dap-service-composition

name	dap-service-composition
description	Use when composing services — ServiceComponent sub-deployments, SharedResource, chaining blueprints, get_environment_capability. Triggers — service component, sub-deployment, dell.nodes.ServiceComponent, or requests to chain deployments.

Service Composition — NativeEdge Blueprints

Runtime Mode

You are running in IDE mode with shell access. Use the bpa CLI for BPA operations. Do not use the function interface unless explicitly instructed by the host.

Service composition lets you build complex applications from smaller, independently deployed pieces. Instead of putting everything in one blueprint, you define a main deployment that spins up sub-deployments — each responsible for one layer (e.g. a VM, a database, a network). The main deployment ties them all together.

Related skill: For the full blueprint authoring reference — node types, intrinsic functions, relationships, multi-file structure — invoke the dap skill (Blueprint Assist). Use this skill (service-composition) when the question is specifically about connecting deployments together.

---

CRITICAL RULES

NEVER write a service component node template from memory. The resource_config shape and available properties must be verified with the bpa CLI before you write any YAML.

Before writing any service composition blueprint:

1. Run bpa knowledge blueprints find "service component" to find a working example
2. Run bpa knowledge blueprints get <id> --include-files to get the actual YAML
3. Run bpa knowledge types get dell.nodes.ServiceComponent to get the exact property schema
4. Write the blueprint based ONLY on what the tools returned
5. Run bpa blueprint lint --file <path> --verify to validate

---

Core Concepts

Term	Meaning
Service component	A node template of type dell.nodes.ServiceComponent. It represents one deployable piece of a larger service.
Sub-deployment	The deployment created when a service component node is installed. It is owned by the parent deployment.
Main deployment	The top-level deployment that contains all the service component nodes.
Component blueprint	The blueprint used by a service component — can be a catalog blueprint or a blueprint archive in a repo.
SharedResource	A node of type dell.nodes.SharedResource that connects to an existing deployment by ID rather than creating a new one.

Rule of thumb: use service composition when two layers have independent lifecycles, or when you want to reuse a blueprint (e.g. a standard VM blueprint) across many applications without duplicating it.

---

Architecture

Main Deployment
+-- service component: vm_layer   <- sub-deployment A (Virtual Machine blueprint)
+-- service component: db_layer   <- sub-deployment B (Database blueprint)
+-- app_node                      <- regular node, depends_on: vm_layer, db_layer

CHANGELOG.yaml (BS-009): The parent blueprint AND each components/<name>/ directory must contain their own CHANGELOG.yaml.

CHANGELOG.yaml requirement (BS-009): The parent blueprint AND each sub-blueprint (component) directory must contain their own CHANGELOG.yaml. When generating a service composition blueprint, create a CHANGELOG.yaml at the top level and one inside each components/<name>/ directory.

---

dell.nodes.ServiceComponent — the Service Component Node Type

This is the node type you use in your blueprint to create a sub-deployment. It has a single key property: resource_config.

Always look up the exact schema before writing:

bpa knowledge types get dell.nodes.ServiceComponent

Canonical resource_config Structure

vm_layer:
  type: dell.nodes.ServiceComponent
  properties:
    resource_config:
      blueprint:
        external_resource: true           # true = catalog/already-uploaded blueprint
        id: Virtual_Machine_for_vSphere   # Blueprint ID in the catalog
        revision_id: "2.1.0.1"           # ALWAYS include the revision
      deployment:
        display_name:                     # Human-readable name for the sub-deployment
          concat:
            - { get_sys: [deployment, name] }
            - "-vm"
        auto_inc_suffix: true             # Append -1, -2 ... to avoid name collisions
        inputs:
          hostname:  { get_input: vm_hostname }
          vcpu:      { get_input: vm_vcpus }
          memory:    { get_input: vm_memory }

Key sub-properties:

Sub-property	Required	Description
blueprint.external_resource	Yes	true = catalog blueprint; false = archive upload
blueprint.id	Yes	Blueprint ID (literal or { get_input: ... })
blueprint.revision_id	Yes	Semver string. Always include this.
blueprint.blueprint_archive	Conditional	URL/path to zip (only when external_resource: false)
deployment.display_name	Recommended	Use get_sys: [deployment, name] so the name is unique
deployment.auto_inc_suffix	Recommended	Always pair with display_name
deployment.inputs	Conditional	Required if the component blueprint has inputs without defaults

---

Three Ways to Source a Component Blueprint

1. Catalog blueprint (most common in production):

blueprint:
  external_resource: true
  id: Virtual_Machine_for_vSphere
  revision_id: "2.1.0.1"

2. Blueprint archive from a repository:

blueprint:
  external_resource: false
  id: my-db-blueprint
  blueprint_archive: https://repo.example.com/blueprints/db-blueprint.zip
  main_file_name: blueprint.yaml   # omit if only one YAML at root

3. Parameterised selection (blueprint ID from input):

blueprint:
  external_resource: true
  id: { get_input: compute_blueprint }
  revision_id: { get_input: compute_revision }

---

deployment.inputs Patterns

Flat pass-through

Map each component input to a top-level input: hostname: { get_input: vm_hostname }

get_environment_capability

Bridge environment-level capabilities into sub-deployments: vsphere_secret_name: { get_environment_capability: vcenter_credentials }

Sibling capabilities

Read output from another service component: join_command: { get_attribute: [init_control_plane, capabilities, kubernetes_join_command] }

For detailed YAML examples and the dynamic precreate script pattern, run bpa knowledge plugins docs service-composition.

