process-lifecyclelisted

PostgreSQL's per-connection multi-process model — postmaster fork, backend startup / initialization / query loop / clean shutdown, auxiliary processes (checkpointer, bgwriter, walwriter, autovacuum launcher, WAL summarizer, pgarch), background workers (bgworker.c registry + parallel/logical-rep workers), signal handling, and the FATAL/ERROR/PANIC hierarchy. Loads when the user asks about how a connection becomes a backend, what runs before the first query, why a query dies mid-flight, how signals + ProcessInterrupts + CHECK_FOR_INTERRUPTS work together, how autovacuum / bgworker workers get scheduled, or when planning a feature that hooks a startup phase / adds a new auxiliary process / touches shutdown ordering. Skip when the question is about client-side (libpq, drivers) or about the SQL-level session properties (that's `tcop` for query dispatch, `gucs-config` for GUCs).
matejformanek/postgres-claude · ★ 0 · AI & Automation · score 70

Install: claude install-skill matejformanek/postgres-claude

# process-lifecycle — postmaster, backends, aux processes, bgworkers PostgreSQL uses a **per-connection process model, not threads**. Every client connection gets its own OS process, forked from the postmaster. New backends do NOT inherit query state — every connection starts fresh through `InitPostgres`. This model shapes almost every feature. ## The five process classes | Class | Files | Lifetime | Example | |---|---|---|---| | **Postmaster** | `postmaster/postmaster.c`, `pmchild.c`, `launch_backend.c`, `fork_process.c` | Cluster-lifetime | The parent process — accepts connections, forks children, reaps exits, restarts on crash. | | **Regular backend** | `tcop/postgres.c`, `tcop/backend_startup.c` | Connection-lifetime | The child that runs SQL for one client. | | **Auxiliary process** | `postmaster/auxprocess.c` + one file each: `checkpointer.c`, `bgwriter.c`, `walwriter.c`, `walsummarizer.c`, `startup.c`, `pgarch.c`, `syslogger.c`, `interrupt.c` | Cluster-lifetime | Always-on infrastructure processes; not for user queries. | | **Bgworker** | `postmaster/bgworker.c` + registered by extensions | Configurable (per session / for lifetime of cluster / restart on crash) | Autovacuum workers, parallel query workers, logical-rep apply workers, extension workers. | | **Autovacuum launcher/worker** | `postmaster/autovacuum.c` | Cluster-lifetime launcher + short-lived workers | Special case: launcher is aux, workers are bgworkers. | ## Backend lifecycle (regular query-serving ba