fix: gracefully handle uninitialized PgLwLock in Docker#28
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PgLwLock is only initialized when the extension is loaded via shared_preload_libraries. If the base Docker image overrides shared_preload_libraries (e.g. via postgresql.auto.conf or conf.d/), pg_duckpipe is not preloaded and status()/worker_status()/metrics() crash with "PgLwLock was not initialized". - Add SHM_AVAILABLE AtomicBool flag set during _PG_init only when process_shared_preload_libraries_in_progress is true - Guard all SHM access functions to return defaults/no-op when the lock is unavailable instead of panicking - Emit WARNING at extension load and NOTICE on SHM reads when not in shared_preload_libraries - Add ALTER SYSTEM in Docker init script to ensure shared_preload_libraries is set in postgresql.auto.conf (overrides any conf.d/ or postgresql.conf settings) - Include pg_ducklake in shared_preload_libraries alongside pg_duckdb and pg_duckpipe Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
PgLwLockis only initialized when the extension is loaded viashared_preload_libraries. If the base Docker image overridesshared_preload_libraries(e.g. viapostgresql.auto.conforconf.d/),pg_duckpipeis not preloaded andstatus()/worker_status()/metrics()crash withERROR: PgLwLock was not initialized.SHM_AVAILABLEAtomicBool flag checked byprocess_shared_preload_libraries_in_progressin_PG_init. All SHM access functions (read_shmem_table_metrics,read_shmem_group_metrics,write_shmem_metrics,clear_shmem_table_slot,clear_shmem_group_slot) now return defaults/no-op when the lock is unavailable. EmitsWARNINGat load time andNOTICEon reads.ALTER SYSTEM SET shared_preload_libraries = 'pg_duckdb,pg_ducklake,pg_duckpipe'in the init script — writes topostgresql.auto.confwhich always takes precedence overpostgresql.confandconf.d/settings. Also updated thepostgresql.conf.sampleline to includepg_ducklake.Test plan
make installcheck— all 30 regression tests passdocker run, connect, callSELECT * FROM duckpipe.status()— should return results (not crash)SHOW shared_preload_librariesincludespg_duckdb,pg_ducklake,pg_duckpipeshared_preload_libraries:CREATE EXTENSION pg_duckpipethenSELECT * FROM duckpipe.status()— should return empty results with NOTICE (not crash)🤖 Generated with Claude Code