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  • What should I learn that I missed by not going to school?

    - by BinaryMuse
    I'm a software engineer at a local university, and I feel I'm able to competently do my job, but recently I've been interested in "filling in" the gaps in my knowledge. I suspect I would have learned some of this in school; for example, I don't have a lot of knowledge of sorting algorithms (something I feel is pretty common in college). So, what knowledge am I likely missing by not going to college that I could study on my own? Bonus points for listing resources that might put me on the right track! Some background: I've programmed in PHP, Java, and Ruby (more seriously in Java and Ruby than PHP); I have some experience with C/C++, though my workload doesn't really lend itself to those languages; I work mostly (recently) with the web, using frameworks such as CakePHP and Rails. I'm familiar with SQL (though probably not with some of the theory). Note: The university I work for has no technical classes, so taking courses on the university's dime is a great idea but not possible for me. :)

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  • No apparent reason for high load average

    - by Oz.
    We have several web servers running on Amazon (ec2) c1.xlarge, over Amazon AMI. The servers are duplicates of each other, running the exact same hardware and software. Each server spec is: 7 GB of memory 20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each) 1690 GB of instance storage 64-bit platform I/O Performance: High API name: c1.xlarge A couple of weeks ago we have run a yum upgrade on one of the servers. Starting on this upgrade the upgraded server started showing a high load average. Needless to say, we did not update the other servers and we can not do so until we understand the reason for this behavior. The strange thing is that when we compare the servers using top or iostat, we can not find the reason for the high load. Note that we have moved traffic from the "problematic" server to the others, which have made the "problematic" server less crowded in terms of requests, and still his load is higher. Do you have any idea what could it be, or where else can we check? Many thanks for the help! Oz. # # proper server # w command # 00:42:26 up 2 days, 19:54, 2 users, load average: 0.41, 0.48, 0.49 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT pts/1 82.80.137.29 00:28 14:05 0.01s 0.01s -bash pts/2 82.80.137.29 00:38 0.00s 0.02s 0.00s w # # proper server # iostat command # Linux 3.2.12-3.2.4.amzn1.x86_64 _x86_64_ (8 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 9.03 0.02 4.26 0.17 0.13 86.39 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn xvdap1 1.63 1.50 55.00 367236 13444008 xvdfp1 4.41 45.93 70.48 11227226 17228552 xvdfp2 2.61 2.01 59.81 491890 14620104 xvdfp3 8.16 14.47 94.23 3536522 23034376 xvdfp4 0.98 0.79 45.86 192818 11209784 # # problematic server # w command # 00:43:26 up 2 days, 21:52, 2 users, load average: 1.35, 1.10, 1.17 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT pts/0 82.80.137.29 00:28 15:04 0.02s 0.02s -bash pts/1 82.80.137.29 00:38 0.00s 0.05s 0.00s w # # problematic server # iostat command # Linux 3.2.20-1.29.6.amzn1.x86_64 _x86_64_ (8 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 7.97 0.04 3.43 0.19 0.07 88.30 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn xvdap1 2.10 1.49 76.54 374660 19253592 xvdfp1 5.64 40.98 85.92 10308946 21612112 xvdfp2 3.97 4.32 93.18 1087090 23439488 xvdfp3 10.87 30.30 115.14 7622474 28961720 xvdfp4 1.12 0.28 65.54 71034 16487112

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  • High quality / high speed dvd reader for Mac Pro

    - by deadprogrammer
    I have a high end Mac pro, but one thing in is that I'm unhappy with is a DVD drive. It's a Hitachi GH41N. Apple calls it a "superdrive", but it's anything but. The damn thing makes an amazing amount of noise, and isn't too fast either. What I want is a state of the art, fast, quiet DVD reader, preferably not even a burner. What should I get?

