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https://issues.apache.org/jira/browse/AVRO-512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13056566#comment-13056566
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Jeremy Lewi commented on AVRO-512:
----------------------------------
I think a deadlock can occur if the subprocess fails to start (e.g if the
executable is specified incorrectly). This happens because the constructor for
TetheredProcess starts the subprocess and then calls outputService.inputPort().
But inputPort() will block until the child process sends a configure message to
the parent; but if the child process wasn't started then I think the parent
deadlocks.
At a minimum we could check that the subprocess hasn't exited yet. This
probably won't prevent all possible deadlocks but it might help.
Below is some code for checking if the process has exited.
//is there a better way to check if the process has exited then the
roundabout way below?
boolean hasexited=false;
try {
//exitValue throws an exception if process hasn't exited
this.subprocess.exitValue();
hasexited=true;
}
catch (IllegalThreadStateException e){
//it hasn't exited yet
hasexited=true;
}
if (hasexited){
//What's the best way to log this
System.out.println("Error: Could not start subprocess");
throw new RuntimeException("Error: Could not start subprocess");
}
> define and implement mapreduce connector protocol
> -------------------------------------------------
>
> Key: AVRO-512
> URL: https://issues.apache.org/jira/browse/AVRO-512
> Project: Avro
> Issue Type: New Feature
> Components: java
> Reporter: Doug Cutting
> Assignee: Doug Cutting
> Fix For: 1.4.0
>
> Attachments: AVRO-512.patch, AVRO-512.patch, AVRO-512.patch,
> AVRO-512.patch
>
>
> Avro should provide Hadoop Mapper and Reducer implementations that connect to
> a subprocess in another programming language, transmitting raw binary values
> to and from that process. This should be modeled after Hadoop Pipes. It
> would allow one to easily write efficient mapreduce programs in non-Java
> languages that process Avro-format data.
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