Thanks for the reply Martin. Telnet works, but it's difficult to say as sometimes AJP also works. I don't need to restart any of the services to resolve this problem. It starts working back again on it's own after few seconds/minutes for future requests. It's random error (until the real trigger is found).
-- Shantanu. On Sep 17, 2010, at 12:07 PM, Martin Hasicek wrote: Hi, you should try to telnet tomcat server from web server. telnet <host> <port> If the telnet is successful, you need to check configuration of mod_proxy_ajp. If the telnet will be not successful, you have network problem. mh Sent from my iPhone On 17.9.2010, at 18:18, Shantanu Pavgi <pa...@uab.edu<mailto:pa...@uab.edu>> wrote: Hi, I have a Apache http server and a Tomcat server configured using AJP connector (mod_proxy_ajp). The http server serves HTML/PHP pages and also proxies Java webapp requests to back-end Tomcat server. System config: * Both servers are running as Virtual Machines * CentOS 5.4 * Apache Tomcat 6.0.26 and Sun JDK 1.6 * Apache http: 2.2.3 (it's old, but that's what comes with default CentOS repo) We are getting HTTP 500/503 errors quite frequently, but they appear to be random in nature and hence difficult to debug. I have tried increasing following config parameters, but it didn't help: * On http server: max and smax connections in proxy_ajp.conf * On Tomcat server: maxThreads and maxSpareThreads in Tomcat's server.xml Following logs were seen on both sides: == Apache http server == * In browser: 500/503 - internal server error. * In Apache logs at debug mode - same logs for 500 and 503 error: {{{ [Wed Sep 15 22:50:09 2010] [debug] ajp_header.c(430): ajp_marshal_into_msgb: Done [Wed Sep 15 22:50:09 2010] [debug] mod_proxy_ajp.c(239): proxy: APR_BUCKET_IS_EOS [Wed Sep 15 22:50:09 2010] [debug] mod_proxy_ajp.c(244): proxy: data to read (max 8186 at 4) [Wed Sep 15 22:50:09 2010] [debug] mod_proxy_ajp.c(259): proxy: got 0 bytes of data [Wed Sep 15 22:50:09 2010] [error] ajp_read_header: ajp_ilink_receive failed [Wed Sep 15 22:50:09 2010] [error] (120006)APR does not understand this error code: proxy: read response failed from 10.0.0.10:9080 (<http://tomcat.lab.uab.edu/>tomcat.lab.uab.edu<http://tomcat.lab.uab.edu/>) [Wed Sep 15 22:50:09 2010] [debug] proxy_util.c(2062): proxy: AJP: has released connection for (<http://tomcat.lab.uab.edu/>tomcat.lab.uab.edu<http://tomcat.lab.uab.edu/>) [Wed Sep 15 22:50:09 2010] [debug] ssl_engine_kernel.c(1765): OpenSSL: Write: SSL negotiation finished successfully [Wed Sep 15 22:50:09 2010] [info] [client 10.0.0.8] Connection closed to child 3 with standard shutdown (server httpd.lab.uab.edu:443) }}} * tcpdump on Apache http server: Shows a packet going out to Tomcat server == Tomcat server == * In Tomcat logs catalina.out: No logs * In Tomcat access logs catalina.out: No logs * tcpdump on Tomcat: No incoming packet seen The request doen't seem to reach Tomcat at all. I have checked syslog (/var/log/messages), but I don't see any dropped packet logs as well. Anyone else had this issues before? Any pointers on how to debugs this would be really helpful. Thanks, Shantanu Pavgi.