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  • The Legend of Zelda – 1980s High School Style [Video]

    - by Asian Angel
    What happens when you mix the Legend of Zelda with the 80s high school scene? Something fun and cheesy that makes you wish there really was a movie based on this! From YouTube: In this charming critically-acclaimed tale of first love, Link, an eternal optimist and adventurer, seeks to capture the heart of Zelda, an unattainable high school beauty and straight-A student. He surprises just about everyone-including himself-when she returns the sentiment. But the high school’s over-possessive, megalomaniacal Principal Ganondorf doesn’t approve and it’s going to take more than just the power of love to conquer all. The Legend of Zelda (1987) Trailer [via Geeks are Sexy] Latest Features How-To Geek ETC How To Remove People and Objects From Photographs In Photoshop Ask How-To Geek: How Can I Monitor My Bandwidth Usage? Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff Here’s a Super Simple Trick to Defeating Fake Anti-Virus Malware How to Change the Default Application for Android Tasks Stop Believing TV’s Lies: The Real Truth About "Enhancing" Images The Legend of Zelda – 1980s High School Style [Video] Suspended Sentence is a Free Cross-Platform Point and Click Game Build a Batman-Style Hidden Bust Switch Make Your Clock Creates a Custom Clock for your Android Homescreen Download the Anime Angels Theme for Windows 7 CyanogenMod Updates; Rolls out Android 2.3 to the Less Fortunate

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  • High server load - [jbd2/md1-8] using 99.99% IO

    - by Alex
    I've been having spike in load over the last week. This usually occurs once or twice a day. I've managed to identify from iotop that [jbd2/md1-8] is using 99.99 % IO. During the high load times there is no high traffic to the server. Server specs are: AMD Opteron 8 core 16 GB RAM 2x2.000 GB 7.200 RPM HDD Software Raid 1 Cloudlinux + Cpanel Mysql is properly tuned Apart from the spikes, the load usually is around 0.80 at most. I've searched around but can't find what [jbd2/md1-8] does exactly. Has anyone had this problem or does anyone know a possible solution? Thank you. UPDATE: TIME TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND 16:05:36 399 be/3 root 0.00 B/s 38.76 K/s 0.00 % 99.99 % [jbd2/md1-8]

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  • How to teach game programming at school ?

    - by jokoon
    I'm in this private school right now, and apart from my progressive stoppage of anti-depressants, I'm having an hard time focusing on what the school wants me to do. The school has a professional contract for a game we have to do with Unity. I don't really learn anything new while using unity, so I don't like using it. We recently learned how to use DirectX, and we have to do some sort of Gradius-precursor clone (Parsec) with directX, in 3D: this annoys me, and I'm currently learning to use Ogre3D by myself by making some game. The teacher is an engineer, and all of us won't be engineers. How would you teach game programming ?

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  • Stuff you learned in school, that you have never used again?

    - by Mercfh
    Obviously we learn plenty of things in our University/College/Whatever that probably don't apply to everyday use, but is there anything that stands out particularly? Maybe something that was concentrated ALOT on? For me it was def. 2 things: OO Concepts and Pointers I still use OO, but not nearly to the amount people made it out to be, i can see where it'd be useful but in my line of work we don't have huge amounts of classes, maybe a couple at most. And there certainly isn't much OO reuse (i finally figured out what that means lol) Pointers are another thing, again I can see where they'd be useful...however I barely barely ever touch them, nor do the others I work with. I guess language choice has alot to do with that but still. What about you guys? edit: For those who are asking I work for a Large Printer company, and most of the Applications we work on are Java+XML and Actionscript for "Printer Apps". But we are moving towards other languages (think like webkits and stuff). So the Code amounts per parts are quite small. I never say OO wasn't useful I just said I personally havent seen it used in my workplace much.

