Pulumi YAML reference

Pulumi programs can be defined in many languages, and the Pulumi YAML dialect offers an additional language for authoring Pulumi programs.

The Pulumi YAML provider supports programs written in YAML or JSON. In both cases, the programs (.yaml or .json files) follow a simple schema, including four top level sections:

In many locations within this schema, values may be expressions which computed a value based on the config, variables, or outputs of resources. These expressions can be provided in two ways:

• If an object is provided as a value, and has a key that has the prefix fn::, the object is treated as an expression, and the expression will be resolved to a new value that will be used in place of the object.
• Any string value is interpreted as an interpolation, with ${...} being replaced by evaluating the expression in the ....

The supported expression forms for each of these is detailed below.

Config

config is a map of config property keys to either values or structured declarations (see here).

In beta, Pulumi YAML projects used the configuration key. This will eventually be deprecated; switching from configuration to config will not break existing projects.

The value of configuration is an object whose keys are logical names by which the config input will be referenced in expressions within the program, and whose values are elements of the schema below. Each item in this object represents an independent config input. Either type or default is required.

Resources

The value of resources is an object whose keys are logical resource names by which the resource will be referenced in expressions within the program, and whose values which are elements of the schema below. Each item in this object represents a resource which will be managed by the Pulumi program.

Resource Options

The value of the options property of a Resource is an object whose keys are resource option names and whose values are elements of the schema below. No resource options are required.

The dependsOn, parent, provider, and providers values permit expressions which must use interpolation syntax to reference resources by name. For example:

    options:
      provider: ${myEksProvider}
      providers:
        aws: ${myAwsProvider}
      dependsOn:
        - ${otherResource}
      parent: ${someParentResource}

Resource Getter

Supplying a get key turns the resource declaration into a Getter Function.

Custom Timeout

The optional customTimeouts property of a resource is an object of the following schema:

Providers and provider versions

There are at least two reasons to explicitly define providers in YAML, or explicitly set their versions while creating resources.

1. Using explicit versions enables pinning the dependencies used, a technique used to improve build reliability.
2. Using explicit providers enables controlling the options for providers used by each resource, as described in Unlock Programmatic Control by Disabling Default Providers.

If a specific provider version is necessary, we prefer the approaches in the order described here.

Default provider

Declaring a default provider simplifies configuring a provider version across all resources for that provider.

To configure the default provider instance for all resources for that provider’s name, use the resources section to declare a provider resource.

For the type property, prefix the name of the provider with pulumi:providers, for example, pulumi:providers:aws. Setting the defaultProvider property to true, defined at the same level as type, configures this as a default provider.

resources:
  aws-provider:
    type: pulumi:providers:aws
    defaultProvider: true
    options:
      version: 6.45.0
  my-bucket:
    type: aws:s3:Bucket

In this example the my-bucket resource, and any other AWS resources, uses the default AWS provider version 6.45.0.

Only one provider of a given type can be declared as the default provider.

Explicit provider

To declare an explicit provider instance for specific resources, declare a provider resource in the resources section. For the type property, prefix the name of the provider with pulumi:providers.

resources:
  provider:
    type: pulumi:providers:azure
    options:
      version: 5.1.0

The provider instance can than be used as described in section Resource Options by setting the provider option:

resources:
  provider:
    type: pulumi:providers:azure
    options:
      version: 5.1.0
  rg:
    type: azure:core:ResourceGroup
    properties:
      location: WestEurope
    options:
      provider: ${provider}

Explicit providers take precedence over default providers.

Resource version

To declare a resource with a specific provider version use the version option as described in Resource Options:

resources:
  something:
    type: aws:s3:Bucket
    properties:
      ...
    options:
      version: 5.6.0

Third party providers

Third party providers may require a pluginDownloadURL option for Pulumi to acquire the provider plugin. The publisher of that provider should provide this URL, following our guide for Authoring & Publishing.

All of the above examples setting a version with a default provider, explicit provider, or on individual resources may be combined with the pluginDownloadURL option to use a third party provider.

