java.io.IOException: error=7, Argument list too long
----------------------------------------------------

                 Key: HIVE-2372
                 URL: https://issues.apache.org/jira/browse/HIVE-2372
             Project: Hive
          Issue Type: Bug
          Components: Query Processor
    Affects Versions: 0.7.0
            Reporter: Sergey Tryuber
            Priority: Critical


I execute a huge query on a table with a lot of 2-level partitions. There is a 
perl reducer in my query. Maps worked ok, but every reducer fails with the 
following exception:

2011-08-11 04:58:29,865 INFO org.apache.hadoop.hive.ql.exec.ScriptOperator: 
Executing [/usr/bin/perl, <reducer.pl>, <my_argument>]
2011-08-11 04:58:29,866 INFO org.apache.hadoop.hive.ql.exec.ScriptOperator: 
tablename=null
2011-08-11 04:58:29,866 INFO org.apache.hadoop.hive.ql.exec.ScriptOperator: 
partname=null
2011-08-11 04:58:29,866 INFO org.apache.hadoop.hive.ql.exec.ScriptOperator: 
alias=null
2011-08-11 04:58:29,935 FATAL ExecReducer: 
org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime Error while 
processing row (tag=0) 
{"key":{"reducesinkkey0":129390185139228,"reducesinkkey1":"00008AF10000000063CA6F"},"value":{"_col0":"00008AF10000000063CA6F","_col1":"2011-07-27
 
22:48:52","_col2":129390185139228,"_col3":2006,"_col4":4100,"_col5":"10017388=6","_col6":1063,"_col7":"NULL","_col8":"address.com","_col9":"NULL","_col10":"NULL"},"alias":0}
        at 
org.apache.hadoop.hive.ql.exec.ExecReducer.reduce(ExecReducer.java:256)
        at 
org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:468)
        at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:416)
        at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:396)
        at 
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1115)
        at org.apache.hadoop.mapred.Child.main(Child.java:262)
Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Cannot initialize 
ScriptOperator
        at 
org.apache.hadoop.hive.ql.exec.ScriptOperator.processOp(ScriptOperator.java:320)
        at org.apache.hadoop.hive.ql.exec.Operator.process(Operator.java:471)
        at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:744)
        at 
org.apache.hadoop.hive.ql.exec.SelectOperator.processOp(SelectOperator.java:84)
        at org.apache.hadoop.hive.ql.exec.Operator.process(Operator.java:471)
        at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:744)
        at 
org.apache.hadoop.hive.ql.exec.ExtractOperator.processOp(ExtractOperator.java:45)
        at org.apache.hadoop.hive.ql.exec.Operator.process(Operator.java:471)
        at 
org.apache.hadoop.hive.ql.exec.ExecReducer.reduce(ExecReducer.java:247)
        ... 7 more
Caused by: java.io.IOException: Cannot run program "/usr/bin/perl": 
java.io.IOException: error=7, Argument list too long
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:460)
        at 
org.apache.hadoop.hive.ql.exec.ScriptOperator.processOp(ScriptOperator.java:279)
        ... 15 more
Caused by: java.io.IOException: java.io.IOException: error=7, Argument list too 
long
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:148)
        at java.lang.ProcessImpl.start(ProcessImpl.java:65)
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:453)
        ... 16 more

It seems to me, I found the cause. ScriptOperator.java puts a lot of configs as 
environment variables to the child reduce process. One of variables is 
mapred.input.dir, which in my case more than 150KB. There are a huge amount of 
input directories in this variable. In short, the problem is that Linux (up to 
2.6.23 kernel version) limits summary size of environment variables for child 
processes to 132KB. This problem could be solved by upgrading the kernel. But 
strings limitations still be 132KB per string in environment variable. So such 
huge variable doesn't work even on my home computer (2.6.32). You can read more 
information on 
(http://www.kernel.org/doc/man-pages/online/pages/man2/execve.2.html).

For now all our work has been stopped because of this problem and I can't find 
the solution. The only solution, which seems to me more reasonable is to get 
rid of this variable in reducers.




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