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• apache & load balancing?

  - by Mani

  In apache, mod_proxy_balancer support loan balancing in the easiest way. My question is: Please refer the https://blogs.oracle.com/oswald/entry/easy_http_load_balancing_with When the result the request is processed by workers (load balancing nodes), it comes to load balancing server and then go to client or directly from workers it goes ? plz answer me. Example: Method 1: Web Client -- Load Balancer - Worker - Load Balancer - Web Client OR Method 2: Web Client -- Load Balancer - Worker - Web Client What is happening in apache load balancer ?

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• apache2 + mod_fastcgi + suexec + php5.2 = unstable on high load

  I am hosting several (~30) different sites on one server with apache2+fastcgi+suexec+php5. Sites have different loads and different execution times of their scripts (some of them process request for 5-7 seconds, some <1sek). Sometimes when single site receives very high load (all php instances of this site are created and used) - whole apache server hangs. Apache (worker mpm) creates new processes up to the upper limit. It looks like it is starting to queue ALL new request for EVERY site, not only the one that has high load and quickly achieves process limits... restart of apache solves the problem... config: FastCgiConfig -singleThreshold 1 -multiThreshold 10 -listen-queue-depth 30 -maxProcesses 80 -maxClassProcesses 12 -idle-timeout 30 -pass-header HTTP_AUTHORIZATION -pass-header If-Modified-Since -pass-header If-None-Match (earlier have default -listen-queue-depth = 100, but it didn't change anything...) Any suggestions? Another question - how is implemented this listen queue? is it one queue for whole apache, or unique queue for every defined php apllication (suexec site)? I would like to achieve something like this: when one site receives high load and its queue is full - server bounces next request, but only for this one site.. Other sites should work properly...

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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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• ubuntu's average load never below "0.00 0.01 0.05"

  - by Karma Fusebox

  I have several ubuntu 12.04 VMs running on a ubuntu 12.04 KVM host. Those of the virtual machines that are totally idle with no services (except syslog and the other "small" standard stuff of a fresh installation) show a constant load of "0.00 0.01 0.05" in top/htop as average 1/5/15. When there are "real" applications running, the load averages behave perfectly normal but they never fall below the mentioned values. While this doesn't affect performance at all and could easily be ignored, it screws up the monitoring graphs in a very annoying way: (Notice how load15 behaves nicely if 0.05 for a short time in the right half of the pic) Unfortunately I don't know what diagnostic outputs might be helpful for you, so here's some default stuff: # top top - 16:31:01 up 1:05, 1 user, load average: 0.00, 0.01, 0.05 Tasks: 62 total, 1 running, 61 sleeping, 0 stopped, 0 zombie Cpu(s): 0.2%us, 0.2%sy, 0.0%ni, 99.2%id, 0.5%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1019464k total, 73452k used, 946012k free, 6140k buffers Swap: 0k total, 0k used, 0k free, 22504k cached . # free -m total used free shared buffers cached Mem: 995 72 923 0 6 21 -/+ buffers/cache: 43 951 Swap: 0 0 0 . # iostat -x /dev/vda Linux 3.2.0-32-virtual (vm3) 11/15/2012 _x86_64_ (2 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 0.25 0.00 0.65 0.20 0.24 98.66 Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util vda 0.14 0.12 0.51 0.22 6.74 1.46 22.50 0.02 23.26 20.64 29.30 7.63 0.56 Need something else? Has anyone ever seen this behavior? Might this be a bug in kvm/ubuntu/kernel 3.x in the end? Thanks a lot!

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• Why can't I access a webserver through a load balancer on my local network?

  - by Karptonite

  When I try to use curl (or wget, lynx, etc) to connect from a server on our local network to our website, which is on a local server behind a CoyotePoint load balancer, curl fails. Ping does not have this problem. When I curl directly to any of the servers behind that load balancer (from and to the same local network), I also have no problem. It doesn't matter whether the local server I'm curling from is behind the load balancer or not. Does anyone have any idea why I can't access my webserver through the load balancer on my local network?

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• How to understand the memory usage and load average in linux server

  - by Tim

  Hi, I am using a linux server which has 128GB of memory and 24 cores. I use top to see how much it is used. Its output is pasted at the end of the post. Here are two questions: (1) I see that each of the running processes occupies a very small percentage of memory (%MEM no more than 0.2%, and most just 0.0%), but how the total memory is almost used as in the fourth line of output ("Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers")? The sum of used percentage of memory over all processes seems unlikely to achieve almost 100%, doesn't it? (2) how to understand the load average on the first line ("load average: 14.04, 14.02, 14.00")? Thanks and regards! Edit: Thanks! I also really like to hear some rough numbers based on used percentage of memory to determine if a server is heavily loaded, since I once became the one who cramed the server without understanding the current load. Is swap regarded as almost the same as memory? For example, when memory and swap are almost of same size, if the memory is almost running out but the swap is still largely free, may I just view it as if the used percentage of memory + swap is still not high and run other new processes? How would you consider together CPU or memory (or memory + swap) usage? Do you become worried if either of them reaches too high or both? Output of top: $ top top - 12:45:33 up 19 days, 23:11, 18 users, load average: 14.04, 14.02, 14.00 Tasks: 484 total, 12 running, 472 sleeping, 0 stopped, 0 zombie Cpu(s): 36.7%us, 19.7%sy, 0.0%ni, 43.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers Swap: 63111312k total, 500556k used, 62610756k free, 124437752k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 6529 sanchez 18 -2 1075m 219m 13m S 100 0.2 13760:23 MATLAB 13210 timothy 18 -2 48336 37m 1216 R 100 0.0 3:56.75 absurdity 13888 timothy 18 -2 48336 37m 1204 R 100 0.0 2:04.89 absurdity 14542 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.34 absurdity 14544 timothy 18 -2 2888 2076 400 R 100 0.0 1:06.14 gatherData 6183 sanchez 18 -2 1133m 195m 13m S 100 0.2 13676:04 MATLAB 6795 sanchez 18 -2 1079m 210m 13m S 100 0.2 13734:26 MATLAB 10178 timothy 18 -2 48336 37m 1204 R 100 0.0 11:33.93 absurdity 12438 timothy 18 -2 48336 37m 1216 R 100 0.0 5:38.17 absurdity 13661 timothy 18 -2 48336 37m 1216 R 100 0.0 2:44.13 absurdity 14098 timothy 18 -2 48336 37m 1204 R 100 0.0 1:58.31 absurdity 14335 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.93 absurdity 14765 timothy 18 -2 48336 37m 1196 R 99 0.0 0:32.57 absurdity 13445 timothy 18 -2 48336 37m 1216 R 99 0.0 3:01.37 absurdity 28990 root 20 0 0 0 0 S 2 0.0 65:50.21 pdflush 12141 tim 18 -2 19380 1660 1024 R 1 0.0 0:04.04 top 1240 root 15 -5 0 0 0 S 0 0.0 16:07.11 kjournald 9019 root 20 0 296m 4460 2616 S 0 0.0 82:19.51 kdm_greet 1 root 20 0 4028 728 592 S 0 0.0 0:03.11 init 2 root 15 -5 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root RT -5 0 0 0 S 0 0.0 0:01.01 migration/0 4 root 15 -5 0 0 0 S 0 0.0 0:08.13 ksoftirqd/0 5 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT -5 0 0 0 S 0 0.0 17:27.31 migration/1 7 root 15 -5 0 0 0 S 0 0.0 0:01.21 ksoftirqd/1 8 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/1 9 root RT -5 0 0 0 S 0 0.0 10:02.56 migration/2 10 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/2 11 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/2 12 root RT -5 0 0 0 S 0 0.0 4:29.53 migration/3 13 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/3

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• C# Silverlight - Delay Child Window Load?!