This declares one of Pulumi’s own providers as a default provider, setting an explicit pluginDownloadURL.

resources:
  aws-provider:
    type: pulumi:providers:aws
    defaultProvider: true
    options:
      version: 6.45.0
      pluginDownloadURL: github://api.github.com/pulumi
  my-bucket:
    type: aws:s3:Bucket

Outputs and Stack References

The value of outputs is an object whose keys are the logical names of the outputs that are available from outside the Pulumi stack (via pulumi stack output), and whose values are potentially computed expressions that resolve to the values of the desired outputs.

outputs:
  outputName: ${resource.id}

Stack references can be used to access the outputs of one stack from within another stack. A stack reference requires the fully qualified name of the stack as an argument in the format of <organization>/<project>/<stack>.

resources:
  reference:
    type: pulumi:pulumi:StackReference
    properties:
      name: org/project/stack

outputs:
  secondOutputName: ${reference.outputs["outputName"]}

The above output will have the value of the outputName output from the stack org/project/stack.

Expressions

Expressions can be used in several contexts:

• the properties of properties of resources
• the properties of options of resources that take references to other resources: parent, dependsOn, provider, and providers
• the values of variables and outputs
• some or all values provided to built-in functions, as specified below

Generally speaking, most values permit an expression and exceptions will be documented as not permitting an expression, as above.

In these contexts, any JSON/YAML value may be provided. If that value is a string, it is interpolated. If that value is an object, and the object has a key with a prefix of fn::, it is evaluated as an expression.

Interpolation

In expression locations, strings are evaluated as interpolations and any nested ${...} expressions within the string value are replaced by the value of the expression .... The syntax of expressions within interpolations permits property access only.

To use ${} in a string literal, escape $ with $$ like so:

variables:
  plainString: $${value}

A string like Hello, ${foo} will convert the expression foo to a string.

If a string contains only an ${...} expression, it’s considered a substitution.

Property Access

Within an expression denoted by ${...} property access is permitted according to the forms below. Config, variables, and resource keys all exist in a single namespace, and in the examples, root or equivalent must be the name of one of these items, and it must be valid to access the foo property of that item if it’s a map or object, or if it’s an array, the index must be valid.

• ${root}
• ${root.foo}
• ${root["foo"]}
• ${root.bar.quux}
• ${root["bar"].quux}
• ${root["bar"]["quux"]}
• ${root[0]}
• ${root[100]}
• ${root[0].foo}
• ${root[0][1].foo}
• ${root.foo.items[0].bar[1]}
• ${root["key with \"escaped\" quotes"]}
• ${root["key with a ."]}
• ${["root key with \"escaped\" quotes"].foo}
• ${["root key with a ."][100]}

We have not discussed types until now, but implicitly every expression has a type, such as number, string, map, array, or even resource. When interpolated, these values must become strings, otherwise they are substituted in. Additionally:

• maps must have string keys and expression values
• arrays have non-negative integer indices and expression values
• property access on a Resource retrieves outputs

Substitution

Expressions denoted by ${...} are only converted to strings when interpolated into a string with surrounding text. If a resource property takes a list or a map for example, that can be provided by a variable whose value can be substituted in. In the example below, the httpPort variable is used to reduce repetition in the two Kubernetes Service resources.

name: kubernetes-port-example
variables:
  httpPort:
    protocol: TCP
    port: 80
    targetPort: 8000
resources:
  serviceOne:
    type: kubernetes:core/v1:Service
    properties:
      spec:
        selector:
          app: "MyApp"
        ports:
          - ${httpPort}
  serviceTwo:
    type: kubernetes:core/v1:Service
    properties:
      spec:
        selector:
          app: "OtherApp"
        ports:
          - ${httpPort}

The last two lines are equivalent as if the variable were substituted for its value:

        ports:
          - protocol: TCP
            port: 80
            targetPort: 8000

Built-in Functions

In any expression location, an object containing a single key beginning with fn:: calls a built-in function.

fn::toBase64

Converts a UTF-8 string into a Base64 encoded string using the standard encoding.

variables:
  greeting:
    fn::toBase64: "Hello, world!"

The expression ${greeting} will return SGVsbG8sIHdvcmxkIQ==

fn::fromBase64

Converts a Base64 encoded string into a UTF-8 string. This will fail if the result is not a valid UTF-8 string

variables:
  greeting:
    fn::fromBase64: SGVsbG8sIFdvcmxkIQ==

The expression ${greeting} will return Hello, World!

fn::toJSON

Converts a value into its JSON representation.

variables:
  item:
    fn::toJSON:
      key1: value1
      key2: 123

The expression ${item} will return a JSON value { "key1": "value1", "key2": 123 }.

fn::invoke

Calls a function from a package and returns either the whole object or a single field if given the return property. This can be any of the functions in the registry providers as well as functions found in the pulumi-std package that includes math functions such as sum and abs, logic functions such as anytrue, and string functions such as split.

