Skip to main content

Java redis client for begineers

I had to use redis in our project in both python and Java. In this post I will cover a basic example of generating counters using Redis. I had to use cassandra db to push data but cassandra doesnt have autoincrement counters at this moment so we will use redis till the new version of cassandra supports it. Redis has memcache like API but the advantage is that its has atomic operations and the data is saved so server restarts will survive the data. The only disadvantage I see is that the java client yet doesnt support consistent hashing but eventually it will.


  1.  Install the redis server by following http://code.google.com/p/redis/wiki/QuickStart
  2.  run it using ./redis-server
  3.  Download JRedis client from http://github.com/alphazero/jredis/downloads
  4.  Run the below program.


import org.jredis.JRedis;
import org.jredis.RedisException;
import org.jredis.connector.ConnectionSpec;
import org.jredis.ri.alphazero.JRedisService;
import org.jredis.ri.alphazero.connection.DefaultConnectionSpec;


public class RedisCounterService {


private String host;

private int port;

private int connectionCount = 3;

private JRedis jredis;

public void setHost(String host) {
this.host = host;
}

public void setPort(int port) {
this.port = port;
}

public void setConnectionCount(int connectionCount) {
this.connectionCount = connectionCount;
}

public void init() {
ConnectionSpec connectionSpec = DefaultConnectionSpec.newSpec(host, port, 0, null);
/*This is a connection pool*/
jredis = new JRedisService(connectionSpec, connectionCount);
}

public Long getNextRevisionNumber(String counterName) throws RedisException {
//Redis API is thread safe so you dont need to synchronize
long nextRevisionNumber = jredis.incr(counterName);
return nextRevisionNumber;
}

public static void main(String []args) throws Exception {
RedisCounterService redis = new RedisCounterService();
redis.setHost("localhost");
redis.setPort(6379);
redis.init();
String counter = "test" + System.currentTimeMillis();
System.out.println(1==redis.getNextRevisionNumber(counter));
System.out.println(2==redis.getNextRevisionNumber(counter));
System.out.println(3==redis.getNextRevisionNumber(counter));
System.out.println(1==redis.getNextRevisionNumber(counter + "new"));
}
}

Comments

  1. Am also going to take a look at NoSQL storages..Cassandra sounds good thing to start from on this field.

    ReplyDelete
  2. You we use cassandra also. I use hector api v2 to connect to cassandra, was going to write a beginer article for that also but somehow didnt got time.

    ReplyDelete

Post a Comment

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…

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…