* filer: SQL store pool defaults survive concurrent walks (idle == open == 50, lifetime 300s)
The code defaults for the four SQL stores were connection_max_idle=2 with NO
default for connection_max_open (unlimited) or lifetime, while the scaffold
filer.toml documents 10/50/300 -- so an env-configured or minimal-toml filer got
the worst possible pool. Under a concurrent listing burst (s3.lifecycle.run-shard
walks 16 shards in parallel) every operation released above the 2 idle slots
closes its TCP connection, so the walk opens a fresh connection per operation
until the filer exhausts its ephemeral ports:
list /buckets/... : failed to connect ... dial tcp ...:5432:
connect: cannot assign requested address
Measured on a production filer: 0 -> 28k TIME_WAIT with only ~1.3k concurrent,
and in the minimal docker-compose reproduction (2000-dir bucket, port range
narrowed to 400): the whole range in TIME_WAIT with only ~12 ESTABLISHED.
Default all three knobs, with idle == open so released connections are kept and
reused: idle connections only accumulate up to the actual peak concurrency and
connection_max_lifetime_seconds recycles them, so a quiet deployment holds
nothing extra. An explicit 0 still disables the caps as before. The scaffold's
connection_max_idle moves 10 -> 50 to match.
With this change the same reproduction completes all 16 shards with the default
configuration (TIME_WAIT peak 19 vs the whole port range).
* filer: trim the SQL pool default comments
One line of the non-obvious why is enough; the rest narrated the code.
Claude-Session: https://claude.ai/code/session_018DWwctzD4T2DmnczPRM47t
* filer: leave the SQL stores' connection_max_open unset
A listing holds its connection for the whole row iteration while its callback
runs another query -- FilerStoreWrapper.maybeReadHardLink does a KvGet per
hard-linked entry -- so every concurrent listing needs two connections from the
same pool. With a default cap, listings past the cap wedge: 60 concurrent
listings over hard-linked entries made no progress at all against a 50
connection pool, and the wrapper's context.WithoutCancel leaves the waiters
without a deadline.
The idle pool is what fixes the connection churn: idle 50 with an unbounded
max_open holds the same 14 postgres sessions across a 16-way listing burst that
opened 455 with idle 2.
Claude-Session: https://claude.ai/code/session_018DWwctzD4T2DmnczPRM47t
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Co-authored-by: Chris Lu <chris.lu@gmail.com>
