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…

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()