[SCB-1622] Improve the transaction compensation mechanism

• Type: Task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: pack-0.6.0
• Component/s: Saga
• Assignee: Lei Zhang
• Reporter: Lei Zhang
• Created: 27/Nov/19 07:57
• Updated: 23/Jun/23 19:29
• Resolved: 03/Mar/21 15:16

Description

Currently, Alpha compensation mechanism has some defects [1]，When the compensation method fails, only the output log without throwing an exception. Alpha does not know that the compensation method failed.

 
Step1: Modify the OnConnected method to bidirectional streaming RPC
This will be needed for the Step2
 
Step2: Catch an exception and send a compensation result to Alpha in the compensation method[1] on the Omega side. Alpha waits for compensation result and catching exception after calling compensation method
1. Received TxCompensateSucceedAckEvent: transaction completed
2. Received TxCompensateFailedAckEvent: throw BusinessCompensationFailureException
3. catch other exception throw OmegaConnectedException 
 
Step3. Added retry and timeout rule to compensate for failures
 Exceeded the number of retries or timeout will change state to suspended

[1] https://github.com/apache/servicecomb-pack/issues/590
 

Sub-Tasks

• Modify the OnConnected method to bidirectional streaming RPC: Resolved
• Wait for compensation feedback after Alpha calls compensation: Resolved
• Rename @Compensable property retries and timeout with the "forward" prefix: Resolved
• Improve encapsulation on txEntityMap of SagaData: Resolved
• Optimize state machine compensation retry strategy using reverseRetries and retryDelayInMilliseconds for FSM: Resolved