Flink stucks在创建检查点时

Question

我有一份很轻松的工作，在创建检查站方面很吃力。它几乎没有州（除了一些Kafka偏移）。

工作本身有以下基本设置：

Kafka索资源-

迭代函数再次执行HTTP调用并转发成功的消息，丢弃4xx并重试5xx。从我的指标中可以看到，所有这些都发生了，我得到了一些5xx（返回迭代源）、一些4xx（忽略）和很多2xx（转发到HDFS）。

如果我查看线程转储，我可以看到某个任务被阻止了：

"Async calls on IterationSource-8 (1/1)" #123 daemon prio=5 os_prio=0 tid=0x00007f174000f800 nid=0x237 waiting for monitor entry [0x00007f17b32f5000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.performCheckpoint(StreamTask.java:747)
    - waiting to lock <0x00000000ace0f128> (a java.lang.Object)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.triggerCheckpoint(StreamTask.java:683)
    at org.apache.flink.runtime.taskmanager.Task$1.run(Task.java:1155)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    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)

这一个正在等待对象监视器，该监视器由以下对象保持：

"IterationSource-8 (1/1)" #63 prio=5 os_prio=0 tid=0x00007f17c00bf000 nid=0x1e0 in Object.wait() [0x00007f17b17d2000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    at org.apache.flink.runtime.io.network.buffer.LocalBufferPool.requestMemorySegment(LocalBufferPool.java:256)
    - locked <0x00000000acd030b0> (a java.util.ArrayDeque)
    at org.apache.flink.runtime.io.network.buffer.LocalBufferPool.requestBufferBuilderBlocking(LocalBufferPool.java:213)
    at org.apache.flink.runtime.io.network.partition.ResultPartition.getBufferBuilder(ResultPartition.java:181)
    at org.apache.flink.runtime.io.network.api.writer.RecordWriter.requestNewBufferBuilder(RecordWriter.java:256)
    at org.apache.flink.runtime.io.network.api.writer.RecordWriter.copyFromSerializerToTargetChannel(RecordWriter.java:184)
    at org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:154)
    at org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:120)
    at org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:107)
    at org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:89)
    at org.apache.flink.streaming.runtime.tasks.StreamIterationHead.performDefaultAction(StreamIterationHead.java:77)
    - locked <0x00000000ace0f128> (a java.lang.Object)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.run(StreamTask.java:298)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:403)
    at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:705)
    at org.apache.flink.runtime.taskmanager.Task.run(Task.java:530)
    at java.lang.Thread.run(Thread.java:748)

仔细查看源代码，我可以看到第二个线程（持有锁）似乎处于某种无休止的循环中：

LocalBufferPool。java：

while (availableMemorySegments.isEmpty()) {
}

亲爱的Flink大师，有什么线索可以看哪个指标吗？我正在使用Flink 1.9.0。

提前感谢任何提示！

Answer 1

在Flink Sink中使用HTTP调用时，我遇到了类似的检查点。经过大量的跟踪和错误，我发现，如果每秒的接收速率低于输入速率，检查点就会被击中。

为此，我为源（输入）指定了1的并行度，为HTTP调用指定了8的并行度。

这不会在等待HTTP响应时阻塞线程，从而发生检查点。我也是Flink的新手，希望一些大师解释为什么在flink中使用HTTP调用时检查点会变慢。