improve(RedisUtils): Log on lost redis connection (#1784)

To aid debugging.

src/utils/RedisUtils.ts

@@ -75,8 +75,19 @@ const redisClients: { [url: string]: RedisClient } = {};
 export async function getRedis(logger?: winston.Logger, url = REDIS_URL): Promise<RedisClient | undefined> {
   if (!redisClients[url]) {
     let redisClient: _RedisClient | undefined = undefined;
+    const reconnectStrategy = (retries: number): number | Error => {
+      // Just implement the default reconnection strategy:
+      // https://github.com/redis/node-redis/blob/HEAD/docs/client-configuration.md#reconnect-strategy
+      const delay = Math.min(retries * 50, 500);
+      logger?.debug({
+        at: "RedisUtils",
+        message: `Lost redis connection, retrying in ${delay} ms.`,
+      });
+      return delay;
+    };
+
     try {
-      redisClient = createClient({ url });
+      redisClient = createClient({ url, socket: { reconnectStrategy } });
       await redisClient.connect();
       logger?.debug({
         at: "RedisUtils#getRedis",