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Fixed metrics gauge callback deadlock #350

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merged 1 commit into from
Jun 12, 2023
Merged

Fixed metrics gauge callback deadlock #350

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2 changes: 1 addition & 1 deletion common/metrics/counter.go
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ func (c *upDownCounter) Sub(diff int) {
c.Add(-diff)
}

func NewUpDownCounter(name string, description string, unit Unit, labels map[string]any) Counter {
func NewUpDownCounter(name string, description string, unit Unit, labels map[string]any) UpDownCounter {
sc, err := meter.Int64UpDownCounter(name,
instrument.WithUnit(string(unit)),
instrument.WithDescription(description))
Expand Down
33 changes: 20 additions & 13 deletions server/shards_director.go
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,9 @@ type shardsDirector struct {
replicationRpcProvider ReplicationRpcProvider
closed bool
log zerolog.Logger

leadersCounter metrics.UpDownCounter
followersCounter metrics.UpDownCounter
}

func NewShardsDirector(config Config, walFactory wal.WalFactory, kvFactory kv.KVFactory, provider ReplicationRpcProvider) ShardsDirector {
Expand All @@ -65,18 +68,12 @@ func NewShardsDirector(config Config, walFactory wal.WalFactory, kvFactory kv.KV
log: log.With().
Str("component", "shards-director").
Logger(),
}

metrics.NewGauge("oxia_server_leaders_count", "The number of leader controllers in a server", "count", nil, func() int64 {
sd.RLock()
defer sd.RUnlock()
return int64(len(sd.leaders))
})
metrics.NewGauge("oxia_server_followers_count", "The number of followers controllers in a server", "count", nil, func() int64 {
sd.RLock()
defer sd.RUnlock()
return int64(len(sd.followers))
})
leadersCounter: metrics.NewUpDownCounter("oxia_server_leaders_count",
"The number of leader controllers in a server", "count", map[string]any{}),
followersCounter: metrics.NewUpDownCounter("oxia_server_followers_count",
"The number of follower controllers in a server", "count", map[string]any{}),
}

return sd
}
Expand Down Expand Up @@ -138,14 +135,18 @@ func (s *shardsDirector) GetOrCreateLeader(namespace string, shardId int64) (Lea
return nil, err
}

delete(s.followers, shardId)
if _, ok := s.followers[shardId]; ok {
s.followersCounter.Dec()
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@mattisonchao mattisonchao Jun 12, 2023 •
edited
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Is it better to call this line behind delete?

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I think it should be ok either way. We already checked the key is in the map, and the delete will not return error either.

delete(s.followers, shardId)
}
}

// Create new leader controller
if lc, err := NewLeaderController(s.config, namespace, shardId, s.replicationRpcProvider, s.walFactory, s.kvFactory); err != nil {
return nil, err
} else {
s.leaders[shardId] = lc
s.leadersCounter.Inc()
return lc, nil
}
}
Expand All @@ -169,14 +170,18 @@ func (s *shardsDirector) GetOrCreateFollower(namespace string, shardId int64) (F
return nil, err
}

delete(s.leaders, shardId)
if _, ok := s.leaders[shardId]; ok {
s.leadersCounter.Dec()
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Is it better to call this line behind delete?

delete(s.leaders, shardId)
}
}

// Create new follower controller
if fc, err := NewFollowerController(s.config, namespace, shardId, s.walFactory, s.kvFactory); err != nil {
return nil, err
} else {
s.followers[shardId] = fc
s.followersCounter.Inc()
return fc, nil
}
}
Expand All @@ -192,6 +197,7 @@ func (s *shardsDirector) DeleteShard(req *proto.DeleteShardRequest) (*proto.Dele
}

delete(s.leaders, req.ShardId)
s.leadersCounter.Dec()
return resp, nil
}

Expand All @@ -202,6 +208,7 @@ func (s *shardsDirector) DeleteShard(req *proto.DeleteShardRequest) (*proto.Dele
}

delete(s.followers, req.ShardId)
s.followersCounter.Dec()
return resp, nil
} else if fc, err := NewFollowerController(s.config, req.Namespace, req.ShardId, s.walFactory, s.kvFactory); err != nil {
return nil, err
Expand Down