xgrr.de – the whole not the half

For years now I was using PHP as a Apache module and not thinking twice about it. Easy to install not much to maintain and working reasonably well. Server too slow? Buy a new server. Recently one of our servers got really slow again with varying timeouts while serving pages. Memory shortage. No new server available I needed to make the most of it and started investigating how to decrease the memory footprint of Apache.

FastCGI was the answer. With PHP as a module installed every Apache process can take up to the maximum amount of memory you defined in php.ini plus what the Apache process needs by himself even though this process is only serving static content. With the switch to FastCGI it was possible to use the threaded version of Apache (mpm_worker). Static contents are now served really fast without need for invoking PHP at all. PHP scripts are served by calling the FastCGI IPC.

As memory is still low Apache and PHP are both configured to “die” after quite a low number of requests served. This can sometimes lead to a small delay while the processes are restarted but ensures that the memory footprint is kept low.

How did I do it? I won’t go into details on how to install Apache, mod_fcgid and PHP because there are loads of howto’s out there. Please find the configuration I’m using below. I’m using Debian and Apache, mod_fcgid and PHP are installed out of the repository. If you have a custom compiled version or different distribution your paths can differ.

Depending on your available hardware it is feasible to tweak the settings for the mpm_worker module so more concurrent clients can be served and/or the amount of requests which is handled before re-creating the thread is higher. It is also very recommended to use eAccelerator in conjunction with this setup. See my post on the topic for more information.

/etc/apache2/apache2.conf (excerpt):

<IfModule mpm_worker_module>
	StartServers           4
	ServerLimit            4
	MaxClients           128
	MinSpareThreads        8
	MaxSpareThreads       16
	ThreadsPerChild       32
	MaxRequestsPerChild  500
</IfModule>

/etc/apache2/mods-available/fcgid.conf:

<IfModule mod_fcgid.c>
	AddHandler fcgid-script .fcgi .php
	FCGIWrapper /var/www/php-fcgi-starter .php

	IdleTimeout		3600
	BusyTimeout		 300
	ProcessLifeTime		7200
	IPCConnectTimeout	  10
	IPCCommTimeout		 360
	MaxProcessCount		  15
	MaxRequestsPerProcess	  -1
	PHP_Fix_Pathinfo_Enable    1
</IfModule>

/var/www/php-fcgi-starter:

#!/bin/sh
PHPRC=/etc/php5/cgi/
export PHPRC
export PHP_FCGI_MAX_REQUESTS=250
export PHP_FCGI_CHILDREN=1
exec /usr/lib/cgi-bin/php

In my series of optimizing one of our servers I added eAccelerator to the setup to improve the performance. One of the bottlenecks of the server is unfortunately memory. Nevertheless even with small memory settings and caching to disk eAccelerator is able to enhance the performance and user experience of our websites and eCommerce platforms by 2-2.5.

For some projects it might come in handy to have a pre-compiled binary shipped to the customer or run as a separate instance. I took a peek at Roadsend PHP which implemented their own engine and is able to compile PHP source into C binaries which can either run on the command line or with special compilation arguments as a FastCGI program.

But before using it productively and changing a lot of source to make it compatible with the way how Roadsend works I wanted to make sure that the promised performance bonus would be really there. I created a very crude script which does nothing more than to iterate an integer to a certain maximum and measures the time to do this.

NOTE: I know that a proper performance test looks differently and I’m aware that Roadsend PHP can put his design into the works when we deal with a lot of includes. I’ll make another test with including random files to compare if this is impacting the results.

<?php
echo “Simple iteration test to compare performance between interpreted PHP and Roadsend PHP<hr />”;

$max = 1000;
if($_GET["max"] != “” && is_numeric($_GET["max"])) {
$max = $_GET["max"];
}

$start = microtime();

for($i = 0; $i < $max; $i++) {
echo $i.”<br />”;
}

$stop = microtime();
$elapsed = $stop – $start;
echo “<hr />Script took $elapsed seconds to execute”;
?>

To the environment. I didn’t set up a clean room environment. I used my server at home with 2G of memory Athlon64 X2 and a RAID5. Nothing special but I think it resembles real-world situations perfectly (unless you setup a new box for every PHP site you build).

Apache (worker – threaded) is used for serving the requests. FastCGIs are served via mod_fcgid. PHP is also run via mod_fcgid which improved the performance of PHP dramatically so far.

Let’s get to it:

max = 1000
Roadsend PHP: 0.005817
Interpreded PHP: 0.001201

max = 10000
Roadsend PHP: 0.06846
Interpreded PHP: 0.012625

These results are not dramatically but significant. It seems that compiling PHP adds overhead to the execution.

