Merge branch 'trs/redis-assertions'

src/config.js

@@ -32,6 +32,19 @@ const __basedir = path.join(__dirname, "..");
 export const PRODUCTION = process.env.NODE_ENV === "production";
 
 
+/**
+ * Running as a Heroku Review app?
+ *
+ * These run in production mode but do not have access to sensitive information
+ * (private S3 buckets, production Redis, production encryption keys, etc).
+ *
+ * See {@link https://devcenter.heroku.com/articles/github-integration-review-apps#injected-environment-variables}.
+ *
+ * @type {boolean}
+ */
+export const REVIEW_APP = !!process.env.HEROKU_PR_NUMBER;
+
+
 /**
  * Path to a JSON file containing configuration values.
  *

src/redis.js

@@ -19,6 +19,7 @@
 
 import Redis from 'ioredis';
 
+import { PRODUCTION, REVIEW_APP } from './config.js';
 import * as utils from './utils/index.js';
 
 
@@ -32,6 +33,40 @@ const REDIS = process.env.REDIS_URL
   ? herokuRedisClient(process.env.REDIS_URL)
   : null;
 
+/* XXX TODO: Provision lowest-tier Heroku Redis addon for review apps and
+ * remove the !REVIEW_APP condition.
+ *
+ * Heroku has good support for this, but to enable it I think we need to switch
+ * how we configure review apps.  Currently they're configured via the Heroku
+ * Dashboard¹.  I think we need to switch to the app.json file² instead, as
+ * described in the review app documentation.³
+ *   -trs, 12 Oct 2023
+ *
+ * ¹ <https://dashboard.heroku.com/pipelines/38f67fc7-d93c-40c6-a182-501da2f89d9d/settings>
+ * ² <https://devcenter.heroku.com/articles/app-json-schema>
+ * ³ <https://devcenter.heroku.com/articles/github-integration-review-apps>
+ */
+if (PRODUCTION && !REVIEW_APP && !REDIS) {
+  throw new Error("REDIS_URL required in production mode");
+}
+
+if (REDIS) {
+  /* Use "info memory" command instead of "config get maxmemory-policy" since
+   * Heroku Redis disables admin commands, which includes "config".
+   */
+  const memoryInfo = new Map(
+    (await REDIS.info("memory"))
+      .split(/\r\n/)
+      .map(line => line.match(/^(?<key>[^:]+):(?<value>.*)$/)?.groups)
+      .filter(matched => matched)
+      .map(({key, value}) => [key.replace(/_/g, "-"), value])
+  );
+  const maxmemoryPolicy = memoryInfo.get("maxmemory-policy");
+  if (maxmemoryPolicy !== "volatile-ttl") {
+    throw new Error(`Redis maxmemory-policy is "${maxmemoryPolicy}", but it *must* be "volatile-ttl".`);
+  }
+}
+
 
 function herokuRedisClient(urlStr) {
   const url = new URL(urlStr);