorry if I seem a little abrasive, but I had some trolls in my last post who didn't read my requirements nor my question, and were trying to go off answering a totally different question. I made it pretty clear, but didn't try to justify my strategy, because I didn't ask about whether my strategy was justifyable. So I apologize if this was lengthy, as it really didn't need to be, but since there are so many trolls here who try to sidetrack questions by responding without addressing the question at hand.

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  • How do I achieve lossless JPEG joining without truncation of partial MCUs?

    - by Karan
    I am working on a project for which I need to join thousands of JPEG images losslessly (I'm not talking about the Lossless JPEG/JPEG 2000/JPEG-LS formats here). Aforementioned images have varying levels of chroma subsampling (1x1, 1x2, 2x1, 2x2), resulting in varying MCU sizes (8x8, 8x16, 16x8, 16x16 px). However, in any given set of images to be joined together, each image has identical characteristics. For now, let's assume I only have 2 images. Image #1 (I1) is 256x256px in size and #2 (I2) is 239x256px in size. 2x2 subsampling is used such that MCU size is 16x16px. I2 thus obviously has partial MCUs at the right edge, since its width is not evenly divisible by 16. (I've read that so-called 'partial' MCUs actually contain the data for a complete MCU, but the image dimensions instruct the renderer to only display the relevant pixels and ignore/hide the extra ones.) Looking around for tools that could help me accomplish this, I came across a modified version of JpegTran, that contains an experimental lossless crop 'n' drop (cut & paste) feature. All the other apps I encountered that support lossless JPEG editing seem to utilise IJG's (JpegTran) code, so this seemed to be the logical choice. Also, given the sheer number of images, I wanted something that could preferably be run from the command-line so that I could automate the process with a script. Unfortunately, while everything else worked fine, it seems JpegTran truncates the partial MCUs instead of retaining them. Thus in the example above, the final joined image contains all of I1, but only 224x256px of I2. Why 224? because 239 = 14x16+15, which means there are 14 full MCUs along the width, and 1 partial MCU (just 1px short of the complete 16px). The last 15px is what is getting blanked, leading to a 495x256px image with 15px of blank (grey) pixels at the right edge. See images below (shame that imgur re-compresses them): (left )+ (right) = As you can clearly see, the red portion (15px) of I2 has been truncated by JpegTran. If the MCUs were 8px in width, the lost portion would have been the right-most 7px of I2. Similarly, joining I3 (256x239px) *below * I1 would cause the loss of 7 or 15px, depending on the MCU height of course: (top) + (bottom) = If this is better suited to some other StackExchange (or even non-SE) site/forum where JPEG/image encoding experts hang out, do let me know. Can what I am attempting even be done, or is the so-called 'lossless' JPEG crop 'n' drop only valid for images with no partial MCUs? (Maybe that is why the feature is still in an "experimental state" more than a decade after being introduced...) Until I know for sure that it is impossible, I am not interested in suggestions for lossy joining. Avoiding any generational loss whatsoever is the sole reason why I'm breaking my head over this, else I'd have had this done and dusted ages ago. Also, I am not interested in suggestions related to switching image formats. I do not control the source of the images. If it can be done, how? Please keep in mind that any alternate apps suggested must ideally be capable of automation, given the requirements stated above. (But given how it's unlikely I'm even going to receive a useful answer given the constraints, I would be happy with any app suggestion just as long as it actually works. I can always look into an AutoIT/AHK script or something later to automate it.) I understand that an odd-sized final image might cause issues, so I am fully prepared to accept any solution, even if it results in blank (preferably black) padding pixels to the right/bottom. What I mean is, I don't care if I1 + I2 is 496x256px (1px padding) or even 512x256px (17px padding) in size, as long as the final image contains all the actual image data from both source images, and the entire process is lossless. Obviously the lesser the padding (if any), the better, but at this point any solution will do. A Windows-based solution would be perfect, but a Linux-based one would be entirely acceptable.

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  • Cannot ping host stale ARP cache?

