* Share metadata-log replays per chunk instead of per file
Log file chunks are immutable: each metadata-log flush uploads one whole
buffer of complete records as a new chunk, and appends only add chunks.
So cache decoded entries per chunk, with no age gate and no fingerprint
revalidation. The per-file cache excluded files younger than two flush
intervals, which is exactly the hot tail that every tailing or
reconnecting subscriber replays — each through a private chunk reader
holding an 8MB buffer and decoding the whole file from byte zero.
A chunk's flush time also upper-bounds every record timestamp inside it,
so a tail replay now skips cold chunks without reading them at all.
If a chunk does not decode standalone (records spanning chunk
boundaries, or a corrupt size prefix), fall back to streaming the whole
file as one byte stream, resuming after the last yielded entry.
* Evict idle metadata-log cache entries
The replay cache only evicted on insert, so once filled it held its full
budget forever. Stamp entries on use and sweep the LRU tail every minute,
dropping anything untouched for five minutes; the cache now holds memory
only while subscribers actually replay.
* Reject implausible records when decoding log chunks
proto.Unmarshal is permissive: empty payloads and unknown-field garbage
parse without error, so a chunk starting mid-record could decode by
coincidence and get cached instead of falling back to the byte stream.
Enforce what the writer guarantees - records are never empty and carry
strictly increasing positive timestamps within one flushed buffer.
* Gate the singleflight test on an open flight
The sleep alone only probabilistically created concurrent misses; a
started channel now proves the loader holds the flight before callers
are released.
Chris LuandGitHub
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