cauchy1988 opened a new pull request, #2410:
URL: https://github.com/apache/incubator-pegasus/pull/2410
## Background
Closes #2152. When using batch APIs (`Batch.asyncCommit` →
`FutureGroup.waitAllComplete`, a.k.a. `commitWaitAllComplete`), a
`NullPointerException` can occur intermittently.
## Root cause
`FutureGroup.waitAllComplete` builds the failure message by dereferencing
`fu.cause()`:
```java
} else {
results.add(Pair.of(
new PException("async task #[" + i + "] await failed: " +
fu.cause().getMessage()),
null));
}
```
A netty `Future.cause()` returns `null` **not only on success**, but also
**while the future is still incomplete**. If `await` times out before the
future ever resolves, `isSuccess()` is `false` (so we enter the `else` branch)
but `cause()` is still `null` — thus `cause().getMessage()` throws NPE,
crashing the entire batch commit instead of reporting just the single failed
task.
The sibling method `waitAllCompleteOrOneFail` is unaffected because it
passes `fu.cause()` directly to the `PException` constructor, which tolerates
`null`.
## Fix
Guard the dereference and fall back to a placeholder message when `cause()`
is `null`:
```java
Throwable cause = fu.cause();
String causeMsg = cause != null ? cause.getMessage() : "unknown cause
(future not completed)";
results.add(Pair.of(new PException("async task #[" + i + "] await failed: "
+ causeMsg), null));
```
This matches the fix suggested by the issue reporter.
## Test
Added `TestFutureGroup.testWaitAllCompleteHandlesNullCause`, which uses
Mockito to mock an incomplete Future (`await`→false, `isSuccess`→false,
`cause`→null) to reproduce the scenario deterministically, without relying on
timing.
Verified both directions:
- **With the fix**: all 3 tests in `TestFutureGroup` pass.
- **Without the fix** (temporarily reverted): the new test fails with the
exact NPE reported in the issue:
```
NullPointerException: Cannot invoke "Throwable.getMessage()" because the
return value of "io.netty.util.concurrent.Future.cause()" is null
at FutureGroup.waitAllComplete(FutureGroup.java:117)
```
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