    - by gkchicago
    I am having a strange issue with a Debian (Lenny/Linux 2.6.26-2-amd64) that has been driving me nuts. On some machines within my network I can ping the host in question just fine, other times I have to manually hard-code the ARP ethernet address for the IP in order to establish connectivity. I've finally worked it down to somehow involving ARP. I just found how to fix it in a way that made it work but I'm looking for help explaining this issue and also I don't trust my fix to be permanent.. My thought process has been the following but I just can't make any sense out of it: Could it be the card? (Intel 82555 rev 4) Could it be because there are two network cards? (Default route is eth0) Could it be because of the network aliases? Lenny? AMD x86_64? Argh.. Thank you for any insight you might have // Ping doesn't go thru [gordon@ubuntu ~]$ ping 192.168.135.101 PING 192.168.135.101 (192.168.135.101) 56(84) bytes of data. --- 192.168.135.101 ping statistics --- 4 packets transmitted, 0 received, 100% packet loss, time 3014ms // Here's the ARP Table, sometimes the .151 address is good, sometimes it // also matches the Gateways MAC like .101 is doing right here. [gordon@ubuntu ~]$ cat /proc/net/arp IP address HW type Flags HW address Mask Device 192.168.135.15 0x1 0x2 00:0B:DB:2B:24:89 * eth0 192.168.135.151 0x1 0x2 00:0B:6A:3A:30:A6 * eth0 192.168.135.1 0x1 0x2 00:1A:A2:2D:2A:04 * eth0 192.168.135.101 0x1 0x2 00:1A:A2:2D:2A:04 * eth0 // Drop the bad arp table listing and set it manually based on /sbin/ifconfig [gordon@ubuntu ~]$ sudo arp -d 192.168.135.101 [gordon@ubuntu ~]$ sudo arp -s 192.168.135.101 00:0B:6A:3A:30:A6 // Ping starts going thru..?!? [gordon@ubuntu ~]$ ping 192.168.135.101 PING 192.168.135.101 (192.168.135.101) 56(84) bytes of data. 64 bytes from 192.168.135.101: icmp_seq=1 ttl=64 time=15.8 ms 64 bytes from 192.168.135.101: icmp_seq=2 ttl=64 time=15.9 ms 64 bytes from 192.168.135.101: icmp_seq=3 ttl=64 time=16.0 ms 64 bytes from 192.168.135.101: icmp_seq=4 ttl=64 time=15.9 ms --- 192.168.135.101 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3012ms rtt min/avg/max/mdev = 15.836/15.943/16.064/0.121 ms The following is my network config on this. gordon@db01:~$ /sbin/ifconfig eth0 Link encap:Ethernet HWaddr 00:0b:6a:3a:30:a6 inet addr:192.168.135.151 Bcast:192.168.135.255 Mask:255.255.255.0 inet6 addr: fe80::20b:6aff:fe3a:30a6/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:15476725 errors:0 dropped:0 overruns:0 frame:0 TX packets:10030036 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:18565307359 (17.2 GiB) TX bytes:3412098075 (3.1 GiB) eth0:0 Link encap:Ethernet HWaddr 00:0b:6a:3a:30:a6 inet addr:192.168.135.150 Bcast:192.168.135.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 eth0:1 Link encap:Ethernet HWaddr 00:0b:6a:3a:30:a6 inet addr:192.168.135.101 Bcast:192.168.135.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 eth1 Link encap:Ethernet HWaddr 00:e0:81:2a:6e:d0 inet addr:10.10.62.1 Bcast:10.10.62.255 Mask:255.255.255.0 inet6 addr: fe80::2e0:81ff:fe2a:6ed0/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:10233315 errors:0 dropped:0 overruns:0 frame:0 TX packets:19400286 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1112500658 (1.0 GiB) TX bytes:27952809020 (26.0 GiB) Interrupt:24 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:387 errors:0 dropped:0 overruns:0 frame:0 TX packets:387 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:41314 (40.3 KiB) TX bytes:41314 (40.3 KiB) gordon@db01:~$ sudo mii-tool -v eth0 eth0: negotiated 100baseTx-FD, link ok product info: Intel 82555 rev 4 basic mode: autonegotiation enabled basic status: autonegotiation complete, link ok capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD gordon@db01:~$ sudo route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface localnet * 255.255.255.0 U 0 0 0 eth0 10.10.62.0 * 255.255.255.0 U 0 0 0 eth1 default 192.168.135.1 0.0.0.0 UG 0 0 0 eth0

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  • how to make bridge networking with KVM work in Fedora19

