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The variable resource allows you to create modular and reusable configuration. Variables are defined using variable resouce, they allow the author of a blueprint to provide default values which can be overriden my the following methods:

  • Variable definition files
  • Flags provided to shipyard run
  • Environment variables

Any variable defined is global to the entire configuration, including any modules used. This allows variables to be overriden, however; care needs to be taken when defining variables to ensure they do not clash. When building a reusable module it is recommended that variables are prefixed with the module name.

Simple example#

The following eample defines two variables version which has a value 1.6.1, and subnet which has a value of To use these variables inside the configuration you use the var.[variable_name] syntax. When using a varialbe on its own it is not required to encapsulate this in a string, as can be seen in the subnet example subnet = var.subnet, however; should you need to concatonate this variable with another then you need to encapsulate the var.[variable_name] inside the parentheses ${}, this is seen in the container image stanza, name = "consul:${var.version}".

variable "version" {  default = "1.6.1"}
variable "subnet`" {  default = ""}
network "onprem" {  subnet = var.subnet}
container "consul" {  image   {    name = "consul:${var.version}"  }
  command = ["consul", "agent", "-dev"]
  network   {    name = "network.onprem"    ip_address = ""  }}

Complex variables#

In addition to specifying simple string variables, it is also possible to define variables which are maps, or arrays. The following example shows the use of both of these types. In addition to the example shown below, a map can also contain an array and an array a map allowing you to mix complex types together.

variable "subnet" {  default = {    main = ""    consul = ""  }}
variable "command" {  default = [    "consul",    "agent",    "-dev"  ]}
network "onprem" {  subnet = var.subnet.main}
container "consul" {  command = var.command}

Overriding variables#

The variable resource allows the specification of a default value for a variable, overriding these variables can be performed using the three following methods:

Variable files#

When reading a configuration folder Shipyard will auotmatically search for and parse files with the extension .vars. Variable files allow you to set the value for complex and simple variables and are specified as seen in the following example:

version = "1.8.1"
subnet = {  main = ""  consul = ""}

In addition to variable files being automatically loaded by Shipyard from the module folder you can specify external files using the command line flag --vars-file. There is no naming convention for variable files specified in this way.

shipyard run --vars-file = ./myvariables.defaults ./module 

Command line arguments#

It is possible to override variables using command line arguments, the run and test commands have the flag --var which has a value variable=value pair that can be used to set a varaible. The --var flag can be specified multiple times.

shipyard run --var "version=1.9.1" --var "another=value" ./module 

Environment variables#

Lastly you can specify variables using environment variables. To define a variable using an environment variable you prefix the name of the variable with SY_VAR_, for example, the variable version when set as an environment variable would be specified as SY_VAR_version.

export SY_VAR_version=1.8.2

Variable load order#

When using variables there is a defined order of precidence. The following list shows the priority order for setting varaibles.

  • variable stanza block
  • .vars files found in the config folder
  • environment variables SY_VAR_[name]
  • command line argumens specified with the --var flag
  • variable files specified using the --var-file command line flag