CODEWITHSUNDEEP
apacheperformancetomcatjbossajp
David Purdue
David Purdue

Reputation: 270

Why would Apache be slow when application server is quick?

We are using Apache as the web server, and it proxies requests to Jboss (think Tomcat) Java application server using AJP.

We have logging on for Apache and for our web application in Jboss.

We are seeing, not always but sometimes, cases where the processing time for a request in Jboss is less than half a second, but in the Apache log for the same request it is taking over 8 seconds to complete the request.

I can't even think where to start looking and I have not come up with a good Google search to try and work out why Apache is sitting on the request for so long. Any help appreciated.

Upvotes: 0

Views: 3506

Answers (2)

Malcolm
Malcolm

Reputation: 116

I don't think apache is acutally slow in your case. I guess you are using keepalived connections between apache and jboss. Under some circumstances, for example the connector is using blocking IO strategy and mean while the number of apache httpd processes are higher than the number of executor threads configurated in jboss connector. It might cause the jboss container thread being blocked after it served a request. You should post your apache and jboss configurations in order to get more specific answers.

Upvotes: 0

pi.
pi.

Reputation: 21532

Disclaimer: Educated guess taken from my experience with running such setups.

Preface

Apache can be configured to allow only a limited number of connections at the same time. In fact this is a prudent way to configure Apache since every connection uses a certain amount of resources and having no upper limit puts you at risk to run into a situation, where your main memory is exhausted and your server becomes unresponsive.

Resource exhaustion

That being said, Apache is usually configured as shown below, your numbers and modules may be different though. The principle still applies.

<IfModule mpm_prefork_module>
    StartServers          5
    MinSpareServers       5
    MaxSpareServers       10
    MaxClients            150
    MaxRequestsPerChild   0
</IfModule>

This indicates that Apache can process at most 150 concurrent connections.

If a client initiates the 151'th connection, the operating system kernel tries to forward this connection to the Apache process, but it won't answer any more connections. The kernel then enqueues the connection until another connection is closed by Apache.

The time it takes until the kernel can successfully initiate the connection will look to the user as if the request as such takes longer to complete.

The application-server on the other hand, doesn't know about the delay and received the request only after the connection has been initiated. To the application-server therefore everything looks normal.

If you don't have enough resources to increase the concurrent connections in Apache, consider switching to a more resource-efficient web-proxy, like nginx or Varnish.

Upvotes: 2

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