improve watcher creation pattern and manager naming

[wdbaruni]

This PR introduces several important changes to the watcher package to unblock changes related to NCL protocol:

1. Introduce two-step watcher creation pattern:

   • Split watcher creation and handler configuration for better control
   • Enables explicit handler setup before starting
   • This pattern is needed to create an NCL dispatcher that manages the watcher's handler, and restart the watcher when needed
   • Add validation to prevent starting without handler
   • Improve error handling for invalid states

2. Fix watcher restart behavior after checkpoints:

   • Ensure proper state restoration when restarting
   • Maintain correct sequence position after checkpoint, and restart from the latest checkpoint and not latest processed event
   • Add tests to verify checkpoint/restart behavior

3. Rename Registry to Manager:

   • More accurately represents its role in managing watcher lifecycles
   • Ensures consistent terminology throughout the codebase

4. Additional improvements:

   • Add documentation for new creation pattern
   • Update tests to cover new scenarios
   • Improve error messages and validation

Summary by CodeRabbit

Release Notes

• New Features

  • Introduced a new Manager type to manage multiple watchers, replacing the previous Registry terminology.
  • Enhanced watcher creation with new configuration options for automatic starting and event handler assignment.
  • Added error handling for scenarios where no handler is set or a duplicate watcher ID is used.

• Documentation

  • Updated README and usage examples to reflect the new Manager terminology and improved clarity on functionality.

• Bug Fixes

  • Improved error handling related to event processing and watcher lifecycle management.

• Tests

  • Implemented a comprehensive test suite for the Manager functionality, ensuring robust coverage of various scenarios.

[coderabbitai[bot]]

[!NOTE] Currently processing new changes in this PR. This may take a few minutes, please wait...

📥 Commits

Reviewing files that changed from the base of the PR and between b9ffe3de84fe093a8b634839c647578920b0bc91 and f7856e347b6ae0bc387e5558ffa68250be44158c.

📒 Files selected for processing (3)

* `pkg/lib/watcher/manager.go` (1 hunks) * `pkg/lib/watcher/types.go` (3 hunks) * `pkg/lib/watcher/watcher_test.go` (27 hunks)

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Walkthrough

The pull request introduces significant changes to the Watcher Library, primarily renaming the "Registry" component to "Manager" across various files. This includes updates to method signatures, documentation, and the introduction of new error handling capabilities. Additionally, new configuration options for creating watchers are added, enhancing flexibility. The changes also involve the addition of a new manager type to manage multiple watchers, along with comprehensive test coverage for the new functionality. Several files related to the old registry implementation have been removed, reflecting a complete transition to the new manager-based architecture.

Changes

File	Change Summary
pkg/lib/watcher/README.md	Updated terminology from "Registry" to "Manager"; modified method signatures and usage examples; added new configuration options for watchers.
pkg/lib/watcher/errors.go	Added new error variables: ErrNoHandler and ErrHandlerExists.
pkg/lib/watcher/manager.go	Introduced manager type; added methods for creating, looking up, and stopping watchers; included lifecycle management functionality.
pkg/lib/watcher/manager_test.go	Added a comprehensive test suite for the manager functionality, covering various scenarios.
pkg/lib/watcher/mocks.go	Updated mock types; renamed methods to align with the new Manager interface.
pkg/lib/watcher/options.go	Enhanced watchOptions struct with new fields and functions for handler and auto-start configurations.
pkg/lib/watcher/registry.go	Removed file; previously managed watchers using the Registry type.
pkg/lib/watcher/registry_test.go	Removed file; contained tests for the old Registry functionality.
pkg/lib/watcher/serializer.go	Updated comments to reflect "Manager" instead of "Registry".
pkg/lib/watcher/types.go	Expanded Watcher interface; replaced Registry interface with Manager interface.
pkg/lib/watcher/watcher.go	Modified watcher struct; updated methods for improved functionality and error handling.
pkg/lib/watcher/watcher_test.go	Refactored test suite to improve context management and error handling.
pkg/node/compute.go	Updated Compute struct to use watcher.Manager; modified watcher setup logic.
pkg/node/requester.go	Changed watcher management from Registry to Manager; refined watcher initialization logic.
pkg/orchestrator/evaluation/watcher_test.go	Updated test suite to use watcher.Manager instead of watcher.Registry.

Possibly related PRs

• #4671: The changes in the main PR regarding the renaming of "Registry" to "Manager" and the introduction of new methods for managing watchers are directly related to the updates in the pkg/node/compute.go and pkg/node/requester.go files, which also reflect the shift from using a Registry to a Manager for handling watchers.

Suggested reviewers

• jamlo

🐇 In the world of watchers, new terms we embrace,
From "Registry" to "Manager," we quicken our pace.
With handlers and options, our watchers now thrive,
In this vibrant new structure, our code comes alive!
So hop along, friends, let’s celebrate this cheer,
For clarity and structure, the future is clear! 🐇✨

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