bazelbuild/bazel

Statistics or information for repository_cache hits

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#26,334 opened on Jun 18, 2025

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 (0 comments) (1 reaction) (0 assignees)Java (25,384 stars) (4,465 forks)batch import
P2help wantedteam-ExternalDepstype: feature request

Description

Description of the feature request:

I can see in CacheHitReportingModule (https://github.com/bazelbuild/bazel/blob/ab371fe096b1ea05fba1cf686c7d6ae15c5d21fa/src/main/java/com/google/devtools/build/lib/bazel/repository/CacheHitReportingModule.java) that events are emitted from the DownloadManager

However information on how many hits to the repository_cache were made are not available in the BEP or the logs in any fashion.

There seems to be some informational log messages only in the case of a failure. It might be nice to emit more info to help understand which artifacts were found in the repository_cache vs. which are not.

This would help understand and catch cases where we are not caching like we believe we are.

Which category does this issue belong to?

No response

What underlying problem are you trying to solve with this feature?

No response

Which operating system are you running Bazel on?

No response

What is the output of bazel info release?

No response

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

No response

Contributor guide

Tech stack
java
Domain
build systemobservability
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Java programmingBasic understanding of Bazel's build system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55
Research direction
The issue requests adding statistics on repository cache hits to the Build Event Protocol (BEP) or logs. The existing CacheHitReportingModule (CacheHitReportingModule.java) and DownloadManager handle cache hits; the goal is to expose which artifacts are found in the cache vs. not. Investigate the current event emission in CacheHitReportingModule and DownloadManager to understand the point to inject new events. Propose adding a new BEP event or log message summarizing cache hit statistics. Since the issue has no comments yet, the first step is to gather more details by commenting asking about the desired format (e.g., per rule or aggregate).
Statistics or information for repository_cache hits · bazelbuild/bazel#26334 | Good First Issue