Implement instantiated services option. Resolve #119 #126
Conversation
ryneeverett
force-pushed
the
instantiated-services
branch
3 times, most recently
from
cbc3a04 to
89a2b10
Compare
This introduces an option to enable instantiated services while maintaining backwards compatibility with the singleton pattern. It also allows passing caller arguments into the `Endpoint` declaration. Resolve ithaka#119. While I think the singleton pattern should be deprecated, put under a feature flag, and discouraged, the first step is probably to give instantiated services some field experience as an optional feature.
ryneeverett
force-pushed
the
instantiated-services
branch
from
89a2b10 to
c28957e
Compare
|
@ryneeverett thanks for creating a pull request to more concretely show how the instantiated services might work. I'm only just now able to sit and think about this for a bit. In general I agree with most of your points and this contribution goes a good way toward that. I still need to spend some time investigating the potential impact to our internal consumption of the package to ensure the design direction and decisions here will not cause undue investment effort. To give you context on service discovery: In a microservice-oriented architecture, services may have one or more hosts that can serve requests for the service, usually because of horizontal scaling which is often automatically managed. Because each host should be treated as ephemeral, no consumers should hold onto an explicit list of hosts but should instead ask a discovery service what hosts are available. One such example of a discovery service is Netflix's Eureka. |
This change is a: (check at least one)
Is this a breaking change? (check one)
Is the:
What does this change address?
Resolve #119. While I think the singleton pattern should be deprecated, put under a feature flag, and discouraged, the first step is probably to give instantiated services some field experience as an optional feature.
How does this change work?
This introduces an option to enable instantiated services while maintaining backwards compatibility with the singleton pattern. See the section I added to the docs and the examples I added to https://github.com/ryneeverett/quasi-apiron starting in
apiron_instantiated_example_*.py, which are adaptions of my previous examples which work with this branch.The implementation works in a backwards compatible way by using meta-programming to store and return a single instance of each service class when instantiated services are not enabled. This enables the rest of the code base to work with services as instantiated classes, regardless of whether this feature is enabled.
Additional context
ServiceBase.get_hosts(and my deletion ofTestServiceBase.test_get_hosts_returns_empty_list_by_default). I don't really understand the service discovery feature which I believe is the main point of that method so I'm liable to have broken something.