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  • Cheapest High Available Web Server [closed]

    - by xyz
    I would like to create a high-available setup (e.g. a small cluster) for a webserver, i.e. it will run Apache, PHP and MySQL. There will be between 2-8 small websites running with only very little traffic and workload. High availability is however very important. I don't want to be dependent on 1 datacenter, so there must be a minimum of 2 servers placed in different datacenters, and if one server goes down, the user must experience no or only a minimum of downtime - and no data loss. I have considered Amazon AWS using their Elastic Load Balancing, since it is possible to buy 2 EC2 instances in 2 availability zones and set up load balancing and RDS (Multi-AZ). However this seems rather expensive. Using the AWS price calculator http://calculator.s3.amazonaws.com/calc5.html it totals to 185$/month the first year (including the free tier). Are my calculations incorrect or is there a cheaper way to make this HA setup? Best regards

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  • How to setup Wordpress High Availability

    - by Ketam
    I have installed Galera Cluster on 3 cluster + 1 management. I wanted to make it like this, Server1: Home (www.domain.com) Server2: For BBpress/Forum (Forum Tab Menu will forward to forum.domain.com) Server3: BuddyPress Activity (Social Tab Menu will forward to social.domain.com) The purpose I am doing this is to distribute my resource and load balancing each other at same time. However, I have difficulty to setup Apache Load-Balancing/mod_proxy/clustering or any suitable to have high availability WordPress. Any best suggestion/solution to make high availability WordPress? Or how to? And another question is I tried to copy whole WordPress files & folders to Server2 connecting to local database (same data inside since it is already on Galera Cluster) but the page blank. Any advice? OS: Centos 6.2 Thanks in advanced.

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  • No clue for high load average on top

    - by Oz.
    We have several machines on Amazon (ec2) of the type c1.xlarge with 16 cpus, running the Amazon AMI. Details on the machine: 7 GB of memory 20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each) 1690 GB of instance storage 64-bit platform I/O Performance: High API name: c1.xlarge One out of the several machines is showing a high load average, since we have run the last yum upgrade a couple of weeks a go. We did not yet update the other machines, and everything looks normal on them. The strange thing is that the top command not showing any hint for the cause of the load. CPUs are 4.8%us, 1.1%sy, 0.0%ni, 94.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st(see below). Mem is about 1.5GB free. Any idea what could it be, or where else can we check? Many thanks for the help. # # top # top - 07:57:42 up 4:18, 1 user, load average: 1.36, 1.45, 1.47 Tasks: 131 total, 1 running, 130 sleeping, 0 stopped, 0 zombie Cpu(s): 4.8%us, 1.1%sy, 0.0%ni, 94.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 7120092k total, 5644920k used, 1475172k free, 532888k buffers Swap: 0k total, 0k used, 0k free, 3463936k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1557 mysql 20 0 1829m 374m 6448 S 14.3 5.4 11:15.09 mysqld 6655 apache 20 0 416m 49m 3744 S 9.3 0.7 0:04.85 httpd 27683 apache 20 0 421m 54m 3708 S 9.0 0.8 0:00.99 httpd 6682 apache 20 0 424m 57m 3788 S 8.3 0.8 0:03.81 httpd 16816 apache 20 0 419m 51m 3760 S 4.3 0.7 0:04.09 httpd 22182 apache 20 0 417m 50m 3756 S 1.7 0.7 0:06.34 httpd 219 root 20 0 0 0 0 S 0.3 0.0 0:00.34 kworker/7:1 699 root 20 0 0 0 0 S 0.3 0.0 0:00.40 kworker/3:1 1 root 20 0 19376 1508 1212 S 0.0 0.0 0:00.29 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:00.71 ksoftirqd/0

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  • High CPU from httpd process

