Table of contents

ADSP service SDK (Flask)

ADSP service SDK (Flask)

Platform services integrate into the foundational capabilities via a Software Development Kit (SDK). The SDK includes interfaces and utilities for handling tenancy, configurations, and registration. The same SDK can be used for development of tenant services.

Note that the SDK provides friendly interfaces on top of APIs. It is intended to speed up service development but is not the only way to access platform capabilities.

Install the ADSP SDK for Flask wheel from release artifacts in the repository.

poetry add https://github.com/GovAlta/adsp-monorepo/releases/download/adsp-service-flask-sdk-v1.3.1/adsp_service_flask_sdk-1.0.0-py3-none-any.whl

Setting up a service account

The SDK requires credentials for a service account and uses this account for accessing platform capabilities. Fine grained configuration is possible and principle of least privilege should be applied.

In order to create the service account.

Create a confidential Client with a client ID in the format: urn:ads:{tenant}:{service} . The SDK does not authenticate end users and so all authentication grant types can be disabled.
Enable service account for the client.
In Service Account Roles, add the appropriate Client Roles for the capabilities that will be accessed:
1. Client urn:ads:platform:tenant-service role platform-service is required.
2. Client urn:ads:platform:configuration-service role configured-service is needed for registration and accessing service specific configuration
3. Client urn:ads:platform:event-service role event-sender is needed for sending domain events.
Additional audiences in the service account access token are required for some capabilities:
1. Client urn:ads:platform:push-service needs to be include via an audience mapper for socket based configuration cache invalidation.

Initializing the SDK

The SDK includes a Flask Extension, Blueprint, and context proxies. Create the extension and initialize on the Flask app to get started.

  from adsp import AdspExtension, AdspRegistration
  from flask import Flask

  app = Flask(__name__)
  extension = AdspExtension()
  extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service."
    )
  )

Enabling service metadata

The service directory aggregates service metadata from the root resource of services registered in the directory. This metadata is used to simplify configuration and for OpenAPI documentation aggregation at https://api.adsp.alberta.ca/{tenant}. SDK includes components for exposing the metadata endpoint.

Enabling service metadata:

  from adsp import AdspExtension, AdspRegistration
  from flask import Flask

  app = Flask(__name__)
  extension = AdspExtension()
  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service.",
      api_path="/hello-world/v1"
    )
  )

  app.register_blueprint(adsp.metadata_blueprint)

Authorizing requests

The SDK extension adds a before_request function to process access tokens. It provides a request_user context value and require_user decorator for authorizing requests.

Require ADSP user for request:

  from adsp_service_flask_sdk import request_user, require_user, User
  ...

  @app.route("hello-world/v1/hello")
  @require_user()
  def hello_world() -> str:
    return f"hello {request_user.name}"

Role-based authorization

The SDK maps Keycloak access token realm_access and resource_access roles to the request user.

Keycloak issued tokens contain client roles nested under realm_access. SDK claim mapping flatten service specific roles from the token and qualifies roles related to other service clients with the client ID.

For example:

  {
    "realm_access": { "roles": ["user"] },
    "resource_access": {
      "my-service": { "roles": ["my-user"] },
      "other-service": { "roles": ["other-user"] }
    }
  }

For my-service, the roles are mapped to role claims:

user
my-user
other-service:other-user

Authorize based on a role:

  from adsp_service_flask_sdk import request_user, require_user, User
  ...

  @app.route("hello-world/v1/hello")
  @require_user("other-service:other-user")
  def hello_world() -> str:
    return f"hello {request_user.name}"

Accessing user information directly and checking for role:

  from adsp_service_flask_sdk import request_user

  has_role = "other-service:other-user" in request_user.roles

Determining tenancy

Requests to platform services are in the context of a specific tenant with few exceptions. The context is implicit when a request is made with a tenant bearer token. It can be explicit in cases where an endpoint allows anonymous access or when a platform service makes a request to another platform service under a core service account.

The SDK extension adds a before_request function that resolves implicit tenancy from user tenancy and explicit from a tenantId query parameter. Resolved tenant is set on the request object; no value is set if tenancy cannot be resolved.

Getting tenancy from the context:

  from adsp_service_flask_sdk import request_tenant
  ...

  @app.route("hello-world/v1/hello")
  @require_user()
  def hello_world() -> str:
    return f"hello {request_tenant.name}"

The handler uses the tenant service client to retrieve tenant information. This is also available from the SDK for direct use. The tenant service is available via dependency injection.

