collector

Collector Module

The github.com/GoogleCloudPlatform/prometheus-engine/collector Go module contains the code is meant to be imported and used inside Prometheus code for the non-trivial forked functionalities that we are eventually upstreaming:

• export: In-memory export pipeline to Google Cloud Monitoring gRPC API. This Go package will be deprecated once Prometheus and GCM supports Remote Write 2.0 fully.
• secrets: Kubernetes secret provider implementation required for the scalable secure scrape support. This package will be deprecated once PROM-47 is implemented.

See the example use in Prometheus GMP fork.

Why hosting them in prometheus-engine?

Hosting this code here has the big disadvantage of circular Prometheus module dependency. Especially the export package requires a low-level prometheus packages that can change over time. However, different Prometheus fork versions require to import export code, which causes us to release multiple versions of this collector supporting new versions of Prometheus code.

The mapping is not 1:1, i.e., we don't need to release collector module for every minor or patch version of Prometheus. We only need to bump Prometheus dependency on breaking changes, which happen occasionally.

The benefit of storing them here is the smaller forked code surface. Forked functionality has to be propagated and carried on multiple versions which is tedious and risky; adding more work and risk than the occasional separate collector module releases.

Releasing

NOTE: This module follows a separate versioning scheme than prometheus-engine, because of a tight circular dependency on a Prometheus module.

To release it:

1. Decide if you want to perform minor or patch release. Minor release should be performed on every Prometheus dependency upgrade and any other major change.
2. Change ./VERSION to the desired version e.g. 0.2.0
3. Git tag the module, allowing external repositories to import our collector module:
   • For the minor release e.g. 0.1.x -> 0.2.0:

VERSION="$(< VERSION)" # Assuming you changed the value to 0.2.0.
git switch main
# Ensure you are on the latest main commit.
git pull origin main # or git reset --hard origin/main
# Create a collector release branch "release/collector/0.2".
git switch -c "release/collector/${VERSION%.*}"
# Create a collector, signed git tag, "collector/v0.2.0".
git tag -s "collector/v${VERSION}" -m "collector/v${VERSION}"
# Push both.
git push origin "release/collector/${VERSION%.*}" "collector/v${VERSION}"

• For the patch release e.g. 0.2.0 -> 0.2.1:

VERSION="$(< VERSION)" # Assuming you changed the value to 0.2.1.
git switch "release/collector/${VERSION%.*}"
# Ensure you are on the latest collector/0.2 commit.
git pull origin "release/collector/${VERSION%.*}" # or git reset --hard "origin/release/collector/${VERSION%.*}"
# Create a collector, signed git tag, "collector/v0.2.1".
git tag -s "collector/v${VERSION}" -m "collector/v${VERSION}"
# Push the tag.
git push origin "collector/v${VERSION}"