Support customize the bucket of histogram metrics by maobaolong · Pull Request #2627 · LMCache/LMCache

maobaolong · 2026-02-21T05:41:59Z

What this PR does / why we need it:

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this PR contains user facing changes - docs added
this PR contains unit tests

Signed-off-by: baoloongmao <baoloongmao@tencent.com>

gemini-code-assist · 2026-02-21T05:42:14Z

Summary of Changes

Hello @maobaolong, 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 enhances the observability features by allowing users to define custom bucket boundaries for Prometheus histogram metrics. This provides greater flexibility in monitoring and analyzing performance data, enabling more granular insights into specific operational ranges. The changes involve updating the Prometheus logging infrastructure to consume configuration settings for buckets and providing clear documentation on how to use this new capability.

Highlights

Custom Prometheus Histogram Buckets: Introduced the ability to customize Prometheus histogram bucket boundaries for various metrics. Users can now define specific bucket ranges to better suit their monitoring needs.
Configuration via extra_config: Custom bucket definitions are provided through the extra_config section, using keys like histogram_bucket_<metric_name> with a list of numeric boundaries.
Updated PrometheusLogger: The PrometheusLogger class was modified to accept and utilize a configuration object, allowing it to dynamically apply custom bucket settings during histogram creation.
Comprehensive Documentation: New documentation was added detailing how to configure custom histogram buckets, including examples and a list of all available metric names that can be customized.
Unit Tests: New unit tests were added to ensure the correct application of default and custom histogram buckets, covering various configuration scenarios.

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Changelog

docs/source/api_reference/configurations.rst
- Added a new section 'Custom Prometheus Histogram Buckets' to the configuration documentation.
- Included instructions and examples for overriding default histogram bucket boundaries using extra_config.
- Provided a list-table enumerating available histogram names and their descriptions for customization.
lmcache/observability.py
- Modified the _create_histogram method to check for custom bucket definitions in the provided configuration.
- Updated the PrometheusLogger.__init__ method to accept an optional config object.
- Updated the PrometheusLogger.GetOrCreate static method to pass the config object to the constructor.
- Updated the LMCacheStatsLogger.__init__ method to accept an optional config object and pass it to PrometheusLogger.GetOrCreate.
lmcache/v1/cache_engine.py
- Modified LMCacheEngine.get_or_create to pass the config object when initializing LMCacheStatsLogger.
lmcache/v1/manager.py
- Updated LMCacheManager._init_scheduler_components to pass the config object to PrometheusLogger.GetOrCreate.
tests/test_observability.py
- Imported MagicMock and PrometheusLogger for testing.
- Added a _cleanup_prometheus_logger fixture to reset the PrometheusLogger singleton and metrics between tests.
- Added helper functions _make_metadata and _make_config for creating mock objects.
- Implemented test_prometheus_logger_default_buckets to verify default bucket behavior.
- Implemented test_prometheus_logger_custom_buckets to confirm custom buckets are applied from configuration.
- Implemented test_prometheus_logger_partial_custom_buckets to ensure only specified histograms receive custom buckets.
- Implemented test_prometheus_logger_get_or_create_with_config to test the GetOrCreate method with custom configuration.

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maobaolong · 2026-02-21T05:42:44Z

@sammshen @chunxiaozheng Would you like to take a look at this PR? Thanks!

gemini-code-assist

Code Review

This pull request introduces a valuable feature allowing customization of Prometheus histogram buckets through extra_config. The implementation is well-structured, propagating the configuration object through the necessary layers. The accompanying documentation is clear, and the unit tests are thorough. My review includes a few suggestions to improve type safety by replacing Optional[Any] with a more specific type hint for the config parameter in lmcache/observability.py.

Signed-off-by: baoloongmao <baoloongmao@tencent.com>

sammshen

LGTM!

chunxiaozheng

lgtm

* Support customize the bucket of histogram metrics Signed-off-by: baoloongmao <baoloongmao@tencent.com> * address comments from gemini-bot Signed-off-by: baoloongmao <baoloongmao@tencent.com> --------- Signed-off-by: baoloongmao <baoloongmao@tencent.com>

* Support customize the bucket of histogram metrics Signed-off-by: baoloongmao <baoloongmao@tencent.com> * address comments from gemini-bot Signed-off-by: baoloongmao <baoloongmao@tencent.com> --------- Signed-off-by: baoloongmao <baoloongmao@tencent.com> Signed-off-by: shaoxiawjc <wjc2800@163.com>

* Support customize the bucket of histogram metrics Signed-off-by: baoloongmao <baoloongmao@tencent.com> * address comments from gemini-bot Signed-off-by: baoloongmao <baoloongmao@tencent.com> --------- Signed-off-by: baoloongmao <baoloongmao@tencent.com> Signed-off-by: Aaron Wu <aaron.wu@dell.com>

Support customize the bucket of histogram metrics

7466dc9

Signed-off-by: baoloongmao <baoloongmao@tencent.com>

gemini-code-assist Bot reviewed Feb 21, 2026

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Comment thread lmcache/observability.py

Comment thread lmcache/observability.py

Comment thread lmcache/observability.py

address comments from gemini-bot

19b4cf1

Signed-off-by: baoloongmao <baoloongmao@tencent.com>

maobaolong added the full Run comprehensive tests on this PR label Feb 21, 2026

sammshen approved these changes Feb 22, 2026

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chunxiaozheng approved these changes Feb 24, 2026

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maobaolong merged commit 841f288 into LMCache:dev Feb 24, 2026
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Support customize the bucket of histogram metrics#2627

Support customize the bucket of histogram metrics#2627
maobaolong merged 2 commits intoLMCache:devfrom
maobaolong:confHistoryBucket

maobaolong commented Feb 21, 2026 •

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maobaolong commented Feb 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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maobaolong commented Feb 21, 2026 •

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