Skip to main content

Haproxy and tomcat JSESSIONID

One of the biggest problems I have been trying to solve at our startup is to put our tomcat nodes in HA mode. Right now if a customer comes, he lands on to a node and remains there forever. This has two major issues:

1) We have to overprovision each node with ability to handle worse case capacity.

2) If two or three high profile customers lands on to same node then we need to move them manually.

3) We need to cut over new nodes and we already have over 100+ nodes. 

Its a pain managing these nodes and I waste lot of my time in chasing node specific issues. I loath when I know I have to chase this env issue.

I really hate human intervention as if it were up to me I would just automate thing and just enjoy the fruits of automation and spend quality time on major issues rather than mundane task,call me lazy but thats a good quality.

So Finally now I am at a stage where I can put nodes behing HAProxy in QA env. today we were testing the HA config and first problem I immediately saw is that we have to use sticky sessions due to some design issue that will take long time to solve. Now we were doing sticky session by JSESSIONID like

      appsession JSESSIONID len 32 timeout 12h request-learn

Immediately I realized that Two tomcats can generate same JSESSIONID so there is a potential for security breach.  Thank god tomcat has a way to add a node identifier to JSESSIONID to solve this issue :).  You can go to conf/server.xml and add jvmRoute to Engine like



This way your JSESSIONID would be generated like BBF8B5EF74EAAECE0278DC92A9F1353D.192.155.4.5_8080

As a side effect now  we would know by looking at cookie as to which node is serving the request and this will help in trouble shooting node specific issues.


I hope to cut down the 100+nodes to 40 nodes after this HA.  I will keep 40 because we have pod/farms in each DC so we need to overprovision each pod else this could have been reduced to 10 or 15 nodes. The pods are there to avoid DC meltdown.

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…

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…

Email slavery

It seems I have become an EmailSlave. The first half of the day is spent in just answering to emails. There are so many emails where I am copied but I need not be. There are many emails  where its a 1-2 page email and somewhere down someone says @KP please answer this.  So it seems daily my work schedule is:
Signin to newrelic and check anomalies for 15 min. Check emails related production exception report and yes there are a ton of these report daily. Need a better tool here as this model is not scalable. I need to reduce the incoming data at me to only see relevant data like what newrelic does. May be I need to create a webapp out of these emails.Check emails for next few minutes before team callsDo team callsThen again back to checking emails until a I have taken a best shot at answering everyone waiting for my reply.Attend team meetings on Tue/Thu
Being an architect and coder at heart I don't feel satisfied at end of the day if there is nothing tangible getting done at the end.…