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Posts: 24
Registered: ‎11-15-2016

HiveServer2 - disable local task execution

Hi,

 

I'm currently experiencing an issue with some hive queries being launched as local tasks in HiveServer2.

In the log of the local task (in /tmp/hive/<query_id>.log) I can see that the issue is that the task runs out of memory:

 

2017-06-23 10:43:39,503 ERROR [main]: mr.MapredLocalTask (MapredLocalTask.java:executeInProcess(377)) - Hive Runtime Error: Map local work exhausted memory
org.apache.hadoop.hive.ql.exec.mapjoin.MapJoinMemoryExhaustionException: 2017-06-23 10:43:39    Processing rows:        200000  Hashtable size: 199999  Memory usage:   572176016       percentage:     0.551
        at org.apache.hadoop.hive.ql.exec.mapjoin.MapJoinMemoryExhaustionHandler.checkMemoryStatus(MapJoinMemoryExhaustionHandler.java:99)
        at org.apache.hadoop.hive.ql.exec.HashTableSinkOperator.processOp(HashTableSinkOperator.java:249)
        at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:815)
        at org.apache.hadoop.hive.ql.exec.FilterOperator.processOp(FilterOperator.java:120)
        at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:815)
        at org.apache.hadoop.hive.ql.exec.TableScanOperator.processOp(TableScanOperator.java:97)
        at org.apache.hadoop.hive.ql.exec.mr.MapredLocalTask.startForward(MapredLocalTask.java:432)
        at org.apache.hadoop.hive.ql.exec.mr.MapredLocalTask.startForward(MapredLocalTask.java:403)
        at org.apache.hadoop.hive.ql.exec.mr.MapredLocalTask.executeInProcess(MapredLocalTask.java:369)
        at org.apache.hadoop.hive.ql.exec.mr.ExecDriver.main(ExecDriver.java:743)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:136)

But I don't understand why HiveServer runs these queries in local mode: from the documentation https://cwiki.apache.org/confluence/display/Hive/GettingStarted#GettingStarted-Hive,Map-ReduceandLoc... this feature should be disabled by default and I haven't changed this.

 

Is there another way to permanently disable this feature on the server? I don't want to run these operations on the server...

Posts: 642
Topics: 3
Kudos: 116
Solutions: 67
Registered: ‎08-16-2016

Re: HiveServer2 - disable local task execution

That setting, mapreduce.framework.name, can be found in the the yarn-site.xml.  Check for it under /etc/hadoop/conf/ and for the value.  If it is there with yarn as the value, then it is likely that HS2 is not running with the correct Hadoop environmental variables like HADOOP_CONF_DIR.  If it isn't there or the value is incorrect then try  installing the YARN gateway role on the HS2 host.

Explorer
Posts: 24
Registered: ‎11-15-2016

Re: HiveServer2 - disable local task execution

Thanks mbigelow for the response.

 

I will add the YARN gateway and try again but I don't think this is the issue because only a subset of the queries are executed in local mode: a lot of other queries are executed via MR (and I have other queries executed via HiveOnSpark).

 

It looks like some queries are "optimized" in local mode.

Posts: 642
Topics: 3
Kudos: 116
Solutions: 67
Registered: ‎08-16-2016

Re: HiveServer2 - disable local task execution

Ah, what you are looking for is the setting:

Fetch Task Query Conversion
hive.fetch.task.conversion

Setting this to none will force all queries to run in MR.
Explorer
Posts: 24
Registered: ‎11-15-2016

Re: HiveServer2 - disable local task execution

I've done a test with:

 

SET hive.fetch.task.conversion=none;

And some tasks are still getting executed in local mode (I've tried a couple of different queries):

 

INFO  : Starting task [Stage-14:MAPREDLOCAL] in serial mode
Posts: 642
Topics: 3
Kudos: 116
Solutions: 67
Registered: ‎08-16-2016

Re: HiveServer2 - disable local task execution

I am not positive on this but I think this is a HS2 setting as the functionality is that at HS2 it decides whether to run it locally or to launch a MR job.

Try applying the change to HS2 and restarting.
Cloudera Employee
Posts: 86
Registered: ‎11-20-2015

Re: HiveServer2 - disable local task execution

The way things are implemented, a MapJoin optimization will always use local task operation.  If you would like to remove all instances of local tasks, you will have to disable MapJoins.

 

Please examine these two explain plans (first with MapJoin enabled, second with disabled)

 

 

| STAGE PLANS:                                       |
|   Stage: Stage-5                                   |
|     Map Reduce Local Work                          |
|       Alias -> Map Local Tables:                   |
|         s07                                        |
|           Fetch Operator                           |
|             limit: -1                              |
|       Alias -> Map Local Operator Tree:            |
|         s07                                        |
|           TableScan                                |
|             alias: s07                             |
|             filterExpr: code is not null (type: boolean) |
|             Statistics: Num rows: 225 Data size: 46055 Basic stats: COMPLETE Column stats: NONE |
|             Filter Operator                        |
|               predicate: code is not null (type: boolean) |
|               Statistics: Num rows: 113 Data size: 23129 Basic stats: COMPLETE Column stats: NONE |
|               HashTable Sink Operator              |
|                 keys:                              |
|                   0 code (type: string)            |
|                   1 code (type: string)            |

 

 

 

| STAGE PLANS:                                       |
|   Stage: Stage-1                                   |
|     Map Reduce                                     |
|       Map Operator Tree:                           |
|           TableScan                                |
|             alias: s07                             |
|             filterExpr: code is not null (type: boolean) |
|             Statistics: Num rows: 225 Data size: 46055 Basic stats: COMPLETE Column stats: NONE |
|             Filter Operator                        |
|               predicate: code is not null (type: boolean) |
|               Statistics: Num rows: 113 Data size: 23129 Basic stats: COMPLETE Column stats: NONE |
|               Reduce Output Operator               |
|                 key expressions: code (type: string) |
|                 sort order: +                      |
|                 Map-reduce partition columns: code (type: string) |
|                 Statistics: Num rows: 113 Data size: 23129 Basic stats: COMPLETE Column stats: NONE |
|                 value expressions: description (type: string), salary (type: int) |
|           TableScan                                |
|             alias: s08                             |
|             filterExpr: code is not null (type: boolean) |
|             Statistics: Num rows: 442 Data size: 46069 Basic stats: COMPLETE Column stats: NONE |
|             Filter Operator                        |
|               predicate: code is not null (type: boolean) |
|               Statistics: Num rows: 221 Data size: 23034 Basic stats: COMPLETE Column stats: NONE |
|               Reduce Output Operator               |
|                 key expressions: code (type: string) |
|                 sort order: +                      |
|                 Map-reduce partition columns: code (type: string) |
|                 Statistics: Num rows: 221 Data size: 23034 Basic stats: COMPLETE Column stats: NONE |
|                 value expressions: salary (type: int) |

 

 

We can see that the first one uses "Map Reduce Local Work" and the second one does not.

 

set hive.auto.convert.join=false;

 

https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties

 

This can be important becaue I'm seeing a case where the Local Job Runners are leaking the log file output from these Local Job Runners into the HS2's /tmp directory in the following format:

 

/tmp/hive_20171219184242_3ecaf468-51c7-4ced-99b3-6bd9eaaa980a.log

 

Disable the MapJoin optimization and these log files are not generated.

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