  - by Goober

  The Scenario Currently I have a C# Silverlight Application That uses the domainservice class and the ADO.Net Entity Framework to communicate with my database. I want to load a child window upon clicking a button with some data that I retrieve from a server-side query to the database. The Process The first part of this process involves two load operations to load separate data from 2 tables. The next part of the process involves combining those lists of data to display in a listbox. The Problem The problem with this is that the first two asynchronous load operations haven't returned the data by the time the section of code to combine these lists of data is reached, thus result in a null value exception..... Initial Load Operations To Get The Data: public void LoadAudits(Guid jobID) { var context = new InmZenDomainContext(); var imageLoadOperation = context.Load(context.GetImageByIDQuery(jobID)); imageLoadOperation.Completed += (sender3, e3) => { imageList = ((LoadOperation<InmZen.Web.Image>)sender3).Entities.ToList(); }; var auditLoadOperation = context.Load(context.GetAuditByJobIDQuery(jobID)); auditLoadOperation.Completed += (sender2, e2) => { auditList = ((LoadOperation<Audit>)sender2).Entities.ToList(); }; } I Then Want To Execute This Immediately: IEnumerable<JobImageAudit> jobImageAuditList = from a in auditList join ai in imageList on a.ImageID equals ai.ImageID select new JobImageAudit { JobID = a.JobID, ImageID = a.ImageID.Value, CreatedBy = a.CreatedBy, CreatedDate = a.CreatedDate, Comment = a.Comment, LowResUrl = ai.LowResUrl, }; auditTrailList.ItemsSource = jobImageAuditList; However I can't because the async calls haven't returned with the data yet... Thus I have to do this (Perform the Load Operations, Then Press A Button On The Child Window To Execute The List Concatenation and binding): private void LoadAuditsButton_Click(object sender, RoutedEventArgs e) { IEnumerable<JobImageAudit> jobImageAuditList = from a in auditList join ai in imageList on a.ImageID equals ai.ImageID select new JobImageAudit { JobID = a.JobID, ImageID = a.ImageID.Value, CreatedBy = a.CreatedBy, CreatedDate = a.CreatedDate, Comment = a.Comment, LowResUrl = ai.LowResUrl, }; auditTrailList.ItemsSource = jobImageAuditList; } Potential Ideas for Solutions: Delay the child window displaying somehow? Potentially use DomainDataSource and the Activity Load control?! Any thoughts, help, solutions, samples comments etc. greatly appreciated.

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• IE 7 can't bind event (using .live()) to dynamically created element using .load()

  - by petron

  Hi All - I'm having trouble getting IE7 to keep a click event bound to an element that is added to the DOM using .load(). Here's some code: $('.mybtn').live('click', function(e){ e.preventDefault(); $('#mypage').load('load-this-page.htm'); }); And here's the html <div id="mypage"> <a href="#" class="mybtn">clickme</a> // stuff goes here </div> On page load the click works but once the div is loaded via the clickme link the click stops working in IE7. The clickme link is within the div on load and also within the load() loaded html file that's why I'm using live(). This code works in FF 3.6, fyi. Anyone have any idea what's up (besides the fact the IE sucks balls)? Thanks!

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• Rails 2 and Ngnix: https pages can't load css or js (but will load graphics)

  - by Max Williams

  ADMISSION: i've posted this same question on stackoverflow, before realising it's probabaly better suited to superuser, but it kind of depends on the answer: If it turns out to be a problem in my nginx config, it's definitely superuser. If it turns out to be a problem in my Rails config (or code) then it's arguably stackoverflow. I'm adding some https pages to my rails site. In order to test it locally, i'm running my site under one mongrel_rails instance (on 3000) and nginx. I've managed to get my nginx config to the point where i can actually go to the https pages, and they load. Except, the javascript and css files all fail to load: looking in the Network tab in chrome web tools, i can see that it is trying to load them via an https url. Eg, one of the non-working file urls is https://cmw-local.co.uk/stylesheets/cmw-logged-out.css?1383759216 I have these set up (or at least think i do) in my nginx config to redirect to the http versions of the static files. This seems to be working for graphics, but not for css and js files. If i click on this in the Network tab, it takes me to the above url, which redirects to the http version. So, the redirect seems to be working in some sense, but not when they're loaded by an https page. Like i say, i thought i had this covered in the second try_files directive in my config below, but maybe not. Can anyone see what i'm doing wrong? thanks, Max Here's my nginx config - sorry it's a bit lengthy! I think the error is likely to be in the first (ssl) server block: server { listen 443 ssl; keepalive_timeout 70; ssl_certificate /home/max/work/charanga/elearn_container/elearn/config/nginx/certs/max-local-server.crt; ssl_certificate_key /home/max/work/charanga/elearn_container/elearn/config/nginx/certs/max-local-server.key; ssl_session_cache shared:SSL:10m; ssl_session_timeout 10m; ssl_protocols SSLv3 TLSv1; ssl_ciphers RC4:HIGH:!aNULL:!MD5; ssl_prefer_server_ciphers on; server_name elearning.dev cmw-dev.co.uk cmw-dev.com cmw-nginx.co.uk cmw-local.co.uk; root /home/max/work/charanga/elearn_container/elearn; # ensure that we serve css, js, other statics when requested # as SSL, but if the files don't exist (i.e. any non /basket controller) # then redirect to the non-https version location / { try_files $uri @non-ssl-redirect; } # securely serve everything under /basket (/basket/checkout etc) # we need general too, because of the email/username checking location ~ ^/(basket|general|cmw/account/check_username_availability) { # make sure cached copies are revalidated once they're stale add_header Cache-Control "public, must-revalidate, proxy-revalidate"; # this serves Rails static files that exist without running # other rewrite tests try_files $uri @rails-ssl; expires 1h; } location @non-ssl-redirect { return 301 http://$host$request_uri; } location @rails-ssl { proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect off; proxy_read_timeout 180; proxy_next_upstream off; proxy_pass http://127.0.0.1:3000; expires 0d; } } #upstream elrs { # server 127.0.0.1:3000; #} server { listen 80; server_name elearning.dev cmw-dev.co.uk cmw-dev.com cmw-nginx.co.uk cmw-local.co.uk; root /home/max/work/charanga/elearn_container/elearn; access_log /home/max/work/charanga/elearn_container/elearn/log/access.log; error_log /home/max/work/charanga/elearn_container/elearn/log/error.log debug; client_max_body_size 50M; index index.html index.htm; # gzip html, css & javascript, but don't gzip javascript for pre-SP2 MSIE6 (i.e. those *without* SV1 in their user-agent string) gzip on; gzip_http_version 1.1; gzip_vary on; gzip_comp_level 6; gzip_proxied any; gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript; #text/html # make sure gzip does not lose large gzipped js or css files # see http://blog.leetsoft.com/2007/7/25/nginx-gzip-ssl gzip_buffers 16 8k; # Disable gzip for certain browsers. #gzip_disable "MSIE [1-6].(?!.*SV1)"; gzip_disable "MSIE [1-6]"; # blank gif like it's 1995 location = /images/blank.gif { empty_gif; } # don't serve files beginning with dots location ~ /\. { access_log off; log_not_found off; deny all; } # we don't care if these are missing location = /robots.txt { log_not_found off; } location = /favicon.ico { log_not_found off; } location ~ affiliate.xml { log_not_found off; } location ~ copyright.xml { log_not_found off; } # convert urls with multiple slashes to a single / if ($request ~ /+ ) { rewrite ^(/)+(.*) /$2 break; } # X-Accel-Redirect # Don't tie up mongrels with serving the lesson zips or exes, let Nginx do it instead location /zips { internal; root /var/www/apps/e_learning_resource/shared/assets; } location /tmp { internal; root /; } location /mnt{ root /; } # resource library thumbnails should be served as usual location ~ ^/resource_library/.*/*thumbnail.jpg$ { if (!-f $request_filename) { rewrite ^(.*)$ /images/no-thumb.png break; } expires 1m; } # don't make Rails generate the dynamic routes to the dcr and swf, we'll do it here location ~ "lesson viewer.dcr" { rewrite ^(.*)$ "/assets/players/lesson viewer.dcr" break; } # we need this rule so we don't serve the older lessonviewer when the rule below is matched location = /assets/players/virgin_lesson_viewer/_cha5513/lessonViewer.swf { rewrite ^(.*)$ /assets/players/virgin_lesson_viewer/_cha5513/lessonViewer.swf break; } location ~ v6lessonViewer.swf { rewrite ^(.*)$ /assets/players/v6lessonViewer.swf break; } location ~ lessonViewer.swf { rewrite ^(.*)$ /assets/players/lessonViewer.swf break; } location ~ lgn111.dat { empty_gif; } # try to get autocomplete school names from memcache first, then # fallback to rails when we can't location /schools/autocomplete { set $memcached_key $uri?q=$arg_q; memcached_pass 127.0.0.1:11211; default_type text/html; error_page 404 =200 @rails; # 404 not really! Hand off to rails } location / { # make sure cached copies are revalidated once they're stale add_header Cache-Control "public, must-revalidate, proxy-revalidate"; # this serves Rails static files that exist without running other rewrite tests try_files $uri @rails; expires 1h; } location @rails { proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect off; proxy_read_timeout 180; proxy_next_upstream off; proxy_pass http://127.0.0.1:3000; expires 0d; } }