The schema is:

Example calling the getAmi function in the AWS provider package:

variables:
  AmazonLinuxAmi:
    fn::invoke:
      function: aws:getAmi
      arguments:
        filters:
          - name: name
            values: ["amzn-ami-hvm-*-x86_64-ebs"]
        owners: ["137112412989"]
        mostRecent: true
      options:
        version: 5.9.0
      return: id

The expression ${AmazonLinuxAmi} will return the AMI ID returned from the aws:getAmi function.

Example calling the sum function in the pulumi-std provider package to subtract 255 from ${route53Weight}:

variables:
  route53Weight: 400
  modifiedWeight:
    fn::invoke:
      function: std:sum
      arguments:
        input:
          - ${route53Weight}
          - -255
      return: result

The expression ${modifiedWeight} will return 145 in this case.

Invoke Options

The value of the options property of an fn::invoke is an object with the following properties.

The parent and provider values permit expressions which must use interpolation syntax to reference resources by name. For example:

    options:
      provider: ${myEksProvider}
      parent: ${someParentResource}

fn::join

Joins strings together separated by a delimiter. Arguments are passed as a list, with the first item being the delimiter, and the second item a list of expressions to concatenate.

variables:
    banana:
        fn::join:
            - 'NaN'
            - - Ba
              - a

The expression ${banana} will have the value "BaNaNa".

fn::split

Splits a string on a delimiter. Arguments are passed as a list, with the first item being the delimiter, and the second item the string to split.

variables:
    fruits:
        fn::split:
            - ", "
            - "apple, orange, banana"

The expression ${fruits} will be a list containing the values ["apple", "orange", "banana"].

fn::select

Selects one of several options given an index. Arguments are passed as a list, with the first item being the index, 0-based, and the second item a list of expressions to select from.

variables:
    policyVersion:
        fn::select:
            - 1
            - - v1
              - v1.1
              - v2.0

The expression ${policyVersion} will have the value v1.1.

fn::*Asset and fn::*Archive

Assets and Archives are intrinsic types to Pulumi, like strings and numbers, and some resources may take these as inputs or return them as outputs. The built-ins create each kind of asset or archive. Each takes all take a single string value.

variables:
  aFile:
    fn::fileAsset: ./file.txt
  aString:
    fn::stringAsset: Hello, world!
  aRemoteAsset:
    fn::remoteAsset: http://worldclockapi.com/api/json/est/now

  aFileArchive:
    fn::fileArchive: ./file.zip
  aRemoteArchive:
    fn::remoteArchive: http://example.com/file.zip
  anAssetArchive:
    fn::assetArchive:
      file:
        fn::stringAsset: Hello, world!
      folder:
        fn::fileArchive: ./folder

fn::secret

Constructs a Secret from an existing value.

variables:
  secret:
    fn::secret:
      fn::invoke:
        function: my:pkg:GetSecretValue

fn::readFile

Reads a file from disk and returns the contents as a string, must be utf-8. This function has special rules for its behavior.

variables:
  someText:
    fn::readFile: ./README.md

Any subpath of the Pulumi project directory is allowed, whether it is absolute, relative, constant, or an expression:

• fn::readFile: ./README.md, a relative subpath
• fn::readFile: ${pulumi.cwd}/example.txt, an absolute subpath
• fn::readFile: /opt/project-dir/example.json, an absolute subpath if the program is in /opt/project-dir

Absolute paths to any location are allowed if they are constants:

• fn::readFile: /etc/lsb-release
• fn::readFile: /usr/share/nginx/html
• fn::readFile: /var/run/secrets/kubernetes.io/serviceaccount/token

Relative paths that escape the project directory and absolute paths that are non-constant are forbidden to prevent path traversals.

• fn::readFile: ../../etc/shadow, a relative path that escapes the project
• fn::readFile: ${pulumi.cwd}/../../.ssh/id_rsa.pub, an expression that returns an absolute path that escapes the project

Built-in variables

Built-in variables accessible within any Pulumi YAML program.

pulumi

The built-in pulumi variable contains three properties, which can be useful for retrieving information about your current workspace.

    variables:
      cwd: ${pulumi.cwd}
      project: ${pulumi.project}
      stack: ${pulumi.stack}

• ${pulumi.cwd} retrieves the current working directory
• ${pulumi.project} retrieves the current project
• ${pulumi.stack} retrieves the current stack