    - by KHWeb
    I am currently getting high CPU on a server that is just running a couple of sites with very low traffic. One of the sites is in still development going live soon. However, this site is very very slow...When browsing through its pages I can see that the CPU goes from 30% to 100% for httpd (see top output below). I have tuned httpd & MySQL, Apache Solr, Tomcat for high performance, and I am using APC. Not sure what to do from here or how to find the culprit as I have a bunch of messages on the httpd log and have been chasing dead ends for some time...any help is greatly appreciated. Server: AuthenticAMD, Quad-Core AMD Opteron(tm) Processor 2352, RAM 16GB Linux 2.6.27 64-bit, Centos 5.5 Plesk 9.5.4, MySQL 5.1.48, PHP 5.2.17 Apache/2.2.3 (CentOS) DAV/2 mod_jk/1.2.15 mod_ssl/2.2.3 OpenSSL/0.9.8e-fips-rhel5 PHP/5.2.17 mod_perl/2.0.4 Perl/v5.8.8 Tomcat6-6.0.29-1.jpp5, Tomcat-native-1.1.20-1.el5, Apache Solr top 17595 apache 20 0 1825m 507m 10m R 100.4 3.2 0:17.50 httpd 17596 apache 20 0 1565m 247m 9936 R 83.1 1.5 0:10.86 httpd 17598 apache 20 0 1430m 110m 6472 S 54.5 0.7 0:08.66 httpd 17599 apache 20 0 1438m 124m 12m S 37.2 0.8 0:11.20 httpd 16197 mysql 20 0 13.0g 2.0g 5440 S 9.6 12.6 297:12.79 mysqld 17617 root 20 0 12748 1172 812 R 0.7 0.0 0:00.88 top 8169 tomcat 20 0 4613m 268m 6056 S 0.3 1.7 6:40.56 java httpd error_log [debug] prefork.c(991): AcceptMutex: sysvsem (default: sysvsem) [info] mod_fcgid: Process manager 17593 started [debug] proxy_util.c(1854): proxy: grabbed scoreboard slot 0 in child 17594 for worker proxy:reverse [debug] proxy_util.c(1967): proxy: initialized single connection worker 0 in child 17594 for (*) [debug] proxy_util.c(1854): proxy: grabbed scoreboard slot 0 in child 17595 for worker proxy:reverse [debug] proxy_util.c(1873): proxy: worker proxy:reverse already initialized [notice] child pid 22782 exit signal Segmentation fault (11) [error] (43)Identifier removed: apr_global_mutex_lock(jk_log_lock) failed [debug] util_ldap.c(2021): LDAP merging Shared Cache conf: shm=0x7fd29a5478c0 rmm=0x7fd29a547918 for VHOST: example.com [info] APR LDAP: Built with OpenLDAP LDAP SDK [info] LDAP: SSL support available [info] Init: Seeding PRNG with 256 bytes of entropy [info] Init: Generating temporary RSA private keys (512/1024 bits) [info] Init: Generating temporary DH parameters (512/1024 bits) [debug] ssl_scache_shmcb.c(374): shmcb_init allocated 512000 bytes of shared memory [debug] ssl_scache_shmcb.c(554): entered shmcb_init_memory() [debug] ssl_scache_shmcb.c(576): for 512000 bytes, recommending 4265 indexes [debug] ssl_scache_shmcb.c(619): shmcb_init_memory choices follow [debug] ssl_scache_shmcb.c(621): division_mask = 0x1F [debug] ssl_scache_shmcb.c(623): division_offset = 96 [debug] ssl_scache_shmcb.c(625): division_size = 15997 [debug] ssl_scache_shmcb.c(627): queue_size = 2136 [debug] ssl_scache_shmcb.c(629): index_num = 133 [debug] ssl_scache_shmcb.c(631): index_offset = 8 [debug] ssl_scache_shmcb.c(633): index_size = 16 [debug] ssl_scache_shmcb.c(635): cache_data_offset = 8 [debug] ssl_scache_shmcb.c(637): cache_data_size = 13853 [debug] ssl_scache_shmcb.c(650): leaving shmcb_init_memory()

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  • High Availability with 2 servers?

