feat(shard-distributor): add shard handover latency metrics #7442
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arzonus
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| if len(newAssignedShardIDs) == 0 { | ||
| // no handovers happened, nothing to do | ||
| return | ||
| } |
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| if len(newAssignedShardIDs) == 0 { | |
| // no handovers happened, nothing to do | |
| return | |
| } |
Nit: This is not necessary, the loop below will just not run if the list is empty
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| for shardID, stats := range request.ShardStats { | ||
| // Update the executor's assigned_state key. | ||
| shardStatsKey := etcdkeys.BuildShardKey(s.prefix, namespace, shardID, etcdkeys.ShardStatisticsKey) | ||
| value, err := json.Marshal(stats) | ||
| if err != nil { | ||
| return fmt.Errorf("marshal assigned shards for shard %s: %w", shardID, err) | ||
| } | ||
| ops = append(ops, clientv3.OpPut(shardStatsKey, string(value))) | ||
| } |
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This will add an action per shard. ETCD cannot handle that - we should do this outside of the main write loop, like we do with shard statistics.
ETCd can by default, at most handle 128 operations in a single transaction. This is configurable, but we cannot have one per shard.
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What changed?
Added metrics to track shard assignment distribution and handover latency in the shard distributor service. This includes:
ShardDistributorShardAssignmentDistributionLatencymetric measuring time from shard assignment to distributionShardDistributorShardHandoverLatencymetric measuring handover time between executorsHandoverTypeenum (GRACEFUL/EMERGENCY) to distinguish handover typesShardAssignmentto track previous executor heartbeat time and handover metadataWhy?
To provide visibility into shard distribution performance and identify potential issues with shard handovers, particularly distinguishing between graceful and emergency handovers.
How did you test it?
Added comprehensive unit tests covering metric emission logic and shard statistics tracking.
Potential risks
Additional storage operations during heartbeat processing (mitigated by running metrics emission in background goroutine).
Release notes
Added shard handover latency metrics for monitoring distribution performance.
Documentation Changes
None required.