Skip to main content

Java Annotations/AOP and being lazy

I have found that if you try to be lazy then you would use AOP and annotations more. I try to be lazy and my blood boil when DRY being violated in the code. My goal is to how to make code simple yet powerful and try to hide complexity from an average developer and if the complexity cant be avoided then keep it in a single layer as much as possible.

AOP allows you to hide the compexity in a single layer transparent to an average junior developer.  For e.g.
1)  I was given a requirement to allow X no of Read and Y no of Write request per node as Berkely db couldnt handle >X+Y requests.  So AOP helped me sort it out. I created an interceptor MetadataThrottlingInterceptor and created two annotations @MetadataWriter and @MetadataReader.  So I just annotated the methods in the storage layer with these annoatations and used a threadpool in the Interceptor class to limit the read/write request.  This allowed me to hide the complexity in a layer and transparent to the developer. A junior developer now has to only annotate new methods with read/write and  if he is not curious he wouldnt even know what these are for.

2) I was given a requirement to track performance of methods of a particular class in Graphite. The problem was that in future developers can add more methods and add more code and what if they move code around and that can lead to wrong numbers being reported. So I just created a PerfInterceptor and added @PerfIntercepted annotation to every method that we wanted to track. Again being lazy helped me to hide the complexity.

3) I added sharding to our storage layer and again I wanted to hide the complexity of sharding to an average developer so I created a MetadataShardingInterceptor and it automatically handles selection of shard. The sql is assumed to written like
select * from ${SCHEMA_NAME}.files_${SHARD_NUMBER}.

The assumption is that every method would contain a customer argument and the AOP layer derives the shard metadata and does replacement transparent to junior developer.

So as you start to think in direction of making life easy for your team or be lazy to avoid DRY violation you tend to use more of AOP and annotation.

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…