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Signed-off-by: Shuaipeng Yu <[email protected]>
pingcap · May 6, 2019 · c88a0c5 · c88a0c5
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commit c88a0c5
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diff --git a/sessionctx/variable/tidb_vars.go b/sessionctx/variable/tidb_vars.go
@@ -220,6 +220,9 @@ const (
 	TiDBBackoffLockFast = "tidb_backoff_lock_fast"
 
 	// tidb_back_off_weight is used to control the max back off time in TiDB.
+	// The default maximum back off time is a small value.
+	// BackOffWeight could multiply it to let the user adjust the maximum time for retrying.
+	// Only positive integers can be accepted, which means that the maximum back off time can only grow.
 	TiDBBackOffWeight = "tidb_back_off_weight"
 
 	// tidb_ddl_reorg_worker_cnt defines the count of ddl reorg workers.

diff --git a/store/tikv/backoff.go b/store/tikv/backoff.go
@@ -241,6 +241,8 @@ func (b *Backoffer) WithVars(vars *kv.Variables) *Backoffer {
 	if vars != nil {
 		b.vars = vars
 	}
+	// maxSleep is the max sleep time in millisecond.
+	// When it is multiplied by BackOffWeight, it should not be greater than MaxInt32.
 	if math.MaxInt32/b.vars.BackOffWeight >= b.maxSleep {
 		b.maxSleep *= b.vars.BackOffWeight
 	}