    - by Tom R
    Is it possible to have a high availability setup with 2 servers? Running Windows Web Server 2008 and MSSQL Web Edition (as I know Express isn't supported)? Getting to the point where our one dedicated server needs scaled out and going to a second server already more than doubles the cost as need to use Web Edition rather than Express (db is only 500MB).

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  • high resolution on small screen size

    - by vishesh
    I have recently got an intel ultrabook,but its screen size is 13.3' and the native resolution is 1600X900.So the problem is that the letters that appear on screen are very small.Reducing resolution blurs the display and making everything bigger also doesn't feel very good.is there a way to get around this problem without changing hardware. I am even ok with this high resolution but I am concerned about the harmful effects it might have on my eyes in long term. Any advice will be very useful.Please help

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  • Why not have a High Level Language based OS? Are Low Level Languages more efficient?

    - by rtindru
    Without being presumptuous, I would like you to consider the possibility of this. Most OS today are based on pretty low level languages (mainly C/C++) Even the new ones such as Android uses JNI & underlying implementation is in C In fact, (this is a personal observation) many programs written in C run a lot faster than their high level counterparts (eg: Transmission (a bittorrent client on Ubuntu) is a whole lot faster than Vuze(Java) or Deluge(Python)). Even python compilers are written in C, although PyPy is an exception. So is there a particular reason for this? Why is it that all our so called "High Level Languages" with the great "OOP" concepts can't be used in making a solid OS? So I have 2 questions basically. Why are applications written in low level languages more efficient than their HLL counterparts? Do low level languages perform better for the simple reason that they are low level and are translated to machine code easier? Why do we not have a full fledged OS based entirely on a High Level Language?

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  • GlusterFs - high load 90-107% CPU

    - by Sara
    I try and try and try to performance and fix problem with gluster, i try all. I served on gluster webpages, php files, images etc. I have problem after update from 3.3.0 to 3.3.1. I try 3.4 when i think maybe fix it but still the same problem. I temporarily have 1 brick, but before upgrade will be fine. Config: Volume Name: ... Type: Replicate Volume ID: ... Status: Started Number of Bricks: 0 x 2 = 1 Transport-type: tcp Bricks: Brick1: ...:/... Options Reconfigured: cluster.stripe-block-size: 128KB performance.cache-max-file-size: 100MB performance.flush-behind: on performance.io-thread-count: 16 performance.cache-size: 256MB auth.allow: ... performance.cache-refresh-timeout: 5 performance.write-behind-window-size: 1024MB I use fuse, hmm "Maybe the high load is due to the unavailable brick" i think about it, but i cant find information on how to safely change type of volume. Maybe u know how?

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  • Providing high availability and failover using MySQL on EC2

    - by crb
    I would like to have a highly-available MySQL system, with automatic failover, running on Amazon EC2 instances. The standard approach to solving this is problem Heartbeat + DRBD, but I've found a lot of posts suggesting DRBD doesn't work on EC2, though none saying exactly why. Obviously, a serial heartbeat or distinct network is out of the question in the virtualised environment. It would also be good to have the different servers be in different availability zones, but we're getting into a much harder problem there. What are peoples' opinion on having a high uptime solution in "the cloud"?

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  • Most suitable high availability solution

    - by Alex Bagnolini
    My company is hosting a website in a server with IIS, SQL Server and a 3rd party windows service (written in C#, source code available for amendments). We bought a new identical server, composed by: 1x Quad Core, 12GB RAM, 4x160GB SATA Raid 5, Windows Server 2008 R2 Datacenter, Public IP. We aim to put all webpages and the 3rd party windows service in an high-availability state. After some lab-testing on how to configure Failover Clustering and Hyper-V, we have deep doubts on what the "best" solution would be, by "best" meaning maintainable and able to correctly handle a physical server failure. Any suggestion on how we should configure the two servers? We don't need all the configuration's step, just an hint on the right direction to follow.

