attilapiros commented on a change in pull request #24499: [SPARK-25888][Core]
Serve local disk persisted blocks by the external service after releasing
executor by dynamic allocation
URL: https://github.com/apache/spark/pull/24499#discussion_r280565768
##########
File path:
common/network-shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockResolver.java
##########
@@ -179,6 +179,18 @@ public ManagedBuffer getBlockData(
return getSortBasedShuffleBlockData(executor, shuffleId, mapId, reduceId);
}
+ public ManagedBuffer getBlockData(
Review comment:
In my next commit three changes regarding the handling of deleted files:
### Short overview of the changes
1) In `ExternalShuffleBlockResolver#getDiskPersistedRddBlockData` file
existence is explicitly checked before creating the `FileSegmentManagedBuffer`
and if the file is missing `null` is passed. Then extended
`OneForOneStreamManager` and `ChunkFetchRequestHandler` to handle correctly
this `null` value (in `ChunkFetchRequestHandler` an `IllegalStateException`
with the `Chunk was not found` message is thrown and this appears in the logs).
2) As the previous point is still not 100% perfect there is a change in
`BlockManager`. At block fetching the buffer size is required to be non-zero if
the blockSize is non zero (blockSize comes from the block manager master). I am
afraid here equality between these two properties cannot be checked as a
MEMORY_ONLY block might be fetched into the disk.
3) In the `Worker` I have added the warning about the overriding / switching
off the `spark.storage.cleanupFilesAfterExecutorExit` setting. I have checked
manually (and also the source code) that the cleanup is really done at the
stopping of the application.
### Manual tests
Several manual tests are done.
#### testing point 1)
After the 1) point
`ExternalShuffleBlockResolver#getDiskPersistedRddBlockData` and related changes
(here the my expectation was to see a re-trigger of the calculations over
silently fetched empty blocks):
~~~
$ grep "Attila: calculate" work/app-20190502115425-0000/*/stdout |wc -l
200
$ grep "Failed to fetch" -A3 work/app-20190502115425-0000/*/stderr
work/app-20190502115425-0000/10/stderr:19/05/02 11:56:07 ERROR
RetryingBlockFetcher: Failed to fetch block rdd_1_2, and will not retry (0
retries)
work/app-20190502115425-0000/10/stderr-org.apache.spark.network.client.ChunkFetchFailureException:
Failure while fetching StreamChunkId{streamId=1537044795002, chunkIndex=0}:
java.lang.IllegalStateException: Chunk was not found
work/app-20190502115425-0000/10/stderr- at
org.apache.spark.network.server.ChunkFetchRequestHandler.channelRead0(ChunkFetchRequestHandler.java:95)
work/app-20190502115425-0000/10/stderr- at
org.apache.spark.network.server.ChunkFetchRequestHandler.channelRead0(ChunkFetchRequestHandler.java:51)
--
work/app-20190502115425-0000/10/stderr:19/05/02 11:56:07 WARN BlockManager:
Failed to fetch block after 1 fetch failures. Most recent failure cause:
work/app-20190502115425-0000/10/stderr-org.apache.spark.SparkException:
Exception thrown in awaitResult:
work/app-20190502115425-0000/10/stderr- at
org.apache.spark.util.ThreadUtils$.awaitResult(ThreadUtils.scala:225)
work/app-20190502115425-0000/10/stderr- at
org.apache.spark.network.BlockTransferService.fetchBlockSync(BlockTransferService.scala:121)
~~~
#### testing point 2)
The `BlockManager` changes also tested separately from the previous point
(this also re-triggers the calculations on its own):
~~~
$ grep "Attila: calculate" work/app-20190502100445-0000/*/stdout | wc -l
200
$ grep "Failed to fetch" -A2 work/app-20190502110418-0000/*/stderr
work/app-20190502110418-0000/10/stderr:19/05/02 11:06:04 WARN BlockManager:
Failed to fetch block after 1 fetch failures. Most recent failure cause:
work/app-20190502110418-0000/10/stderr-java.lang.IllegalStateException:
Empty buffer received for non empty block
work/app-20190502110418-0000/10/stderr- at
org.apache.spark.storage.BlockManager.getRemoteManagedBuffer(BlockManager.scala:904)
--
work/app-20190502110418-0000/11/stderr:19/05/02 11:06:04 WARN BlockManager:
Failed to fetch block after 1 fetch failures. Most recent failure cause:
work/app-20190502110418-0000/11/stderr-java.lang.IllegalStateException:
Empty buffer received for non empty block
work/app-20190502110418-0000/11/stderr- at
org.apache.spark.storage.BlockManager.getRemoteManagedBuffer(BlockManager.scala:904)
--
work/app-20190502110418-0000/12/stderr:19/05/02 11:06:07 WARN BlockManager:
Failed to fetch block after 1 fetch failures. Most recent failure cause:
work/app-20190502110418-0000/12/stderr-java.lang.IllegalStateException:
Empty buffer received for non empty block
~~~
#### testing together
Finally I have tested the whole solution:
~~~
$ grep "Attila" work/app-20190502202206-0000/*/stdout | wc -l
100
~~~~
Along the test app is changed to do a local reduce on the collected RDD:
```scala
println("Calling collect on the first RDD: " + rdd.collect().reduce(_ + _))
```
This can be found in the logs:
```
Attila: sum: 4950
```
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