From 7e11ac247736b9ba210399ae2ef96058f41d42e4 Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Fri, 29 Sep 2023 00:52:47 +0300
Subject: [PATCH] Make node join existing quorum when seeing a VOTE message for
 larger term

Fixes testAdd and testRestart (with initialTerm = 1000)
---
 tinyraft.js | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/tinyraft.js b/tinyraft.js
index a59aaae..e2219f6 100644
--- a/tinyraft.js
+++ b/tinyraft.js
@@ -156,13 +156,33 @@ class TinyRaft extends EventEmitter
 
     onReceiveVote(from, msg)
     {
-        if (msg.term != this.term)
+        if (!msg.leader || msg.term < this.term)
         {
             return;
         }
-        this.voted++;
+        if (msg.term > this.term)
+        {
+            this.term = msg.term;
+            this.leader = msg.leader;
+            // Repeat VOTE to the leader to join it
+            this.send(this.leader, { type: VOTE, term: this.term, leader: this.leader });
+        }
+        // add <from> as voter for <msg.leader>
         this.votes[msg.leader] = this.votes[msg.leader] || [];
-        this.votes[msg.leader].push(from);
+        let found = false;
+        for (const voter of this.votes[msg.leader])
+        {
+            if (voter == from)
+            {
+                found = true;
+                break;
+            }
+        }
+        if (!found)
+        {
+            this.voted++;
+            this.votes[msg.leader].push(from);
+        }
         const n = this.votes[msg.leader].length;
         if (n == 1 + (0 | this.nodes.length/2))
         {