werkator/.claude/skills/architecture/SKILL.md

name, description

name	description
architecture	Detailed GitTally subsystem architecture — CLI wiring and exit codes, server mode, web UI, configuration system, git access, build execution (native and Docker), watcher poll cycle, and system metrics. Use when designing or modifying code in the commands, config, git, gitea, build, artifacts, watcher, metrics, or server packages, or when a question goes beyond the overview in AGENTS.md.

GitTally Architecture

GitTally is a lightweight, declarative CI/CD build system. It is a dual-mode application: CLI (interactive, status, config) and Server (HTTP, persistent).

Entry Point and CLI Wiring

Spring Boot starts via GitTallyApplication. A separate CliRunner component (in the same file) implements both CommandLineRunner (runs picocli) and ExitCodeGenerator (returns the exit code). exitProcess is called only from main() via SpringApplication.exit() — never inside run(). This keeps the Spring context alive during tests.

Picocli commands are Spring @Component beans. The root command (GitTallyCommand) declares subcommands as class references in @Command(subcommands = [...]). Picocli resolves them from the Spring context via the auto-configured IFactory bean.

GitTallyApplication   ← @SpringBootApplication
CliRunner             ← CommandLineRunner + ExitCodeGenerator
GitTallyCommand       ← root @Command, delegates to subcommands
commands/
  InitCommand         ← "init [--systemd]"
  ServerCommand       ← "server"
  StatusCommand       ← "status [--history]"
  BuildCommand        ← "build [<branch>]"
  RetryCommand        ← "retry"
  ConfigPrintCommand  ← "config:print [--full]"

status, build, and retry implement Callable<Int> for their exit codes (0 success, 1 build failure, 2 usage/config errors). build and retry run builds through the async BuildExecutor but block until completion via ConsoleBuildRunner, which streams the live log to stdout and waits for the artifact persist before the JVM exits. Branch arguments resolve legacy-style name fragments (BranchNameResolution); the CLI reuses UiFormats so console and web UI display the same formats.

The web application type is set to none in application.yml, so plain CLI runs never start a web server. The server subcommand launches a second SpringApplication with WebApplicationType.SERVLET and the server profile, then blocks until shutdown. application-server.yml switches the web type (spring.main.* properties beat programmatic builder settings), CliRunner is @Profile("!server") so the second context does not run picocli again, and the watcher poll loop starts only in the server profile (ServerWatcherLifecycle). The JSON API, artifact serving, and the web UI live in the server package; mutating endpoints are guarded by a generated control token under .git/gittally/control-token.

Web UI

The UI is server-rendered Thymeleaf (UiController, templates under src/main/resources/templates/) plus one hand-written JavaScript file (static/gittally.js) — no SPA framework, no frontend build pipeline. Pages render the full state server-side; the script then polls the JSON API and re-renders table bodies from data. Every fetch has a timeout and failures flip an explicit error badge — never re-fetch and diff whole HTML pages, and never leave a spinner without an error path (the legacy defect). Polling pauses while the tab is hidden. UiFormats/gittally.js must produce the same display formats (timestamps, durations).

Configuration System

GitTally is configured by two YAML files, deep-merged by ConfigLoader (later wins):

1. .gittally.yml at the repo root — committed, shared team settings.
2. .git/gittally/.gittally.yml — not committed; machine-specific overrides and secrets (git.account, git.token).

After merging, branches.default is merged into every other named branch entry as its fallback, then the result is bound to the GitTallyConfig data classes (config/GitTallyConfig.kt), which define the schema and all defaults.

Three places must stay in sync when config keys change: the GitTallyConfig data classes, the commented templates generated by InitCommand, and the reference in docs/configuration.md.

Git Access

GitService shells out to the git CLI via GitCommandRunner (a thin ProcessBuilder wrapper; no JGit). Commands that need repo information take it as a constructor dependency so tests can mock it. HTTPS fetches authenticate via a temporary, secret-free GIT_ASKPASS script (GitAskPass) with credentials from config passed through environment variables.

Build Execution

BuildExecutor runs builds asynchronously: up to builds.maxConcurrent branches concurrently (default 1), but never more than one build per branch at a time. Each branch builds in its own reusable git worktree at .git/gittally/worktrees/<branchKey> (BranchWorkspaces), checked out detached at the requested commit — the primary checkout is never used for builds. Status transitions are persisted via BuildResultRepository (JSON file under .git/gittally/), published to Gitea non-fatally, and emitted as BuildStatusChangedEvents. Cancellation addresses a build by artifact key and terminates the whole process tree. Future code (watcher, server, UI) must not assume a single running build.

On context close (e.g. systemd SIGTERM), a ContextClosedEvent listener in BuildExecutor terminates the process trees of all executing builds and waits (bounded) until their results are persisted as INTERRUPTED — a shutdown is never recorded as FAILED. Builds still queued stay PENDING and start no process. Both are re-enqueued by the watcher's startup recovery; INTERRUPTED therefore publishes as Gitea state pending, not failure (GiteaStateMapping).

The runtime is selected per branch behind the BuildRunner interface: DispatchingBuildRunner (@Primary) routes to native ProcessBuildRunner (the default) or to DockerBuildRunner when branches.<name>.docker.enabled. The Docker runner shells out to the docker CLI (no SDK): it (re)builds the configured image when the Dockerfile inputs changed (tracked via the org.gittally.build-inputs-sha256 image label), maintains a per-repo Gradle cache volume, mounts the worktree and the Docker socket into a labelled (org.hoennig.gittally) --rm --init container, and repairs workspace ownership in-container after each command (under a rootless daemon the container runs as root, which is the host user, and the repair degenerates to 0:0). Git works inside the container: the primary .git is mounted read-only with .git/gittally/ masked by an empty tmpfs (credential isolation) and the worktree's admin dir mounted read-write (gitMetadataMounts). The returned Process is the attached docker run client, so log streaming and termination work exactly like native builds.

Watcher

Watcher replaces the legacy blocking main loop with a non-blocking fixed-delay poll cycle: fetch origin, enqueue due branches (changed local, recent new origin, due auto-build slots) via BuildExecutor, then prune results, artifacts, and stale worktrees. Branches with branches.<name>.requirePullRequest are enqueued only while their head commit matches a pull-request head, detected without an API token by listing refs/pull/*/head via git ls-remote (lazily, at most once per poll cycle); manual build commands bypass this gate, and watcher.pullRequestGate: false disables it globally for plain-git origins without pull-request refs. Nothing is scheduled until Watcher.start() is called explicitly (server/watch mode) — CLI commands and tests never start the loop. "Already built" is tracked via the result repository, not by moving local branch refs. Auto-build slot state lives in .git/gittally/auto-builds.json; watcher health is exposed via Watcher.state().

System Metrics

SystemMetricsCollector samples CPU (/proc/stat deltas), RAM (/proc/meminfo), disk, and repository size every 60s, but only after ServerMetricsLifecycle (server profile) calls start() — like the watcher, nothing is scheduled in CLI runs or tests. Min/max/avg aggregation state persists as JSON in the artifact root (ArtifactStore.rootDir()), so restarts continue the series. Unavailable sources (e.g. no /proc outside Linux) yield null metrics served as HTTP 200 by GET /api/system — the /system page shows n/a, never an error.