Test: Fix flaky leader index in waitLeader function

[MrDXY]

Summary

The waitLeader function currently has an issue where it returns the wrong leader index in certain scenarios. When iterating through nodes to find the leader, if the leader changes during the iteration, the function incorrectly returns the default value instead of the actual leader index.

Example

In the function, waitLeader:

raft/rafttest/node_test.go

Lines 130 to 151 in e1bfcf7

	func waitLeader(ns []*node) int {
	var l map[uint64]struct{}
	var lindex int
	for {
	l = make(map[uint64]struct{})
	for i, n := range ns {
	lead := n.Status().SoftState.Lead
	if lead != 0 {
	l[lead] = struct{}{}
	if n.id == lead {
	lindex = i
	}
	}
	}
	if len(l) == 1 {
	return lindex
	}
	}
	}

Let's say,

1. i is 3 now, and we still don't have a leader elected.
2. Then node[1] is elected as a leader,
3. i is 4 now, and the leader of node[4] has changed from 0 to 1 in step2. So l[lead] = struct{}{} will be executed. But n.id == lead is false, lindex still equals 0.
4. The iteration ends, and len(l) now equals 1. This function will return lindex, which is 0. But 0 is not the real leader index, but the default value.

Proposed Changes

To address this issue, the proposed solution involves initializing the lindex variable to -1 instead of 0. This change ensures that lindex holds a distinct value indicating 'not found' rather than potentially conflating it with the index of the first element.

Changes Made

• Initialized lindex variable to -1 instead of 0.

Impact

This change ensures that the waitLeader function correctly returns the leader index, avoiding confusion between 'not found' and the index of the first element.

Fixes #181

[ahrtr]

lgtm

Thanks for the fix