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• New host, high load?

  - by dotancohen

  A few minutes ago I signed up at a new webhost. I have yet to move my sites over. Upon initial SSH connection, I checked the load and memory usage, they do seem rather higher than I would like: # uptime 12:06:51 up 71 days, 23:23, 1 user, load average: 9.02, 9.49, 9.45 # free total used free shared buffers cached Mem: 33014800 31927192 1087608 0 2384812 17729816 -/+ buffers/cache: 11812564 21202236 Swap: 16787916 8584 16779332 Is that a bit to packed? I'm only paying about $5 USD per month, so I don't expect <0.1 loads, but ~10 is worrisome. Is it not? Also, there is no /etc/issue file so I tried other methods to guess the OS: # uname -a Linux box358.bluehost.com 2.6.32-20120131.55.1.bh6.x86_64 #1 SMP Tue Jan 31 15:43:27 EST 2012 x86_64 x86_64 x86_64 GNU/Linux # which yum /usr/bin/yum # which apt-get # That looks like CentOS / RHEL 6.2 possibly?

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• Server load is spiking from 2 to 250

  - by Hakzona

  Hello, I'am using Wordpress 2.9. Webserver 8GB from Hostgator. I'am fighting with this problem for long time but still can not find the solution. Php switched to run as an apache module, Php 5 in DSO, Apache suEXEC, eaccelerator installed, but this configuration started making huge server load on server. Server load spiking from 1 to 250 (4 cpus) and server stops, after period of time its back again and stops in about 10 minutes. It started happening when hostgator support team installed eaccelerator on server. What can make this problem and how can I fix it?

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• The Incremental Architect&acute;s Napkin - #2 - Balancing the forces

