[CELEBORN-2429][CIP-22] Batch worker/application heartbeats into aggregated raft log entries - #3810
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…egated raft log entries Aggregate heartbeats on the leader over a short time window (default 1s) into one BatchHeartbeat raft entry, cutting raft write volume by ~100x at peak. Off by default: celeborn.master.ha.heartbeat.batch.enabled.
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What changes were proposed in this pull request?
In HA mode, aggregate worker/application heartbeats on the master leader over a short time window (default 1s) and replicate them as ONE
BatchHeartbeatraft log entry, instead of one entry per heartbeat.HeartbeatAggregatoron the leader: pending heartbeats are kept in per-worker/per-app maps (newest wins, buffer intrinsically bounded), a scheduled thread flushes one batch per window; heartbeat RPCs are enqueued asynchronously and replied immediately from leader-local memory.BatchHeartbeatRequest/PbBatchHeartbeatRequest(Type.BatchHeartbeat = 31);MetaHandlerexpands the batch and applies each child heartbeat through the samehandleWorkerHeartbeat/handleAppHeartbeathelpers as the single-entry path.celeborn.master.ha.heartbeat.batch.enabled(false),celeborn.master.ha.heartbeat.batch.interval(1s).Design doc (CIP-22 Batched Heartbeat Raft Writes): https://docs.google.com/document/d/1YXDCjk_kR_5jyRGmUz1DqImjnAtsr7oFEwpYKK1NxAE/edit?usp=sharing
Why are the changes needed?
Heartbeats are the most frequent metadata writes: A/10 + W/30 raft entries/s for A apps and W workers. On one of our production clusters at peak (900+ running apps + 200 workers, ~97 heartbeat entries/s), follower apply lag (
RatisApplyCompletedIndexDiff) grows in lockstep withRunningApplicationCount(~50 -> 1000). A follower flame graph shows the cost is the per-entry raft pipeline (appendEntries ~35%, log flush/fsync ~20%), not apply compute (~7.7%).Heartbeats are periodic, self-healing, timeout-tolerant, and their replies are built from leader-local memory — they do not need a synchronous raft commit each. Batching cuts raft write volume by ~100x at peak.
Does this PR resolve a correctness bug?
Does this PR introduce any user-facing change?
How was this patch tested?
HeartbeatAggregatorSuiteJ(single-node raft, full offer → submit → replicate → apply chain): N offers produce far fewer entries; empty windows produce none; duplicate keys within one window collapse to the newest heartbeat.MasterStateMachineSuiteJ#testBatchHeartbeat: batched entry applies correctly and survives theResourceRequest→PbMetaRequestwire round-trip.