From fe8820b964dac7c25b9785c32ee3242e14c1cd17 Mon Sep 17 00:00:00 2001
From: ohad-israeli <ohadisra@gmail.com>
Date: Mon, 7 Dec 2020 20:31:23 +0200
Subject: [PATCH] feat(cluster): support retrying MOVED with a delay

Add delay to MOVED response. In case a MOVED response is recieved from the cluster use a delayed queue to retry commands
---
 README.md                        |  7 ++++--
 lib/cluster/ClusterOptions.ts    | 12 ++++++++++
 lib/cluster/index.ts             | 15 ++++++++++--
 test/functional/cluster/moved.ts | 40 ++++++++++++++++++++++++++++++++
 4 files changed, 70 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index b8947131..dea4dee0 100644
--- a/README.md
+++ b/README.md
@@ -889,9 +889,12 @@ cluster.get("foo", (err, res) => {
       will resend the commands after the specified time (in ms).
     - `retryDelayOnTryAgain`: If this option is a number (by default, it is `100`), the client
       will resend the commands rejected with `TRYAGAIN` error after the specified time (in ms).
+    - `retryDelayOnMoved`: By default, this value is `0` (in ms), which means when a `MOVED` error is received, the client will resend
+      the command instantly to the node returned together with the `MOVED` error. However, sometimes it takes time for a cluster to become
+      state stabilized after a failover, so adding a delay before resending can prevent a ping pong effect.
     - `redisOptions`: Default options passed to the constructor of `Redis` when connecting to a node.
-    - `slotsRefreshTimeout`: Milliseconds before a timeout occurs while refreshing slots from the cluster (default `1000`)
-    - `slotsRefreshInterval`: Milliseconds between every automatic slots refresh (default `5000`)
+    - `slotsRefreshTimeout`: Milliseconds before a timeout occurs while refreshing slots from the cluster (default `1000`).
+    - `slotsRefreshInterval`: Milliseconds between every automatic slots refresh (default `5000`).
 
 ### Read-write splitting
 
diff --git a/lib/cluster/ClusterOptions.ts b/lib/cluster/ClusterOptions.ts
index 6b76b2bc..bcc14b40 100644
--- a/lib/cluster/ClusterOptions.ts
+++ b/lib/cluster/ClusterOptions.ts
@@ -94,6 +94,17 @@ export interface IClusterOptions {
    */
   retryDelayOnTryAgain?: number;
 
+  /**
+   * By default, this value is 0, which means when a `MOVED` error is received,
+   * the client will resend the command instantly to the node returned together with
+   * the `MOVED` error. However, sometimes it takes time for a cluster to become
+   * state stabilized after a failover, so adding a delay before resending can
+   * prevent a ping pong effect.
+   *
+   * @default 0
+   */
+  retryDelayOnMoved?: number;
+
   /**
    * The milliseconds before a timeout occurs while refreshing
    * slots from the cluster.
@@ -184,6 +195,7 @@ export const DEFAULT_CLUSTER_OPTIONS: IClusterOptions = {
   enableReadyCheck: true,
   scaleReads: "master",
   maxRedirections: 16,
+  retryDelayOnMoved: 0,
   retryDelayOnFailover: 100,
   retryDelayOnClusterDown: 100,
   retryDelayOnTryAgain: 100,
diff --git a/lib/cluster/index.ts b/lib/cluster/index.ts
index f6f17d5c..ea16cb2c 100644
--- a/lib/cluster/index.ts
+++ b/lib/cluster/index.ts
@@ -745,8 +745,19 @@ class Cluster extends EventEmitter {
       return;
     }
     const errv = error.message.split(" ");
-    if (errv[0] === "MOVED" || errv[0] === "ASK") {
-      handlers[errv[0] === "MOVED" ? "moved" : "ask"](errv[1], errv[2]);
+    if (errv[0] === "MOVED") {
+      const timeout = this.options.retryDelayOnMoved;
+      if (timeout && typeof timeout === "number") {
+        this.delayQueue.push(
+          "moved",
+          handlers.moved.bind(null, errv[1], errv[2]),
+          { timeout }
+        );
+      } else {
+        handlers.moved(errv[1], errv[2]);
+      }
+    } else if (errv[0] === "ASK") {
+      handlers.ask(errv[1], errv[2]);
     } else if (errv[0] === "TRYAGAIN") {
       this.delayQueue.push("tryagain", handlers.tryagain, {
         timeout: this.options.retryDelayOnTryAgain,
diff --git a/test/functional/cluster/moved.ts b/test/functional/cluster/moved.ts
index 276bd8b2..1b2527da 100644
--- a/test/functional/cluster/moved.ts
+++ b/test/functional/cluster/moved.ts
@@ -2,6 +2,7 @@ import * as calculateSlot from "cluster-key-slot";
 import MockServer from "../../helpers/mock_server";
 import { expect } from "chai";
 import { Cluster } from "../../../lib";
+import * as sinon from "sinon";
 
 describe("cluster:MOVED", function () {
   it("should auto redirect the command to the correct nodes", function (done) {
@@ -117,4 +118,43 @@ describe("cluster:MOVED", function () {
       cluster.get("foo");
     });
   });
+
+  it("should supports retryDelayOnMoved", (done) => {
+    let cluster = undefined;
+    const slotTable = [[0, 16383, ["127.0.0.1", 30001]]];
+    new MockServer(30001, function (argv) {
+      if (argv[0] === "cluster" && argv[1] === "slots") {
+        return slotTable;
+      }
+      if (argv[0] === "get" && argv[1] === "foo") {
+        return new Error("MOVED " + calculateSlot("foo") + " 127.0.0.1:30002");
+      }
+    });
+
+    new MockServer(30002, function (argv) {
+      if (argv[0] === "cluster" && argv[1] === "slots") {
+        return slotTable;
+      }
+      if (argv[0] === "get" && argv[1] === "foo") {
+        cluster.disconnect();
+        done();
+      }
+    });
+
+    const retryDelayOnMoved = 789;
+    cluster = new Cluster([{ host: "127.0.0.1", port: "30001" }], {
+      retryDelayOnMoved,
+    });
+    cluster.on("ready", function () {
+      sinon.stub(global, "setTimeout").callsFake((body, ms) => {
+        if (ms === retryDelayOnMoved) {
+          process.nextTick(() => {
+            body();
+          });
+        }
+      });
+
+      cluster.get("foo");
+    });
+  });
 });