From NOSQL to MySql (BDB to mysql)

From NOSQL to MySql (BDB to mysql) - Part3

We finally migrated 14 nodes this weekend. As there were millions of files to be migrated even after running 5 parallel thread on each node it took close to 3-4 hours per node. We were running 3 nodes at a time otherwise the db load was shooting up high. As we cant afford to have a downtime on weekdays, the migration has to happen on weekend nights. On Friday night it we were up till 6:00 AM and on Saturday night we were up till 4:00 AM. We wanted to do more nodes but the no of files per host was going overboard and I wanted to be conservative to start with, if the mysql servers can handle more then later we would consolidate shards or move them to this host. New mysql hosts are going to be provisioned next week so hoping to migrate more nodes this week. Monday was a calm day after long time as we chose all nodes that were spiking to be migrated first.

Db loads in all DCs are low and even app nodes are low, Surprisingly slave dbs are getting pounded more than master db after last week's optimisation in code to move some heavily used queries to slave that can handle stale data, a good sign as we can easily add more slaves to spread the load.


Master db load on one DC

Slave DB load on one DC

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Part2
Part3
Part4
Part5

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RabbitMQ java clients for beginners

Here is a sample of a consumer and producer example for RabbitMQ. The steps are
Download Erlang Download Rabbit MQ Server Download 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…

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…

Programming fun at startup

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