    - by netllama
    I'm attempting to get several virtual machines setup on a Fedora-19 host system, with the traditional bridge network devices (br0, br1, etc). I've done this many times before with older versions of Fedora (16, 14, etc), and it just works. However, for reasons that I cannot figure out, the bridge doesn't seem to be working in Fedora19. While I can successfully connect to the outside world (local network + internet) from inside a VM, nothing can communicate with the VM from outside (local network). I'm referring to something as trivial as pinging. From inside the VM, I can ping anything successfully (0% packet loss). However, from outside the VM (on the host, or any other system on the same network), I see 100% packet loss when pinging the IP address of the VM. My first question is simply, does anyone else have this working successfully in F19? And if so, what steps did you need to follow? I'm not using NetworkManager at all, its all the network service. There are no firewalls involved anywhere (iptables & firewall services are currently disabled). Here's the current host configuration: # brctl show bridge name bridge id STP enabled interfaces br0 8000.38eaa792efe5 no em2 vnet1 br1 8000.38eaa792efe6 no em3 br2 8000.38eaa792efe7 no em4 vnet0 virbr0 8000.525400db3ebf yes virbr0-nic # more /etc/sysconfig/network-scripts/ifcfg-em2 TYPE=Ethernet BRIDGE="br0" NAME=em2 DEVICE="em2" UUID=aeaa839e-c89c-4d6e-9daa-79b6a1b919bd ONBOOT=yes HWADDR=38:EA:A7:92:EF:E5 NM_CONTROLLED="no" # more /etc/sysconfig/network-scripts/ifcfg-br0 TYPE=Bridge NM_CONTROLLED="no" BOOTPROTO=dhcp NAME=br0 DEVICE="br0" ONBOOT=yes # ifconfig em2 ;ifconfig br0 em2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet6 fe80::3aea:a7ff:fe92:efe5 prefixlen 64 scopeid 0x20<link> ether 38:ea:a7:92:ef:e5 txqueuelen 1000 (Ethernet) RX packets 100093 bytes 52354831 (49.9 MiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 25321 bytes 15791341 (15.0 MiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device memory 0xf7d00000-f7e00000 br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 10.31.99.226 netmask 255.255.252.0 broadcast 10.31.99.255 inet6 fe80::3aea:a7ff:fe92:efe5 prefixlen 64 scopeid 0x20<link> ether 38:ea:a7:92:ef:e5 txqueuelen 0 (Ethernet) RX packets 19619 bytes 1963328 (1.8 MiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 11 bytes 1074 (1.0 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 Relevant section from /etc/libvirt/qemu/foo.xml (one of the VMs with this problem): <interface type='bridge'> <mac address='52:54:00:26:22:9d'/> <source bridge='br0'/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> # ps -ef | grep qemu qemu 1491 1 82 13:25 ? 00:42:09 /usr/bin/qemu-system-x86_64 -machine accel=kvm -name cuda-linux64-build5 -S -machine pc-0.13,accel=kvm,usb=off -cpu SandyBridge,+pdpe1gb,+osxsave,+dca,+pcid,+pdcm,+xtpr,+tm2,+est,+smx,+vmx,+ds_cpl,+monitor,+dtes64,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme -m 16384 -smp 6,sockets=6,cores=1,threads=1 -uuid 6e930234-bdfd-044d-2787-22d4bbbe30b1 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/cuda-linux64-build5.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/libvirt/images/cuda-linux64-build5.img,if=none,id=drive-virtio-disk0,format=raw,cache=writeback -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -netdev tap,fd=25,id=hostnet0,vhost=on,vhostfd=26 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:26:22:9d,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -vnc 127.0.0.1:1 -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 I can provide additional information, if requested. thanks!

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  • Intermittent 404 on select assets, LAMP stack

    - by Tom Lagier
    We have a LAMP stack WordPress server that is serving most assets correctly. However, one plugin's CSS file and several images are returning soft 404s roughly 20% of the time. I can't find any reference to the 404 in the access logs, but the browser is definitely receiving a 404 response from somewhere (WordPress, I would assume). When I use an alias URL that does not match the site URL but does resolve to the asset path, the resource loads correctly 100% of the time. However, using the site url only resolves for the select, problematic assets 20% of the time. You can test one of the problematic assets here: http://www.mreco.org/wp-content/uploads/2014/05/zero-cost.jpg However the alias link always resolves correctly: http://mr-eco.wordpress.promocampaigns.com/wp-content/uploads/2014/05/zero-cost.jpg Stranger, if I attempt to access outdated content that definitely does not exist on the server, at the live URL it returns the content roughly 50% of the time. Using the alias link, it 404s 100% of the time - the correct behavior. Error log and PHP error log are clean. A sample access log (pulled from grep 'zero-cost.jpg' /var/log/httpd/mr-eco-access_log) from several refreshes of the live direct link (where I am not seeing any 404's): 10.166.202.202 - - [28/May/2014:20:27:41 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:42 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:43 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:43 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.176.201.37 - - [28/May/2014:20:27:56 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 200 57027 Chrome's dev tools list the following network activity before displaying 404 page content: zero-cost.jpg /wp-content/uploads/2014/05 GET 404 Not Found text/html Other 15.9?KB 73.2?KB 953?ms 947?ms My Apache configuration is standard, I've listed the virtual host entry and .htaccess file below. I can provide other parts of Apache config if necessary. Virtual host: <VirtualHost *:80> DocumentRoot /var/www/public_html/mr-eco.wordpress.promocampaigns.com ServerName www.mreco.org ServerAlias mreco.org mr-eco.wordpress.promocampaigns.com ErrorLog logs/mr-eco-error_log CustomLog logs/mr-eco-access_log common <Directory /var/www/public_html/mr-eco.wordpress.promocampaigns.com> AllowOverride All SetOutputFilter DEFLATE </Directory> </VirtualHost> .htaccess: # BEGIN WordPress <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule> # END WordPress I have checked for multiple A records and can confirm that there is a single A record pointing at the domain: ;; ANSWER SECTION: mreco.org. 60 IN A 50.18.58.174 I'm fairly new to systems administration, and at a complete loss as to what could cause this. In the past, inconsistently 404ing assets have been because of out-of-sync instances behind a load balancer. In this case, it is a single instance behind the load balancer. Because of the inconsistency, it feels like a caching issue. We don't make use of Apache caching, and as far as I know WordPress should not be caching either. What I've done so far: Reset WordPress permalinks Disabled WordPress plugins Re-generated WordPress .htaccess file Swapped ServerName and ServerAlias directives Cleared browser cache Confirmed disk location of resources Checked PHP, access, and error logs Confirmed correct DNS setup (can post if necessary) I'm at a total loss. Thanks for helping me out!

