111 lines
3.7 KiB
Markdown
111 lines
3.7 KiB
Markdown
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---
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title: "Streamline access to stack outputs with OutputDetails"
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date: 2023-03-24
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meta_desc: >-
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You can now read and transform outputs from stack references
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without calling Output.apply.
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meta_image: meta.png
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authors: [abhinav-gupta]
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tags: [features, stack-reference]
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---
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You can use the new `StackReference.getOutputDetails` method
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to get output values from other stacks directly—without calling `Output.apply`.
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<!--more-->
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## What are Stack References?
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> If you already understand stack references,
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> skip on to [Introducing `OutputDetails`](#introducing-outputdetails).
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Stack references are a useful feature of Pulumi
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that you can use to access output values from one stack in another.
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For instance,
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let's say you have a 'network' stack that provisions an AWS VPC,
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and an 'app' stack that deploys your application on an EC2 instance in that VPC.
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The app stack can reference the output of the network stack
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to obtain the VPC ID, which it needs to configure the EC2 instance.
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```typescript
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const network = new pulumi.StackReference("acmecorp/network/other");
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const vpcId = network.getOutput("vpcId");
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```
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The `getOutput` method above returns an `Output` value that holds the result.
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You can call `Output.apply` to perform transformations on the output value.
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As an example,
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if you need to extract a subnet ID from a JSON string in the output,
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you can use the following code:
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```typescript
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const subnetConfig = network.getOutput("subnetConfig");
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const subnetId = subnetConfig.apply(output => JSON.parse(output).subnetId);
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```
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This approach works but is limited because
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the output value obtained from the `apply` transformation
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is also an `Output` value.
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You cannot access or manipulate this value directly,
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and you must continue to use `apply` repeatedly to consume the value.
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As an aid in resolving this problem, we have introduced `OutputDetails`.
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These provide direct access to the output of one stack from another stack.
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## Introducing `OutputDetails`
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We've added a new method, `StackReference.getOutputDetails`,
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to allow direct access to output values from stack references.
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This method can be used as follows:
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```typescript
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const vpcIdDetails = await network.getOutputDetails("vpcId");
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const vpcId = vpcIdDetails.value;
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```
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Unlike the `getOutput` method,
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the resulting value is a plain value, not an `Output` value.
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As a result, there is no need to call `apply` repeatedly
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to transform or consume the value.
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Revisiting the previous example of extracting a value from a JSON string,
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`getOutputDetails` can be used as shown below:
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```typescript
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const subnetConfig = (await network.getOutputDetails("subnetConfig")).value;
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const subnetId = JSON.parse(subnetConfig).subnetId;
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console.log(`Using subnet ID ${subnetId}`);
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```
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### What about secrets?
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`getOutputDetails` can also be used to access secret outputs
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generated by the referenced stack.
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For example, if the referenced stack sets up a database
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and produces the password as a stack output,
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you can access it as follows:
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```typescript
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const passwordDetails = await dbStack.getOutputDetails("databasePassword");
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const password = passwordDetails.secretValue;
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```
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### Can we do this for all `Output` values?
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Unfortunately, it is not feasible to do this to every `Output` value.
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Stack references are unique in that
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the referenced stack must already have deployed
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for the reference to be resolved.
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Therefore, when the stack reference is created,
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the outputs of the referenced stack are available immediately.
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This is not the case for other `Output` values.
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Their values only become available as `pulumi update` runs,
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so we cannot access them in the same way.
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## Availability
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This feature is available in all stable SDKs for Pulumi,
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starting from v3.55.0.
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Give it a spin and share your thoughts with us on [Slack](https://slack.pulumi.com/)!
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