---

Capability Patterns

Function	When to use
get_attribute: [node, capabilities, key]	Reading a capability from a sibling service component node in the same blueprint
get_environment_capability: key	Reading a capability from the NED environment (ECE layer, vSphere environment)
get_capability: [deployment_id, key]	Reading a capability from a deployment by ID — used with SharedResource
get_secret: { get_attribute: [...] }	When the capability value is a secret key, not the secret value itself

Common mistake: using get_attribute on a service component node without the capabilities middle segment. The correct 3-part path is [node_id, capabilities, cap_name].

For detailed defining/consuming capability examples, run bpa knowledge plugins docs service-composition.

---

SharedResource — Connecting to an Existing Deployment

Use dell.nodes.SharedResource to consume an existing deployment (e.g. a K8S cluster deployed separately) rather than create a new one:

k3s_cluster:
  type: dell.nodes.SharedResource
  properties:
    resource_config:
      deployment:
        id: { get_input: k3s_deployment_id }   # No blueprint section — reference by ID

Read its capabilities with get_capability:

kubeconfig_file_content:
  get_secret:
    get_capability:
      - { get_input: k3s_deployment_id }
      - kubeconfig_secret_name

---

Workflow for Building a Service Composition Blueprint

1. bpa knowledge blueprints find "service component vm application" — find a matching example
2. bpa knowledge blueprints get <id> --include-files — get the actual YAML
3. For each component blueprint: verify it exists (bpa orchestrator blueprints list), get its revision, know its required inputs and exported capabilities
4. bpa knowledge types get dell.nodes.ServiceComponent — get the exact property schema
5. Write the blueprint based ONLY on what steps 1-4 returned
6. bpa blueprint lint --file blueprint.yaml --verify — validate
7. bpa blueprint validate-all --file blueprint.yaml — validate node templates (if plugin source available)

---

Retrieval

Understand composition patterns (multi-file, scaling):

bpa knowledge plugins docs service-composition

Search for specific topics:

bpa knowledge docs search "service component"
bpa knowledge docs search "SharedResource"

Find a working blueprint example:

bpa knowledge blueprints find "service composition"

---

Optional Components (Conditional Node Instantiation)

Some deployments include service component nodes that should only be provisioned when a user requests them (e.g., an optional monitoring stack, a GPU node, extra storage). The control_installation + jmespath pattern provides conditional instantiation without requiring separate blueprints.

Pattern: control_installation with a Boolean Input

For dell.nodes.ServiceComponent nodes, use control_installation inside resource_config:

inputs:
  install_monitoring:
    type: boolean
    display_label: Enable Monitoring
    description: When true, the monitoring stack will be deployed.
    default: false
    hidden: false
    allow_update: false
    constraints:
      - valid_values: [true, false]
        error_message: Must be true or false.

node_templates:
  monitoring_stack:
    type: dell.nodes.ServiceComponent
    properties:
      resource_config:
        blueprint:
          external_resource: true
          id: Monitoring_Stack
          revision_id: "1.0.0"
        deployment:
          display_name:
            concat:
              - { get_sys: [deployment, name] }
               
           
           {}
        
          
            
               
               [{ {   }}]
          
            
               
               [{ {   }}]

Key rules:

• Both install and uninstall must use the same jmespath expression to keep them in sync.
• The expression must return an integer (0 or 1), not a boolean.
• 0 = the sub-deployment is NOT created during install. 1 = it IS created.
• allow_update: false on the controlling boolean — changing it after deployment requires a deployment update workflow.

Pattern: scalable.default_instances (Non-ServiceComponent Nodes)

For regular nodes (not ServiceComponent), use the scalable capability instead:

node_templates:
  optional_node:
    type: dell.nodes.Root
    capabilities:
      scalable:
        properties:
          default_instances:
            jmespath:
              - 'length([?enable_feature == `true`]) || `0`'
              - [{"enable_feature": { get_input: enable_feature }}]

• default_instances: 0 — Node defined but install workflow skips it (zero instances created)
• default_instances: 1 — Node instantiated normally

Dependent Inputs with only_with

Use only_with on inputs that only make sense when the optional feature is enabled:

inputs:
  monitoring_retention_days:
    type: integer
    display_label: Retention Days
    description: Only relevant when monitoring is enabled.
    default: 30
    only_with: install_monitoring

only_with hides the input in the DAP orchestrator UI when the referenced boolean is false.

Map form (match a specific value): only_with also accepts a map so you can gate on a specific value, not just a boolean true:

inputs:
  ingress_host:
    type: string
    display_label: Ingress Host
    required: true        # mandatory ONLY while the gate is satisfied
    only_with:
      ingress_enabled: "true"

Conditionally-required pattern: combine required: true with only_with so a field is shown and mandatory only when its feature/toggle is on (and is skipped entirely otherwise). This surfaces the requirement in the form up front instead of failing later at validation time. Used in the JFrog Platform blueprint for license_secret_ref / master_key_secret_ref / join_key_secret_ref (gated on their Apply ... Secret toggle) and ingress_class_name / ingress_host (gated on Kubernetes Ingress mode).