Page History

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• Impalad - debug port is 30000 + x , where x is the running number of impalads started. If 3 daemons are started, the ports range from 3000[0-2].
• Catalogd - debug port is 30000 + x, where x is the size of the cluster. If 3 daemons are started the debug port is 3000330030.

As soon as the JVM is started, it is possible to connect using the above ports. The simplest debugger is jdb:

(jdb is not too convenient by default, so it is recommended to wrap jdb in the rlwrap command, e.g.: alias jdb='rlwrap jdb')

jdb -attach localhost:3000030030

Using Eclipse to attach to a running Impalad JVM

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define hook-stop
  handle SIGSEGV stop print pass
end
define hook-run
  handle SIGSEGV nostop noprint pass
end
define hook-continue
  handle SIGSEGV nostop noprint pass
end

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The follow bash function is useful for getting the stack traces of all the threads (there are usually plenty of them).

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Additional .gdbinit fun can be had by using some of the "pretty printer" functions available for STL/Boost libraries. These are each added directly into the .gdbinit file as functions, or (with GDB v7+) using Python extensions. This helps to output data structures in a much easier to read format. Some examples are:
STL support
STL via Python
Boost support via Pythonpretty printers for GDB

Debugging on a cluster machine

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It is possible to debug impala core dumps generated on a different OS: Debugging Impala Core Dumps on Another System