On 5/19/2015 1:51 AM, Jani, Vrushank wrote: > We have production SOLR deployed on AWS Cloud. We have currently 4 live SOLR > servers running on m3xlarge EC2 server instances behind ELB (Elastic Load > Balancer) on AWS cloud. We run Apache SOLR in Tomcat container which is > sitting behind Apache httpd. Apache httpd is using prefork mpm and the > request flows from ELB to Apache Httpd Server to Tomcat (via AJP). > > Last few days, we are seeing increase in the requests around 20000 requests > minute hitting the LB. In effect we see ELB Surge Queue Length continuously > being around 100. > Surge Queue Length: represents the total number of request pending submission > to the instances, queued by the load balancer; > > This is causing latencies and time outs from Client applications. Our first > reaction was that we don't have enough max connections set either in HTTPD or > Tomcat. What we saw, the servers are very lightly loaded with very low CPU > and memory utilisation. Apache preform settings are as below on each servers > with keep-alive turned off. > > <IfModule prefork.c> > StartServers 8 > MinSpareServers 5 > MaxSpareServers 20 > ServerLimit 256 > MaxClients 256 > MaxRequestsPerChild 4000 > </IfModule> > > > Tomcat server.xml has following settings. > > <Connector port="8080" protocol="AJP/1.3" address="127.0.0.1" > maxThreads="500" connectionTimeout="60000"/> > For HTTPD – we see that there are lots of TIME_WAIT connections Apache port > around 7000+ but ESTABLISHED connections are around 20. > For Tomact – we see about 60 ESTABLISHED connections on tomcat AJP port. > > So the servers and connections doesn't look like fully utilised to the > capacity. There is no visible stress anywhere. However we still get requests > being queued up on LB because they can not be served from underlying servers. > > Can you please help me resolving this issue? Can you see any apparent problem > here? Am I missing any configuration or settings for SOLR?
I'm curious about why you have Apache sitting in front of Tomcat. About the only reason I can think of to require that step is that you are using it to require authentication or to deny access to things like the admin UI. If you are not doing anything in Apache other than proxying the traffic, then drop the middleman and use the container directly with its own HTTP connector. Or even better, use the Jetty included with Solr. You should set maxThreads to 10000 in your Tomcat configuration, effectively removing the limit. Solr is a multi-threaded Java servlet, with background threads as well as request-based threads. Tomcat requires threads for handling connections, but Solr also requires threads for its own operation. The maxThreads limit counts *all* of those threads, not just the Tomcat threads. Thanks, Shawn
