Yes, We can kick off the recovery process or status verify process in Alpha if the distribute transaction is in suspend status, but in this case we need Alpha talk to customer Application to tell if we need to do the recovery again or just do some auditing there. It depends on the customer's configuration.
Willem Jiang Twitter: willemjiang Weibo: 姜宁willem On Mon, Jul 22, 2019 at 11:38 PM Zheng Feng <[email protected]> wrote: > > Hi Willem, > > In the term of providing some further processing extension, you mean that > the customer could help the state machine to recovery from the suspension > states ? > > Willem Jiang <[email protected]> 于2019年7月22日周一 下午11:28写道： > > > If we provide the async compensation call, we need to do lots of thing > > on Alpha and Omega side. My suggestion we just use provide sync way to > > get the feedback of compensation immediately to keep the design > > simpler. > > > > As we are reimplementing the Alpha with state machine, there are some > > suspension state which could be caused by the timeout or the missing > > event message. > > I had a long talk with ZhangLei, we are agree that we could leave the > > status check or recovery to the customer by providing some further > > processing extension, as there are too many detail things in customer > > code to think about. > > > > Anyway, it's my pleasure to have this kind of discussion with the > > team, it's the beauty of Open Source project development, we are > > tackling the interesting problem by working together from different > > company :) > > > > Willem Jiang > > > > Twitter: willemjiang > > Weibo: 姜宁willem > > > > On Mon, Jul 22, 2019 at 5:14 PM Zheng Feng <[email protected]> wrote: > > > > > > In term of the compensation method, I think I had discussed with Willem > > > before that it could introduce the @Status annotation for the alpha > > server > > > to query the compensation status. When the compensation method is async > > > which means it can not response immediately, it would return the > > > COMPENSATING result and the alpha server could query the @Status method > > to > > > check the compensation status, if this method returns COMPENSATE_OK, the > > > alpha server will mark the local transaction is compensated otherwise > > will > > > mark it with compensate_failed. > > > > > > Daniel Qian <[email protected]> 于2019年7月21日周日 下午8:37写道： > > > > > > > I rethink the idea I proposed, yes, provide low level apis is a bad > > idea, > > > > and I also don't suggest that let user code use omega-xxx-transport > > api. > > > > > > > > I think the essential issues are three: > > > > > > > > 1. How to pass tx context info across threads > > > > 2. How to asynchronously tell Alpha that Saga is ended or aborted, > > which > > > > means not triggered on @SagaStart method returns. > > > > 3. How to asynchronously tell Alpha that LocalTx is ended or > > aborted, > > > > which means not triggered on @Compensable method returns. > > > > > > > > I think we can keep using @SagaStart @Compensable for the > > XXXStartedEvent, > > > > and provide a helper to manually end/abort Saga/LocalTx. Thanks for PR > > #506 > > > > (SCB-1385) we can use TransactionContext to achieve that. Below is a > > code > > > > sample: > > > > > > > > > > > > @SagaStart(async=true) > > > > public void foo() { > > > > TransactionContext txContext = OmegaContext.getTransactionContext(); > > > > someAsyncCall() > > > > .onSuccess(Callback() { > > > > omega.endSaga(txContext); > > > > }) > > > > .onException(Callback() { > > > > omega.abortSaga(txContext); > > > > }) > > > > } > > > > > > > > @Compensable(async=true, compensationMethod="rollbackBar") > > > > public void bar() { > > > > TransactionContext txContext = OmegaContext.getTransactionContext(); > > > > someAsyncCall() > > > > .onSuccess(Callback() { > > > > omega.endTx(txContext); > > > > }) > > > > .onException(Callback() { > > > > omega.abortTx(txContext); > > > > }) > > > > } > > > > > > > > The async attribute on @SagaStart and @Compensable prevents > > Saga/LocalTx > > > > ended when method returns. > > > > TransactionContext object can be passed around safely because it's > > > > immutable. > > > > What I have not considered clearly is that how to deal with > > compensation > > > > method if it's also async. > > > > > > > > > > > > Willem Jiang <[email protected]> 于2019年7月20日周六 下午10:30写道： > > > > > > > > > > Yeah, I agree we need provide some low level API for the user to > > pass. > > > > > In the recent change of SCB-1386, I introduce the TransactionContext > > > > > object which holds the reference of GID and LID, we may add some > > other > > > > > transaction context information there too. > > > > > If the sub transaction is happened in other JVM, we need to pass the > > > > > TxContext across the JVM with help of omega-xxx-transport. > > > > > > > > > > We already have some internal API to send the message from Omega to > > > > > Alpha, I prefer to use annotation instead of expose low level API to > > > > > the user. > > > > > > > > > > Willem Jiang > > > > > > > > > > Twitter: willemjiang > > > > > Weibo: 姜宁willem > > > > > > > > > > On Sat, Jul 20, 2019 at 9:50 PM Daniel Qian <[email protected]> > > > > wrote: > > > > > > > > > > > > After look into SCB-163, SCB-1385 and SCB-1386 I have some > > thoughts on > > > > Saga > > > > > > involved in async invocation. > > > > > > Current implementation is basically based on sync invocation, > > there are > > > > > > some assumption: > > > > > > > > > > > > 1. When @SagaStart method returns, the Saga finished. > > > > > > 2. When @Compensable method returns/throws exception, the Local > > Tx > > > > > > succeeds/failed. > > > > > > 3. When compensationMethod returns, the Local Tx is compensated. > > > > > > > > > > > > Even if considering what SCB-100 provided: > > > > > > > > > > > > 1. Add @OmegaContextAware annotation enabling > > > > > > java.util.concurrent.Executor inject OmegaConext into threads it > > > > > > manages/spawns > > > > > > 2. Make OmegaContext use InheritableThreadLocal field let child > > > > thread > > > > > > inherit parent thread's Local Tx info > > > > > > > > > > > > There are still some limitations: > > > > > > > > > > > > 1. @OmegaContextAware is only viable if you use spring framework > > > > > > 2. @OmegaContextAware and OmegaContext's InheritableThreadLocal > > > > field > > > > > > assuming that the calling thread or initator thread has Local Tx > > > > info. > > > > > > > > > > > > > > > > > > What if user code use producer-consumer pattern in which > > > > > > InheritableThreadLocal can't work? > > > > > > What if user code use a thread scheduling library which we cannot > > use > > > > > > @OmegaContextAware,RxJava and Reactor, for example? > > > > > > I think we could provide some low-level APIs that user code can > > manualy > > > > > > starts/ends Saga and Local Tx, something like below: > > > > > > > > > > > > TxContext context = omega.startSaga(); > > > > > > TxContext subTxContext = omega.startTx(TxContext parentTxContext); > > > > > > omega.endTx(TxContext); > > > > > > omega.abortTx(TxContext); > > > > > > omega.abortSaga(TxContext); > > > > > > omega.endSaga(TxContext); > > > > > > > > > > > > TxContext is just a immutable dto like this: > > > > > > > > > > > > public class TxContext { > > > > > > private final String globalTxId; > > > > > > private final String localTxId; > > > > > > } > > > > > > > > > > > > Above is a just a rough idea. So any thoughts? > > > > > > -- > > > > > > Daniel Qian > > > > > > > > > > > > 博客：https://segmentfault.com/u/chanjarster > > > > > > github：https://github.com/chanjarster > > > > > > > > > > > > > > > > -- > > > > Daniel Qian > > > > > > > > 博客：https://segmentfault.com/u/chanjarster > > > > github：https://github.com/chanjarster > > > > > >