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  • Unable to watch a high resolution and high frame rate video

    - by Abhijith Madhav
    I have a video of a tennis match whose Resolution = 1280 * 720 Codec = H264 Frame rate = 50fps (Copy paste from info given by totem media player) My laptop is not powerful enough to play this video smoothly. How can I reduce the frame-rate of this video so that my laptop can play it? I have observed that my laptop can play videos with 25fps without an issue. I use ubuntu. I wouldn't mind using windows to edit/re-encode this video.

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  • VMware Virtual vCenter and High Availability

    - by rufo
    To continue with this question: Should be Vmware vCenter server high available? According to the response there even if vCenter is down HA will continue to work. So, if my vCenter is a VM, using the express sql edition in the same VM, and that VM is hosted in the same cluster it manages (and the cluster is setup for HA): Am I correct to assume that if the host that hosts the vCenter goes down HA will vmotion the vCenter VM to another host and it will continue to function? BTW: my environment is small, two ESXi 5.0 hosts, with about 50 VMs, using iSCSI shared storaged for everything.

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  • High availability for Windows Service under Windows Server 2003

    - by empi
    Hi. I have a following situation: I need to deploy a windows service that listens for incoming request on tcp port (basically WCF service). I have a High Availability requirement - the service must be deployed on two servers and if the service stops (only the service, not the whole server) on one server, all the requests must be redirected to the second one. For me it looks like a basic failover scenario. How can I achieve this on Windows Server 2003? Should I use Microsoft Cluster Service or Network Load Balancing? The important part is that the process of swapping the servers should not concern the clients (the client must see only single address / single host or domain name). Thanks in advance for help.

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  • Very fast Laptop Heating due to very high CPU usage by dwm.exe

    - by Sushan Shrestha
    My laptop gets heated very fast and when I check the task manager, I find dwm.exe consuming very high CPU (mostly 100%). In the beginning I found the message "The graphic adapter has been stopped and recovered".Also I am getting one error message "Cidaemon.exe has stopped working" very frequently. During this period also, cpu usage is 100% which is consumed by dwm.exe. I have run ccleaner and Kingsoft PC doctor monitor to fix the register problem but the problem has not been solved. My display adaptor is : NVIDIA NVS 5200M. After the driver update, I am not getting "The graphic adapter has been stopped and recovered" but dwm.exe is still consuming 100% CPU one time in about 5 mins. Multiple restarts has not helped. Laptop Model: Dell Latitude E6430. Thanks in advance.

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  • Providing high availability and failover using MySQL on EC2

    - by crb
    I would like to have a highly-available MySQL system, with automatic failover, running on Amazon EC2 instances. The standard approach to solving this is problem Heartbeat + DRBD, but I've found a lot of posts suggesting DRBD doesn't work on EC2, though none saying exactly why. Obviously, a serial heartbeat or distinct network is out of the question in the virtualised environment. It would also be good to have the different servers be in different availability zones, but we're getting into a much harder problem there. What are peoples' opinion on having a high uptime solution in "the cloud"? Note: This question was asked before RDS with multi-AZ was announced, which is the nice automatic answer for today's modern IT professional. :)

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  • Happy New Year! Back to school :)

    - by Jim Wang
    A brand new year is upon us and it’s time to get cracking with WebMatrix again…and go back to school :).  Last year we ran a successful product walkthrough for WebMatrix Beta 2 with our students from around the world, gathering awesome feedback for the final version of WebMatrix which is coming soon!  I’d like to take this chance to thank all the students who participated in this effort…you have really helped make the final product much better than it would have been otherwise. In 2011, we’re looking, as always, at bigger and better things.  One of the ideas that has been floating around is the concept of a WebMatrix college course that you could take for actual credit.  Of course, this is going to require coordination with college educators, but we think we’re up to the challenge :) If your school is still using an antiquated language to teach their web development 101 course, and you’d like to switch to WebMatrix, we’d like to hear your voice – better yet if you have contacts from your school and would like to be one of the first to give the program a try!  Comment on this post or email wptsdrext at microsoft.com.  We look forward to partnering with you guys ^^.

