--- layout: "intro" page_title: "Clustering" sidebar_current: "getting-started-cluster" description: |- Join another Nomad client to create your first cluster. --- # Clustering We have started our first agent and run a job against it in development mode. This demonstrates the ease of use and the workflow of Nomad, but did not show how this could be extended to a scalable, production-grade configuration. In this step, we will create our first real cluster with multiple nodes. ## Starting the Server The first step is to create the config file for the server. Either download the [file from the repository][server.hcl], or paste this into a file called `server.hcl`: ```hcl # Increase log verbosity log_level = "DEBUG" # Setup data dir data_dir = "/tmp/server1" # Enable the server server { enabled = true # Self-elect, should be 3 or 5 for production bootstrap_expect = 1 } ``` This is a fairly minimal server configuration file, but it is enough to start an agent in server only mode and have it elected as a leader. The major change that should be made for production is to run more than one server, and to change the corresponding `bootstrap_expect` value. Once the file is created, start the agent in a new tab: ```text $ nomad agent -config server.hcl ==> WARNING: Bootstrap mode enabled! Potentially unsafe operation. ==> Starting Nomad agent... ==> Nomad agent configuration: Client: false Log Level: DEBUG Region: global (DC: dc1) Server: true Version: 0.7.0 ==> Nomad agent started! Log data will stream in below: [INFO] serf: EventMemberJoin: nomad.global 127.0.0.1 [INFO] nomad: starting 4 scheduling worker(s) for [service batch _core] [INFO] raft: Node at 127.0.0.1:4647 [Follower] entering Follower state [INFO] nomad: adding server nomad.global (Addr: 127.0.0.1:4647) (DC: dc1) [WARN] raft: Heartbeat timeout reached, starting election [INFO] raft: Node at 127.0.0.1:4647 [Candidate] entering Candidate state [DEBUG] raft: Votes needed: 1 [DEBUG] raft: Vote granted. Tally: 1 [INFO] raft: Election won. Tally: 1 [INFO] raft: Node at 127.0.0.1:4647 [Leader] entering Leader state [INFO] nomad: cluster leadership acquired [INFO] raft: Disabling EnableSingleNode (bootstrap) [DEBUG] raft: Node 127.0.0.1:4647 updated peer set (2): [127.0.0.1:4647] ``` We can see above that client mode is disabled, and that we are only running as the server. This means that this server will manage state and make scheduling decisions but will not run any tasks. Now we need some agents to run tasks! ## Starting the Clients Similar to the server, we must first configure the clients. Either download the configuration for `client1` and `client2` from the [repository here](https://github.com/hashicorp/nomad/tree/master/demo/vagrant), or paste the following into `client1.hcl`: ```hcl # Increase log verbosity log_level = "DEBUG" # Setup data dir data_dir = "/tmp/client1" # Give the agent a unique name. Defaults to hostname name = "client1" # Enable the client client { enabled = true # For demo assume we are talking to server1. For production, # this should be like "nomad.service.consul:4647" and a system # like Consul used for service discovery. servers = ["127.0.0.1:4647"] } # Modify our port to avoid a collision with server1 ports { http = 5656 } ``` Copy that file to `client2.hcl`. Change the `data_dir` to be `/tmp/client2`, the `name` to `client2`, and the `http` port to 5657. Once you have created both `client1.hcl` and `client2.hcl`, open a tab for each and start the agents: ```text $ sudo nomad agent -config client1.hcl ==> Starting Nomad agent... ==> Nomad agent configuration: Client: true Log Level: DEBUG Region: global (DC: dc1) Server: false Version: 0.7.0 ==> Nomad agent started! Log data will stream in below: [DEBUG] client: applied fingerprints [host memory storage arch cpu] [DEBUG] client: available drivers [docker exec] [DEBUG] client: node registration complete ... ``` In the output we can see the agent is running in client mode only. This agent will be available to run tasks but will not participate in managing the cluster or making scheduling decisions. Using the [`node status` command](/docs/commands/node/status.html) we should see both nodes in the `ready` state: ```text $ nomad node status ID DC Name Class Drain Eligibility Status fca62612 dc1 client1 false eligible ready c887deef dc1 client2 false eligible ready ``` We now have a simple three node cluster running. The only difference between a demo and full production cluster is that we are running a single server instead of three or five. ## Submit a Job Now that we have a simple cluster, we can use it to schedule a job. We should still have the `example.nomad` job file from before, but verify that the `count` is still set to 3. Then, use the [`job run` command](/docs/commands/job/run.html) to submit the job: ```text $ nomad job run example.nomad ==> Monitoring evaluation "8e0a7cf9" Evaluation triggered by job "example" Evaluation within deployment: "0917b771" Allocation "501154ac" created: node "c887deef", group "cache" Allocation "7e2b3900" created: node "fca62612", group "cache" Allocation "9c66fcaf" created: node "c887deef", group "cache" Evaluation status changed: "pending" -> "complete" ==> Evaluation "8e0a7cf9" finished with status "complete" ``` We can see in the output that the scheduler assigned two of the tasks for one of the client nodes and the remaining task to the second client. We can again use the [`status` command](/docs/commands/status.html) to verify: ``` $ nomad status example ID = example Name = example Submit Date = 07/26/17 16:34:58 UTC Type = service Priority = 50 Datacenters = dc1 Status = running Periodic = false Parameterized = false Summary Task Group Queued Starting Running Failed Complete Lost cache 0 0 3 0 0 0 Latest Deployment ID = fc49bd6c Status = running Description = Deployment is running Deployed Task Group Desired Placed Healthy Unhealthy cache 3 3 0 0 Allocations ID Eval ID Node ID Task Group Desired Status Created At 501154ac 8e0a7cf9 c887deef cache run running 08/08/16 21:03:19 CDT 7e2b3900 8e0a7cf9 fca62612 cache run running 08/08/16 21:03:19 CDT 9c66fcaf 8e0a7cf9 c887deef cache run running 08/08/16 21:03:19 CDT ``` We can see that all our tasks have been allocated and are running. Once we are satisfied that our job is happily running, we can tear it down with `nomad job stop`. ## Next Steps Nomad is now up and running. The cluster can be entirely managed from the commandline, but Nomad also comes with a web interface that is hosted alongside the HTTP API. Next, we'll [visit the UI in the browser](ui.html). [server.hcl]: https://raw.githubusercontent.com/hashicorp/nomad/master/demo/vagrant/server.hcl