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/06/02/the-incremental-architectacutes-napkin---2---balancing-the-forces.aspxCategorizing requirements is the prerequisite for ecconomic architectural decisions. Not all requirements are created equal. However, to truely understand and describe the requirement forces pulling on software development, I think further examination of the requirements aspects is varranted. Aspects of Functionality There are two sides to Functionality requirements. It´s about what a software should do. I call that the Operations it implements. Operations are defined by expressions and control structures or calls to frameworks of some sort, i.e. (business) logic statements. Operations calculate, transform, aggregate, validate, send, receive, load, store etc. Operations are about behavior; they take input and produce output by considering state. I´m not using the term “function” here, because functions - or methods or sub-programs - are not necessary to implement Operations. Functions belong to a different sub-aspect of requirements (see below). Operations alone are not enough, though, to make a customer happy with regard to his/her Functionality requirements. Only correctly implemented Operations provide full value. This should make clear, why testing is so important. And not just manual tests during development of some operational feature, but automated tests. Because only automated tests scale when over time the number of operations increases. Without automated tests there is no guarantee formerly correct operations are still correct after more got added. To retest all previous operations manually is infeasible. So whoever relies just on manual tests is not really balancing the two forces Operations and Correctness. With manual tests more weight is put on the side of the scale of Operations. That might be ok for a short period of time - but in the long run it will bite you. You need to plan for Correctness in the long run from the first day of your project on. Aspects of Quality As important as Functionality is, it´s not the driver for software development. No software has ever been written to just implement some operation in code. We don´t need computers just to do something. All computers can do with software we can do without them. Well, at least given enough time and resources. We could calculate the most complex formulas without computers. We could do auctions with millions of people without computers. The only reason we want computers to help us with this and a million other Operations is… We don´t want to wait for the results very long. Or we want less errors. Or we want easier accessability to complicated solutions. So the main reason for customers to buy/order software is some Quality. They want some Functionality with a higher Quality (e.g. performance, scalability, usability, security…) than without the software. But Qualities come in at least two flavors: Most important are Primary Qualities. That´s the Qualities software truely is written for. Take an online auction website for example. Its Primary Qualities are performance, scalability, and usability, I´d say. Auctions should come within reach of millions of people; setting up an auction should be very easy; finding a suitable auction and bidding on it should be as fast as possible. Only if those Qualities have been implemented does security become relevant. A secure auction website is important - but not as important as a fast auction website. Nobody would want to use the most secure auction website if it was unbearably slow. But there would be people willing to use the fastest auction website even it was lacking security. That´s why security - with regard to online auction software - is not a Primary Quality, but just a Secondary Quality. It´s a supporting quality, so to speak. It does not deliver value by itself. With a password manager software this might be different. There security might be a Primary Quality. Please get me right: I don´t want to denigrate any Quality. There´s a long list of non-functional requirements at Wikipedia. They are all created equal - but that does not mean they are equally important for all software projects. When confronted with Quality requirements check with the customer which are primary and which are secondary. That will help to make good economical decisions when in a crunch. Resources are always limited - but requirements are a bottomless ocean. Aspects of Security of Investment Functionality and Quality are traditionally the requirement aspects cared for most - by customers and developers alike. Even today, when pressure rises in a project, tunnel vision will focus on them. Any measures to create and hold up Security of Investment (SoI) will be out of the window pretty quickly. Resistance to customers and/or management is futile. As long as SoI is not placed on equal footing with Functionality and Quality it´s bound to suffer under pressure. To look closer at what SoI means will help to become more conscious about it and make customers and management aware of the risks of neglecting it. SoI to me has two facets: Production Efficiency (PE) is about speed of delivering value. Customers like short response times. Short response times mean less money spent. So whatever makes software development faster supports this requirement. This must not lead to duct tape programming and banging out features by the dozen, though. Because customers don´t just want Operations and Quality, but also Correctness. So if Correctness gets compromised by focussing too much on Production Efficiency it will fire back. Customers want PE not just today, but over the whole course of a software´s lifecycle. That means, it´s not just about coding speed, but equally about code quality. If code quality leads to rework the PE is on an unsatisfactory level. Also if code production leads to waste it´s unsatisfactory. Because the effort which went into waste could have been used to produce value. Rework and waste cost money. Rework and waste abound, however, as long as PE is not addressed explicitly with management and customers. Thanks to the Agile and Lean movements that´s increasingly the case. Nevertheless more could and should be done in many teams. Each and every developer should keep in mind that Production Efficiency is as important to the customer as Functionality and Quality - whether he/she states it or not. Making software development more efficient is important - but still sooner or later even agile projects are going to hit a glas ceiling. At least as long as they neglect the second SoI facet: Evolvability. Delivering correct high quality functionality in short cycles today is good. But not just any software structure will allow this to happen for an indefinite amount of time.[1] The less explicitly software was designed the sooner it´s going to get stuck. Big ball of mud, monolith, brownfield, legacy code, technical debt… there are many names for software structures that have lost the ability to evolve, to be easily changed to accomodate new requirements. An evolvable code base is the opposite of a brownfield. It´s code which can be easily understood (by developers with sufficient domain expertise) and then easily changed to accomodate new requirements. Ideally the costs of adding feature X to an evolvable code base is independent of when it is requested - or at least the costs should only increase linearly, not exponentially.[2] Clean Code, Agile Architecture, and even traditional Software Engineering are concerned with Evolvability. However, it seems no systematic way of achieving it has been layed out yet. TDD + SOLID help - but still… When I look at the design ability reality in teams I see much room for improvement. As stated previously, SoI - or to be more precise: Evolvability - can hardly be measured. Plus the customer rarely states an explicit expectation with regard to it. That´s why I think, special care must be taken to not neglect it. Postponing it to some large refactorings should not be an option. Rather Evolvability needs to be a core concern for every single developer day. This should not mean Evolvability is more important than any of the other requirement aspects. But neither is it less important. That´s why more effort needs to be invested into it, to bring it on par with the other aspects, which usually are much more in focus. In closing As you see, requirements are of quite different kinds. To not take that into account will make it harder to understand the customer, and to make economic decisions. Those sub-aspects of requirements are forces pulling in different directions. To improve performance might have an impact on Evolvability. To increase Production Efficiency might have an impact on security etc. No requirement aspect should go unchecked when deciding how to allocate resources. Balancing should be explicit. And it should be possible to trace back each decision to a requirement. Why is there a null-check on parameters at the start of the method? Why are there 5000 LOC in this method? Why are there interfaces on those classes? Why is this functionality running on the threadpool? Why is this function defined on that class? Why is this class depending on three other classes? These and a thousand more questions are not to mean anything should be different in a code base. But it´s important to know the reason behind all of these decisions. Because not knowing the reason possibly means waste and having decided suboptimally. And how do we ensure to balance all requirement aspects? That needs practices and transparency. Practices means doing things a certain way and not another, even though that might be possible. We´re dealing with dangerous tools here. Like a knife is a dangerous tool. Harm can be done if we use our tools in just any way at the whim of the moment. Over the centuries rules and practices have been established how to use knifes. You don´t put them in peoples´ legs just because you´re feeling like it. You hand over a knife with the handle towards the receiver. You might not even be allowed to cut round food like potatos or eggs with it. The same should be the case for dangerous tools like object-orientation, remote communication, threads etc. We need practices to use them in a way so requirements are balanced almost automatically. In addition, to be able to work on software as a team we need transparency. We need means to share our thoughts, to work jointly on mental models. So far our tools are focused on working with code. Testing frameworks, build servers, DI containers, intellisense, refactoring support… That´s all nice and well. I don´t want to miss any of that. But I think it´s not enough. We´re missing mental tools, tools for making thinking and talking about software (independently of code) easier. You might think, enough of such tools already exist like all those UML diagram types or Flow Charts. But then, isn´t it strange, hardly any team is using them to design software? Or is that just due to a lack of education? I don´t think so. It´s a matter value/weight ratio: the current mental tools are too heavy weight compared to the value they deliver. So my conclusion is, we need lightweight tools to really be able to balance requirements. Software development is complex. We need guidance not to forget important aspects. That´s like with flying an airplane. Pilots don´t just jump in and take off for their destination. Yes, there are times when they are “flying by the seats of their pants”, when they are just experts doing thing intuitively. But most of the time they are going through honed practices called checklist. See “The Checklist Manifesto” for very enlightening details on this. Maybe then I should say it like this: We need more checklists for the complex businss of software development.[3] But that´s what software development mostly is about: changing software over an unknown period of time. It needs to be corrected in order to finally provide promised operations. It needs to be enhanced to provide ever more operations and qualities. All this without knowing when it´s going to stop. Probably never - until “maintainability” hits a wall when the technical debt is too large, the brownfield too deep. Software development is not a sprint, is not a marathon, not even an ultra marathon. Because to all this there is a foreseeable end. Software development is like continuously and foreever running… ? And sometimes I dare to think that costs could even decrease over time. Think of it: With each feature a software becomes richer in functionality. So with each additional feature the chance of there being already functionality helping its implementation increases. That should lead to less costs of feature X if it´s requested later than sooner. X requested later could stand on the shoulders of previous features. Alas, reality seems to be far from this despite 20+ years of admonishing developers to think in terms of reusability.[1] ? Please don´t get me wrong: I don´t want to bog down the “art” of software development with heavyweight practices and heaps of rules to follow. The framework we need should be lightweight. It should not stand in the way of delivering value to the customer. It´s purpose is even to make that easier by helping us to focus and decreasing waste and rework. ?

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• Why doesn't jquery .load() load a text file from an external website?

  - by Edward Tanguay

  In the example below, when I click the button, it says "Load was performed" but no text is shown. I have a clientaccesspolicy.xml in the root directory and am able to asynchronously load the same file from silverlight. So I would think I should be able to access from AJAX as well. What do I have to change so that the text of the file http://www.tanguay.info/knowsite/data.txt is properly displayed in the #content element? <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <script type="text/javascript" src="http://www.google.com/jsapi"></script> <script type="text/javascript"> google.load("jquery", "1.3.2"); google.setOnLoadCallback(function() { $('#loadButton').click(loadDataFromExernalWebsite); }); function loadDataFromExernalWebsite() { $('#content').load('http://www.tanguay.info/knowsite/data.txt', function() { alert('Load was performed.'); }); } </script> </head> <body> <p>Click the button to load content:</p> <p id="content"></p> <input id="loadButton" type="button" value="load content"/> </body> </html>

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• What is causing the unusual high load average?

