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https://issues.apache.org/jira/browse/HADOOP-7256?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ramkrishna.s.vasudevan updated HADOOP-7256:
-------------------------------------------
Description:
Problem Statement:
===============
There are chances of resource leak and stream not getting closed
Take the case when after copying data we try to close the Input and output
stream followed by closing of the socket.
Suppose an exception occurs while closing the input stream(due to runtime
exception) then the subsequent operations of closing the output stream and
socket may not happen and there is a chance of resource leak.
Scenario
=======
During long run of map reduce jobs, the copyFromLocalFile() api is getting
called.
Here we found some exceptions happening. As a result of this we found the lsof
value raising leading to resource leak.
Solution:
=======
While doing a close operation of any resource catch the RuntimeException also
rather than catching the IOException alone.
Additionally there are places where we try to close a resource in the catch
block.
If this close fails, we just throw and come out of the current flow.
In order to avoid this, we can carry out the close operation in the finally
block.
Probable reasons for getting RunTimeExceptions:
=====================================
We may get runtime exception from customised hadoop streams like
FSDataOutputStream.close() . So better to handle RunTimeExceptions also.
was:
Problem Statement:
===============
There are chances of resource leak and stream not getting closed
Take the case when after copying data we try to close the Input and output
stream followed by closing of the socket.
Suppose an exception occurs while closing the input stream(due to runtime
exception) then the subsequent operations of closing the output stream and
socket may not happen and there is a chance of resource leak.
Scenario
=======
During long run of map reduce jobs, the copyFromLocalFile() api is getting
called.
Here we found some exceptions happening. As a result of this we found the lsof
value raising leading to resource leak.
Solution:
=======
While doing a close operation of any resource catch the RuntimeException also
rather than catching the IOException alone.
Additionally there are places where we try to close a resource in the catch
block.
If this close fails, we just throw and come out of the current flow.
In order to avoid this, we can carry out the close operation in the finally
block.
Probable reasons for getting RunTimeExceptions:
=====================================
We have many wrapped stream for writing and reading.
These wrappers are prone to errors.
> Resource leak during failure scenario of closing of resources.
> ---------------------------------------------------------------
>
> Key: HADOOP-7256
> URL: https://issues.apache.org/jira/browse/HADOOP-7256
> Project: Hadoop Common
> Issue Type: Bug
> Affects Versions: 0.20.2, 0.21.0
> Reporter: ramkrishna.s.vasudevan
> Priority: Minor
> Original Estimate: 8h
> Remaining Estimate: 8h
>
> Problem Statement:
> ===============
> There are chances of resource leak and stream not getting closed
> Take the case when after copying data we try to close the Input and output
> stream followed by closing of the socket.
> Suppose an exception occurs while closing the input stream(due to runtime
> exception) then the subsequent operations of closing the output stream and
> socket may not happen and there is a chance of resource leak.
> Scenario
> =======
> During long run of map reduce jobs, the copyFromLocalFile() api is getting
> called.
> Here we found some exceptions happening. As a result of this we found the
> lsof value raising leading to resource leak.
> Solution:
> =======
> While doing a close operation of any resource catch the RuntimeException also
> rather than catching the IOException alone.
> Additionally there are places where we try to close a resource in the catch
> block.
> If this close fails, we just throw and come out of the current flow.
> In order to avoid this, we can carry out the close operation in the finally
> block.
> Probable reasons for getting RunTimeExceptions:
> =====================================
> We may get runtime exception from customised hadoop streams like
> FSDataOutputStream.close() . So better to handle RunTimeExceptions also.
>
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