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Introduction to Nomad Namespaces and Quotas

This repo is a short walkthrough from a lightning talk I presented at HashiConf EU in 2021

Requirements

  • Nomad 1.1.0 Enterprise installed (To work with Quotas)
  • Export your export NOMAD_ADDR=http://IPADDRESS-FOR-NOMAD-SERVER:4646/
  • Directory on your computer to work in
  • Comfortable with working in the CLI.

Namespaces.

What are namespaces

Namespaces are a way within Nomad to separate Nomad Users, jobs and their resources from each other.

These Namespaces can be secured using Nomad ACL policies to restrict rights. Tokens can be granted access to

These objects that can be namespaced include:

  • Jobs.
  • Allocations.
  • Deployments.
  • Evaluations.

Some Nomad Objects are not namespaced as they are shared accross the complete cluster.

  • Nodes.
  • ACL Policies.
  • Sentinel Policies.
  • Quota Specifications.

Creating Namespaces

Check your connectivity to the nomad cluster

nomad server members

This should return a list of the servers in your cluster

Name                 Address        Port  Status  Leader  Protocol  Build      Datacenter  Region
nmd-svr1.tpi-region  192.168.1.100  4648  alive   true    2         1.1.0+ent  tpi-dc1     tpi-region
nmd-svr2.tpi-region  192.168.1.101  4648  alive   false   2         1.1.0+ent  tpi-dc1     tpi-region
nmd-svr3.tpi-region  192.168.1.102  4648  alive   false   2         1.1.0+ent  tpi-dc1     tpi-region

Lets check the current namespace list

nomad namespace list

Should return the default namespace

Name     Description
default  Default shared namespace

Creating namespaces is very easy

nomad namespace apply -description "QA webserver namespace" web-qa

Lets check namespace list again

nomad namespace list

Should return the full list of namespaces including web-qa

Name     Description
default  Default shared namespace
web-qa   QA webserver namespace

Running a Job in a Namespace.

Running a job in a specific Namespace is easy. Just add the namespace parameter to your jobs specification.

job "example" {
  datacenters = ["dc1"]
  ## Run in the QA environments
  namespace = "web-qa"

Then run the job as normal with

nomad job run example-namespace.nomad

checking the status of the job in a namespace

This is done with adding -namespace web-qa to your normal nomad command

nomad job status -namespace=web-qa

There is a great guide on the Nomad website about namespaces HashiCorp Learn Nomad

Nomad Resource Quotas

Enterprise Feature

What are Resource Quotas

Nomad Enterprise provides support for resource quotas, which allow operators to restrict the aggregate resource usage of namespaces.

Once a quota specification is attached to a namespace, the Nomad cluster will count all resource usage by jobs in that namespace toward the quota limits. If the resource is exhausted, allocations within the namespaces will be queued until resources become available—by other jobs finishing or the quota being expanded.

In this section we will assign a quota to the tpi-region region.

Creating Quota configuration

As with all HashiCorp Products, Nomad quota configuration is written in the HCL language. To get an example quota specification you can run

nomad quota init

It will produce a file like this in the directory

name = "default-quota"
description = "Limit the shared default namespace"

# Create a limit for the global region. Additional limits may
# be specified in-order to limit other regions.
limit {
    region = "tpi-region"
    region_limit {
        cpu = 2500
        memory = 1000
    }
}

You can then update the specification with the settings you would like.

Deploying Quota Configuration to the Nomad cluster

You can deploy the configuration to the cluster by running

nomad quota apply web-qa-quota.hcl

You can see that the Quota has been deployted by running

nomad quota list

It should look like this.

Name                      Description
web-qa-quota  Limit the tpi-region web-qa namespace

Attach the Quota to the Namespace

You can attach the quota you have just created to the namespace we crested earlier by running.

nomad namespace apply -quota web-qa-quota web-qa

You can see that the quota is attached correctly by running

nomad quota status web-qa

Now we can increase the number of instances to 6 to use up our quota. We just increase the count parameter to 6, save the spec file and then run the job again. We use the -detach switch to not enter monitor mode but just return the allocation number

nomad job run -detach example-quota.nomad

If you now go to the Nomad UI on http://IPADDRESS-FOR-NOMAD-SERVER:4646/ you will see that the allocation is not fully deployed as the resource limit has been reached.

You can also see the same data in the console using the cli by running

nomad status -namespace web-qa example