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:
All services are installed and then enabled in parents/children order
This behaves as any other set of services
Disabling a
Parent Service
will disable all itsChildren Services
All services are installed and then enabled in random order
Children Services
will wait on Enabling stateOnce the
Parent Service
becomes available they will switch to Enabled
Children Services
are installed first withoutParent Service
presentTrying to enable these services will fail with logs in Service Manger indicating the reason
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
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:
A Cybus::Container running a database
Service ID will be
mssqldatabase
A Cybus::Connection connecting to the database
Service ID will be
serviceaconnection
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
SQL Connection
SQL Endpoint
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