Apache Camel Meets Redis
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Join For FreeCamel is the best of bread Integration framework and in this post I'm going to show you how to make it even more powerful by leveraging another great project - Redis. Camel 2.11 is on its way to be released soon with lots of new features, bug fixes and components. Couple of these new components are authored by me, redis-component being my favourite one. Redis - a ligth key/value store is an amazing piece of Italian software designed for speed (same as Lamborghini - a two-seater Italian car designed for speed). Written in C and having an in-memory closer to the metal nature, Redis performs extremely well (Lamborgini's motto is "Closer to the Road"). Redis is often referred to as a data structure server since keys can contain strings, hashes, lists and sorted sets. A fast and light data structure server is like a super sportscars for software engineers - it just flies. If you want to find out more about Redis' and Lamborghini's unique performance characteristics google around and you will see for yourself.
Getting started with Redis is easy: download, make, and start a redis-server. After these steps, you ready to use it from your Camel application. The component uses internally Spring Data which in turn uses Jedis driver, but with possibility to switch to other Redis drivers. Here are few use cases where the camel-redis component is a good fit:
<bean id="idempotentRepository" class="org.apache.camel.component.redis.processor.idempotent.RedisIdempotentRepository"> <constructor-arg value="test-repo"/> </bean> <route> <from uri="direct:start"/> <idempotentConsumer messageIdRepositoryRef="idempotentRepository"> <simple>${in.body.id}</simple> <to uri="mock:result"/> </idempotentConsumer> </route>
- volatile-lru remove a key among the ones with an expire set, trying to remove keys not recently used.
- volatile-ttl remove a key among the ones with an expire set, trying to remove keys with short remaining time to live.
- volatile-random remove a random key among the ones with an expire set.
- allkeys-lru like volatile-lru, but will remove every kind of key, both normal keys or keys with an expire set.
- allkeys-random like volatile-random, but will remove every kind of keys, both normal keys and keys with an expire set.
<?xml version="1.0" encoding="UTF-8"?> <route> <from uri="direct:start"/> <setHeader headerName="CamelRedis.Command"> <constant>SET</constant> </setHeader> <setHeader headerName="CamelRedis.Key"> <constant>keyOne</constant> </setHeader> <setHeader headerName="CamelRedis.Value"> <constant>valueOne</constant> </setHeader> <to uri="redis://localhost:6379"/> </route>
direct: provides direct, synchronous invocation in the same camel context.
seda: asynchronous behavior, where messages are exchanged on a BlockingQueue, again in the same camel context.
vm: asynchronous behavior like seda, but also supports communication across CamelContext as long as they are in the same JVM.
Complex applications usually consist of more than one standalone Camel instances running on separate machines. For this kind of scenarios, Camel provides jms, activemq, combination of AWS SNS with SQS, for messaging between instances.
Redis has a simpler solution for the Publish/Subscribe messaging paradigm. Subscribers subscribes to one or more channels, by specifying the channel names or using pattern matching for receiving messages from multiple channels. Then the publisher publishes the messages to a channel, and Redis makes sure it reaches all the matching subscribers.
<?xml version="1.0" encoding="UTF-8"?> <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring"> <route startupOrder="1"> <from uri="redis://localhost:6379?command=SUBSCRIBE&channels=testChannel"/> <to uri="mock:result"/> </route> <route startupOrder="2"> <from uri="direct:start"/> <setHeader headerName="CamelRedis.Command"> <constant>PUBLISH</constant> </setHeader> <setHeader headerName="CamelRedis.CHANNEL"> <constant>testChannel</constant> </setHeader> <setHeader headerName="CamelRedis.MESSAGE"> <constant>Test Message</constant> </setHeader> <to uri="redis://localhost:6379"/> </route> </camelContext>
The Claim Check from the EIP patterns allows you to replace message content with a claim check (a unique key), which can be used to retrieve the message content at a later time. The message content can be stored temporarily in Redis.
Redis is also very popular for implementing counters, leaderboards, tagging systems and many more functionalities. Now, with two swiss army knives under your belt, the integrations to make are limited only by your imagination.
Published at DZone with permission of Bilgin Ibryam, DZone MVB. See the original article here.
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