feat(storage): SQLite read-pool to alleviate writer contention#88
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feat(storage): SQLite read-pool to alleviate writer contention#88
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SQLite hardcodes MaxOpen=1 (correct: SQLite has a single-writer model), but
the Go driver pool serializes ALL operations through that one connection.
API/MCP read handlers were queueing behind in-flight writes/retention/VACUUM,
producing slow tail latency under load.
This change opens a separate *gorm.DB against the same file with MaxOpen=N
(default 4, range [1,32]) and PRAGMA query_only=ON. Read-only Repository
methods route through a new r.reader() accessor; writes (BatchCreate*,
Update*, Purge*, VacuumDB, FTS5/DDL) stay on r.db. WAL mode is already
enabled, so each read connection has its own snapshot and reads do not
block writers.
- New: internal/storage/factory.go: NewSQLiteReadPool(dsn, maxOpen).
- internal/storage/repository.go: readPool field, reader() accessor,
sqliteReadPoolSizeFromEnv() parser, NewRepository wiring (SQLite-only,
graceful fallback on factory failure), Close() now closes both pools.
- internal/storage/{log,trace,metrics,graph,archive}_repo.go: every
read-only path routed through reader(); writes unchanged.
- New: internal/storage/sqlite_read_pool_test.go: env parsing, query_only
INSERT-rejection, reader() identity fallback, concurrent reads + writes
with p99 latency assertion (<200ms; observed 22.85ms).
- CLAUDE.md: DB_SQLITE_READ_POOL_SIZE documented.
Non-SQLite drivers ignore the setting; reader() falls back to the writer
when readPool is nil. NewRepositoryFromDB does not open a read pool — its
doc now notes this so test authors aren't surprised by SQLite contention.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
*gorm.DBagainst the SQLite file withMaxOpen=N(default 4, range [1,32]) andPRAGMA query_only=ON. Read handlers route through a newr.reader()accessor; writes stay onr.db(which keepsMaxOpen=1per SQLite's single-writer model).DB_SQLITE_READ_POOL_SIZE(default 4;0/off/false/nodisables and falls back to writer). Non-SQLite drivers ignore the flag.Changes
internal/storage/factory.go::NewSQLiteReadPool(dsn, maxOpen)factory.internal/storage/repository.go:readPoolfield +reader()accessor, env parser,NewRepositorywiring (SQLite-only, graceful fallback on factory failure),Close()closes both pools (read-pool errors logged viaslog.Warn).internal/storage/{log,trace,metrics,graph,archive}_repo.go: every read-only path routed throughreader(); writes (BatchCreate*, Update*, Purge*, Vacuum, FTS5/DDL) unchanged.internal/storage/sqlite_read_pool_test.go: env parsing,query_only=ONINSERT-rejection,reader()identity fallback, concurrent reads + writes with p99 latency assertion.CLAUDE.md:DB_SQLITE_READ_POOL_SIZEdocumented.Test plan
🤖 Generated with Claude Code