slfan1989 commented on code in PR #1281:
URL: https://github.com/apache/ratis/pull/1281#discussion_r2366012249
##########
ratis-server/src/test/java/org/apache/ratis/WatchRequestTests.java:
##########
@@ -302,7 +302,6 @@ static void checkAll(List<CompletableFuture<WatchReplies>>
watches, Logger log)
final WatchReplies watchReplies = watches.get(i).get(GET_TIMEOUT_SECOND,
TimeUnit.SECONDS);
final long logIndex = watchReplies.logIndex;
log.info("checkAll {}: logIndex={}", i, logIndex);
- final RaftClientReply watchAllReply = watchReplies.getAll();
Review Comment:
@adoroszlai I’ve analyzed this error in detail, but I still don’t fully
understand why the NPE is triggered. Below is the flow I’ve worked through —
could you and @szetszwo please take a look and let me know if I’ve missed
anything, or share any suggestions?
The failing test case:
`TestWatchRequestWithGrpc#testWatchRequestAsyncChangeLeader`
Error stack trace:
```
at org.apache.ratis.WatchRequestTests.checkAll(WatchRequestTests.java:305)
at
org.apache.ratis.WatchRequestTests.runTestWatchRequestAsyncChangeLeader(WatchRequestTests.java:370)
```
The issue occurs at line 305 in checkAll, corresponding to the following
code:
```
RaftClientReply getAll() throws Exception {
return get(all, "all");
}
RaftClientReply get(CompletableFuture<RaftClientReply> f, String name)
throws Exception {
final RaftClientReply reply = f.get(GET_TIMEOUT_SECOND, TimeUnit.SECONDS);
...
}
```
Here, all is null, so calling f.get(...) results in a NPE.
The value of all comes from:
```
new WatchReplies(logIndex,
...
writeClient.async().watch(logIndex, ReplicationLevel.ALL),
...
log)
```
From this, the only possible explanation is that
`writeClient.async().watch(logIndex, ReplicationLevel.ALL)` returned `null`,
which caused WatchReplies.all to be null and eventually led to the NPE inside
checkAll.
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