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Add balancer meter fixes #4470 #4471
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Add balancer meter fixes #4470 #4471
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I believe that the
migrations
variable in the Manager contains all of the in-flight migrations. Theparams.migrationsOut
contains the tablets that need to be migrated from this call to the balancer. I think based on what I'm seeing here, it's double counting. I wonder if we just want the size of themigrations
list as that will encompass newly added, newly removed, and migrations waiting to happen.There was a problem hiding this comment.
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If you want to capture the newly added migrations, then it might make sense to capture the migration completions (which are in the TabletGroupWatcher) and cancellations (which happen in a couple places in the Manager).
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So to complete the #4470 ask, just recording
migrations.size()
would be sufficient.migrationsOut().size()
seems useful as a secondary metric for alerting if balancer progress stalls.Doing some general tests and with a single balancer call, both of the currently implemented metrics come back with the same values.
I think keeping
migrations.size()
under themigrations.needed
metric makes sense.in-progress
wording may need to be tweaked a bit to better describe last set of migrations generated.For users, a possible alert condition would be
migrationsOut().size()
is 0 whilemigrations.size()
is still greater than 0.There was a problem hiding this comment.
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put up #4699 as a continuation of these changes.