[mutianf]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
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Fixes #<issue_number_goes_here> 🦕

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[gemini-code-assist]

Code Review

This pull request introduces a background health monitor for the accelerator daemon in the Google Cloud Bigtable Python client. It adds a hand-rolled gRPC health check codec to avoid external dependencies, updates the AcceleratorBreaker to support a reversible 'degraded' state alongside the permanent 'tripped' state, and implements a background polling loop (_AcceleratorHealthMonitor) in both async and sync clients to dynamically route traffic away from the daemon if it becomes unresponsive. Comprehensive unit tests are also added to verify the codec, state machine, and polling behavior. There are no review comments, so we have no feedback to provide.

[sushanb]

LGTM. All three of my prior inline suggestions landed verbatim (metrics.close placement, dead except branch removed, Event-pair breaker keeping bypass() lock-free). The health-monitor rework (ThreadPool→daemon Thread, weakref.finalize for request_stop, bounded-wait close) is a solid tightening — nothing new to flag.