From 31c881e90e88cc824cf67d5cef66a7fabef2a0e8 Mon Sep 17 00:00:00 2001 From: John Olmsted Date: Tue, 28 May 2024 10:16:52 -0400 Subject: [PATCH] Default reconnect strategy uses exponential backoff and jitter (#2736) * Default reconnect strategy uses exponential backoff and jitter Both are recommended parts of client reconnect strategies to prevent thundering herd problems when many clients lose their connection at once (for example, during a Redis upgrade). * Move default retry strategy to constant * Plain english explanation of default 'socket.reconnectStrategy' * Extract default connect strategy into helper function --- docs/client-configuration.md | 13 ++++++++++--- packages/client/lib/client/socket.ts | 13 +++++++++++-- 2 files changed, 21 insertions(+), 5 deletions(-) diff --git a/docs/client-configuration.md b/docs/client-configuration.md index 69a2db16c3..deb68437e1 100644 --- a/docs/client-configuration.md +++ b/docs/client-configuration.md @@ -13,7 +13,7 @@ | socket.keepAlive | `true` | Toggle [`keep-alive`](https://nodejs.org/api/net.html#socketsetkeepaliveenable-initialdelay) functionality | | socket.keepAliveInitialDelay | `5000` | If set to a positive number, it sets the initial delay before the first keepalive probe is sent on an idle socket | | socket.tls | | See explanation and examples [below](#TLS) | -| socket.reconnectStrategy | `retries => Math.min(retries * 50, 500)` | A function containing the [Reconnect Strategy](#reconnect-strategy) logic | +| socket.reconnectStrategy | Exponential backoff with a maximum of 2000 ms; plus 0-200 ms random jitter. | A function containing the [Reconnect Strategy](#reconnect-strategy) logic | | username | | ACL username ([see ACL guide](https://redis.io/topics/acl)) | | password | | ACL password or the old "--requirepass" password | | name | | Client name ([see `CLIENT SETNAME`](https://redis.io/commands/client-setname)) | @@ -35,12 +35,19 @@ When the socket closes unexpectedly (without calling `.quit()`/`.disconnect()`), 2. `number` -> wait for `X` milliseconds before reconnecting. 3. `(retries: number, cause: Error) => false | number | Error` -> `number` is the same as configuring a `number` directly, `Error` is the same as `false`, but with a custom error. -By default the strategy is `Math.min(retries * 50, 500)`, but it can be overwritten like so: +By default the strategy uses exponential backoff, but it can be overwritten like so: ```javascript createClient({ socket: { - reconnectStrategy: retries => Math.min(retries * 50, 1000) + reconnectStrategy: retries => { + // Generate a random jitter between 0 – 200 ms: + const jitter = Math.floor(Math.random() * 200); + // Delay is an exponential back off, (times^2) * 50 ms, with a maximum value of 2000 ms: + const delay = Math.min(Math.pow(2, retries) * 50, 2000); + + return delay + jitter; + } } }); ``` diff --git a/packages/client/lib/client/socket.ts b/packages/client/lib/client/socket.ts index dcadad4c3d..3c2666e106 100644 --- a/packages/client/lib/client/socket.ts +++ b/packages/client/lib/client/socket.ts @@ -97,12 +97,12 @@ export default class RedisSocket extends EventEmitter { return retryIn; } catch (err) { this.emit('error', err); - return Math.min(retries * 50, 500); + return this.defaultReconnectStrategy(retries); } }; } - return retries => Math.min(retries * 50, 500); + return this.defaultReconnectStrategy; } #createSocketFactory(options?: RedisSocketOptions) { @@ -333,4 +333,13 @@ export default class RedisSocket extends EventEmitter { this.#isSocketUnrefed = true; this.#socket?.unref(); } + + defaultReconnectStrategy(retries: number) { + // Generate a random jitter between 0 – 200 ms: + const jitter = Math.floor(Math.random() * 200); + // Delay is an exponential back off, (times^2) * 50 ms, with a maximum value of 2000 ms: + const delay = Math.min(Math.pow(2, retries) * 50, 2000); + + return delay + jitter; + } }