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  • simple and reliable centralized logging inside Amazon VPC

    - by Nakedible
    I need to set up centralized logging for a set of servers (10-20) in an Amazon VPC. The logging should be as to not lose any log messages in case any single server goes offline - or in the case that an entire availability zone goes offline. It should also tolerate packet loss and other normal network conditions without losing or duplicating messages. It should store the messages durably, at the minimum on two different EBS volumes in two availability zones, but S3 is a good place as well. It should also be realtime so that the messages arrive within seconds of their generation to two different availability zones. I also need to sync logfiles not generated via syslog, so a syslog-only centralized logging solution would not fulfill all the needs, although I guess that limitation could be worked around. I have already reviewed a few solutions, and I will list them here: Flume to Flume to S3: I could set up two logservers as Flume hosts which would store log messages either locally or in S3, and configure all the servers with Flume to send all messages to both servers, using the end-to-end reliability options. That way the loss of a single server shouldn't cause lost messages and all messages would arrive in two availability zones in realtime. However, there would need to be some way to join the logs of the two servers, deduplicating all the messages delivered to both. This could be done by adding a unique id on the sending side to each message and then write some manual deduplication runs on the logfiles. I haven't found an easy solution to the duplication problem. Logstash to Logstash to ElasticSearch: I could install Logstash on the servers and have them deliver to a central server via AMQP, with the durability options turned on. However, for this to work I would need to use some of the clustering capable AMQP implementations, or fan out the deliver just as in the Flume case. AMQP seems to be a yet another moving part with several implementations and no real guidance on what works best this sort of setup. And I'm not entirely convinced that I could get actual end-to-end durability from logstash to elasticsearch, assuming crashing servers in between. The fan-out solutions run in to the deduplication problem again. The best solution that would seem to handle all the cases, would be Beetle, which seems to provide high availability and deduplication via a redis store. However, I haven't seen any guidance on how to set this up with Logstash and Redis is one more moving part again for something that shouldn't be terribly difficult. Logstash to ElasticSearch: I could run Logstash on all the servers, have all the filtering and processing rules in the servers themselves and just have them log directly to a removet ElasticSearch server. I think this should bring me reliable logging and I can use the ElasticSearch clustering features to share the database transparently. However, I am not sure if the setup actually survives Logstash restarts and intermittent network problems without duplicating messages in a failover case or similar. But this approach sounds pretty promising. rsync: I could just rsync all the relevant log files to two different servers. The reliability aspect should be perfect here, as the files should be identical to the source files after a sync is done. However, doing an rsync several times per second doesn't sound fun. Also, I need the logs to be untamperable after they have been sent, so the rsyncs would need to be in append-only mode. And log rotations mess things up unless I'm careful. rsyslog with RELP: I could set up rsyslog to send messages to two remote hosts via RELP and have a local queue to store the messages. There is the deduplication problem again, and RELP itself might also duplicate some messages. However, this would only handle the things that log via syslog. None of these solutions seem terribly good, and they have many unknowns still, so I am asking for more information here from people who have set up centralized reliable logging as to what are the best tools to achieve that goal.

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  • Win 7 Netbook refuses to ping JetDirect card (all other PCs work)

    - by Luke Puplett
    I have an odd thing occuring here. From a Windows 7 netbook, I cannot ping an HP printer on the network, while all other machines (Win7/Vista) can. And the netbook can also ping everything else on the LAN. Example showing that the netbook can ping 192.168.3.4 but not 3.6. C:\Users\backdoor>ping w7ue1m Pinging w7ue1m.corp.biz.co.uk [192.168.3.4] with 32 bytes of data: Reply from 192.168.3.4: bytes=32 time=7ms TTL=128 Reply from 192.168.3.4: bytes=32 time=4ms TTL=128 Reply from 192.168.3.4: bytes=32 time=2ms TTL=128 Reply from 192.168.3.4: bytes=32 time=2ms TTL=128 Ping statistics for 192.168.3.4: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 2ms, Maximum = 7ms, Average = 3ms C:\Users\backdoor>ping uktnprint1 Pinging uktnprint1.corp.biz.co.uk [192.168.3.6] with 32 bytes of data: Reply from 192.168.3.0: Destination host unreachable. Reply from 192.168.3.0: Destination host unreachable. Reply from 192.168.3.0: Destination host unreachable. Reply from 192.168.3.0: Destination host unreachable. Ping statistics for 192.168.3.6: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),`enter code here` The IPCONFIG result for the netbook is fine. IPv4 Address. . . . . . . . . . . : 192.168.3.0 Subnet Mask . . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . . : 192.168.1.1 Most unusual network thing I've seen in years. I must reiterate that only this netbook is having trouble pinging/printing. Thanks, Luke ** UPDATE ** Am now on a Vista box, and here's the IPCONFIG: IPv4 Address. . . . . . . . . . . : 192.168.3.3 Subnet Mask . . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . . : 192.168.1.1 Pinging uktnprint1.corp.biz.co.uk [192.168.3.6] with 32 bytes of data: Reply from 192.168.3.6: bytes=32 time=2ms TTL=60 Firewall is off. I'll look into the chance of an IP conflict because it's the only thing I can think of - compare arp caches of each machine. Cheers!

