Skip to main content

Contextual Thread dumps

Due to some business policy changes we recently started seeing some changes in usage pattern of our application leading to unexplained app node spikes. These spikes were temporary and by the time we go and try to take jstacks it might have disappeared. So we configured a quartz job to take jstack every 5 min(wrote a quartz instead of cron because cron needs to be manually configured on each node and we have tons of nodes to ops was always missing or misconfiguring it) and dump it in to a folder and we keep last 500 copies. That way I can go and correlate what was going on in the tomcat during the time of the spike (I had to get lucky for spike to happen when quartz job was running but I was lucky as most spikes spanned 3-5 mins). Now from those thread dumps I can figure out what was going on like how many thread are doing "searches" v/s how many thread are coming from Webdav or how many threads are doing add file. But one question that keep on coming was who are the customers who are doing them. For e.g. if we saw 50 threads doing webdav propfinds, it would be good to know if most of these requests are coming from same customer or diff customer. So I went and added customer domain name to each thread in a servlet filter for each incoming request. This helped me find issues at a much faster rate as I no longer need to go and correlate it in the logs as to what thread was doing at that time. I found lots of patterns by just adding contextual information to threads. Below is how the information is in the thread name.

Thread[http-6280-Processor169|D-avlapp05,5,main]
RUNNABLE

      
   at java.lang.Thread.dumpThreads(Native Method)
   at java.lang.Thread.getAllStackTraces(Thread.java:1487)
   at com.sslinc.infrastructure.perf.ThreadDumpBean.(ThreadDumpBean.java:17)
   at org.apache.jsp.static_.admin.threadDump_jsp._jspService(threadDump_jsp.java:58)
   at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
   at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
   at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
   at java.lang.Thread.run(Thread.java:619)
      

Thread[multi-file-upload-commit-a5611a5a-3e5a-44ee-a005-8042ee732d9d-13900185618|D-krisgsc1,5,main]
WAITING

      
   at sun.misc.Unsafe.park(Native Method)
   at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
   at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1925)
   at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:358)
   at com.sslinc.ui.web.servlet.UploadProcessThread.run(UploadProcessThread.java:120)
      

Comments

Popular posts from this blog

RabbitMQ java clients for beginners

Here is a sample of a consumer and producer example for RabbitMQ. The steps are
Download ErlangDownload Rabbit MQ ServerDownload Rabbit MQ Java client jarsCompile and run the below two class and you are done.
This sample create a Durable Exchange, Queue and a Message. You will have to start the consumer first before you start the for the first time.

For more information on AMQP, Exchanges, Queues, read this excellent tutorial
http://blogs.digitar.com/jjww/2009/01/rabbits-and-warrens/

+++++++++++++++++RabbitMQProducer.java+++++++++++++++++++++++++++
import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.*; public class RabbitMQProducer { public static void main(String []args) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setUsername("guest"); factory.setPassword("guest"); factory.setVirtualHost("/"); factory.setHost("127.0.0.1"); factory.setPort(5672); Conne…

Logging to Graphite monitoring tool from java

We use Graphite as a tool for monitoring some stats and watch trends. A requirement is to monitor impact of new releases as build is deployed to app nodes to see if things like
1) Has the memcache usage increased.
2) Has the no of Java exceptions went up.
3) Is the app using more tomcat threads.
Here is a screenshot

We changed the installer to log a deploy event when a new build is deployed. I wrote a simple spring bean to log graphite events using java. Logging to graphite is easy, all you need to do is open a socket and send lines of events.
import org.slf4j.Logger;import org.slf4j.LoggerFactory; import java.io.OutputStreamWriter; import java.io.Writer; import java.net.Socket; import java.util.HashMap; import java.util.Map; public class GraphiteLogger { private static final Logger logger = LoggerFactory.getLogger(GraphiteLogger.class); private String graphiteHost; private int graphitePort; public String getGraphiteHost() { return graphiteHost; } public void setGraphite…

What a rocky start to labor day weekend

Woke up by earthquake at 7:00 AM in morning and then couldn't get to sleep. I took a bath, made my tea and started checking emails and saw that after last night deployment three storage node out of 100s of nodes were running into Full GC. What was special about the 3 nodes was that each one was in a different Data centre but it was named same app02.  This got me curious I asked the node to be taken out of rotation and take a heap dump.  Yesterday night a new release has happened and I had upgraded spymemcached library version as new relic now natively supports instrumentation on it so it was a suspect. And the hunch was a bullseye, the heap dump clearly showed it taking 1.3G and full GCs were taking 6 sec but not claiming anything.



I have a quartz job in each jvm that takes a thread dump every 5 minutes and saves last 300 of them, checking few of them quickly showed a common thread among all 3 data centres. It seems there was a long running job that was trying to replicate pending…