  - by James

  I noticed on Tuesday night of last week, the load average went up sharply and it seemed abnormal since the traffic is small. Usually, the numbers usually average around .40 or lower and my server stuff (mysql, php and apache) are optimized. I noticed that the IOWait is unusually high even though the processes is barely using any CPU. top - 01:44:39 up 1 day, 21:13, 1 user, load average: 1.41, 1.09, 0.86 Tasks: 60 total, 1 running, 59 sleeping, 0 stopped, 0 zombie Cpu0 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu2 : 0.0%us, 0.3%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu3 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu4 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu5 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu6 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu7 : 0.0%us, 0.0%sy, 0.0%ni, 91.5%id, 8.5%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1048576k total, 331944k used, 716632k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 15 0 2468 1376 1140 S 0 0.1 0:00.92 init 1656 root 15 0 13652 5212 664 S 0 0.5 0:00.00 apache2 9323 root 18 0 13652 5212 664 S 0 0.5 0:00.00 apache2 10079 root 18 0 3972 1248 972 S 0 0.1 0:00.00 su 10080 root 15 0 4612 1956 1448 S 0 0.2 0:00.01 bash 11298 root 15 0 13652 5212 664 S 0 0.5 0:00.00 apache2 11778 chikorit 15 0 2344 1092 884 S 0 0.1 0:00.05 top 15384 root 18 0 17544 13m 1568 S 0 1.3 0:02.28 miniserv.pl 15585 root 15 0 8280 2736 2168 S 0 0.3 0:00.02 sshd 15608 chikorit 15 0 8280 1436 860 S 0 0.1 0:00.02 sshd Here is the VMStat procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 1 0 0 768644 0 0 0 0 14 23 0 10 1 0 99 0 IOStat - Nothing unusal Total DISK READ: 67.13 K/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND 19496 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19501 be/4 mysql 3.95 K/s 0.00 B/s 0.00 % 0.00 % mysqld 19568 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19569 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19570 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19571 be/4 chikorit 7.90 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19573 be/4 chikorit 7.90 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 1 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % init 11778 be/4 chikorit 0.00 B/s 0.00 B/s 0.00 % 0.00 % top 19470 be/4 mysql 0.00 B/s 0.00 B/s 0.00 % 0.00 % mysqld Load Average Chart - http://i.stack.imgur.com/kYsD0.png I want to be sure if this is not a MySQL problem before making sure. Also, this is a Ubuntu 10.04 LTS Server on OpenVZ. Edit: This will probably give a good picture on the IO Wait top - 22:12:22 up 17:41, 1 user, load average: 1.10, 1.09, 0.93 Tasks: 33 total, 1 running, 32 sleeping, 0 stopped, 0 zombie Cpu(s): 0.6%us, 0.2%sy, 0.0%ni, 89.0%id, 10.1%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1048576k total, 260708k used, 787868k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 15 0 2468 1376 1140 S 0 0.1 0:00.88 init 5849 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 8063 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 9732 root 16 0 8280 2728 2168 S 0 0.3 0:00.02 sshd 9746 chikorit 18 0 8412 1444 864 S 0 0.1 0:01.10 sshd 9747 chikorit 18 0 4576 1960 1488 S 0 0.2 0:00.24 bash 13706 chikorit 15 0 2344 1088 884 R 0 0.1 0:00.03 top 15745 chikorit 15 0 12968 5108 1280 S 0 0.5 0:00.00 apache2 15751 chikorit 15 0 72184 25m 18m S 0 2.5 0:00.37 php5-fpm 15790 chikorit 18 0 12472 4640 1192 S 0 0.4 0:00.00 apache2 15797 chikorit 15 0 72888 23m 16m S 0 2.3 0:00.06 php5-fpm 16038 root 15 0 67772 2848 592 D 0 0.3 0:00.00 php5-fpm 16309 syslog 18 0 24084 1316 992 S 0 0.1 0:00.07 rsyslogd 16316 root 15 0 5472 908 500 S 0 0.1 0:00.00 sshd 16326 root 15 0 2304 908 712 S 0 0.1 0:00.02 cron 17464 root 15 0 10252 7560 856 D 0 0.7 0:01.88 psad 17466 root 18 0 1684 276 208 S 0 0.0 0:00.31 psadwatchd 17559 root 18 0 11444 2020 732 S 0 0.2 0:00.47 sendmail-mta 17688 root 15 0 10252 5388 1136 S 0 0.5 0:03.81 python 17752 teamspea 19 0 44648 7308 4676 S 0 0.7 1:09.70 ts3server_linux 18098 root 15 0 12336 6380 3032 S 0 0.6 0:00.47 apache2 18099 chikorit 18 0 10368 2536 464 S 0 0.2 0:00.00 apache2 18120 ntp 15 0 4336 1316 984 S 0 0.1 0:00.87 ntpd 18379 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 18387 mysql 15 0 62796 36m 5864 S 0 3.6 1:43.26 mysqld 19584 root 15 0 12336 4028 668 S 0 0.4 0:00.02 apache2 22498 root 16 0 12336 4028 668 S 0 0.4 0:00.00 apache2 24260 root 15 0 67772 3612 1356 S 0 0.3 0:00.22 php5-fpm 27712 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 27730 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 30343 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 30366 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 This is the free ram as of today. total used free shared buffers cached Mem: 1024 302 721 0 0 0 -/+ buffers/cache: 302 721 Swap: 0 0 0 Update: Looking into the logs, particularly the PHP5-FPM, which is causing the CPU spike. I found that its segment faulting for some apparent reason. [03-Jun-2012 06:11:20] NOTICE: [pool www] child 14132 started [03-Jun-2012 06:11:25] WARNING: [pool www] child 13664 exited on signal 11 (SIGSEGV) after 53.686322 seconds from start [03-Jun-2012 06:11:25] NOTICE: [pool www] child 14328 started [03-Jun-2012 06:11:25] WARNING: [pool www] child 14132 exited on signal 11 (SIGSEGV) after 4.708681 seconds from start [03-Jun-2012 06:11:25] NOTICE: [pool www] child 14329 started [03-Jun-2012 06:11:58] WARNING: [pool www] child 14328 exited on signal 11 (SIGSEGV) after 32.981228 seconds from start [03-Jun-2012 06:11:58] NOTICE: [pool www] child 15745 started [03-Jun-2012 06:12:25] WARNING: [pool www] child 15745 exited on signal 11 (SIGSEGV) after 27.442864 seconds from start [03-Jun-2012 06:12:25] NOTICE: [pool www] child 17446 started [03-Jun-2012 06:12:25] WARNING: [pool www] child 14329 exited on signal 11 (SIGSEGV) after 60.411278 seconds from start [03-Jun-2012 06:12:25] NOTICE: [pool www] child 17447 started [03-Jun-2012 06:13:02] WARNING: [pool www] child 17446 exited on signal 11 (SIGSEGV) after 36.746793 seconds from start [03-Jun-2012 06:13:02] NOTICE: [pool www] child 18133 started [03-Jun-2012 06:13:48] WARNING: [pool www] child 17447 exited on signal 11 (SIGSEGV) after 82.710107 seconds from start I'm thinking that this might be causing the problem. If that is the cause, probably switching it off that to fastcgi/fcgid might resolve it... but still, I want to see if something else might be causing it to do this.

