More than 120 counters in hadoop

问题:

There's a limit for Hadoop counter size. It's 120 by default. I try to use the configuration "mapreduce.job.counters.limit" to change that, but it doesn't work. I've seen the source code. It's like the instance of JobConf in class "org.apache.hadoop.mapred.Counters" is private. Have anybody seen that before? What's your solution? THX :)

回答1:

You can override that property in mapred-site.xml on your JT, TT, client nodes but make sure that this will be a system-wide modification:

<configuration>
  ...
  <property>
    <name>mapreduce.job.counters.limit</name>
    <value>500</value>
  </property>
  ...
</configuration>

Then restart the mapreduce service on your cluster.

回答2:

In Hadoop 2, this configuration parameter is called

mapreduce.job.counters.max

Setting it on the command line or in your Configuration object isn't enough, though. You need to call the static method

org.apache.hadoop.mapreduce.counters.Limits.init()

in the setup() method of your mapper or reducer to get the setting to take effect.

Tested with 2.6.0 and 2.7.1.

回答3:

The para is set by config file, while paras below will take effect

mapreduce.job.counters.max=1000 
mapreduce.job.counters.groups.max=500 
mapreduce.job.counters.group.name.max=1000 
mapreduce.job.counters.counter.name.max=500 

回答4:

Just adding this in case anyone else faces the same problem we did: increasing the counters from with MRJob.

To raise the number of counters, add emr_configurations to your mrjob.conf (or pass it to MRJob as a config parameter):

runners:
  emr:
    emr_configurations:
      - Classification: mapred-site
        Properties:
          mapreduce.job.counters.max: 1024
          mapreduce.job.counters.counter.name.max: 256
          mapreduce.job.counters.groups.max: 256
          mapreduce.job.counters.group.name.max: 256

回答5:

We can customize the limits as command line options only for specific jobs, instead of making change in mapred-site.xml.

-Dmapreduce.job.counters.limit=x
-Dmapreduce.job.counters.groups.max=y

NOTE: x and y are custom values based on your environment/requirement.