chore: improve random cron generation

src/alert-open-prs.ts

@@ -6,6 +6,7 @@
 import { cdk } from "projen";
 import { GithubWorkflow } from "projen/lib/github";
 import { JobPermission } from "projen/lib/github/workflows-model";
+import { generateRandomCron, Schedule } from "./util/random-cron";
 
 const DEFAULT_MAX_HOURS_OPEN = 2;
 
@@ -25,8 +26,17 @@ export class AlertOpenPrs {
 
     const workflow = new GithubWorkflow(project.github!, "alert-open-prs");
     workflow.on({
-      workflowDispatch: {},
-      schedule: [{ cron: "* */12 * * 1-5" }], // every 12 hours, Monday-Friday
+      // run on weekdays sometime during working hours (8am-4pm UTC)
+      schedule: [
+        {
+          cron: generateRandomCron({
+            project,
+            maxHour: 8,
+            hourOffset: 8,
+            schedule: Schedule.Weekdays,
+          }),
+        },
+      ],
     });
     workflow.addJob("check-open-prs", {
       runsOn: ["ubuntu-latest"],

src/index.ts

@@ -20,6 +20,7 @@ import { PackageInfo } from "./package-info";
 import { ProviderUpgrade } from "./provider-upgrade";
 import { CheckForUpgradesScriptFile } from "./scripts/check-for-upgrades";
 import { ShouldReleaseScriptFile } from "./scripts/should-release";
+import { generateRandomCron } from "./util/random-cron";
 
 // ensure new projects start with 1.0.0 so that every following breaking change leads to an increased major version
 const MIN_MAJOR_VERSION = 1;
@@ -450,6 +451,13 @@ export class CdktfProviderProject extends cdk.JsiiProject {
         " or cancel via faking a SHA if release was cancelled";
     }
 
+    const staleWorkflow = this.tryFindObjectFile(".github/workflows/stale.yml");
+    staleWorkflow?.addOverride("on.schedule", [
+      {
+        cron: generateRandomCron({ project: this, maxHour: 4, hourOffset: 1 }),
+      },
+    ]);
+
     // Submodule documentation generation
     this.gitignore.exclude("API.md"); // ignore the old file, we now generate it in the docs folder
     this.addDevDeps("jsii-docgen@^10.2.3");

src/lock-issues.ts

@@ -3,9 +3,9 @@
  * SPDX-License-Identifier: MPL-2.0
  */
 
-import { createHash } from "crypto";
 import { javascript } from "projen";
 import { JobPermission } from "projen/lib/github/workflows-model";
+import { generateRandomCron } from "./util/random-cron";
 
 /**
  * Automatically locks issues and PRs after 7 days. Note that 90% of the issues and PRs
@@ -18,14 +18,9 @@ export class LockIssues {
 
     if (!workflow) throw new Error("no workflow defined");
 
-    const projectNameHash = createHash("md5")
-      .update(project.name)
-      .digest("hex");
-    const scheduleHour = parseInt(projectNameHash.slice(0, 2), 16) % 24;
-    const scheduleMinute = parseInt(projectNameHash.slice(2, 4), 16) % 24;
-
     workflow.on({
-      schedule: [{ cron: `${scheduleHour} ${scheduleMinute} * * *` }],
+      // run daily sometime between midnight and 6am UTC
+      schedule: [{ cron: generateRandomCron({ project, maxHour: 6 }) }],
     });
 
     workflow.addJob("lock", {

src/util/random-cron.ts

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) HashiCorp, Inc.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
+import { createHash } from "crypto";
+import { javascript } from "projen";
+
+export enum Schedule {
+  Daily = "DAILY",
+  Weekly = "WEEKLY",
+  Monthly = "MONTHLY",
+  Weekdays = "WEEKDAYS",
+}
+
+export interface RandomCronOptions {
+  project: javascript.NodeProject;
+  maxHour?: number;
+  hourOffset?: number;
+  schedule?: Schedule;
+}
+
+export function generateRandomCron(options: RandomCronOptions) {
+  const maxHour = options.maxHour ? Math.round(options.maxHour) : 24;
+  const hourOffset = options.hourOffset ? Math.round(options.hourOffset) : 0;
+  const schedule = options.schedule || Schedule.Daily; // default to daily
+
+  const project = options.project;
+  const hash = createHash("md5").update(project.name).digest("hex");
+  const hour = maxHour === 0 ? 0 : parseInt(hash.slice(0, 2), 16) % maxHour;
+  const minute = parseInt(hash.slice(2, 4), 16) % 60;
+
+  const dayOfMonth = schedule === Schedule.Monthly ? "1" : "*";
+  const dayOfWeek =
+    schedule === Schedule.Weekly
+      ? "1"
+      : schedule === Schedule.Weekdays
+      ? "1-5"
+      : "*";
+
+  return `${minute} ${(hour + hourOffset) % 24} ${dayOfMonth} * ${dayOfWeek}`;
+}