This sample Nomad job attempts to clone a github repository from a github account, and then perform ls command to verify if it downloaded.
However, the cool thing is, it uses parameterized construct to parameterize the repository name so I can re-use this nomad job to clone any repository at runtime.
As a Nomad beginner, it took me quite some time (though, I must mention Nomad is super easy to get started with!) to fully wire together components required to parameterize a nomad job.
Therefore, writing it up so that folks like me can benefit from this.
This tutorial assumes you have Nomad setup in your environment.
Another requirement is for job file to have the Scheduler Type specified as batch -
type = "batch"
You declare which variables are required and which ones are optional
parameterized {
meta_required = ["REPOSITORY_NAME"]
meta_optional = ["FIRST_NAME", "LAST_NAME"]
}
Here, we have declared variable REPOSITORY_NAME as a required variable and FIRST_NAME and LAST_NAME as optional.
This example attempts to download a repository whose name is parameterized. Therefore we need to reference the name like the following -
artifact {
source = "git@github.com:rohitkothari/${NOMAD_META_REPOSITORY_NAME}"
destination = "local/config/"
options {
sshkey = "_BASE64_SSH_KEY_STRING_"
}
}
As you can see, the variable declared as REPOSITORY_NAME is available to be referenced as NOMAD_META_REPOSITORY_NAME.
This is because you Nomad treats all the user-defined variables as meta variables and thus the prefix NOMAD_META_.
$ nomad run ansible.nomad
Job registration successful
At this stage, the job has been registered, however it has not started any container or allocation yet.
We finally dispatch the registered job (i.e. create a new running instance of our registered job) named "ansible" -
$ nomad job dispatch -meta REPOSITORY_NAME=Hello-World ansible
Dispatched Job ID = ansible/dispatch-1497641508-d0858f30
Evaluation ID = f2fea7fe
==> Monitoring evaluation "f2fea7fe"
Evaluation triggered by job "ansible/dispatch-1497641508-d0858f30"
Allocation "d46fbe73" created: node "ec25b9c7", group "cache"
Evaluation status changed: "pending" -> "complete"
==> Evaluation "f2fea7fe" finished with status "complete"
As you can see above, we dynamically inject the value of variable REPOSITORY_NAME while dispatching the job.
You can declare as many variables as you want and inject them at runtime like above.
This completes the demo of configuring a Hashicorp nomad job for user-defined variables and injecting their values dynamically at runtime.
Rest of this doc shows various status commands and the entire job file for reference.
$ nomad status ansible/dispatch-1497641508-d0858f30
ID = ansible/dispatch-1497641508-d0858f30
Name = ansible/dispatch-1497641508-d0858f30
Type = batch
Priority = 50
Datacenters = dc1
Status = dead
Periodic = false
Parameterized = false
Summary
Task Group Queued Starting Running Failed Complete Lost
cache 0 0 0 0 1 0
Allocations
ID Eval ID Node ID Task Group Desired Status Created At
d46fbe73 f2fea7fe ec25b9c7 cache run complete 06/16/17 19:31:48 UTC
As you can see, this shows you the list of "Allocations" (i.e. the executed container).
You can check the status of a specific allocation ID -
$ nomad alloc-status d46fbe73
ID = d46fbe73
Eval ID = f2fea7fe
Name = ansible/dispatch-1497641508-d0858f30.cache[0]
Node ID = ec25b9c7
Job ID = ansible/dispatch-1497641508-d0858f30
Client Status = complete
Client Description = <none>
Desired Status = run
Desired Description = <none>
Created At = 06/16/17 19:31:48 UTC
Task "ansible" is "dead"
Task Resources
CPU Memory Disk IOPS Addresses
500 MHz 256 MiB 300 MiB 0 db: 10.78.1.169:39408
Recent Events:
Time Type Description
06/16/17 19:31:50 UTC Terminated Exit Code: 0
06/16/17 19:31:50 UTC Started Task started by client
06/16/17 19:31:48 UTC Downloading Artifacts Client is downloading artifacts
06/16/17 19:31:48 UTC Task Setup Building Task Directory
06/16/17 19:31:48 UTC Received Task received by client
You can also check the logs generated by an allocation ID (for this example, it performs command "ls" on downloaded github repository) -
$ nomad logs d46fbe73
README.md
job "ansible" {
datacenters = ["dc1"]
type = "batch"
parameterized {
meta_required = ["REPOSITORY_NAME"]
meta_optional = ["FIRST_NAME", "LAST_NAME"]
}
group "cache" {
count = 1
ephemeral_disk {
size = 300
}
task "ansible" {
driver = "docker"
config {
image = "ansible/centos7-ansible:stable"
command = "ls"
args = ["local/config/"]
}
artifact {
source = "git@github.com:rohitkothari/${NOMAD_META_REPOSITORY_NAME}"
destination = "local/config/"
options {
sshkey = "_BASE64_SSH_KEY_STRING_"
}
}
resources {
cpu = 500 # 500 MHz
memory = 256 # 256MB
network {
mbits = 10
port "db" {}
}
}
}
}
}