» Resource Utilization

Understanding the resource utilization of an application is important, and Nomad supports reporting detailed statistics in many of its drivers. The main interface for seeing resource utilization is the alloc status command with the -stats flag.

This section will utilize the job named "docs" from the previous sections, but these operations and command largely apply to all jobs in Nomad.

As a reminder, here is the output of the run command from the previous example:

$ nomad job run docs.nomad
==> Monitoring evaluation "42d788a3"
    Evaluation triggered by job "docs"
    Allocation "04d9627d" created: node "a1f934c9", group "example"
    Allocation "e7b8d4f5" created: node "012ea79b", group "example"
    Allocation "5cbf23a1" modified: node "1e1aa1e0", group "example"
    Evaluation status changed: "pending" -> "complete"
==> Evaluation "42d788a3" finished with status "complete"

To see the detailed usage statistics, we can issue the command:

$ nomad alloc status -stats 04d9627d
ID            = 04d9627d
Eval ID       = 42d788a3
Name          = docs.example[2]
Node ID       = a1f934c9
Job ID        = docs
Client Status = running

Task "server" is "running"
Task Resources
CPU        Memory          Disk     IOPS  Addresses
75/100 MHz  784 KiB/10 MiB  300 MiB  0     http: 10.1.1.196:5678

Memory Stats
Cache   Max Usage  RSS      Swap
56 KiB  1.3 MiB    784 KiB  0 B

CPU Stats
Percent  Throttled Periods  Throttled Time
0.00%    0                  0

Recent Events:
Time         Type      Description
<timestamp>  Started   Task started by client
<timestamp>  Received  Task received by client

Here we can see that we are near the limit of our configured CPU but we have plenty of memory headroom. We can use this information to alter our job's resources to better reflect is actually needs:

resource {
  cpu    = 200
  memory = 10
}

Adjusting resources is very important for a variety of reasons:

  • Ensuring your application does not get OOM killed if it hits its memory limit.
  • Ensuring the application performs well by ensuring it has some CPU allowance.
  • Optimizing cluster density by reserving what you need and not over-allocating.

While single point in time resource usage measurements are useful, it is often more useful to graph resource usage over time to better understand and estimate resource usage. Nomad supports outputting resource data to statsite and statsd and is the recommended way of monitoring resources. For more information about outputting telemetry see the Telemetry Guide.

For more advanced use cases, the resource usage data is also accessible via the client's HTTP API. See the documentation of the Client's allocation HTTP API.