Transaction Compensation Plugin

As HIP CDR follows a service-oriented architecture, distributed transactions across services are required. The Transaction Compensation Plugin allows to rollback transactions in accordance with the Saga Pattern.

For this purpose, a REST API can be used by external services to invoke the transaction compensation functions.

The transaction compensation uses the openEHR Contribution objects for the rollback.

Parameters / Environment Variables

The Transaction Compensation Plugin does not need any parameters to be provided.

REST API

Execute Rollback

GET {{ehrbase-url}}/ehrbase/rest/admin/ehr/{ehr_id}/contribution/{contribution_id}/rollback

Executes a rollback based a contribution ID.

Example request:

GET /ehrbase/rest/admin/ehr/{ehr_id}/contribution/{contribution_id}/rollback HTTP/1.1
Host: localhost:8080

Example response:

HTTP/1.1 200 OK
Vary: Accept

Status Codes:

• 200 OK – Contribution was successfully rolled back

• 500 Internal Server Error – internal system error. The whole compensation transaction is rolled back

Dealing with parallel access

Before starting the rollback the ehr_id, contribution id, and status will be saved in a DB. If there already is an entry with the same ehr but status not finished, then the thread will block till it is set to finished or it will time out.

Rollback Algorithm

The objects in the contribution are rolled back: * in a serial way, * an inverse order and * in one database transaction. If at any point an exception representing a 501 or 500 happens, the whole compensation transaction is rolled back. If all objects have been rolled back successfully, the respective contribution object is deleted from the database.