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• HTTPS request to a specific load-balanced virtual host (using Shibboleth for SSO)?

  - by Gary S. Weaver

  In one environment, we have three servers load balanced that have a single Tomcat instance on each, fronted by two different Apache virtual hosts. Each of those two virtual hosts (served by all three servers) has its own different load balancer. Internally, the first host (we'll call it barfoo) is served by port 443 (HTTPS) with its cert and the second host (we'll call it foobar) is served by port 1443 (HTTPS). When you hit foobar, it goes to the load balancer which is using IP affinity for that host, so you can easily test login/HTTPS on one of the servers serving foobar, but not the others (because you keep getting that server for the lifetime of the LB session, iirc). In addition, each of the servers are using Shibboleth v2 for authN/SSO, using mod_shib (iirc). So, a normal request to foobar hits the LB, is directed to the 3rd server (and will do that from then on for as long as the LB session lasts), then Apache, then to the Shibboleth SP which looks at the request, makes you login via negotiation with the Shibboleth IdP, then you hit Apache again which in turn hits Tomcat, renders, and returns the response. (I'm leaving out some steps there.) We'd like to hit one of the individual servers (foobar-03.acme.org which we'll say has IP 1.2.3.4) via HTTPS (skipping the load balancer), so we at first try putting this in /etc/hosts: 1.2.3.4 foobar.acme.org But since foobar.acme.org is a secondary virtual host running on 1443, it attempts to get barfoo.acme.org rather than foobar.acme.org at port 1443 and see that the cert for barfoo.acme.org is invalid for this case since it doesn't match the request's host, foobar.acme.org. I thought an ssh tunnel might be easy enough, so I tried: ssh -L 7777:foobar-03.acme.org:1443 [email protected] I tried just hitting https://localhost:7777/webappname in a browser, but when the Shibboleth login is over, it again tries to redirect to barfoo.acme.org, which is the default host for 443, and we get into an infinite redirect loop. I then tried setting up an SSH tunnel with privileged port 443 locally going to 443 of foobar-03.acme.org as the hostname for that virtual host: sudo ssh -L 443:foobar-03.acme.org:1443 [email protected] I also edited /etc/hosts to add: 127.0.0.1 foobar.acme.org This finally worked and I was able to get the browser to hit the individual HTTPS host at https://foobar.acme.org/webappname, bypassing the load balancer. This was a bit of a pain and wouldn't work for everyone, due to the requirement to use the local 443 port and ssh to the server. Is there an easier way to browse to and log into an individual host in this case?

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• Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 3

