* filer.sync: send log file chunk fids to clients for direct volume server reads
Instead of the server reading persisted log files from volume servers, parsing
entries, and streaming them over gRPC (serial bottleneck), clients that opt in
via client_supports_metadata_chunks receive log file chunk references (fids)
and read directly from volume servers in parallel.
New proto messages:
- LogFileChunkRef: chunk fids + timestamp + filer ID for one log file
- SubscribeMetadataRequest.client_supports_metadata_chunks: client opt-in
- SubscribeMetadataResponse.log_file_refs: server sends refs during backlog
Server changes:
- CollectLogFileRefs: lists log files and returns chunk refs without any
volume server I/O (metadata-only operation)
- SubscribeMetadata/SubscribeLocalMetadata: when client opts in, sends refs
during persisted log phase, then falls back to normal streaming for
in-memory events
Client changes:
- ReadLogFileRefs: reads log files from volume servers, parses entries,
filters by path prefix, invokes processEventFn
- MetadataFollowOption.LogFileReaderFn: factory for chunk readers,
enables metadata chunks when non-nil
- Both filer_pb_tail.go and meta_aggregator.go recv loops accumulate
refs then process them at the disk→memory transition
Backward compatible: old clients don't set the flag, get existing behavior.
Ref: #8771
* filer.sync: merge entries across filers in timestamp order on client side
ReadLogFileRefs now groups refs by filer ID and merges entries from
multiple filers using a min-heap priority queue — the same algorithm
the server uses in OrderedLogVisitor + LogEntryItemPriorityQueue.
This ensures events are processed in correct timestamp order even when
log files from different filers have interleaved timestamps. Single-filer
case takes the fast path (no heap allocation).
* filer.sync: integration tests for direct-read metadata chunks
Three test categories:
1. Merge correctness (TestReadLogFileRefsMergeOrder):
Verifies entries from 3 filers are delivered in strict timestamp order,
matching the server-side OrderedLogVisitor guarantee.
2. Path filtering (TestReadLogFileRefsPathFilter):
Verifies client-side path prefix filtering works correctly.
3. Throughput comparison (TestDirectReadVsServerSideThroughput):
3 filers × 7 files × 300 events = 6300 events, 2ms per file read:
server-side: 6300 events 218ms 28,873 events/sec
direct-read: 6300 events 51ms 123,566 events/sec (4.3x)
parallel: 6300 events 17ms 378,628 events/sec (13.1x)
Direct-read eliminates gRPC send overhead per event (4.3x).
Parallel per-filer reading eliminates serial file I/O (13.1x).
* filer.sync: parallel per-filer reads with prefetching in ReadLogFileRefs
ReadLogFileRefs now has two levels of I/O overlap:
1. Cross-filer parallelism: one goroutine per filer reads its files
concurrently. Entries feed into per-filer channels, merged by the
main goroutine via min-heap (same ordering guarantee as the server's
OrderedLogVisitor).
2. Within-filer prefetching: while the current file's entries are being
consumed by the merge heap, the next file is already being read from
the volume server in a background goroutine.
Single-filer fast path avoids the heap and channels.
Test results (3 filers × 7 files × 300 events, 2ms per file read):
server-side sequential: 6300 events 212ms 29,760 events/sec
parallel + prefetch: 6300 events 36ms 177,443 events/sec
Speedup: 6.0x
* filer.sync: address all review comments on metadata chunks PR
Critical fixes:
- sendLogFileRefs: bypass pipelinedSender, send directly on gRPC stream.
Ref messages have TsNs=0 and were being incorrectly batched into the
Events field by the adaptive batching logic, corrupting ref delivery.
- readLogFileEntries: use io.ReadFull instead of reader.Read to prevent
partial reads from corrupting size values or protobuf data.
- Error handling: only skip chunk-not-found errors (matching server-side
isChunkNotFoundError). Other I/O or decode failures are propagated so
the follower can retry.
High-priority fixes:
- CollectLogFileRefs: remove incorrect +24h padding from stopTime. The
extra day caused unnecessary log file refs to be collected.
- Path filtering: ReadLogFileRefs now accepts PathFilter struct with
PathPrefix, AdditionalPathPrefixes, and DirectoriesToWatch. Uses
util.Join for path construction (avoids "//foo" on root). Excludes
/.system/log/ internal entries. Matches server-side
eachEventNotificationFn filtering logic.
Medium-priority fixes:
- CollectLogFileRefs: accept context.Context, propagate to
ListDirectoryEntries calls for cancellation support.
- NewChunkStreamReaderFromLookup: accept context.Context, propagate to
doNewChunkStreamReader.
Test fixes:
- Check error returns from ReadLogFileRefs in all test call sites.
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Co-authored-by: Copilot <copilot@github.com>
Chris Lu