[GitHub] hoesler opened a new pull request #6748: fix(indexer): don't flush closed stream

[GitBox <gi...@apache.org>]

hoesler opened a new pull request #6748: fix(indexer): don't flush closed stream
URL: https://github.com/apache/incubator-druid/pull/6748
 
 
   I want to use s3 as a deep storage for druid (0.13-incubating). Therefore, I configured the _druid-hdfs-storage_ extension with an s3a url: `druid.storage.storageDirectory: s3a://****` (s3a is now better supported, thankfully to the hadoop version upgrade [2.8.3] in druid 0.13). This fails, however, for the following reason:
   
   The descriptor pusher [writes descriptor files](https://github.com/apache/incubator-druid/blob/cf15aac71f9f0f2ba41a2304d6b72719e6f7ec69/indexing-hadoop/src/main/java/org/apache/druid/indexer/JobHelper.java#L490) using the jackson object mapper to an output stream. The mapper will close the stream automatically. Therefore, flushing the stream afterwards might fail, depending on the implementation (and should by the contract of [OutputStream.close](https://docs.oracle.com/javase/8/docs/api/java/io/OutputStream.html#close--)). The s3a filesystem, for example, checks if the stream is open before flushing:
   
   ```
   Error: java.io.IOException: Filesystem {bucket=********, key='*********/0_descriptor.json'} closed
   	at org.apache.hadoop.fs.s3a.S3ABlockOutputStream.checkOpen(S3ABlockOutputStream.java:221)
   	at org.apache.hadoop.fs.s3a.S3ABlockOutputStream.flush(S3ABlockOutputStream.java:233)
   	at java.io.FilterOutputStream.flush(FilterOutputStream.java:140)
   	at java.io.DataOutputStream.flush(DataOutputStream.java:123)
   	at org.apache.druid.indexer.JobHelper$3.push(JobHelper.java:491)
   	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   	at java.lang.reflect.Method.invoke(Method.java:498)
   	at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:409)
   	at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeMethod(RetryInvocationHandler.java:163)
   	at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invoke(RetryInvocationHandler.java:155)
   	at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeOnce(RetryInvocationHandler.java:95)
   	at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:346)
   	at com.sun.proxy.$Proxy90.push(Unknown Source)
   	at org.apache.druid.indexer.JobHelper.writeSegmentDescriptor(JobHelper.java:503)
   	at org.apache.druid.indexer.JobHelper.serializeOutIndex(JobHelper.java:454)
   	at org.apache.druid.indexer.IndexGeneratorJob$IndexGeneratorReducer.reduce(IndexGeneratorJob.java:811)
   	at org.apache.druid.indexer.IndexGeneratorJob$IndexGeneratorReducer.reduce(IndexGeneratorJob.java:562)
   	at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:171)
   	at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:627)
   	at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:389)
   	at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:175)
   	at java.security.AccessController.doPrivileged(Native Method)
   	at javax.security.auth.Subject.doAs(Subject.java:422)
   	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1840)
   	at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:169)
   ```
   
   This PR fixes this bug, by removing the flush call.

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