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  1. call setChannelTransacted(true) on the RabbitTemplate Spring Bean.

  2. register a org.springframework.amqp.rabbit.transaction.RabbitTransactionManager Spring Bean

  3. add the org.springframework.transaction.annotation.Transactional Annotations to the code which we want to wrap in a Rabbit Transaction. This Transactional Annotation works for both Mongo and Rabbit Transactions.

Transactions in MongoDB

Transactions are a relatively new feature of MongoDB (since v4.0)

...

  1. register a org.springframework.data.mongo.MongoTransactionManager Spring Bean.

  2. add the org.springframework.transaction.annotation.Transactional annotations Annotations to the code which we want to wrap in a MongoDB Transaction. This Transactional Annotation works for both Mongo and Rabbit Transactions.

  3. make sure any Mongo Collections (Collections are a similar to Tables in a typical RDBMS) you need to use within a Transaction are created outside of the Transaction, in advance. When using Mongo Transactions - you can no longer create a collection ‘on demand’ within a transaction by simply inserting into it. To work around this there is a class com.hee.tis.esr.common.transactions.MongoCollectionInitializerConfig which looks for instances of Spring Data Repositories and creates any Mongo Collections required on application startup. This is a temporary solution until we are using something like mongobee to make sure Collections are created as part of the Microservice Installation process.

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#

Class Name

Description

1

ImportTransactionConfig

A Spring Annotation used to pull in the Transaction Support.

ESR Microservices wanting to pull in TransactionSupport should add the @ImportTransactionConfig annotation to their Spring Boot “Application” class.

2

MongoCollectionInitializerConfig

Looks for Spring Data Mongo Repositories on startup and creates the required Collections in MongoDB if they don’t already exist.

3

NoopTransactionManager

Noop/Dummy Transaction Manager class. SeeTxConfigNoop

4

TxConfig

On application startup, logs the actual TransactionManager being used. This is just to help with debugging.

5

TxConfigGlobal

Creates a ChainedTransactionManager parent to wrap the Rabbit and/or Mongo Transaction Managers, if required. If created, this Spring Bean is named txManagerGlobal.

6

TxConfigMongo

Creates a MongoTransactionManager Spring Bean if the property app.transactions.mongo.enabled has value 'true’.

If created, this Spring Bean is named txManagerMongo

7

TxConfigNoop

Creates a Spring Bean using NoopTransactionManager if there is no Bean named txManagerGlobal. If created, this Spring Bean is named txManagerNoop

8

TxConfigRabbit

If the property app.transactions.rabbit.enabled has value 'true’ do the following:

  • Create the RabbitTransactionManager Spring Bean namedtxManagerRabbit

    • call setChannelTransacted(true) on the RabbitTemplate.

9

TxConstants

Contains public constant values related to this package. Things like Spring Bean names and important property names.

Testing Transaction Support

We have done some work to allow us to test Transactions that apply to both Rabbit and MongoDB using Test Containers. By using Test Containers we use actual instances of MongoDB and RabbitMQ run in Docker Containers in our tests - this is useful because we are using actual instances not ‘test’ instances which might behave different from the ‘real' thing.

The base code for testing transactions is within the following packages

  • com.hee.tis.esr.common.transactions.test

#

Class

Description

1

2

3

4

5

6

  • com.hee.tis.esr.common.autoconfigure

This package contains the class 'EmbeddedMongodbReplicaSetBootstrapConfiguration'. This class it loaded via Spring AutoConfiguration because it’s referred to in the smallsrc/test/resources/META-INF/spring.factories file.

Code Block
org.springframework.cloud.bootstrap.BootstrapConfiguration=\
com.hee.tis.esr.common.autoconfigure.EmbeddedMongodbReplicaSetBootstrapConfiguration


This class starts up MongoDB in a Test Container in ReplicaSet mode. It also sets the following properties which can them be used by the test code:

Code Block
embedded.mongodb.port
embedded.mongodb.host
embedded.mongodb.database
embedded.mongodb.replicaset

We had to write custom code to setup MongoDB in a TestContainer in ReplicaSet mode so we can test transactions. Our custom code is based on the classcom.playtika.test.mongodb.EmbeddedMongodbBootstrapConfiguration from the library “com.playtika.testcontainers:embedded-mongodb:1.32“ - it starts MongoDB within a Test Container but it’s not in ReplicaSet mode.