Hamad application scheduling scheme 06 of hashicopy (configure task)

One background

Most applications require some kind of local configuration . Although command line arguments are the simplest method , But many applications need to provide more complex configurations through environment variables or configuration files . This section discusses how to configure Nomad Jobs to support many common configuration use cases .

Two Define application parameters

Many tasks accept configuration through command-line parameters . for example , consider http-echo The server , It's a small go Binary , Render the provided text as a web page . The binary file accepts two parameters ：

• listen The flag contains the address to listen on ： port
• -text- Present as HTML The text of the page

stay Nomad outside , The server starts like this ：

http-echo -listen=":5678" -text="hello world"

Nomad Equivalent job documents may be as follows ：

job "docs" {  datacenters = ["dc1"]  group "example" {    network {      port "http" {        static = "5678"      }    }    task "server" {      driver = "exec"      config {        command = "/bin/http-echo"        args = [          "-listen",          ":5678",          "-text",          "hello world",        ]      }    }  }}

Be careful ： For this job specification , You must be on each client's /bin Folder http-echo.Nomad You can also choose to use artifact resources to get binaries .

Nomad There are many drivers , Most of them support args Parameters pass parameters to their tasks . This parameter also supports Nomad Variable interpolation . for example , If you wish Nomad Dynamically allocate a high port to bind services , Instead of relying on a static port to execute the previous job ：

job "docs" {  datacenters = ["dc1"]  group "example" {    network {      port "http" {        static = "5678"      }    }    task "server" {      driver = "exec"      config {        command = "/bin/http-echo"        args = [          "-listen",          ":${NOMAD_PORT_http}",          "-text",          "hello world",        ]      }    }  }}

3、 ... and Set the environment variable

Some applications can be configured through environment variables . The twelve element application documentation recommends configuring the application through environment variables .Nomad There are two ways to support custom environment variables ：

• Interpolation in the environment section
• Templating in the templates section

3.1 env stanza

Each task may have a... That specifies environment variables env section ：

task "server" {  env {    my_key = "my-value"  }}

env Section also supports interpolation ：

task "server" {  env {    LISTEN_PORT = "${NOMAD_PORT_http}"  }}

For more information , see also env Section document .

Four Load external configuration file

Many applications use files for configuration .Nomad Supports downloading files using the artifact section , And templating them before starting the task . This allows the transfer of configuration files and other assets necessary for the task to function properly .
Here is a sample job , It pulls down the configuration file as an artifact and templates it ：

job "docs" {  datacenters = ["dc1"]  group "example" {    task "server" {      driver = "exec"      artifact {        source      = "http://example.com/config.hcl.tmpl"        destination = "local/config.hcl.tmpl"      }      template {        source      = "local/config.hcl.tmpl"        destination = "local/config.hcl"      }      config {        command = "my-app"        args = [          "-config", "local/config.hcl",        ]      }    }  }}

More information about artifact resources , Refer to the artifact section documentation .

Reference link

• https://learn.hashicorp.com/tutorials/nomad/jobs-configuring?in=nomad/manage-jobs