[core] Rename NotifyUnblocked to CancelGetRequest

[edoakes]

The NotifyUnblocked naming is legacy from before Ray 1.0.

Also removed task_id from various places that we didn't need it.

Note there is an ongoing bugfix to cancel only the specific get request instead of all requests for the worker: #54495

[gemini-code-assist]

Summary of Changes

Hello @edoakes, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request primarily focuses on refactoring and clarifying the communication protocols between Ray workers and the raylet, specifically concerning object fetching and waiting. It renames a key message type to better reflect its intent and simplifies the API for managing object dependencies, leading to a more robust and understandable codebase.

Highlights

• Core Renaming: The primary change involves renaming the NotifyUnblocked message type and associated functions to CancelGetRequest. This clarifies the intent of the message, which is to cancel outstanding object get requests rather than simply notifying that a worker is unblocked.
• API Simplification: The task_id parameter has been removed from FetchOrReconstruct and Wait calls across the core worker, raylet client, and raylet components. This simplifies the API by removing a redundant identifier for these operations.
• Object Resolution Refactoring: The internal AsyncResolveObjects and AsyncResolveObjectsFinish functions within the NodeManager have been consolidated and refactored into a single AsyncGetOrWait function. This streamlines the logic for handling object fetching and waiting requests from workers, making the dependency management more cohesive.

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[gemini-code-assist]

Code Review

This pull request is a nice refactoring that renames NotifyUnblocked to the more descriptive CancelGetRequest and simplifies the related logic by removing task_id from several messages and functions. The new function AsyncGetOrWait is also a good improvement in terms of clarity.

However, I have a significant concern about removing task_id from the wire protocol for FetchOrReconstruct, CancelGetRequest, and WaitRequest. This change makes it impossible to distinguish between dependency requests from different concurrent tasks within the same worker (e.g., in an async actor). This could lead to correctness issues where one task's operation (like a get completing) inadvertently cancels another task's pending operation. I've left a few comments on the flatbuffer schema changes to discuss this further. If this is not a concern, the rest of the changes look solid.

[dayshah]

I finally understand what NotifyUnblocked did

Also probably needs a better description for big change of not cancelling gets when we finish wait

[edoakes]

@dayshah I'll make this a pure refactor and split out the behavior change per discussion

[edoakes]

@dayshah I updated the PR to revert the behavior change and will do that separately.