Fency

Idempotency barrier for RabbitMQ consumers.

License	The Apache License, Version 2.0
Categories	Spring Boot Container Microservices Redis Data Databases
GroupId	io.fency
ArtifactId	fency-spring-boot-starter-redis
Last Version	0.1.2
Release Date	May 15, 2019
Type	jar
Description	Fency Idempotency barrier for RabbitMQ consumers.
Project URL	https://github.com/fencyio/fency
Source Code Management	https://github.com/fencyio/fency

Download fency-spring-boot-starter-redis

Filename	Size
fency-spring-boot-starter-redis-0.1.2.pom
fency-spring-boot-starter-redis-0.1.2.jar	412 bytes
fency-spring-boot-starter-redis-0.1.2-sources.jar	261 bytes
fency-spring-boot-starter-redis-0.1.2-javadoc.jar	261 bytes

How to add to project

Apache Maven

<!-- https://jarcasting.com/artifacts/io.fency/fency-spring-boot-starter-redis/ -->
<dependency>
    <groupId>io.fency</groupId>
    <artifactId>fency-spring-boot-starter-redis</artifactId>
    <version>0.1.2</version>
</dependency>

Gradle Groovy

// https://jarcasting.com/artifacts/io.fency/fency-spring-boot-starter-redis/
implementation 'io.fency:fency-spring-boot-starter-redis:0.1.2'

Gradle Kotlin

// https://jarcasting.com/artifacts/io.fency/fency-spring-boot-starter-redis/
implementation ("io.fency:fency-spring-boot-starter-redis:0.1.2")

Apache Buildr

'io.fency:fency-spring-boot-starter-redis:jar:0.1.2'

Apache Ivy

<dependency org="io.fency" name="fency-spring-boot-starter-redis" rev="0.1.2">
  <artifact name="fency-spring-boot-starter-redis" type="jar" />
</dependency>

Groovy Grape

@Grapes(
@Grab(group='io.fency', module='fency-spring-boot-starter-redis', version='0.1.2')
)

Scala SBT

libraryDependencies += "io.fency" % "fency-spring-boot-starter-redis" % "0.1.2"

Leiningen

[io.fency/fency-spring-boot-starter-redis "0.1.2"]

Dependencies

compile (3)

Group / Artifact	Type	Version
org.springframework.boot : spring-boot-starter	jar	2.1.4.RELEASE
io.fency : fency-spring-boot-autoconfigure	jar	0.1.2
io.fency : fency-redis	jar	0.1.2

Project Modules

There are no modules declared in this project.

Fency: an idempotency barrier for RabbitMQ consumers

Theoretical concept

Even when a sender application sends a message only once, the receiver application may receive the message more than once.

The term idempotent is used in mathematics to describe a function that produces the same result if it is applied to itself: f(x) = f(f(x)). In Messaging this concepts translates into a message that has the same effect whether it is received once or multiple times. This means that a message can safely be resent without causing any problems even if the receiver receives duplicates of the same message.

The recipient can explicitly de-dupe messages by keeping track of messages that it already received. A unique message identifier simplifies this task and helps detect those cases where two legitimate messages with the same message content arrive.

In order to detect and eliminate duplicate messages based on the message identifier, the message recipient has to keep a list of already received message identifiers.

Technical implementation

In order to store the processed message metadata, we have to be in a transactional context. If something goes wrong, the transaction has to be roll backed.

1. The MessageInterceptor creates an MessageContext and stores it in a ThreadLocal

2. The IdempotencyBarrier is an aspect around the @IdempotentConsumer annotation. It retrieves the MessageContext and checks if the message already exists. The unique message key is composed by the messageId and the consumerQueueName.

If the message does not exist, the target method is invoked and the message metadata is stored in a datastore.

If the message already exists, an error message is logged and the target method is not invoked.

Usage

• Maven

<dependency>
  <groupId>io.fency</groupId>
  <artifactId>fency-spring-boot-starter-redis</artifactId>
  <version>0.1.1</version>
</dependency>

• Gradle

implementation 'io.fency:fency-spring-boot-starter-redis:+'

Annotate your consumers with @IdempotentConsumer.

See sample app: fency-spring-boot-sample-app

Note for spring integration users

If you are already using spring integration, have a look here

References

• Idempotent receiver

Fency

Idempotency barrier for RabbitMQ consumers

Versions

Version
0.1.2 May 15, 2019
0.1.1 Apr 19, 2019
0.1.0 Feb 28, 2019