  - by Tarun Arora

  Welcome back once again, in Part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies, in Part 2 of Load and Web Performance Testing using Visual Studio 2010 I discussed the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. In part 3 I’ll be discussing Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, Asp.net Profiler and some closing thoughts. Test Results – I see some creepy worms! In Part 2 we put together a web performance test and a load test, lets run the test to see load test to see how the Web site responds to the load simulation. While the load test is running you will be able to see close to real time analysis in the Load Test Analyser window. You can use the Load Test Analyser to conduct load test analysis in three ways: Monitor a running load test - A condensed set of the performance counter data is maintained in memory. To prevent the results memory requirements from growing unbounded, up to 200 samples for each performance counter are maintained. This includes 100 evenly spaced samples that span the current elapsed time of the run and the most recent 100 samples.         After the load test run is completed - The test controller spools all collected performance counter data to a database while the test is running. Additional data, such as timing details and error details, is loaded into the database when the test completes. The performance data for a completed test is loaded from the database and analysed by the Load Test Analyser. Below you can see a screen shot of the summary view, this provides key results in a format that is compact and easy to read. You can also print the load test summary, this is generated after the test has completed or been stopped.         Analyse the load test results of a previously run load test – We’ll see this in the section where i discuss comparison between two test runs. The performance counters can be plotted on the graphs. You also have the option to highlight a selected part of the test and view details, drill down to the user activity chart where you can hover over to see more details of the test run.   Generate Report => Test Run Comparisons The level of reports you can generate using the Load Test Analyser is astonishing. You have the option to create excel reports and conduct side by side analysis of two test results or to track trend analysis. The tools also allows you to export the graph data either to MS Excel or to a CSV file. You can view the ASP.NET profiler report to conduct further analysis as well. View Data and Diagnostic Attachments opens the Choose Diagnostic Data Adapter Attachment dialog box to select an adapter to analyse the result type. For example, you can select an IntelliTrace adapter, click OK and open the IntelliTrace summary for the test agent that was used in the load test.   Compare results This creates a set of reports that compares the data from two load test results using tables and bar charts. I have taken these screen shots from the MSDN documentation, I would highly recommend exploring the wealth of knowledge available on MSDN. Leaving Thoughts While load testing the application with an excessive load for a longer duration of time, i managed to bring the IIS to its knees by piling up a huge queue of requests waiting to be processed. This clearly means that the IIS had run out of threads as all the threads were busy processing existing request, one easy way of fixing this is by increasing the default number of allocated threads, but this might escalate the problem. The better suggestion is to try and drill down to the actual root cause of the problem. When ever the garbage collection runs it stops processing any pages so all requests that come in during that period are queued up, but realistically the garbage collection completes in fraction of a a second. To understand this better lets look at the .net heap, it is divided into large heap and small heap, anything greater than 85kB in size will be allocated to the Large object heap, the Large object heap is non compacting and remember large objects are expensive to move around, so if you are allocating something in the large object heap, make sure that you really need it! The small object heap on the other hand is divided into generations, so all objects that are supposed to be short-lived are suppose to live in Gen-0 and the long living objects eventually move to Gen-2 as garbage collection goes through.  As you can see in the picture below all < 85 KB size objects are first assigned to Gen-0, when Gen-0 fills up and a new object comes in and finds Gen-0 full, the garbage collection process is started, the process checks for all the dead objects and assigns them as the valid candidate for deletion to free up memory and promotes all the remaining objects in Gen-0 to Gen-1. So in the future when ever you clean up Gen-1 you have to clean up Gen-0 as well. When you fill up Gen – 0 again, all of Gen – 1 dead objects are drenched and rest are moved to Gen-2 and Gen-0 objects are moved to Gen-1 to free up Gen-0, but by this time your Garbage collection process has started to take much more time than it usually takes. Now as I mentioned earlier when garbage collection is being run all page requests that come in during that period are queued up. Does this explain why possibly page requests are getting queued up, apart from this it could also be the case that you are waiting for a long running database process to complete.      Lets explore the heap a bit more… What is really a case of crisis is when the objects are living long enough to make it to Gen-2 and then dying, this is definitely a high cost operation. But sometimes you need objects in memory, for example when you cache data you hold on to the objects because you need to use them right across the user session, which is acceptable. But if you wanted to see what extreme caching can do to your server then write a simple application that chucks in a lot of data in cache, run a load test over it for about 10-15 minutes, forcing a lot of data in memory causing the heap to run out of memory. If you get to such a state where you start running out of memory the IIS as a mode of recovery restarts the worker process. It is great way to free up all your memory in the heap but this would clear the cache. The problem with this is if the customer had 10 items in their shopping basket and that data was stored in the application cache, the user basket will now be empty forcing them either to get frustrated and go to a competitor website or if the customer is really patient, give it another try! How can you address this, well two ways of addressing this; 1. Workaround – A x86 bit processor only allows a maximum of 4GB of RAM, this means the machine effectively has around 3.4 GB of RAM available, the OS needs about 1.5 GB of RAM to run efficiently, the IIS and .net framework also need their share of memory, leaving you a heap of around 800 MB to play with. Because Team builds by default build your application in ‘Compile as any mode’ it means the application is build such that it will run in x86 bit mode if run on a x86 bit processor and run in a x64 bit mode if run on a x64 but processor. The problem with this is not all applications are really x64 bit compatible specially if you are using com objects or external libraries. So, as a quick win if you compiled your application in x86 bit mode by changing the compile as any selection to compile as x86 in the team build, you will be able to run your application on a x64 bit machine in x86 bit mode (WOW – By running Windows on Windows) and what that means is, you could use 8GB+ worth of RAM, if you take away everything else your application will roughly get a heap size of at least 4 GB to play with, which is immense. If you need a heap size of more than 4 GB you have either build a software for NASA or there is something fundamentally wrong in your application. 2. Solution – Now that you have put a workaround in place the IIS will not restart the worker process that regularly, which means you can take a breather and start working to get to the root cause of this memory leak. But this begs a question “How do I Identify possible memory leaks in my application?” Well i won’t say that there is one single tool that can tell you where the memory leak is, but trust me, ‘Performance Profiling’ is a great start point, it definitely gets you started in the right direction, let’s have a look at how. Performance Wizard - Start the Performance Wizard and select Instrumentation, this lets you measure function call counts and timings. Before running the performance session right click the performance session settings and chose properties from the context menu to bring up the Performance session properties page and as shown in the screen shot below, check the check boxes in the group ‘.NET memory profiling collection’ namely ‘Collect .NET object allocation information’ and ‘Also collect the .NET Object lifetime information’.    Now if you fire off the profiling session on your pages you will notice that the results allows you to view ‘Object Lifetime’ which shows you the number of objects that made it to Gen-0, Gen-1, Gen-2, Large heap, etc. Another great feature about the profile is that if your application has > 5% cases where objects die right after making to the Gen-2 storage a threshold alert is generated to alert you. Since you have the option to also view the most expensive methods and by capturing the IntelliTrace data you can drill in to narrow down to the line of code that is the root cause of the problem. Well now that we have seen how crucial memory management is and how easy Visual Studio Ultimate 2010 makes it for us to identify and reproduce the problem with the best of breed tools in the product. Caching One of the main ways to improve performance is Caching. Which basically means you tell the web server that instead of going to the database for each request you keep the data in the webserver and when the user asks for it you serve it from the webserver itself. BUT that can have consequences! Let’s look at some code, trust me caching code is not very intuitive, I define a cache key for almost all searches made through the common search page and cache the results. The approach works fine, first time i get the data from the database and second time data is served from the cache, significant performance improvement, EXCEPT when two users try to do the same operation and run into each other. But it is easy to handle this by adding the lock as you can see in the snippet below. So, as long as a user comes in and finds that the cache is empty, the user locks and starts to get the cache no more concurrency issues. But lets say you are processing 10 requests per second, by the time i have locked the operation to get the results from the database, 9 other users came in and found that the cache key is null so after i have come out and populated the cache they will still go in to get the results again. The application will still be faster because the next set of 10 users and so on would continue to get data from the cache. BUT if we added another null check after locking to build the cache and before actual call to the db then the 9 users who follow me would not make the extra trip to the database at all and that would really increase the performance, but didn’t i say that the code won’t be very intuitive, may be you should leave a comment you don’t want another developer to come in and think what a fresher why is he checking for the cache key null twice !!! The downside of caching is, you are storing the data outside of the database and the data could be wrong because the updates applied to the database would make the data cached at the web server out of sync. So, how do you invalidate the cache? Well if you only had one way of updating the data lets say only one entry point to the data update you can write some logic to say that every time new data is entered set the cache object to null. But this approach will not work as soon as you have several ways of feeding data to the system or your system is scaled out across a farm of web servers. The perfect solution to this is Micro Caching which means you cache the query for a set time duration and invalidate the cache after that set duration. The advantage is every time the user queries for that data with in the time span for which you have cached the results there are no calls made to the database and the data is served right from the server which makes the response immensely quick. Now figuring out the appropriate time span for which you micro cache the query results really depends on the application. Lets say your website gets 10 requests per second, if you retain the cache results for even 1 minute you will have immense performance gains. You would reduce 90% hits to the database for searching. Ever wondered why when you go to e-bookers.com or xpedia.com or yatra.com to book a flight and you click on the book button because the fare seems too exciting and you get an error message telling you that the fare is not valid any more. Yes, exactly => That is a cache failure! These travel sites or price compare engines are not going to hit the database every time you hit the compare button instead the results will be served from the cache, because the query results are micro cached, its a perfect trade-off, by micro caching the results the site gains 100% performance benefits but every once in a while annoys a customer because the fare has expired. But the trade off works in the favour of these sites as they are still able to process up to 30+ page requests per second which means cater to the site traffic by may be losing 1 customer every once in a while to a competitor who is also using a similar caching technique what are the odds that the user will not come back to their site sooner or later? Recap   Resources Below are some Key resource you might like to review. I would highly recommend the documentation, walkthroughs and videos available on MSDN. You can always make use of Fiddler to debug Web Performance Tests. Some community test extensions and plug ins available on Codeplex might also be of interest to you. The Road Ahead Thank you for taking the time out and reading this blog post, you may also want to read Part I and Part II if you haven’t so far. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. Next ‘Load Testing in the cloud’, I’ll be working on exploring the possibilities of running Test controller/Agents in the Cloud. See you on the other side! Thank You!   Share this post : CodeProject

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• php-fpm: very high server load

  - by Derp Derpington

  Since today my webserver (nginx + php-fpm + mysql on a VPS) is very slow. htop says: 1 [|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||100.0%] Tasks: 63 total, 13 running 2 [|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||100.0%] Load average: 11.67 10.95 6.95 3 [|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||100.0%] Uptime: 00:18:40 4 [|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||100.0%] 5 [|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||100.0%] 6 [|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||100.0%] Mem[||||||||||| 137/1280MB] Swp[ 0/0MB] PID USER PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command 6802 www 20 0 76232 12320 5716 R 27.0 0.9 0:06.48 php-fpm: pool www 7048 www 20 0 75200 12136 5700 R 52.0 0.9 0:03.64 php-fpm: pool www 6699 www 20 0 74176 11124 5700 R 27.0 0.8 0:07.36 php-fpm: pool www 7029 www 20 0 73668 10380 5676 R 42.0 0.8 0:03.52 php-fpm: pool www 6995 www 20 0 76228 12456 5644 R 42.0 1.0 0:03.98 php-fpm: pool www 6858 www 20 0 74172 10684 5620 R 35.0 0.8 0:05.52 php-fpm: pool www 6998 www 20 0 75200 12072 5620 R 37.0 0.9 0:03.95 php-fpm: pool www 7098 www 20 0 75200 12052 5616 R 42.0 0.9 0:02.33 php-fpm: pool www 7093 www 20 0 76228 12496 5612 R 37.0 1.0 0:03.02 php-fpm: pool www 7226 www 20 0 74692 11080 5588 R 32.0 0.8 0:00.66 php-fpm: pool www CPU: (cat /proc/cpuinfo | grep model) model : 44 model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz model : 44 model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz model : 44 model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz model : 44 model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz model : 44 model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz model : 44 model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz I think a load of 10 and 100% cpu usage is not normal... How can i fix that?

