[RATIS-1202] Executor thread crashes on NPE

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Assignee: Rui Wang
• Reporter: Rui Wang
• Created: 04/Dec/20 03:48
• Updated: 04/Dec/20 06:42
• Resolved: 04/Dec/20 06:42

Description

If you change  the FileStore state machine implementation to 

 

  @Override
  public CompletableFuture<DataStream> stream(RaftClientRequest request) {
    return CompletableFuture.completedFuture(null);
  }

This will create a NPE at https://github.com/apache/incubator-ratis/blob/04ff37ef6fdef100cb7a424ba9f7b438aec2c9ba/ratis-netty/src/main/java/org/apache/ratis/netty/server/DataStreamManagement.java#L243.

However, it seems like the exception in thread in executor cannot be caught by

      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable throwable) {
        Optional.ofNullable(requestRef.getAndSetNull())
            .ifPresent(request -> requests.replyDataStreamException(throwable, request, ctx));
      }

as the exception is printed directly.

2020-12-03 20:22:08,680 WARN  server.DataStreamManagement (DataStreamManagement.java:sendDataStreamException(329)) - Failed to process DataStreamRequestByteBuf:STREAM_CLOSE,id=0,offset=2097152,length=0
java.util.concurrent.CompletionException: java.lang.NullPointerException
	at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273)
	at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280)
	at java.util.concurrent.CompletableFuture.uniApply(CompletableFuture.java:604)
	at java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:577)
	at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
	at org.apache.ratis.netty.server.DataStreamManagement.writeTo(DataStreamManagement.java:243)
	at org.apache.ratis.netty.server.DataStreamManagement$LocalStream.lambda$null$1(DataStreamManagement.java:80)
	at java.util.concurrent.CompletableFuture.uniApply(CompletableFuture.java:602)
	... 5 more