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https://issues.apache.org/jira/browse/SCB-1006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16672470#comment-16672470
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Zheng Feng commented on SCB-1006:
---------------------------------
[~njiang] It looks like the coordinator will call the endMethod after all the
compensations are OK and still hold the lock during the compensating time ?
This could provide the isolate on the application level. But there is a
deadlock risk when the coordinator fails to call the method due to the network
error. It would be better if the lock is able to be timeout.
> Support SagaEnd Callback invocation
> -----------------------------------
>
> Key: SCB-1006
> URL: https://issues.apache.org/jira/browse/SCB-1006
> Project: Apache ServiceComb
> Issue Type: Improvement
> Components: Saga
> Reporter: Willem Jiang
> Priority: Major
> Labels: improvement, pack
>
> Here is the use case for using the lock to provide the isolation in Saga.
> We just want to release this lock after the saga invocation is finished. Here
> is the code snippet for it. method2 wraps the Saga event to release the
> lock.
> {code}
> @SagaStart
> void doSagaTx() {
> doLocalTx1();
> doLocalTx1();
> }
> @Compensable(timeout=5, compensationMethod="cancelLocalTx1")
> void doLocalTx1(){
> ...
> }
> void cancelLocalTx1(){
> ....
> }
> @Compensable(timeout=5, compensationMethod="cancelLocalTx2")
> void doLocalTx2(){
> ...
> }
> void cancelLocalTx2(){
> ....
> }
> void method2() {
> Lock resourceLock = getResourceLock();
> if (resourceLock.tryLock()) {
> try {
> doSagaTx();
> } finally {
> resourceLock.release();
> }
> } else {
> // Resource was locked
> }
> }
> {code}
> But, this method is not good enough, as if there are something wrong inside
> of the Saga transaction, we need to wait for a while to let the transaction
> coordinator to finish the compensation invocation before release the
> resource lock.
> If ServiceComb saga can provide a callback when the saga transaction is
> finished, it could save lots of my time. The code just like this.
> {code}
> @SagaStart(endMethod="sagaTxEnd")
> void doSagaTx(resourceLock) {
> doLocalTx1();
> doLocalTx1();
> }
> void sagaTxEnd(resourceLock){
> resourceLock.release();
> }
> @Compensable(timeout=5, compensationMethod="cancelLocalTx1")
> void doLocalTx1(){
> ...
> }
> void cancelLocalTx1(){
> ....
> }
> @Compensable(timeout=5, compensationMethod="cancelLocalTx2")
> void doLocalTx2(){
> ...
> }
> void cancelLocalTx2(){
> ....
> }
> void method2() {
> Lock resourceLock = getResourceLock();
> if (resourceLock.tryLock()) {
> doSagaTx(resourceLock);
> } else {
> // Resource was locked
> }
> }
> {code}
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