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  • Cisco 678 Will Not Work using PPPoE - Possibly Because I Configured it Incorrectly..?

    - by Brian Stinar
    I am attempting to configure a Cisco 678 because I am totally sick on my Actiontec. However, I am running into some problems. It seems as though the Cisco is able to train the line, but I am unable to ping out. I am all right at programming, but still learning a lot when it comes to being a system administrator. I apologize in advance if I did something ridiculous, or am attempting to configure this device to do something it was not designed to do. It is almost like I am not correctly configuring the device to grab it's IP using PPPoA (like my Actiontec.) The output from "show running" (below) makes me think this too. Below are the commands I ran in order to configure this: # en # set nvram erase # write # reboot # en # set nat enable # set dhcp server enable # set PPP wan0-0 ipcp 0.0.0.0 # set ppp wan0-0 dns 0.0.0.0 # set PPP wan0-0 login xxxxx // My actual login # set PPP wan0-0 password yyyyy // My actual password # set PPP restart enabled # set int wan0-0 close # set int wan0-0 vpi 0 # set int wan0-0 vci 32 # set int wan0-0 open # write # reboot Here is the output from a few commands I thought could provide some useful information: cbos#ping 74.125.224.113 Sending 1 8 byte ping(s) to 74.125.224.113 every 2 second(s) Request timed out cbos#show version Cisco Broadband Operating System CBOS (tm) 678 Software (C678-I-M), Version v2.4.9 - Release Software Copyright (c) 1986-2001 by cisco Systems, Inc. Compiled Nov 17 2004 15:26:29 DMT FULL firmware version G96 NVRAM image at 0x1030f000 cbos#show errors - Current Error Messages - ## Ticks Module Level Message 0 000:00:00:00 PPP Info IPCP Open Event on wan0-0 1 000:00:00:14 ATM Info Wan0 Up 2 000:00:00:14 PPP Info PPP Up Event on wan0-0 3 000:00:01:54 PPP Info PPP Down Event on wan0-0 Total Number of Error Messages: 4 cbos#show interface wan0 wan0 ADSL Physical Port Line Trained Actual Configuration: Overhead Framing: 3 Trellis Coding: Enabled Standard Compliance: T1.413 Downstream Data Rate: 1184 Kbps Upstream Data Rate: 928 Kbps Interleave S Downstream: 4 Interleave D Downstream: 16 Interleave R Downstream: 16 Interleave S Upstream: 4 Interleave D Upstream: 8 Interleave R Upstream: 16 Modem Microcode: G96 DSP version: 0 Operating State: Showtime/Data Mode Configured: Echo Cancellation: Disabled Overhead Framing: 3 Coding Gain: Auto TX Power Attenuation: 0dB Trellis Coding: Enabled Bit Swapping: Disabled Standard Compliance: T1.413 Remote Standard Compliance: T1.413 Tx Start Bin: 0x6 Tx End Bin: 0x1f Data Interface: Utopia L1 Status: Local SNR Margin: 19.0dB Local Coding Gain: 7.5dB Local Transmit Power: 12.5dB Local Attenuation: 46.0dB Remote Attenuation: 31.0dB Local Counters: Interleaved RS Corrected Bytes: 0 Interleaved Symbols with CRC Errors: 2 No Cell Delineation Interleaved: 0 Out of Cell Delineation Interleaved: 0 Header Error Check Counter Interleaved: 0 Count of Severely Errored Frames: 0 Count of Loss of Signal Frames: 0 Remote Counters: Interleaved RS Corrected Bytes: 0 Interleaved Symbols with CRC Errors: 1 No Cell Delineation Interleaved: 0 Header Error Check Counter Interleaved: 0 Count of Severely Errored Frames: 0 Count of Loss of Signal Frames: 0 cbos#show int wan0-0 WAN0-0 ATM Logical Port PVC (VPI 0, VCI 32) is configured. ScalaRate set to Auto AAL 5 UBR Traffic IP Port Enabled cbos#show running Warning: traffic may pause while NVRAM is being accessed [[ CBOS = Section Start ]] NSOS MD5 Enable Password = XXXX NSOS MD5 Root Password = XXXX NSOS MD5 Commander Password = XXXX [[ PPP Device Driver = Section Start ]] PPP Port User Name = 00, "XXXX" PPP Port User Password = 00, XXXX PPP Port Option = 00, IPCP,IP Address,3,Auto,Negotiation Not Required,Negotiable ,IP,0.0.0.0 PPP Port Option = 00, IPCP,Primary DNS Server,129,Auto,Negotiation Not Required, Negotiable,IP,0.0.0.0 PPP Port Option = 00, IPCP,Secondary DNS Server,131,Auto,Negotiation Not Require d,Negotiable,IP,0.0.0.0 [[ ATM WAN Device Driver = Section Start ]] ATM WAN Virtual Connection Parms = 00, 0, 32, 0 [[ DHCP = Section Start ]] DHCP Server = enabled [[ IP Routing = Section Start ]] IP NAT = enabled [[ WEB = Section Start ]] WEB = enabled cbos# wtf...? Thank you all very much for taking the time to read this, and the help.

