Long URLs in combination with Apache httpd and Tomcat

Question

I'm currently in the process of configuring Apache httpd to direct all traffic for '/api/foo' to a specific Tomcat instance via AJP (using mod_proxy_ajp). For this purpose I have the following ProxyPass rule in my httpd configuration file:

ProxyPass /api/foo ajp://localhost:9999/api/foo connectiontimeout=300 timeout=300 retry=3

This Tomcat instance has the following connector defined in its server.xml:

<Connector port="9999" protocol="AJP/1.3" redirectPort="9443"/>

With this configuration I reach my Tomcat instance correctly when visiting /api/foo. However, when the URL becomes bigger than 300 characters I can't seem to reach my Tomcat instance, sometimes.

The first hour it could be that I get a timeouts and the other hour it could be that everything comes through just fine.

When I get timeouts, I see the following errors in my httpd error log:

[error] (70007)The timeout specified has expired: ajp_ilink_receive() can't receive header
[error] ajp_read_header: ajp_ilink_receive failed
[error] (70007)The timeout specified has expired: proxy: read response failed from 127.0.0.1:9999 (localhost)

And the following result in my httpd access log:

"GET /api/foo/barrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr HTTP/1.1" 503 323 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:33.0) Gecko/20100101 Firefox/33.0"

The strange thing is that this request doesn't seem to reach my Tomcat instance. I don't see anything reaching my application logging, and I also don't see the request in my Tomcat access log.

Does anyone have an idea what could be the cause of this problem? The timeout is set to more than 1 minute, so I'd expect the request to at least reach my Tomcat instance...

As a last note, I've tried setting the AJP connector's packageSize to 65536 and Apache httpd's LimitRequestFieldSize and ProxyIOBufferSize to 65536. This didn't solve the problem.

Ross Ross · Accepted Answer · 2014-12-19T00:51:27

In the absence of a better answer I though I would share my experience with a similar and possibly the same problem and give you a recommendation to change the connector you are using.

I have also received the same ajp_read_header: ajp_ilink_receive failed errors while using mod_proxy_ajp in slightly different environments using apache 2.2 & tomcat 6.

I've tried many various and recommended fixes including the connector timeout and other connector settings when we encountered our issue.

From what I've read, some of these will work in different scenarios and the error ajp_ilink_receive failed message seems to be quite generic. In your case this occurs when the URL is longer than 300 characters - well sometimes at least..

After trying many of the different connector properties both from within the tomcat server.xml and the apache ProxyPass settings appended after the ajp:// URI I pretty much gave up going down this path. Since then I have tried mod_proxy and mod_jk which both seem fix the issue or at the very least there is no more ajp error. But this wouldn't happen with mod_proxy anyway because it doesnt connect with ajp.

So I suggest to change your tomcat connector to either mod_proxy or mod_jk. There are various write ups on the differences but the pages here and here on tomcat expect are a reasonably good source of information. You;ll want to choose between mod_proxy and mod_jk based on your setup. mod_jk, while different, is actually not too hard to set up (but you may have to build the mod_jk.so for apache).

Summarising the different connectors;

mod_jk: highest recommendation. ajp connector. purpose designed. different configuration setup that resides outside apache. difficult to configure when connecting a webapp with a certian name to a different url name.
mod_proxy: http connector. reportedly more stable than mod_proxy_ajp. problems with passing ssl variables?
mod_proxy_ajp: least recommended but most common. ajp connector. extension of mod_proxy. easy implementation.

If this doesn't work for some reason. Others have had success looking into problems on the tomcat side such as long running queries.

Long URLs in combination with Apache httpd and Tomcat

1 Answers