Services

Every dependency is represented as a service.

What is a service?

A service is a unit within a larger Jetwhisk app. Any functionality that is not completely functional (or pure) should be encapsulated in a service to allow smarter management.

Instances

But services can't just exist. So on every instantiation, a new instance is created and stored alongside any others. By default, instances are not destroyed until the Orchestrator shuts down, but they can be set to destroy sooner if needed.

The nice thing about the instance system is that you never have to think about the instances themselves. Jetwhisk will just plumb together instances, so all you have to think about is the service layer.

Instance status

• Ready

  This instance is ready to be depended upon.

• Active

  This instance is currently executing instructions.

• Satisfied

  Every dependency of this instance is ready.

• Failed

  This instance was not able to run to completion.

• Done

  This instance has done all that it needs to do and can be safely destroyed.

Instantiation scopes

• Global

  A singular, shared instance of the service will be made available to all other requesting instances.

• Sandbox

  Each requesting service will get access to its own instance of the service, shared between all its instances.

• Instanced

  Each requesting instance gets its own copy of the service.

Service types

• Trigger

  For a self-contained service that should be considered ephemeral, like setting up a global variable, adding a polyfill or checking the status of something. These shouldn't have APIs accessible through the service system.

• Persistent

  For a service that has a lifecycle and that will be used in code.

Statuses between types

Service type	Trigger	Persistent
Ready when...	The called function exits without an error	The service says it is
Active when...	The service is satisfied but not done	Any method is executing
Satisfied when...	When all dependencies are ready	When all dependencies are ready
Failed when...	The called function throws an error	The service either throws an error or fails to instantiate
Done when...	The called function exits without an error	The service says it is