Add stop-on-signals and auto-cancellation

When workflows are cancelled, any started builds are left running. This
is not usually desired, for example if using workflow concurrency[^1] to
cancel redundant builds. In cases like this, we'd want to also stop any
triggered builds.

This commit adds a `stop-on-signals` input with a default value of
`SIGINT` and updates the action to listen for the listed signal(s) and
stop any already-started build in response. This accomplishes the
desired behavior in the common case.

[^1]: https://docs.github.com/en/actions/using-jobs/using-concurrency#example-using-concurrency-to-cancel-any-in-progress-job-or-run

README.md

@@ -120,6 +120,13 @@ The only required input is `project-name`.
 1. **disable-github-env-vars** (optional) :
    Set to `true` if you want do disable github environment variables in codebuild.
 
+1. **stop-on-signals** (optional) :
+   Comma-separated list of signals that will cause any started builds to be
+   stopped. The default value is `SIGINT`, which is what GitHub sends processes
+   when a workflow is cancelled. This means you can use concurrency settings or
+   other GitHub features that cause workflow cancellations without leaving
+   orphan builds running. Set to an empty string to disable.
+
 ### Outputs
 
 1. **aws-build-id** : The CodeBuild build ID of the build that the action ran.

action.yml

@@ -46,6 +46,10 @@ inputs:
   artifacts-type-override:
       description: 'The type of build output artifact'
       required: false
+  stop-on-signals:
+    description: 'Comma separated list of process signals on which to stop the build. Default is SIGINT.'
+    required: false
+    default: 'SIGINT'
 outputs:
   aws-build-id:
     description: 'The AWS CodeBuild Build ID for this build.'

code-build.js

@@ -23,10 +23,16 @@ function runBuild() {
 
   const inputs = githubInputs();
 
-  const config = (({ updateInterval, updateBackOff, hideCloudWatchLogs }) => ({
+  const config = (({
     updateInterval,
     updateBackOff,
     hideCloudWatchLogs,
+    stopOnSignals,
+  }) => ({
+    updateInterval,
+    updateBackOff,
+    hideCloudWatchLogs,
+    stopOnSignals,
   }))(inputs);
 
   // Get input options for startBuild
@@ -39,10 +45,27 @@ async function build(sdk, params, config) {
   // Start the build
   const start = await sdk.codeBuild.startBuild(params);
 
+  // Set up signal handling to stop the build on cancellation
+  setupSignalHandlers(sdk, start.build.id, config.stopOnSignals);
+
   // Wait for the build to "complete"
   return waitForBuildEndTime(sdk, start.build, config);
 }
 
+function setupSignalHandlers(sdk, id, signals) {
+  signals.forEach((s) => {
+    core.info(`Installing signal handler for ${s}`);
+    process.on(s, async () => {
+      try {
+        core.info(`Caught ${s}, attempting to stop build...`);
+        await sdk.codeBuild.stopBuild({ id }).promise();
+      } catch (ex) {
+        core.error(`Error stopping build: ${ex}`);
+      }
+    });
+  });
+}
+
 async function waitForBuildEndTime(
   sdk,
   { id, logs },
@@ -226,6 +249,12 @@ function githubInputs() {
   const artifactsTypeOverride =
     core.getInput("artifacts-type-override", { required: false }) || undefined;
 
+  const stopOnSignals = core
+    .getInput("stop-on-signals", { required: false })
+    .split(",")
+    .map((i) => i.trim())
+    .filter((i) => i !== "");
+
   return {
     projectName,
     owner,
@@ -243,6 +272,7 @@ function githubInputs() {
     hideCloudWatchLogs,
     disableGithubEnvVars,
     artifactsTypeOverride,
+    stopOnSignals,
   };
 }