Yes... and I had to figure out the answer to that same question about
two months ago myself. It was a question I
asked myself generally as:
What run-time attributes of a task are remembered/persisted across
task fail & restart sequences?.
Stated that way, the question involved not only task-id and task-index
persistence, but also whether Storm might
redistribute any Field Group that the failed task may have been
receiving, to surviving tasks... after all, the
in-memory state of the failed task was gone, so it's was possible to
redistribute it's Fields Group somewhere
else (in the interest of keeping things moving in Storm).
I couldn't find documentation on this and an understanding was necessary
because, for my purposes, it determined
whether-or-not (and how) I could recover the in-memory state of a failed
task (without replay).
So I took to instrumenting tests using REDIS Sets which, because of item
uniqueness in Sets, allowed me to easily
spot run-time attribute changes of a task before and after simulated
failures (via UNIX 'kill -9').
I wrote up my setup and findings in following little PDF document.
Basically what I found, at least anecdotally,
was that the task-ids, task-indices, as well as their Fields Groups (if
any) were preserved. This, in turn,
meant I could create task-unique identifiers like so, 'fqid =
componentID + . + taskIndex', as unique keys
into REDIS datastructures from which I could recover because,
essentially, 'fqid' didn't change before and after
failure.
Maybe this will help you...
http://didata.us/assets.d/DiData-StormRedis-Portfolio.pdf
Regards,
Noel
On 03/14/2014 06:35 PM, [email protected] wrote:
I believe once the topology is submitted you can count on the task
id's remaining the same. I use this to reload object data if one is
restarted. They could move to a different slot but should have the
same id.
Rick Rankin
Principal, Analytics & Assurance Services
Technical Risk Office: Cyber Security
Kaiser Permanente
Phone: 510.847.5269
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From: Manikandan <[email protected]>
To: [email protected]
Date: 03/14/2014 03:21 PM
Subject: Worker Task id during recovery
------------------------------------------------------------------------
Hi
When the worker dies and brought back by the supervisor, whats the
task id given to the new worker? Is it always same/different as/from
the old one?
Thanks & Regards
Manikandan