Getting tenant information using the tenant service:

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service."
    )
  )

  @app.route("hello-world/v1/hello")
  @require_user()
  def hello_world() -> str:
    tenant_id = request.args.get("tenantId")
    tenant = adsp.tenant_service.get_tenant(AdspId.parse(tenant_id))
    ...

Finding services

Service discovery in ADSP is handled using client side service discovery with a directory of services providing a register of available services.

Getting a service URL from the directory:

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service."
    )
  )

  @app.route("hello-world/v1/hello")
  @require_user()
  def hello_world() -> str:
    service_url = adsp.directory.get_service_url(AdspId.parse("urn:ads:platform:tenant-service"))
    ...

Handling configuration

Platform services can make use of a common configuration service for managing configuration. The SDK allows services to define their configuration schema and access configuration.

Defining the configuration json schema:

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service.",
      configuration=ConfigurationDefinition(
        "Configuration of messages.",
        {"type": "object", "properties":{"responses":{"type":"object"}}}
      )
    )
  )

Each service can have core configuration that applies across tenants and configuration specific to each tenant. The SDK provides a get_configuration function that uses the current service and context tenant.

Getting configuration via the context:

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service.",
      configuration=ConfigurationDefinition(
        "Configuration of messages.",
        {"type": "object", "properties":{"responses":{"type":"object"}}}
      )
    )
  )

  @app.route("hello-world/v1/hello")
  @require_user()
  def hello_world() -> str:
    tenant_config, core_config = adsp.get_configuration()
    ...

The function uses a configuration service client to retrieve configuration. This is also available from the SDK via dependency injection for direct use.

Getting configuration using the configuration service:

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service.",
      configuration=ConfigurationDefinition(
        "Configuration of messages.",
        {"type": "object", "properties":{"responses":{"type":"object"}}}
      )
    )
  )

  @app.route("hello-world/v1/hello")
  @require_user()
  def hello_world() -> str:
    tenant_config, core_config = adsp.configuration_service.get_configuration(
      service_id, request_tenant.id
    )
    ...

Converting configuration

Services may want to apply transformations on the retrieved configuration. The SDK allows services to provide functions for combining core and tenant configuration. For example, services can use these to generate effective configuration when tenant overrides parts of core configuration.

Provide conversion functions:

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service.",
      configuration=ConfigurationDefinition(
        "Configuration of messages.",
        {"type": "object", "properties":{"responses":{"type":"object"}}}
        lambda tenant_config, core_config: core_config.update(tenant_config.items())
      )
    )
  )

Registering event definitions, notification types, etc.

The SDK allows services to register configuration for some platform services.

roles defines the client roles of the service. New tenant realms are created with a client that includes the roles specified here.
events defines the domain events of the service signalled for domain significant changes.

Defining configuration for other platform services:

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service.",
      roles=[ServiceRole(HELLO_WORLDER, "Role that allows people to hello the world.")],
      events=[
        DomainEventDefinition(
          HELLO_WORLD_EVENT,
          "Signalled when a hello world message is posted to the API.",
          payload_schema={
            "type": "object",
            "properties": {
              "fromUserId": {"type": "string"},
              "fromUser": {"type": "string"},
              "message": {"type": "string"},
              "response": {"type": "string"},
            },
          },
        )
      ]
    )
  )

Sending domain events

Domain events can be sent using the event service.

  adsp = extension.init_app(
    app,
    AdspRegistration(
      display_name="My platform service",
      description="Hello world platform service.",
      roles=[ServiceRole(HELLO_WORLDER, "Role that allows people to hello the world.")],
      events=[
        DomainEventDefinition(
          HELLO_WORLD_EVENT,
          "Signalled when a hello world message is posted to the API.",
          payload_schema={
            ...
          },
        )
      ]
    )
  )

  @app.route("hello-world/v1/hello")
  @require_user()
  def hello_world() -> str:
    message = request.args.get("message")
    ...
    adsp.event_service.send(
      DomainEvent(
        HELLO_WORLD_EVENT,
        datetime.utcnow(),
        {
            "fromUserId": request_user.id,
            "fromUser": request_user.name,
            "message": message,
            "response": response,
        },
      )
    )
    ...

Additional utilities

The SDK provides several other useful utilities.

ADSP ID

Utilities for handling ADSP URNs.