# vm spam patch
RewriteEngine On
RewriteCond %{THE_REQUEST} ^.*(page=shop\.recommend).* [NC]
RewriteRule ^.*$ - [F,L]
Today I installed Varnish on a pretty standard system (CentOS + WHM) and the service wouldn't start. The system log (/var/log/messages) contained the following:
Oct 7 04:15:46 server varnishd[20836]: Child (20846) Panic message: Assert error in WRK_BgThread(), cache_pool.c line 582:#012 Condition((pthread_create(thr, ((void *)0), wrk_bgthread, bt)) == 0) not true.#012errno = 11 (Resource temporarily unavailable)#012thread = (cache-main)#012ident = Linux,2.6.32-358.2.1.el6.x86_64,x86_64,-sfile,-smalloc,-hcritbit,no_waiter#012
The settings for number of processes and file descriptors in /etc/security/limits.{conf,d} were correct and it still didn't start. The problem turned out to be with stack size - I have no idea why this is happening in just this one system and works with every other centos, but the solution was as following:
1. Patch /etc/init.d/varnish adding a new ulimit call in start()
# Stack size
ulimit -s unlimited
2. Increase system limits in /etc/security/limits.conf accordingly
varnish stack soft unlimited varnish stack hard unlimited
3. Restart Varnish
After successfully running Varnish this way, be sure to change the stack limit back to a reasonable size! Unlimited is not a very wise setting, but helps debugging the problem. Now Varnish and Joomla could happily work together.
Nextend makes pretty and well-written modules for Joomla and Wordpress. I've optimized a website which uses one of them and it had a weird issue: sometimes the module would appear unstyled and CSS/JS files in the "media/nextend/cache/" directory returned 404. After reading some code the solution was obvious: Varnish was set to cache pages for at least 2 hours, while the Nextend module only cached it for 15 minutes, and deleted old files. Because every time it creates a new directory for updated cache content, it deletes old ones - cached HTML pages were referencing URLs which did not exist any more.
The solution was very simple: in Joomla admin go to Extensions - Plugins - Nextend Library, then click Configure in the Basic Options and set the cache time to the same value your Varnish installation uses. For the best Varnish + Joomla experience, see our offer.
The new zend opcache extension built into the latest version of PHP is, as we've checked, a bit faster than the current best - XCache. There's, however, a security concern.
Both extensions make it possible to clear the whole cache programatically (from within a script). In Zend it's the opcache_reset() function and in XCache it's xcache_clear_cache(XC_TYPE_PHP).
If you run shared hosting, you allow your users to execute arbitrary code in your PHP interpreter. This, naturally, includes the two functions mentioned above. If you rely on the opcode cache to provide desired level of service for your customers, you don't want them to clear everybody's caches. If a malicious or badly written script clears your cache, say, every minute - there is no benefit from caching. The whole idea is that you cache the most used files once, and use the cached version from RAM. What this means for a shared host is increased CPU and possibly disk IO usage. In some cases, this can turn into a Denial of Service (DoS) attack.
So let's take this simple script and see what Zend Opcache will do when you execute it:
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
opcache_reset();
echo 'OK';
Well, Zend happily cleared the cache. Now let's see what XCache does:
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
xcache_clear_cache(XC_TYPE_PHP);
echo 'OK';
The XCache developer envisioned this problem. Certain functions, which affect other users' experience, trigger a login page. The username and password is set by an administrator system-wide in php.ini and is not viewable by regular users.
If you run a shared host and want to speed it up using opcode caching, you should use XCache rather than the new Zend Opcache. Zend is only better by 10%, it's not a number worth risking a DoS attack. On the other hand, if you and only you control the code that's run on your servers, this security issue won't affect you.
You could (and should) use the disable_functions directive in php.ini
PHP 5.5 has a new feature: built-in opcode cache! It's an alternative for extensions like XCache, APC or eAccelerator. Let's see how it performs compared to established solutions.
Server: OpenVZ container running on 1 Xeon W3520 CPU core, high I/O priority (to ensure CPU-bound execution), 1 GB RAM. Requests originating from another VPS on that system.
Software: Debian 7.0 i386, nginx 1.2.1, PHP 5.5.0 from dotdeb, XCache SVN trunk from 2013-06-23 (r1269).
