Inter-Service Referencing

A service within a commissioning file describes resources and their relations by referencing each other. In addition to referencing resources within the same commissioning file, you can also reference resources from other commissioning files. This is called inter-service referencing.

Inter-service referencing allows resources in one service to depend on resources in another service. For example, an endpoint in a file can be linked to a connection resource defined in another service by referencing that connection.

To reference resources in another commissioning file, you must not specify the Service ID directly. Instead, you must define a parameter that specifies the appropriate Service ID at run time. For more details, see Service ID and Resource ID.

• Example: If the parameter is otherServiceName, write the reference as !ref '${otherServiceName}::resourceId'.

An example of this can be seen in the multiple files example. Here, a commissioning file references other services using the machineService parameter, with the inter-service reference written as !ref '${machineService}::defaultRole'.

Interactions across Referenced Services

Given the flexibility Connectware offers to build advance relationships between services it is important to understand what behaviors are expected in different scenarios.

• Let’s define services that reference other services Children Services

• Let’s define a service that is referenced by other services Parent Service

Expected Behaviors

Following are four scenarios and how the services behave in each case:

1. All services are installed and then enabled in parents/children order

   1. This behaves as any other set of services

   2. Disabling a Parent Service will disable all its Children Services

2. All services are installed and then enabled in random order

   1. Children Services will wait on Enabling state

   2. Once the Parent Service becomes available they will switch to Enabled

3. Children Services are installed first without Parent Service present

   1. Trying to enable these services will fail with logs in Service Manger indicating the reason

   2. You will see a log starting with Failed enabling service because: Could not resolve cross-service reference... and some extra details about the unresolvable reference

4. Parents services are installed first without children presents

   • No special behavior, once Children Services are added this is the same scenario as cases 1 and 2

Example

The following Service Commissioning Files will be deployed:

1. A Cybus::Container running a database

   • Service ID will be mssqldatabase

2. A Cybus::Connection connecting to the database

   • Service ID will be serviceaconnection

3. A Cybus::Endpoint using referencing to use that Connection

   • Service ID will be servicebendpoint

You can reproduce all the behaviors described above using these Service Commissioning Files.

SQL Database

description: MSSQL Database
metadata:
    name: MSSQL Database

definitions:
    password: password1234!

resources:
    mssqlDatabase:
        type: Cybus::Container
        properties:
            image: mcr.microsoft.com/mssql/server
            ports:
                - '1433:1433'
            environment:
                ACCEPT_EULA: 'Y'
                SA_PASSWORD: !ref password

SQL Connection

description: MSSQL Connection
metadata:
    name: Service A Connection

parameters:
    ip_host:
        type: string
        title: IP address or hostname where Connectware is installed

definitions:
    port: 1433
    database: master
    username: sa
    password: password1234!

resources:
    mssqlConnection:
        type: Cybus::Connection
        properties:
            protocol: Mssql
            connection:
                host: !ref ip_host
                port: !ref port
                username: !ref username
                password: !ref password
                database: !ref database
                useEncryption: false

SQL Endpoint

description: Service B
metadata:
    name: Service B Endpoint

parameters:
    mssqlConnectionServiceId:
        type: string
        title: Service ID of the MSSQL Connection

resources:
    mssqlVersionB:
        type: Cybus::Endpoint
        properties:
            protocol: Mssql
            connection: !ref '${mssqlConnectionServiceId}::mssqlConnection'
            subscribe:
                query: 'SELECT @@version'
                interval: 1000