[分享] seata1.5.2 如何在二阶段发生异常时告警

# 场景描述
RM二阶段发生异常时，TC是会进行不断的重试。直到成功为止
那么，问题就来了。一直重试虽然在一定程度上可能成功，但大部分情况下一直重试是不会成功的
这个时候，是需要作出一定的告警措施，比如发邮件，发钉钉之类的

比较幸运的是，seata提供了SPI，这样可以比较方便的实现。经过一番研究尝试，终于找到比较好的实现方式。如下，enjoy!

# Step One
> 注入自己实现的SPI
新建文件: src/main/resources/META-INF/services/io.seata.core.model.ResourceManager
文件内容如下。注意，是实现类的全路径来的，不懂SPI机制可先自行谷歌
```
com.xxx.MyTCCResourceManager
```

# Step Two
com.xxx.MyTCCResourceManager类代码。大部分抄官方的io.seata.rm.tcc.TCCResourceManager代码即可，这里只列出关键代码
```
@Override
public BranchStatus branchCommit(BranchType branchType, String xid, long branchId, String resourceId,
String applicationData) throws TransactionException {
TCCResource tccResource = (TCCResource)tccResourceCache.get(resourceId);
if (tccResource == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not exist, resourceId: %s", resourceId));
}
Object targetTCCBean = tccResource.getTargetBean();
Method commitMethod = tccResource.getCommitMethod();
if (targetTCCBean == null || commitMethod == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not available, resourceId: %s", resourceId));
}
try {
//BusinessActionContext
BusinessActionContext businessActionContext = getBusinessActionContext(xid, branchId, resourceId,
applicationData);
Object[] args = this.getTwoPhaseCommitArgs(tccResource, businessActionContext);
Object ret;
boolean result;
// add idempotent and anti hanging
if (Boolean.TRUE.equals(businessActionContext.getActionContext(Constants.USE_TCC_FENCE))) {
try {
result = TCCFenceHandler.commitFence(commitMethod, targetTCCBean, xid, branchId, args);
} catch (SkipCallbackWrapperException | UndeclaredThrowableException e) {
throw e.getCause();
}
} else {
ret = commitMethod.invoke(targetTCCBean, args);
if (ret != null) {
if (ret instanceof TwoPhaseResult) {
result = ((TwoPhaseResult)ret).isSuccess();
} else {
result = (boolean)ret;
}
} else {
result = true;
}
}
LOGGER.info("TCC resource commit result : {}, xid: {}, branchId: {}, resourceId: {}", result, xid, branchId, resourceId);
if (!result) {
// !!!FBI WARNING!!! 关键地方。把你做告警的代码放这里就可以了！！！
}
return result ? BranchStatus.PhaseTwo_Committed : BranchStatus.PhaseTwo_CommitFailed_Retryable;
} catch (Throwable t) {
String msg = String.format("commit TCC resource error, resourceId: %s, xid: %s.", resourceId, xid);
LOGGER.error(msg, t);
// !!!FBI WARNING!!! 关键地方。把你做告警的代码放这里就可以了！！！
return BranchStatus.PhaseTwo_CommitFailed_Retryable;
}
}

@Override
public BranchStatus branchRollback(BranchType branchType, String xid, long branchId, String resourceId,
String applicationData) throws TransactionException {
TCCResource tccResource = (TCCResource)tccResourceCache.get(resourceId);
if (tccResource == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not exist, resourceId: %s", resourceId));
}
Object targetTCCBean = tccResource.getTargetBean();
Method rollbackMethod = tccResource.getRollbackMethod();
if (targetTCCBean == null || rollbackMethod == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not available, resourceId: %s", resourceId));
}
try {
//BusinessActionContext
BusinessActionContext businessActionContext = getBusinessActionContext(xid, branchId, resourceId,
applicationData);
Object[] args = this.getTwoPhaseRollbackArgs(tccResource, businessActionContext);
Object ret;
boolean result;
// add idempotent and anti hanging
if (Boolean.TRUE.equals(businessActionContext.getActionContext(Constants.USE_TCC_FENCE))) {
try {
result = TCCFenceHandler.rollbackFence(rollbackMethod, targetTCCBean, xid, branchId,
args, tccResource.getActionName());
} catch (SkipCallbackWrapperException | UndeclaredThrowableException e) {
throw e.getCause();
}
} else {
ret = rollbackMethod.invoke(targetTCCBean, args);
if (ret != null) {
if (ret instanceof TwoPhaseResult) {
result = ((TwoPhaseResult)ret).isSuccess();
} else {
result = (boolean)ret;
}
} else {
result = true;
}
}
LOGGER.info("TCC resource rollback result : {}, xid: {}, branchId: {}, resourceId: {}", result, xid, branchId, resourceId);
if (!result) {
// !!!FBI WARNING!!! 关键地方。把你做告警的代码放这里就可以了！！！
}
return result ? BranchStatus.PhaseTwo_Rollbacked : BranchStatus.PhaseTwo_RollbackFailed_Retryable;
} catch (Throwable t) {
String msg = String.format("rollback TCC resource error, resourceId: %s, xid: %s.", resourceId, xid);
LOGGER.error(msg, t);
// !!!FBI WARNING!!! 关键地方。把你做告警的代码放这里就可以了！！！
return BranchStatus.PhaseTwo_RollbackFailed_Retryable;
}
}
```

Start with the issue's META-INF/services/io.seata.core.model.ResourceManager descriptor and the shown branchCommit and branchRollback entry points. The issue does not identify a repository documentation location or a concrete change, so first confirm whether the SPI-based alerting guidance should be converted into project documentation; completion criteria need maintainer agreement.

Written by the indexing model from the issue text.