Github user danny0405 commented on the issue:
https://github.com/apache/storm/pull/1874
@erikdw thx for your nice review, i have fixed the headline and ticket
title.
For this PR, the ratio is still 1:1 for tasks and executors for a
component, but not for the Storm before this PR [only for rebalance command].
For the old storm, The key here is that TOPOLOGY-TASKS is not changed for a
component when we do rebalance, we only change the executors number. Thus, when
we rebalance a smaller executors number for a component, the old bigger
TOPOLOGY-TASKS is partitioned into smaller number of executors, it works [we
finally reduce the executors], but some executors will have more than one
tasks; When we rebalance a bigger executors number for a component, it doesn't
work at all because the old smaller TOPOLOGY-TASKS is partitioned into bigger
number of executors, so some executors will not have task assigned and will not
start.
For example, for the old storm, if we have a topology named
example-topology which contains component like Spout S1[1 executors] -- Bolt
B1[2 executors] -- Bolt B2[4 executors], if we do a command `storm rebalance
example-topology -e B1=1` it will work, and the only executor for B1 will have
2 tasks inside; but for command `storm rebalance example-topology -e B1=4`, it
doesn't work at all and nothing changes finally.
For this PR, all the commands above work, and the ratio for tasks and
executors of a component is always 1:1
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