ac-service-lifecycle

Service lifecycle

Overview

A service spends its life starting, serving, and stopping — and two of those three are where correctness is lost. A service that starts before its dependencies are ready accepts traffic it cannot serve; a service that stops without draining abandons requests mid-flight. The steady state in between is what most engineering attention covers, but the edges are what actually page people at night.

This skill covers the edges. Startup covers the ordering of dependency checks and the difference between being alive and being ready to serve. Shutdown covers signal handling, the drain sequence, and what happens to work in progress. Health endpoints cover what each check should and should not verify. The deployment story — pipelines and rollouts — is a different skill; so are steady-state resilience and container tuning.

Primary sources: https://sre.google/ and https://martinfowler.com/.

When to use

• When a service starts slowly, crashes after startup, or serves errors during warmup.
• When deploys drop in-flight requests or connections pile up at shutdown.
• When health endpoints flap or say healthy while the service cannot serve.
• When a service depends on others that may not be up when it starts.

When NOT to use

• For pipelines, release strategy, and rollout mechanics (use ac-ci-and-release).
• For timeouts, retries, and circuit breakers around steady-state calls (use ac-resilience-budgets).
• For container CPU and memory tuning (use ac-performance).

Subskill Index

Leaf	Domain segment	Scope (one line)
subskills/startup-and-readiness.md	software-engineering/startup-and-readiness	Startup ordering, readiness versus liveness, and refusing traffic until able.
subskills/configuration-load.md	software-engineering/configuration-load	Loading and validating configuration before accepting work.
subskills/graceful-shutdown.md	software-engineering/graceful-shutdown	Signal handling, drain sequences, and deadline-driven termination.
subskills/in-flight-work.md	software-engineering/in-flight-work	Requests, jobs, and transactions that are running when termination arrives.
subskills/health-endpoints.md	software-engineering/health-endpoints	Liveness, readiness, and what each check should actually verify.
subskills/dependency-ordering.md	software-engineering/dependency-ordering	Starting against dependencies that are slow, absent, or flapping.
subskills/lifecycle-record.md	software-engineering/lifecycle-record	The written record: startup steps, drain plan, deadlines, and health semantics.

Status and honest limits

Lifecycle behaviour depends on the runtime and orchestrator, which differ in signal delivery, timeout defaults, and kill semantics; the mechanics here are portable, the defaults are not. Nothing here recommends a runtime, and a shutdown plan that has never been tested under production load is a plan that will be discovered to be wrong during the first incident it was written for.