(This test may or may not reflect what is happening on dedicated servers. Unfortunately, we don't have a spare server-grade physical machine at the moment. That being said, the machine which held the VPS is under a small network and IO load.
pm = dynamic pm.max_children = 25 pm.start_servers = 4 pm.min_spare_servers = 2 pm.max_spare_servers = 10 pm.max_requests = 5000
Zend Opcache has been configured as following:
root@opcode:/var/www# grep ^opcache /etc/php5/fpm/php.ini opcache.enable=1 opcache.enable_cli=1 opcache.memory_consumption=128 opcache.interned_strings_buffer=4 opcache.max_accelerated_files=3907 opcache.fast_shutdown=1
XCache has been configured as following:
xcache.size = 128M xcache.count = 3 xcache.cacher = On
Joomla! 3.1.1. Installation was tricky, installation/application/framework.php had to be edited, this line in particular: ini_set('display_errors', true); - otherwise AJAX calls didn't succeed because JSON has been polluted with error messages.
The "Default English" sample data set has been installed. Joomla cache has been disabled because it's not what we want to test.
The Apache Benchmark has been used to measure average response time and number of requests served per seconds. The command line was:
ab -n 10000 -c 20
Ten thousands requests have been performed by 20 concurrent threads. This corresponds with the pm.max_children=25 setting in php.ini.
Performance is clearly CPU-bound. CPU usage is 100%, RAM utilization is about 880 MB out of 1GB. Disk I/O is negligible measured from both within the container (%wa 0) and the hypervisor (%wa 7).
Apache Benchmark output (Unfold)
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 176.31.28.48 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests
Server Software: nginx/1.2.1
Server Hostname: 176.31.28.48
Server Port: 80
Document Path: /
Document Length: 8626 bytes
Concurrency Level: 20
Time taken for tests: 1743.994 seconds
Complete requests: 10000
Failed requests: 0
Write errors: 0
Total transferred: 89890000 bytes
HTML transferred: 86260000 bytes
Requests per second: 5.73 [#/sec] (mean)
Time per request: 3487.989 [ms] (mean)
Time per request: 174.399 [ms] (mean, across all concurrent requests)
Transfer rate: 50.33 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 1
Processing: 656 3483 1020.6 3166 9587
Waiting: 403 2999 778.5 2812 8757
Total: 656 3483 1020.6 3166 9587
Percentage of the requests served within a certain time (ms)
50% 3166
66% 3528
75% 3849
80% 4091
90% 4797
95% 5540
98% 6695
99% 7420
100% 9587 (longest request)
It looks like the CPU hasn't been fully utilized with 20 concurrent requests. The usage fluctuated between 70% and 90%. I/O and memory usage were, as previously, within reasonable limits.
Apache Benchmark output (Unfold)
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 176.31.28.48 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests
Server Software: nginx/1.2.1
Server Hostname: 176.31.28.48
Server Port: 80
Document Path: /
Document Length: 8626 bytes
Concurrency Level: 20
Time taken for tests: 658.408 seconds
Complete requests: 10000
Failed requests: 0
Write errors: 0
Total transferred: 89890000 bytes
HTML transferred: 86260000 bytes
Requests per second: 15.19 [#/sec] (mean)
Time per request: 1316.817 [ms] (mean)
Time per request: 65.841 [ms] (mean, across all concurrent requests)
Transfer rate: 133.33 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 1
Processing: 421 1316 426.2 1214 5664
Waiting: 275 1053 355.8 986 4329
Total: 421 1316 426.2 1214 5664
Percentage of the requests served within a certain time (ms)
50% 1214
66% 1333
75% 1448
80% 1537
90% 1826
95% 2065
98% 2484
99% 2780
100% 5664 (longest request)
Just like previously, the load has been CPU-bound even after enabling XCache.
Apache Benchmark output (Unfold)
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 176.31.28.48 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests
Server Software: nginx/1.2.1
Server Hostname: 176.31.28.48
Server Port: 80
Document Path: /
Document Length: 8626 bytes
Concurrency Level: 20
Time taken for tests: 769.788 seconds
Complete requests: 10000
Failed requests: 0
Write errors: 0
Total transferred: 89890000 bytes
HTML transferred: 86260000 bytes
Requests per second: 12.99 [#/sec] (mean)
Time per request: 1539.576 [ms] (mean)
Time per request: 76.979 [ms] (mean, across all concurrent requests)
Transfer rate: 114.04 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 1
Processing: 601 1538 431.1 1439 4401
Waiting: 393 1232 361.6 1178 4205
Total: 601 1539 431.1 1440 4401
Percentage of the requests served within a certain time (ms)
50% 1440
66% 1582
75% 1696
80% 1784
90% 2079
95% 2333
98% 2847
99% 3179
100% 4401 (longest request)
Time graph: less is better
Requests per second graph: more is better
Well, XCache is no more the best opcode cache around. We're looking forward to widespread adoption of PHP 5.5+. Unfortunately, there is currently no GUI for nicely analyzing cache usage, like XCache has. However, Zend exposes a new function, accelerator_get_status(), which could be used to create such a GUI - so certainly somebody will release relevant GUI in the next weeks.
