fix: keep app online during deploy preparation

src/lib/deploy-workflow-contract.test.ts

@@ -6,6 +6,7 @@ const liveVar = "${" + "LIVE}";
 const stageVar = "${" + "STAGE}";
 const userVar = "${" + "DEPLOY_USER}";
 const groupVar = "${" + "DEPLOY_GROUP}";
+const cutoverStartedVar = "${" + "CUTOVER_STARTED}";
 
 function toContainLiteral(workflow: string, literal: string) {
 	return workflow.indexOf(literal) >= 0;
@@ -66,7 +67,7 @@ describe("production deploy workflow", () => {
 		expect(deployJob).toContain("pnpm typecheck");
 	});
 
-	it("swaps a built .next artifact during a short service cutover", () => {
+	it("migrates while the current app is online, then swaps the built artifact", () => {
 		expect(deployJob).toContain("mv .next .next.prev");
 		expect(toContainLiteral(deployJob, `mv "${stageVar}/.next" .next`)).toBe(
 			true,
@@ -84,12 +85,31 @@ describe("production deploy workflow", () => {
 			startLabelAt,
 		);
 		expect(buildAt).toBeGreaterThan(-1);
-		expect(stopAt).toBeGreaterThan(buildAt);
-		expect(migrateAt).toBeGreaterThan(stopAt);
-		expect(startLabelAt).toBeGreaterThan(migrateAt);
+		expect(migrateAt).toBeGreaterThan(buildAt);
+		expect(stopAt).toBeGreaterThan(migrateAt);
+		expect(startLabelAt).toBeGreaterThan(stopAt);
 		expect(startAt).toBeGreaterThan(startLabelAt);
 	});
 
+	it("does not restart the healthy app when deployment fails before cutover", () => {
+		const handlerStart = deployJob.indexOf("error_handler() {");
+		const handlerEnd = deployJob.indexOf("trap 'error_handler", handlerStart);
+		const handler = deployJob.slice(handlerStart, handlerEnd);
+		const cutoverGuardAt = handler.indexOf(
+			`if [ "${cutoverStartedVar}" = "1" ]; then`,
+		);
+		const restartAt = handler.indexOf("pm2 restart next", cutoverGuardAt);
+		const stageCleanupAt = handler.indexOf(`if [ -n "${stageVar}"`, restartAt);
+
+		expect(handlerStart).toBeGreaterThan(-1);
+		expect(cutoverGuardAt).toBeGreaterThan(-1);
+		expect(restartAt).toBeGreaterThan(cutoverGuardAt);
+		expect(stageCleanupAt).toBeGreaterThan(restartAt);
+		expect(handler.slice(restartAt, stageCleanupAt)).toContain(
+			"\n            fi",
+		);
+	});
+
 	it("does not override onlyBuiltDependencies (uses pnpm-workspace.yaml)", () => {
 		expect(workflow).not.toContain("PNPM_CONFIG_ONLY_BUILT_DEPENDENCIES");
 	});