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  • Linux Tuning for High Traffic JBoss Server with LDAP Binds

    - by Levi Stanley
    I'm configuring a high traffic Linux server (RedHat) and running into a limit I haven't been able to track down. I need to be able to handle sustained 300 requests per second throughput using Nginx and JBoss. The point of this server is to run checks on a user's account when that user signs in. Each request goes through Nginx to JBoss (specifically Torquebox with JBoss A7 with a Sinatra app) and then makes an LDAP request to bind that user and retrieve several attributes. It is during the bind that these errors occur. I'm able to reproduce this going directly to JBoss, so that rules out Nginx at least. I get a variety of error messages, though oddly JBoss stopped writing to the log file recently. It used to report errors about creating native threads. Now I just see "java.net.SocketException: Connection reset" and "org.apache.http.conn.HttpHostConnectException: Connection to http://my.awesome.server:8080 refused" as responses in jmeter. To the best of my knowledge, I have plenty of available file handles, processes, sockets, and ports, yet the issue persists. Unfortunately, I have very little experience tuning servers. I've found a couple useful documents - Ipsysctl tutorial 1.0.4 and Linux Tuning - but those documents are a bit over my head (and just entering the the configuration described in Linux Tuning doesn't fix my issue. Here are the configuration changes I've tried (webproxy is the user that runs Nginx and JBoss): /etc/security/limits.conf webproxy soft nofile 65536 webproxy hard nofile 65536 webproxy soft nproc 65536 webproxy hard nproc 65536 root soft nofile 65536 root hard nofile 65536 root soft nproc 65536 root hard nofile 65536 First attempt /etc/sysctl.conf sysctl net.core.somaxconn = 8192 sysctl net.ipv4.ip_local_port_range = 32768 65535 sysctl net.ipv4.tcp_fin_timeout = 15 sysctl net.ipv4.tcp_keepalive_time = 1800 sysctl net.ipv4.tcp_keepalive_intvl = 35 sysctl net.ipv4.tcp_tw_recycle = 1 sysctl net.ipv4.tcp_tw_reuse = 1 Second attempt /etc/sysctl.conf net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 net.ipv4.tcp_rmem = 4096 87380 16777216 net.ipv4.tcp_wmem = 4096 65536 16777216 net.core.netdev_max_backlog = 30000 net.ipv4.tcp_congestion_control=htcp net.ipv4.tcp_mtu_probing=1 Any ideas what might be happening here? Or better yet, are there some good documentation resources designed for beginners?

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  • Large, high performance object or key/value store for HTTP serving on Linux

    - by Tommy
    I have a service that serves images to end users at a very high rate using plain HTTP. The images vary between 4 and 64kbytes, and there are 1.300.000.000 of them in total. The dataset is about 30TiB in size and changes (new objects, updates, deletes) make out less than 1% of the requests. The number of requests pr. second vary from 240 to 9000 and is dispersed pretty much all over, with few objects being especially "hot". As of now, these images are files on a ext3 filesystem distributed read only across a large amount of mid range servers. This poses several problems: Using a fileysystem is very inefficient since the metadata size is large, the inode/dentry cache is volatile on linux and some daemons tend to stat()/readdir() it's way through the directory structure, which in my case becomes very expensive. Updating the dataset is very time consuming and requires remounting between set A and B. The only reasonable handling is operating on the block device for backup, copying, etc. What I would like is a deamon that: speaks HTTP (get, put, delete and perhaps update) stores data it in an efficient structure. The index should remain in memory, and considering the amount of objects, the overhead must be small. The software should be able to handle massive connections with slow (if any) time needed to ramp up. Index should be read in memory at startup. Statistics would be nice, but not mandatory. I have experimented a bit with riak, redis, mongodb, kyoto and varnish with persistent storage, but I haven't had the chance to dig in really deep yet.

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