EDIT: We didn't have to wait long - as a reader pointed out, there is a GUI for Zend Optimizer.
As usual, if you need help, we will make your website fast for you.
Our contribution to the open source community, the Celery-PHP library, had one drawback: it needed a PECL extension that was pretty hard to compile, and not shipped with the most popular distributions. I can only imagine how hard it must have been for some people to set up a working environment.
So during the last month the library has undergone massive refactoring to abstract away the parts responsible for connecting to a queue. This allowed to create pluggable queue backend objects. Right now two are implemented: "pecl", the old code utilizing a PECL extension, and "php-amqplib", using a pure PHP AMQP library.
If you've used Celery-PHP before, you won't notice any difference. The library will just default to using PECL.
Here's how it works: I've added an extra parameter to the constructor of Celery class. If not supplied, it triggers an auto-detection system which first looks for the PECL extension, then checks if PHP-amqplib has been installed by composer, and gives up if neither of these is present. You can force the queue type by passing a string - currently 'pecl' and 'php-amqplib' are accepted.
The new PHP-AMQPLib backend passed most unit tests, but the ones checking how it behaves on long running tasks. The problem is that AMQPLib doesn't allow specifying an arbitrary interval when waiting for a new message, it's always an integer number of seconds. For this reason some tests don't behave as expected, but it shouldn't affect real-life code other than that "asynchronous" checks for result take a whole second. I've prepared a pull request to address this problem, but the developer didn't decide to pull it in yet.
If you want to try it out, pull the code from its branch on github. It will be available in the main branch once it's well tested and the php-amqplib pull request goes through (so vote for it if you want to use PECL-less Celery!).
Updated Celery binding for PHP is available from Github.
I've ran unit tests with latest Celery and RabbitMQ from Debian Squeeze. They went well without any change in code logic.
I've came across some problems during setup of testing environment, mainly during installation of php-pecl-amqp. The install_amqp.sh script is now updated with current librabbitmq-c URL and other minor changes to build properly on Squeeze. I've also updated documentation about testing and updated celeryconfig.py in test scenario to use Celery 3.0-style BROKER_URL variable instead of BROKER_HOST etc. used in Celery 2.x.
Software versions used:
A new version of Varnish-Joomla patch is available. The most interesting news is Joomla! 3.1 support.
Other than that, patches for Joomla! 2.5 and 3.0 have been updated to the latest version of their respective families (2.5.11 and 3.0.4).
A bug pointed by Yves Lavoie has been fixed too. It could make the patched system error out in some rare circumstances.
If you're an existing customer, contact us to get the latest package.
If you're interested in purchasing the patch, please head to Order section of the product page: make your Joomla! faster
Administrating a server set up by someone else can be a real pain. One of the problems I have regularly encountered on clients' systems has been database administration. While you can perform some tasks from command line, I really can't imagine working without a tool like PHPMyAdmin.
PHPMyAdmin, however, has a number of problems. The main one for me is its installation process which is much harder than necessary and involves editing configuration files. Consulting time spent installing PMA vs doing actual work is rather hard to explain to customers. So I started looking for alternatives.
The tool I've found performed beyond my wildest expectations. It consists of a single file (which is, by the way, interesting - they "compile" a nice, readable PHP source tree into a single minified PHP file). Not only it supports MySQL, but works with Postgres, SQLite, MS SQL and Oracle. It has a pretty, minimalistic interface. It's fast - not only it executes fast on the server, but it generates small pages so working on a slow network isn't a problem. And - best of all - the one-step installation process consists of uploading a single PHP file to the server.
Adminer, the tool I'm writing about, supports everything I care for. Some things could be done better or easier, but it's a really viable PHPMyAdmin alternative - I never found myself in a position where I couldn't do something and had to install PMA.
As usual, if you need help making your website faster, be sure to contact us.
A recent upgrade of our project management software, Chili Project, was a good opportunity to make it run like other services - ran from Supervisord, connected via FastCGI. Unfortunately, Rails doesn't make it easy to listen for FCGI connections on a named socket.
After some research, I've found a way to run Chilli Project (and, in fact, any rails app) this way. I've put this little script into scripts/ subdirectory of the rails app:
Also, for completeness: contents of /etc/supervisor/conf.d/redmine.conf
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