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  • File Server - Storage configuration: RAID vs LVM vs ZFS something else... ?

    - by privatehuff
    We are a small company that does video editing, among other things, and need a place to keep backup copies of large media files and make it easy to share them. I've got a box set up with Ubuntu Server and 4 x 500 GB drives. They're currently set up with Samba as four shared folders that Mac/Windows workstations can see fine, but I want a better solution. There are two major reasons for this: 500 GB is not really big enough (some projects are larger) It is cumbersome to manage the current setup, because individual hard drives have different amounts of free space and duplicated data (for backup). It is confusing now and that will only get worse once there are multiple servers. ("the project is on sever2 in share4" etc) So, I need a way to combine hard drives in such a way as to avoid complete data loss with the failure of a single drive, and so users see only a single share on each server. I've done linux software RAID5 and had a bad experience with it, but would try it again. LVM looks ok but it seems like no one uses it. ZFS seems interesting but it is relatively "new". What is the most efficient and least risky way to to combine the hdd's that is convenient for my users? Edit: The Goal here is basically to create servers that contain an arbitrary number of hard drives but limit complexity from an end-user perspective. (i.e. they see one "folder" per server) Backing up data is not an issue here, but how each solution responds to hardware failure is a serious concern. That is why I lump RAID, LVM, ZFS, and who-knows-what together. My prior experience with RAID5 was also on an Ubuntu Server box and there was a tricky and unlikely set of circumstances that led to complete data loss. I could avoid that again but was left with a feeling that I was adding an unnecessary additional point of failure to the system. I haven't used RAID10 but we are on commodity hardware and the most data drives per box is pretty much fixed at 6. We've got a lot of 500 GB drives and 1.5 TB is pretty small. (Still an option for at least one server, however) I have no experience with LVM and have read conflicting reports on how it handles drive failure. If a (non-striped) LVM setup could handle a single drive failing and only loose whichever files had a portion stored on that drive (and stored most files on a single drive only) we could even live with that. But as long as I have to learn something totally new, I may as well go all the way to ZFS. Unlike LVM, though, I would also have to change my operating system (?) so that increases the distance between where I am and where I want to be. I used a version of solaris at uni and wouldn't mind it terribly, though. On the other end on the IT spectrum, I think I may also explore FreeNAS and/or Openfiler, but that doesn't really solve the how-to-combine-drives issue.

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  • A failed disk (Pay for professional service or SpinRite?)(new edit)

    - by huggie
    EDIT: After much negotiating and begging and seeing through promotion smoke screen, thanks to the nice representative who took my case, I now know that the engineer has already fixed my NTFS partition (I guess it might be a bad block in the partition table?). She told me that the problem was considered minor, and I should be able to boot normally and just copy stuff out. Whew..I'm glad I didn't agree to the NTD $16,000 deal. New question (should this be in a new thread?): is it safer to use the linux "dd" command or is it better to boot normally into Windows XP and just copy stuff out? EDIT2: Thanks to all the help. I give the best answer to Console as it's most directed related to my question. But many suggestion are helpful and informational. ---- ORIGINAL POST BELOW --- Hi, in my previous post (You don't need to read but it's at http://superuser.com/questions/48838/windows-xp-a-disk-read-error-occurred), I said that my hard disk was not booting and is showing "a disk read error occurred". I took it to a recovery professional. A representative responded today told me that the NTFS partitions have a "NTFS partition system crash". I have no idea what that means. The engineer handling my drive will not be available for contact till tomorrow. Now the company charges me NTD (New Taiwan Dollar) $16,000 to recover lost data, that's kind of a lot considering that my graduate student monthly stipend is currently NTD $32,000 (max. allowed by regulation, may be lower, may change depend on funding). Now I'm weighting in between the options. Option A: let the professional recovers it with the half of my monthly stipend. If file/directories I designated are not recovered I don't pay a penny. (other than the initial examination fee of NTD $1000 which I've already paid.) Option B: let me try SpinRite, if failed, back to Option A. I spoke to the representative at the company they recommended me not to handle it on my own (yeah of course that's what they all want to say, right?), and at the price tag the disk error is probably relatively minor and data recoverable. But the representative really did not have detailed information of the disk failure so I didn't take her recommendation readily. Though one thing I heed was that she said that what they would do is to duplicate the disk before attempting discovery, so there would be no data loss (Is this true? can't duplicating invoke further data loss?). That sounds very good to me. Or maybe a third option: Option C: Negotiate with them to pay them to duplicate the disk hopefully for a much smaller price tag. Let me try SpinRite, if failed, back to Option A. This is a difficult decision. Ultimately I want my data back, but if a cheaper way is available to achieve the same thing... Can operating with SpinRite also corrupt data in someway? I've no idea what happened to my drive. I'll attempt to contact the engineer and hope to get it clarified and make an edit here.

