Proposal: handle SIGTERM by default to initiate graceful worker shutdown #3135

Summary

A Temporal Java worker installs no graceful-shutdown signal handling by default. The JVM runs shutdown hooks on SIGTERM, but the SDK registers none that drain the worker, so a bare worker exits without stopping polling or draining in-flight work. In-flight activities are abandoned and retried server-side after their timeouts.

Proposal: consider a built-in option to initiate WorkerFactory shutdown on SIGTERM by default (opt-out-able), so the common containerized case — stop polling → drain → cancel — works without extra wiring.

Current workaround

A JVM shutdown hook calling WorkerFactory.shutdown() → awaitTermination(timeout) → shutdownNow() (plus WorkerOptions.setAllowActivityHeartbeatDuringShutdown(true) to let a heartbeating activity finish during the drain); or run under the Spring Boot starter, which wires it.

Precedent

The TypeScript SDK already does this: its Runtime installs handlers for SIGINT/SIGTERM/SIGQUIT/SIGUSR2 by default and calls shutdown() on every worker.

Trade-offs / open questions (why it is not already the default)

• A worker usually runs inside a larger process (HTTP server, DI host, other lifecycle). A library installing a process-global signal handler can conflict with the host application's own signal handling, so any default must be clearly opt-out-able and should no-op when a host framework already owns the signal.
• Default-on vs. an explicit opt-in flag?
• If added, match the TypeScript semantics and honor the existing grace/drain config.

Why this comes up

SIGTERM-before-SIGKILL is the standard stop protocol for Kubernetes, Cloud Run, ECS, docker stop, and systemd. Users commonly expect a worker to drain on SIGTERM without extra wiring, and it is a recurring support question (e.g. https://community.temporal.io/t/proper-way-to-shutdown-on-sigterm-sigint/5485).

Related: #2026.

One of a set of sibling issues on default SIGTERM handling across the SDKs that do not auto-handle it today (Go, Python, Java, .NET, Ruby, Rust). TypeScript already does; PHP delegates process lifecycle to RoadRunner.