Skip to main content

Pagespeed and cache flush

Ran into an issue where customers would complain that random logins are slow and then subsequent request are fast. Took a long time to debug because it was totally random.

Finally found that because we give each customer a unique subdomain like XXX.yyy.com page speed was caching the aggregated bundles per subdomain.  When we configure pagespeed we never configured the cache size so by default it was taking 100M.  Before we did Tomcat HA domains were pinned to a node so we never ran into the issue but after HA any customer can be served from any node so we were running into an issue where every hour the cache was flushed and domains would see this random login. 

Took almost 2-3 hours to debug the issue and the only reason I was able to figure out the issue because I was thinking like if I had to write pagespeed how would I write it. Also I  ran a du on the cache and it was 267M and luckily I saw the apache error logs that the cache clean had ran and ran du again and it was 97M.  I feel like accomplishing something today :).

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…

Spring query timeout or transaction timeout

If you are using spring to manage transactions then you can specify default transaction timeout using

    <bean id="transactionManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
        <property name="defaultTimeout" value="30" /> <!--30 sec--->             
    </bean>

or you can override the timeout in the annotation

    @Transactional(readOnly = false, timeout=30)


or if you are doing it programatic transactions then you can do


DataSourceTransactionManager transactionManager = new DataSourceTransactionManager(dataSource);
transactionManager.setDefaultTimeout(30);

 or you can override the timeout for one particular transaction

TransactionTemplate transactionTemplate = new TransactionTemplate();
transactionTemplate.setTimeout(30);

Python adding pid file

I have a thumbnail generator that launches multiple processes and the correct way to shut it down is to send kill -HUP to the parent process. To automate I had to write a pid file from python, it was a piece of cake
def writePidFile(): pid = str(os.getpid()) f = open('thumbnail_rabbit_consumer.pid', 'w') f.write(pid) f.close()