Request Chaining

Request chaining allows you to create dependencies between checks within the same Canary, enabling complex multi-step verification workflows. A check can depend on other checks and access their output data through templating.

Use Cases

• Authentication flows: Login first, then use the token for subsequent API calls
• Multi-step API workflows: Create a resource, then verify its state
• Data-dependent checks: Fetch configuration from one endpoint, use it in another

How It Works

1. Define checks with unique names
2. Use dependsOn to specify which checks must complete first
3. Access previous check outputs via outputs.<checkName>.<field>

Checks are executed in topological order based on their dependencies, ensuring dependent checks only run after their prerequisites complete successfully.

Example

http-depends-on.yaml
apiVersion: canaries.flanksource.com/v1
kind: Canary
metadata:
  name: http-depends-on
spec:
  schedule: "@every 5m"
  http:
    - name: getUuid
      url: https://httpbin.flanksource.com/uuid
      test:
        expr: "code == 200 && json.uuid != ''"

    - name: useUuid
      url: https://httpbin.flanksource.com/get
      dependsOn:
        - getUuid
      test:
        # Verify we can access the output from the previous check
        expr: "code == 200 && outputs.getUuid.json.uuid != ''"

Fields

Field	Description	Scheme
dependsOn	List of check names that must complete before this check runs	[]string

Accessing Outputs

When a check has dependencies, it can access the outputs from those checks using the outputs object:

Expression	Description
outputs.<checkName>.json	Parsed JSON response body
outputs.<checkName>.code	HTTP response code
outputs.<checkName>.headers	Response headers
outputs.<checkName>.content	Raw response body

Example: Using Previous Check Output

apiVersion: canaries.flanksource.com/v1
kind: Canary
metadata:
  name: auth-flow
spec:
  schedule: "@every 5m"
  http:
    - name: login
      url: https://api.example.com/auth/login
      method: POST
      body: '{"username": "user", "password": "pass"}'
      test:
        expr: "code == 200 && json.token != ''"

    - name: get-profile
      url: https://api.example.com/profile
      dependsOn:
        - login
      headers:
        - name: Authorization
          # Use the token from the login check
          value: "Bearer $(.outputs.login.json.token)"
      test:
        expr: "code == 200"

Execution Order

Checks are automatically sorted using topological ordering based on their dependencies. If check B depends on check A, then:

1. Check A executes first
2. If Check A succeeds, Check B executes with access to A's outputs
3. If Check A fails, Check B is skipped

Limitations

• Circular dependencies are not allowed
• dependsOn only works within the same Canary resource
• All referenced check names must exist in the same Canary