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  • AGENT: The World's Smartest Watch

    - by Rob Chartier
    AGENT: The World's Smartest Watch by Secret Labs + House of Horology Disclaimer: Most if not all of this content has been gleaned from the comments on the Kickstarter project page and comments section. Any discrepancies between this post and any documentation on agentwatches.com, kickstarter.com, etc.., those official sites take precedence. Overview The next generation smartwatch with brand-new technology. World-class developer tools, unparalleled battery life, Qi wireless charging. Kickstarter Page, Comments Funding period : May 21, 2013 - Jun 20, 2013 MSRP : $249 Other Urls http://www.agentwatches.com/ https://www.facebook.com/agentwatches http://twitter.com/agentwatches http://pinterest.com/agentwatches/ http://paper.li/robchartier/1371234640 Developer Story The first official launch of the preview SDK and emulator will happen on 20-Jun-2013.  All development will be done in Visual Studio 2012, using the .NET Micro Framework SDK 2.3.  The SDK will ship with the first round of the expected API for developers along with an emulator. With that said, there is no need to wait for the SDK.  You can download the tooling now and get started with Apps and Faces immediately.  The only thing that you will not be able to work with is the API; but for example, watch faces, you can start building the basic face rendering with the Bitmap graphics drawing in the .NET Micro Framework.   Does it look good? Before we dig into any more of the gory details, here are a few photos of the current available prototype models.   The watch on the tiny QI Charter   If you wander too far away from your phone, your watch will let you know with a vibration and a message, all but one button will dismiss the message.   An app showing the premium weather data!   Nice stitching on the straps, leather and silicon will be available, along with a few lengths to choose from (short, regular, long lengths). On to those gory details…. Hardware Specs Processor 120MHz ARM Cortex-M4 processor (ATSAM4SD32) with secondary AVR co-processor Flash & RAM 2MB of onboard flash and 160KB of RAM 1/4 of the onboard flash will be used by the OS The flash is permanent (non-volatile) storage. Bluetooth Bluetooth 4.0 BD/EDR + LE Bluetooth 4.0 is backwards compatible with Bluetooth 2.1, so classic Bluetooth functions (BD/EDR, SPP/AVRCP/PBAP/etc.) will work fine. Sensors 3D Accelerometer (Motion) ST LSM303DLHC Ambient Light Sensor Hardware power metering Vibration Motor (You can pulse it to create vibration patterns, not sure about the vibration strength - driven with PWM) No piezo/speaker or microphone. Other QI Wireless Charging, no NFC, no wall adapter included Custom LED Backlight No GPS in the watch. It uses the GPS in your phone. AGENT watch apps are deployed and debugged wirelessly from your PC via Bluetooth. RoHS, Pb-free Battery Expected to use a CR2430-sized rechargeable battery – replaceable (Mouser, Amazon) Estimated charging time from empty is 2 hours with provided charger 7 Days typical with Bluetooth on, 30 days with Bluetooth off (watch-face only mode) The battery should last at least 2 years, with 100s of charge cycles. Physical dimensions Roughly 38mm top-to-bottom on the front face 35mm left-to-right on the front face and around 12mm in depth 22mm strap Two ~1/16" hex screws to attach the watch pin The top watchcase material candidates are PVD stainless steel, brushed matte ceramic, and high-quality polycarbonate (TBD). The glass lens is mineral glass, Anti-glare glass lens Strap options Leather and silicon straps will be available Expected to have three sizes Display 1.28" Sharp Memory Display The display stays on 100% of the time. Dimensions: 128x128 pixels Buttons Custom "Pusher" buttons, they will not make noise like a mouse click, and are very durable. The top-left button activates the backlight; bottom-left changes apps; three buttons on the right are up/select/down and can be used for custom purposes by apps. Backup reset procedure is currently activated by holding the home/menu button and the top-right user button for about ten seconds Device Support Android 2.3 or newer iPhone 4S or newer Windows Phone 8 or newer Heart Rate monitors - Bluetooth SPP or Bluetooth LE (GATT) is what you'll want the heart monitor to support. Almost limitless Bluetooth device support! Internationalization & Localization Full UTF8 Support from the ground up. AGENT's user interface is in English. Your content (caller ID, music tracks, notifications) will be in your native language. We have a plan to cover most major character sets, with Latin characters pre-loaded on the watch. Simplified Chinese will be available Feature overview Phone lost alert Caller ID Music Control (possible volume control) Wireless Charging Timer Stopwatch Vibrating Alarm (possibly custom vibrations for caller id) A few default watch faces Airplane mode (by demand or low power) Can be turned off completely Customizable 3rd party watch faces, applications which can be loaded over bluetooth. Sample apps that maybe installed Weather Sample Apps not installed Exercise App Other Possible Skype integration over Bluetooth. They will provide an AGENT app for your smartphone (iPhone, Android, Windows Phone). You'll be able to use it to load apps onto the watch.. You will be able to cancel phone calls. With compatible phones you can also answer, end, etc. They are adopting the standard hands-free profile to provide these features and caller ID.