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• HA Proxy won't load balance my web requests. What have I done wrong?

  - by Josh Smeaton

  I've finally got HA Proxy set up and running in a way I think I want. However, it is not load balancing the web requests it receives. All requests are currently being forwarded to the first server in the cluster. I'm going to paste my configuration below - if anyone can see where I may have gone wrong, I'd appreciate it. This is my first stab at configuring web servers in a *nix environment. First up, I have HA Proxy running on the same host as the first server in the apache cluster. We are moving these servers to virtual later on, and they will have different virtual hosts, but I wanted to get this running now. Both web servers are receiving their health checks, and are reporting back correctly. The haproxy?stats page correctly reports servers that are up and down. I've tested this by altering the name of the file that is checked. I haven't put any load onto these servers yet. I've just opened up the URLs on several tabs (private browsing), and had several co-workers hit the URL too. All of the traffic goes to WEB1. Am I balancing incorrectly? global maxconn 10000 nbproc 8 pidfile /var/run/haproxy.pid log 127.0.0.1 local0 debug daemon defaults log global mode http retries 3 option redispatch maxconn 5000 contimeout 5000 clitimeout 50000 srvtimeout 50000 listen WEBHAEXT :80,:8443 mode http cookie sessionbalance insert indirect nocache balance roundrobin option httpclose option forwardfor except 127.0.0.1 option httpchk HEAD health_check.txt stats enable stats auth rah:rah server WEB1 10.90.2.131:81 cookie WEB_1 check server WEB2 10.90.2.130:80 cookie WEB_2 check

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• Best Solution for Load Balancing geographically distributed NFS File Access?

  - by DairyKnight

  I'm trying to find an optimum solution for accessing the NFS file share in my company. We have a central file server in North America and has 30GB~50GB of updated data everyday. And it's very slow for our Europe and Asia branches to access directly. Therefore, I'm trying to setup two replicate servers in those continents. I'm currently using rsync, but wonder if there exists a better solution acts more like a distributed RAID, which allows the user to transparently access the file whether synced or not. And user request will be dispatched to remote server if the file is not yet synced. I'm now looking into DRBD, but it seems not to have the functionality of auto-dispatching requests. Does anyone know if there's a better solution?

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• 100% CPU load on Ubuntu 10.04.3 LTS 64bit

  - by deadtired

  I have 2 days since I am trying to fix this issue, with no success. The server is a mysql database server. Hardware: DELL Poweredge 1950, 2x Intel Xeon Quad Core E5345 @ 2.33GHz, 16 Gb mem, 2x 146Gb SAS (software RAID1) Software: Ubuntu 10.04.3 LTS, MySQL 5.1.41 Issue: while mysql is not used and runs with no database, everything seems alright. As soon as I install a database, it has the reason to bring all 8 cores in 100% with low memory consumption. So, you can imagine the load average goes high (I saw 212 load average for the first time). The server doesn't become unresponsive, but you can see it's slow while browsing the project installed. Additional info: the database used is not more than 24MB and it was moved from a server with less resources and a lot more larger databases. So it's not the database/project. my.cnf is not a reason also, as I used both default one and the one I use on the same distribution on another server.What is interesting is that mysql doesn't close any process and runs to the limit of the max_connections. Logs are quiet. Nothing there. I switched to this Ubuntu version after I suspected some problems in the newly Ubuntu 11.10 server. This one worked alright for an hour after I made a kernel upgrade to 3.0.1 (it was using the memory also) I tested disk speed and seems alright. Some more output on the running server: dstat -cndymlp -N total -D total 3: htop command: Idea? Did anyone meet the same problem? Any fix you can think of?

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• jQyery bind on ajax load() event

  - by Andrei C

  Hi guys. I have a page which display multiple blocks with results details. Inside each block I have some tags with thichbox jQuery plugin attached( class="thichbox"). http://jquery.com/demo/thickbox/ here is an example of one kind of ampersant tag: <a class="thickbox" title="Please Sign In" href="userloginredir.php?height=220&width=350&deal=3"> Problem comes when I added a jQuery pagination to the page because of to many results displaying on the page. The div component with the results inside is updated through ajax load() event. Below is the pagination script. $(document).ready(function(){ //References var pages = $("#menu_deals li"); var loading = $("#loading_deals"); var content = $("#content_deals"); //show loading bar function showLoading(){ loading .css({visibility:"visible"}) .css({opacity:"1"}) .css({display:"block"}) ; } //hide loading bar function hideLoading(){ loading.fadeTo(1000, 0); }; //Manage click events pages.live('click',function(){ //show the loading bar showLoading(); //Highlight current page number pages.css({'background-color' : ''}); $(this).css({'background-color' : 'yellow'}); //Load content var pageNum = this.id; var targetUrl = "ajax_search_results.php?page=" + pageNum + "&" + $("#dealsForm").serialize() + " #content_d"; content.load(targetUrl, hideLoading); }); //default - 1st page $("#1").css({'background-color' : 'yellow'}); var targetUrl = "ajax_search_results.php?page=1&" + $("#dealsForm").serialize() + " #content_d"; showLoading(); content.load(targetUrl, hideLoading); }); When I added pagination(code above), the thickbox events are not recognized anymore and instead of poping out a window with the login form inside it opens the results in new page (is acting like clicking on a normal link) From my jQuery knowledge this means that the components are not defined in the DOM because the content is updated after document ready triggered. I'm trying to bind the load event with something like this: content.bind('load',???); But I don't know how to pass the load params, targetUrl and the callback function hideLoading, when binding the load event. Please help me out in this matter, already took me more time than possible allowed. Thank you!

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• jQuery flicker using .load

  - by Dave Macaulay

  Hey guys, I'm using jQuery to dynamically load php pages into my page using the .load() function, so far this has been successful but if you click on various links to update the div with the .load() it starts to flicker between the new clicked page and the old one, this is pretty annoying and has anyone got a fix? Current code: $(document).ready(function(){ $('a').click(function() { $('#content').load($(this).attr("href")); return false; }); });

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• Enable load movie button event on other flash movie

  - by Nasir

  In my flash movie I load another flash movie with button on it. The problem is when I trigger the button the event on the load flash not function. When I check the button it trigger event trough root function on the parent clip. How I can enable the button event on the load movie when I load it on my flash movie?

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• How do I mirror a MySQL database?

  - by user366133

  I'm running two load balanced servers for one website, and I'd like the databases to be synchronized. Queries may be run on either of the two servers because they are both production sites, so the replication can't just work one way. It doesn't have to be in real-time, just fairly accurate so people don't notice a difference when they get switched to a different server.

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• Optimizing perceived load time for social sharing widgets on a page?

  - by Lucka

  I have placed the facebook "like" and some other social bookmarking websites link on my blog, such as Google Buzz, Digg, Twitter, etc. I just noticed that it takes a while to load my blog page as it need to load the data from the social networking sites (such as number of likes etc). How can I place the links efficiently so that first my blog content loads, and meanwhile it loads data from these websites -- in other words, these sharing widgets should not hang my blog page while waiting for data from external sites?

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