When I was playing around with Funambol last week I was brutally stopped by an Exception thrown somewhere in the code of the Funambol DS Server.

java.lang.NullPointerException
at com.funambol.server.session.SyncSessionHandler.processInitSyncMapMessage(SyncSessionHandler.java:905)
at com.funambol.server.session.SyncSessionHandler.processMessage(SyncSessionHandler.java:521)
at com.funambol.server.engine.SyncAdapter.processInputMessage(SyncAdapter.java:533)
at com.funambol.server.engine.SyncAdapter.processXMLMessage(SyncAdapter.java:254)
at com.funambol.transport.http.server.LocalSyncHolder.processXMLMessage(LocalSyncHolder.java:97)
at com.funambol.transport.http.server.Sync4jServlet.doPost(Sync4jServlet.java:399)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.funambol.transport.http.server.LogContextFilter.doFilter(LogContextFilter.java:132)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.funambol.transport.http.server.SyncResponseTimeFilter.doFilter(SyncResponseTimeFilter.java:159)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:769)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:698)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:891)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
at java.lang.Thread.run(Unknown Source)

I decided to make the effort and have a look at the code. That was actually what was taking me so long to fix the problem at hand. Today I got a fix on the actual problem. The offending code is in the handling of the session. When I configured my Funambol I supplied the URI of the service I want to create which is at this point in time not the real URI. What happens during the authentication handshake is that the session is bound to this specific URI. This means that if the client requests a specific URI the server overwrites this URI with the one set in Funambol.xml and the session is only valid for this URI.

During sync it is checked if the client is authenticated which is not the case or at least not for the URI specified in the Funambol.xml. In this case a clause in the code is reached which provokes the NullPointerException stated above.

If you have this problem, make sure that the URI in your Funambol.xml file is either empty (then the URI provided by the client is taken) or that your clients use the URI which is specified.

Surely eBooks are discussed controversially in the media. On the one side you have the publishers and the authors who are afraid of losing their market. Then of course you have the papers which turnover is declining as time progresses. Nevertheless digital versions of books, papers and magazines are more and more demanded by the public. With new technology such as the Kindle by Amazon and other high-tech gadgets it is also becoming very easy to consume these digitals.

But then you want more. And there it stops. Where to get your new eBook fix? There are a lot of different sites out there. Most of them feature PDA documents optimized for hand helds. With the enforcing of the market you can easily miss good sources.

With friends of mine I started a portal which collects links to interesting offerings on the net. We already started to gather links to commercial and non-profit organizations. We’re just started a few days back and have almost 100 links together. Have a look for yourself on ebook-spot.de!

Finally. I always wanted to put my hands on a real SAN. At school I missed the chance by 3 months (after I finished the project “System Administration” they decided to buy two 19” SAN racks – bastards) but now I got the chance to do some real shizzle. VMware Infrastructure linked to a SAN (okay it’s not a complete 19” rack but it’s a SAN). Let you guys know what I find out.

Last weeks have been crazy. Selma left for New York and Panama. I went to stuttgart the first time. And tonight for good as well. It’s strange to  move all your personal stuff out of the apparment. But that’s happend now. See it back in six months when we come back…

I’m really pissed of by the Spring Web Flow framework. The idea to create determined flow for certain use cases is great. And Web Flow does help to create your forms and stuff. But it seems that the current release has some really strange issues when having a composite object attached to a form while using checkboxes to select a subset of this object. Unfortunately the Spring forums aren’t that helpful because absolutely nobody reacts. Dunno if this because my problem is too exotic or I simply didn’t get the right tone. For me it’s definately the last time using Spring Web Flow…

The last two days were absolutely frustrating. For me a old school PHP scripter (okay recently I converted to the PHP OOP fraction but still) it’s quite new to develop applications for JEE (formerly known as J2EE). I managed to see light at the end of the tunnel – no it was not the train – when I decided to drop the strange Spring WebFlow integration I desired to use. Now the concept of the application I’m supposed to develop for HP is clear and I’m waiting for our partner to create the framework so I can test it. Once you’re into the JEE way it’s quite cool because you’re mapping about everything to POJOs and this makes working quite cool.

Didn’t want to do this for a long time. I’m a PHP kind of guy for a very long time and programmed a lot of applications based on PHP and MySQL. Nevertheless now is the time I’m needed to dive into JEE (former J2EE). I’m curious what this will bring. Spring, Struts and Co are big question marks above my head…