session: support leader-and-follower for tidb_replica_read #14761
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Signed-off-by: qupeng <qupeng@pingcap.com>
lysu
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Feb 13, 2020
store/tikv/region_cache.go
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| if len(candidates) == 0 { | ||
| return r.workTiKVIdx | ||
| } else { | ||
| return int32(seed) % int32(len(candidates)) |
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stores value are [leader, tiflash, tiflash, follower, follower]
seed be 2, len(candidates) be 3 and this method will return idx = 2 then r.getStorePeer will return a tiflash node in AnyStorePeer
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or stores value are [leader, follower(fail), follower(fail), follower(ok), follower(ok)] have same problem
Signed-off-by: qupeng <qupeng@pingcap.com>
Signed-off-by: qupeng <qupeng@pingcap.com>
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/run-all-tests |
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LGTM |
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tiancaiamao
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Feb 14, 2020
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/merge |
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@hicqu merge failed. |
Signed-off-by: qupeng <qupeng@pingcap.com>
Signed-off-by: qupeng <qupeng@pingcap.com>
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/merge |
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/run-all-tests |
tiancaiamao
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Feb 14, 2020
tiancaiamao
approved these changes
Feb 14, 2020
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/rebuild |
| @@ -93,13 +93,14 @@ const ( | |||
| ReplicaReadLeader ReplicaReadType = 1 << iota | |||
| // ReplicaReadFollower stands for 'read from follower'. | |||
| ReplicaReadFollower | |||
| // ReplicaReadLearner stands for 'read from learner'. | |||
| ReplicaReadLearner | |||
| // ReplicaReadMixed stands for 'read from leader and follower and learner'. | |||
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Signed-off-by: qupeng qupeng@pingcap.com
What problem does this PR solve?
Currently there is no option to support load balance for TiKV peers, we can only read from leader or followers, not both.
What is changed and how it works?
Support leader-and-follower for tidb_replica_read, which is a simple load balance strategy in all peers of a given region.
Check List
Tests
Unit test
Code changes
Has exported variable/fields change
Side effects
Related changes
Need to cherry-pick to release-4.0-beta.
Release note
support leader-and-follower for tidb_replica_read.