amoghrajesh opened a new pull request, #59883:
URL: https://github.com/apache/airflow/pull/59883
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## Why?
Simply stating, for client server separation.
The airflow.listeners module was used between airflow-core and task-sdk and
is still needed that way. By extracting it to shared library, I intend to solve
the problem of cross dependency between airflow core and task-sdk.
## What's done?
1. Created shared/listeners/ library containing:
- ListenerManager class (manages plugin registration and hook dispatching)
- Hook specifications (lifecycle, taskinstance, dagrun, asset, importerrors)
- hookimpl marker for implementing listeners
2. For both airflow-core and task-sdk now:
- Import shared listener infrastructure via symlinks (`_shared/listeners/`)
- Provide thin wrappers that call `integrate_listener_plugins()` to load
Airflow plugins and register the listeners with airflow.
## Open Questions and Direction to proceed
1. Plugin Discovery on workers
- Current state even before this change: task SDK workers use
`integrate_listener_plugins()` from airflow-core to discover listeners via the
Airflow plugins.
- Proposal for thisis that we can create a lightweight plugin discovery
mechanism for task-sdk which will use entry points (importlib.metadata) to
discover provider listeners like the plugins code already does. The benefit of
this is that it will allow us / providers to register listeners without full
Airflow plugins needed in task sdk:
https://github.com/apache/airflow/blob/main/airflow-core/src/airflow/plugins_manager.py#L508-L515
(cc @potiuk)
2. What do providers do?
- My proposal is that they use the task sdk building blocks present in
`sdk.listeners` to write plugins while we figure out (1) from above which
registers those written listeners with airflow.
## TODO
- [ ] Update providers using listeners manager to consume from task sdk once
1, 2 qns are clarified from above
- [ ] Deprecation warning for `airflow.listeners.spec`? I think its ok to
delete as-is since its an internal module
- [ ] Update documentation
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