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balance_region: remove unnecessary retry when pick region from a store. #5397

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AndreMouche opened this issue Aug 4, 2022 · 0 comments · May be fixed by #5398
Open

balance_region: remove unnecessary retry when pick region from a store. #5397

AndreMouche opened this issue Aug 4, 2022 · 0 comments · May be fixed by #5398
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type/enhancement The issue or PR belongs to an enhancement.

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@AndreMouche
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Enhancement Task

In scheduler balance region, we try and retry to pick a region from a store until success with the following priority:

  • pending region
  • follower
  • leader
  • learner

pd/server/schedulers/balance_region.go

Lines 170 to 194 in 99e38eb

for i := 0; i < retryLimit; i++ {
schedulerCounter.WithLabelValues(s.GetName(), "total").Inc()
// Priority pick the region that has a pending peer.
// Pending region may means the disk is overload, remove the pending region firstly.
plan.region = filter.SelectOneRegion(cluster.RandPendingRegions(plan.SourceStoreID(), s.conf.Ranges),
baseRegionFilters...)
if plan.region == nil {
// Then pick the region that has a follower in the source store.
plan.region = filter.SelectOneRegion(cluster.RandFollowerRegions(plan.SourceStoreID(), s.conf.Ranges),
append(baseRegionFilters, pendingFilter)...)
}
if plan.region == nil {
// Then pick the region has the leader in the source store.
plan.region = filter.SelectOneRegion(cluster.RandLeaderRegions(plan.SourceStoreID(), s.conf.Ranges),
append(baseRegionFilters, pendingFilter)...)
}
if plan.region == nil {
// Finally pick learner.
plan.region = filter.SelectOneRegion(cluster.RandLearnerRegions(plan.SourceStoreID(), s.conf.Ranges),
append(baseRegionFilters, pendingFilter)...)
}
if plan.region == nil {
schedulerCounter.WithLabelValues(s.GetName(), "no-region").Inc()
continue
}

However, I think if we failed to pick a region from pending regions, the possibility of successfully pick a region from the pending region is very very low, so could we skip to pick from pending in the next retry once we get no region from pending regions?
@AndreMouche AndreMouche added the type/enhancement The issue or PR belongs to an enhancement. label Aug 4, 2022
@AndreMouche AndreMouche linked a pull request Aug 4, 2022 that will close this issue
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balance_region: remove the unnecessary retry when try to pick a region to transfer AndreMouche/pd
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@AndreMouche