Consul Leader Election

Simple library(100% written in F#) to use leader election functionality based on Consul.

Leader election to do distributed locking

Leader election is quite a simple concept. The service nodes are registered against a host using a specific common key. Usually key format is "services/Your_Service_Name/leader". One of the nodes is elected as a leader and performs the job, while the other ones are being idle. This lock to a specific node is held as long as the session of the node remains on the host. When the session is gone, the leadership is open to be taken by the next node that checks for it.

How to install

To install Consul Leader Election via NuGet, run this command in NuGet package manager console:

PM> Install-Package SBTech.Consul.LeaderElection

Example

Full example you can find by this link.

var consulClient = new ConsulClient(); // using http://localhost:8500
var config = ElectionMonitorConfig.Default(serviceName: "test_node", client: consulClient);

var electionMonitor = new LeaderElectionMonitor(config);
electionMonitor.LeaderChanged += (s, e) =>
{
    if (e.IsLeader)
        Console.WriteLine($"[Master] at {DateTime.Now.ToString("hh:mm:ss")}");
    else
        Console.WriteLine($"[Slave] at {DateTime.Now.ToString("hh:mm:ss")}");
};

var joinedCluster = electionMonitor.Start().Wait(timeout: TimeSpan.FromSeconds(30));
if (joinedCluster)
{
    if (electionMonitor.IsLeader)
        Console.WriteLine($"Joined cluster as [Master] at {DateTime.Now.ToString("hh:mm:ss")}");
    else
        Console.WriteLine($"Joined cluster as [Slave] at {DateTime.Now.ToString("hh:mm:ss")}");
}
else
{
    Console.WriteLine($"TestNode failed to join cluster at {DateTime.Now.ToString("hh:mm:ss")}");
}

electionMonitor.Start();

Configuration

var consulClient = new ConsulClient(); // using http://localhost:8500
var config = new ElectionMonitorConfig(
    // Parameters are described here https://github.com/PlayFab/consuldotnet                 
    client: consulClient,
    sessionOptions: new SessionEntry(), 
    lockOptions: new KVPair("key"),

    //How often to try to acquire a lock
    tryAcquireLockInterval: TimeSpan.FromSeconds(1)
);