Distributed Leader Election in Go

In distributed systems, ensuring that only one instance of a service is designated as the "leader" at any given time is crucial for coordinating tasks, preventing race conditions, and maintaining data consistency. This challenge asks you to implement a basic leader election mechanism in Go.

Problem Description

Your task is to create a Go program that simulates a distributed environment where multiple nodes (processes) compete to become the leader. The system should ensure that at any point, at most one node is elected as the leader. When the current leader fails or is removed, a new leader should be elected among the remaining nodes.

Key Requirements:

Election Mechanism: Implement a way for nodes to signal their intent to be a leader and to detect if another node has already claimed leadership.
Leader Identification: Each node should be able to identify itself and its peers. The leader should be uniquely identifiable.
Leader Health Check (Simulated): Implement a simple mechanism to simulate the leader "going down." When this happens, the remaining nodes should initiate a new election.
Concurrency: The solution must be robust to concurrent operations from multiple nodes.

Expected Behavior:

When the system starts, nodes should attempt to elect a leader.
Once a leader is elected, it should continue to perform its leader duties (simulated by periodic logging).
If the leader is simulated to fail, the remaining nodes should detect this and start a new election process.
The election process should be fair, meaning that eventually, one of the remaining active nodes should become the new leader.

Edge Cases to Consider:

What happens if multiple nodes attempt to become leader simultaneously?
What happens if the leader fails during an election?
What happens if all nodes fail simultaneously?

Examples

Example 1: Initial Election

Scenario: Three nodes (Node A, Node B, Node C) start simultaneously.

Input:

Node A, Node B, Node C are active.

Output (after some time):

Node A: "I am the leader!"
Node B: "Node A is the leader."
Node C: "Node A is the leader."

Explanation: Node A successfully elected itself as the leader, and other nodes acknowledge this.

Example 2: Leader Failure and Re-election

Scenario: Node A was the leader. It then fails.

Input:

Node A fails. Node B and Node C are active.

Output (after Node A fails):

Node B: "I am the leader!"
Node C: "Node B is the leader."

Explanation: Node A is no longer active. Nodes B and C initiate a new election. Node B successfully becomes the new leader, and Node C acknowledges it.

Example 3: Multiple Nodes Competing

Scenario: Node B and Node C are active. Both attempt to claim leadership simultaneously.

Input:

Node B and Node C are active. Both initiate election concurrently.

Output (a possible outcome):

Node B: "I am the leader!"
Node C: "Node B is the leader."

Explanation: In a concurrent scenario, one node will ultimately succeed in claiming leadership. The mechanism should ensure only one becomes the leader.

Constraints

You will simulate N nodes, where N can be between 2 and 10.
Each node will have a unique identifier (e.g., an integer ID).
Communication between nodes will be simulated using Go channels or a shared data structure (e.g., a mutex-protected map or variable). You are not expected to implement actual network communication.
The "leader failure" can be simulated by stopping a goroutine representing the leader and removing its identifier from the active nodes list.
The election algorithm should aim for a low probability of split-brain (multiple leaders) in the absence of failures.

Notes

Consider using a logical clock or a simple voting mechanism for election.
You might need to use Go's concurrency primitives like sync.Mutex, sync.WaitGroup, and channels to manage communication and state between nodes.
Think about how nodes will detect the failure of another node. A simple timeout mechanism can be used for this simulation.
The goal is to demonstrate the principles of leader election, not to build a production-ready fault-tolerant system.

Good luck!

Distributed Leader Election in Go

Problem Description

Key Requirements:

Election Mechanism: Implement a way for nodes to signal their intent to be a leader and to detect if another node has already claimed leadership.
Leader Identification: Each node should be able to identify itself and its peers. The leader should be uniquely identifiable.
Leader Health Check (Simulated): Implement a simple mechanism to simulate the leader "going down." When this happens, the remaining nodes should initiate a new election.
Concurrency: The solution must be robust to concurrent operations from multiple nodes.

Expected Behavior:

When the system starts, nodes should attempt to elect a leader.
Once a leader is elected, it should continue to perform its leader duties (simulated by periodic logging).
If the leader is simulated to fail, the remaining nodes should detect this and start a new election process.
The election process should be fair, meaning that eventually, one of the remaining active nodes should become the new leader.

Edge Cases to Consider:

What happens if multiple nodes attempt to become leader simultaneously?
What happens if the leader fails during an election?
What happens if all nodes fail simultaneously?

Examples

Example 1: Initial Election

Scenario: Three nodes (Node A, Node B, Node C) start simultaneously.

Input:

Node A, Node B, Node C are active.

Output (after some time):

Node A: "I am the leader!"
Node B: "Node A is the leader."
Node C: "Node A is the leader."

Explanation: Node A successfully elected itself as the leader, and other nodes acknowledge this.

Example 2: Leader Failure and Re-election

Scenario: Node A was the leader. It then fails.

Input:

Node A fails. Node B and Node C are active.

Output (after Node A fails):

Node B: "I am the leader!"
Node C: "Node B is the leader."

Explanation: Node A is no longer active. Nodes B and C initiate a new election. Node B successfully becomes the new leader, and Node C acknowledges it.

Example 3: Multiple Nodes Competing

Scenario: Node B and Node C are active. Both attempt to claim leadership simultaneously.

Input:

Node B and Node C are active. Both initiate election concurrently.

Output (a possible outcome):

Node B: "I am the leader!"
Node C: "Node B is the leader."

Explanation: In a concurrent scenario, one node will ultimately succeed in claiming leadership. The mechanism should ensure only one becomes the leader.

Constraints

You will simulate N nodes, where N can be between 2 and 10.
Each node will have a unique identifier (e.g., an integer ID).
Communication between nodes will be simulated using Go channels or a shared data structure (e.g., a mutex-protected map or variable). You are not expected to implement actual network communication.
The "leader failure" can be simulated by stopping a goroutine representing the leader and removing its identifier from the active nodes list.
The election algorithm should aim for a low probability of split-brain (multiple leaders) in the absence of failures.

Notes

Consider using a logical clock or a simple voting mechanism for election.
You might need to use Go's concurrency primitives like sync.Mutex, sync.WaitGroup, and channels to manage communication and state between nodes.
Think about how nodes will detect the failure of another node. A simple timeout mechanism can be used for this simulation.
The goal is to demonstrate the principles of leader election, not to build a production-ready fault-tolerant system.

Good luck!