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  • Understanding and Controlling Parallel Query Processing in SQL Server

    Data warehousing and general reporting applications tend to be CPU intensive because they need to read and process a large number of rows. To facilitate quick data processing for queries that touch a large amount of data, Microsoft SQL Server exploits the power of multiple logical processors to provide parallel query processing operations such as parallel scans. Through extensive testing, we have learned that, for most large queries that are executed in a parallel fashion, SQL Server can deliver linear or nearly linear response time speedup as the number of logical processors increases. However, some queries in high parallelism scenarios perform suboptimally. There are also some parallelism issues that can occur in a multi-user parallel query workload. This white paper describes parallel performance problems you might encounter when you run such queries and workloads, and it explains why these issues occur. In addition, it presents how data warehouse developers can detect these issues, and how they can work around them or mitigate them.

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  • Parallelism in .NET – Part 16, Creating Tasks via a TaskFactory

    - by Reed
    The Task class in the Task Parallel Library supplies a large set of features.  However, when creating the task, and assigning it to a TaskScheduler, and starting the Task, there are quite a few steps involved.  This gets even more cumbersome when multiple tasks are involved.  Each task must be constructed, duplicating any options required, then started individually, potentially on a specific scheduler.  At first glance, this makes the new Task class seem like more work than ThreadPool.QueueUserWorkItem in .NET 3.5. In order to simplify this process, and make Tasks simple to use in simple cases, without sacrificing their power and flexibility, the Task Parallel Library added a new class: TaskFactory. The TaskFactory class is intended to “Provide support for creating and scheduling Task objects.”  Its entire purpose is to simplify development when working with Task instances.  The Task class provides access to the default TaskFactory via the Task.Factory static property.  By default, TaskFactory uses the default TaskScheduler to schedule tasks on a ThreadPool thread.  By using Task.Factory, we can automatically create and start a task in a single “fire and forget” manner, similar to how we did with ThreadPool.QueueUserWorkItem: Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This provides us with the same level of simplicity we had with ThreadPool.QueueUserWorkItem, but even more power.  For example, we can now easily wait on the task: // Start our task on a background thread var task = Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); // Do other work on the main thread, // while the task above executes in the background this.ExecuteWorkSynchronously(); // Wait for the background task to finish task.Wait(); TaskFactory simplifies creation and startup of simple background tasks dramatically. In addition to using the default TaskFactory, it’s often useful to construct a custom TaskFactory.  The TaskFactory class includes an entire set of constructors which allow you to specify the default configuration for every Task instance created by that factory.  This is particularly useful when using a custom TaskScheduler.  For example, look at the sample code for starting a task on the UI thread in Part 15: // Given the following, constructed on the UI thread // TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // When inside a background task, we can do string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); This is actually quite a bit more complicated than necessary.  When we create the uiScheduler instance, we can use that to construct a TaskFactory that will automatically schedule tasks on the UI thread.  To do that, we’d create the following on our main thread, prior to constructing our background tasks: // Construct a task scheduler from the current SynchronizationContext (UI thread) var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // Construct a new TaskFactory using our UI scheduler var uiTaskFactory = new TaskFactory(uiScheduler); If we do this, when we’re on a background thread, we can use this new TaskFactory to marshal a Task back onto the UI thread.  Our previous code simplifies to: // When inside a background task, we can do string status = GetUpdatedStatus(); // Update our UI uiTaskFactory.StartNew( () => statusLabel.Text = status); Notice how much simpler this becomes!  By taking advantage of the convenience provided by a custom TaskFactory, we can now marshal to set data on the UI thread in a single, clear line of code!

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