Migrate from OpenCensus library #1909

tiffanny29631 · 2025-10-21T22:52:26Z

Earlier discussions #1881

The migration replaces OpenCensus libraries with OpenTelemetry SDK while preserving:

Metric names, type and descriptions
Recording patterns
Pipeline architecture and data flow
Sidecar configurations
Export destinations (Prometheus, Cloud Monitoring, Cloud Monarch)

Key Changes

1. Library Dependencies

Before (OpenCensus):

import (
    "go.opencensus.io/stats"
    "go.opencensus.io/stats/view"
    "go.opencensus.io/tag"
    "contrib.go.opencensus.io/exporter/ocagent"
)

After (OpenTelemetry):

import (
    "go.opentelemetry.io/otel"
    "go.opentelemetry.io/otel/metric"
    "go.opentelemetry.io/otel/attribute"
    "go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
    "go.opentelemetry.io/otel/sdk/metric"
    "go.opentelemetry.io/otel/sdk/resource"
)

2. Metric Instrument Types

OpenCensus	OpenTelemetry	Description
`stats.Int64`	`metric.Int64Counter`	Counter metrics
`stats.Int64`	`metric.Int64Gauge`	Gauge metrics
`stats.Float64`	`metric.Float64Histogram`	Histogram metrics

3. Recording Patterns

Before (OpenCensus):

stats.Record(ctx, measurement)

After (OpenTelemetry):

instrument.Record(ctx, value, metric.WithAttributes(attrs...))

4. Tag/Attribute System

Before (OpenCensus):

tagCtx, _ := tag.New(ctx, tag.Upsert(KeyStatus, "success"))

After (OpenTelemetry):

attrs := []attribute.KeyValue{
    attribute.String("status", "success"),
}

5. Exporter Configuration

Before (OpenCensus):

oce, err := ocagent.NewExporter(ocagent.WithInsecure())

After (OpenTelemetry):

exporter, err := otlpmetricgrpc.New(
    context.Background(),
    otlpmetricgrpc.WithInsecure(),
    otlpmetricgrpc.WithEndpoint("otel-collector:4317"),
)

google-oss-prow · 2025-10-21T22:52:31Z

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gemini-code-assist · 2025-10-21T22:55:24Z

Summary of Changes

Hello @tiffanny29631, 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 completes a significant migration by replacing the existing OpenCensus metrics implementation with OpenTelemetry. The core purpose is to standardize on OpenTelemetry for observability, ensuring that the system continues to collect and export metrics consistently to various destinations. The changes involve updating core metric definitions, initialization routines, and exporter configurations across multiple components, along with corresponding adjustments to documentation and test utilities.

Highlights

Migration to OpenTelemetry SDK: The codebase has been migrated from using OpenCensus libraries to the OpenTelemetry SDK for metrics collection. This change preserves existing metric names, types, descriptions, recording patterns, pipeline architecture, data flow, sidecar configurations, and export destinations (Prometheus, Cloud Monitoring, Cloud Monarch).
Updated Metric Initialization and Recording: All components (hydration-controller, reconciler-manager, reconciler, resourcegroup) now use new OpenTelemetry initialization functions (InitializeOTelKustomizeMetrics, InitializeOTelMetrics, InitializeOTelResourceGroupMetrics) and record metrics using the OpenTelemetry API (metric.Int64Gauge, metric.Float64Histogram, metric.Int64Counter) with attribute.KeyValue for labels.
OTLP Exporter Configuration: The metric exporters have been updated to use the OTLP gRPC exporter (otlpmetricgrpc.New) instead of the OpenCensus Agent exporter. This includes changes to how exporters are registered and shut down, and updates to related configuration files (otel-collector-config.yaml, otel-agent-cm.yaml, otel-agent-reconciler-cm.yaml) to use otlp receivers and endpoints.
Dependency Updates: The go.mod and go.sum files have been updated to remove OpenCensus dependencies (contrib.go.opencensus.io/exporter/ocagent, go.opencensus.io) and introduce OpenTelemetry dependencies (go.opentelemetry.io/otel, go.opentelemetry.io/otel/metric, go.opentelemetry.io/otel/sdk, go.opentelemetry.io/otel/sdk/metric, go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc). The github.com/cenkalti/backoff/v5 library has also been added.
Test Infrastructure Modernization: The testing framework has been updated to use testmetrics.NewTestExporter() and testmetrics.ResetGlobalMetrics() for metric validation, replacing the OpenCensus-specific testmetrics.RegisterMetrics() and view.RegisterExporter() calls. This ensures compatibility with the new OpenTelemetry metric system.

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Code Review

This pull request successfully migrates the project from OpenCensus to OpenTelemetry for metrics. The changes are comprehensive, covering library dependencies, metric instrumentation, recording patterns, and exporter configurations across the codebase. The test suite has also been updated to validate the new OpenTelemetry metrics. My review focuses on improving the robustness of the new implementation, particularly around shutdown contexts and resource attribute configuration.

cmd/hydration-controller/main.go

cmd/reconciler-manager/main.go

cmd/reconciler/main.go

pkg/kmetrics/register.go

pkg/metrics/record.go

pkg/metrics/register.go

sdowell · 2025-10-21T23:27:48Z

@tiffanny29631 will you be responding/incorporating the feedback from #1881?

tiffanny29631 · 2025-10-22T00:02:56Z

@tiffanny29631 will you be responding/incorporating the feedback from #1881?

Working on it now

Change is meant to be transparent to user. Using OTel SDK for metric composing in: kmetrics, core metrics, resource group metrics; Using otlp receiver in otel-agent and otel-collector; Configured deployment for new ports and component; Refactor metric composing and recording; Metric prefix remain the same to minimize breaking change. Tests updated.

- pass on context in register

tiffanny29631 · 2025-10-22T19:00:42Z

@sdowell comments in #1881 addressed.

tiffanny29631 requested a review from sdowell October 21, 2025 22:52

google-oss-prow bot requested review from janetkuo and mikebz October 21, 2025 22:52

google-oss-prow bot added the size/XXL label Oct 21, 2025

gemini-code-assist bot reviewed Oct 21, 2025

View reviewed changes

tiffanny29631 force-pushed the oc-migration branch 3 times, most recently from 25f0018 to 44c34df Compare October 21, 2025 23:59

tiffanny29631 added 5 commits October 22, 2025 00:36

cleanup

67f09a6

- pass on context in register

cleanup: restore record.go under kmetrics

0512a71

cleanup: restore record.go under resourcegroup metrics

97d941b

cleanup: refactor testexporter for readability

7598e6d

tiffanny29631 force-pushed the oc-migration branch from 44c34df to 7598e6d Compare October 22, 2025 04:23

tiffanny29631 mentioned this pull request Oct 22, 2025

Migrate from OpenCensus library #1881

Closed

tiffanny29631 added 2 commits October 22, 2025 06:37

gemini comment: fail fast when record sees metric not initialized

5654af2

gemini comment: use context with timeout for exporter graceful shutdown

c6402fc

tiffanny29631 force-pushed the oc-migration branch from 0b90260 to c6402fc Compare October 22, 2025 17:53

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Migrate from OpenCensus library #1909

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tiffanny29631 commented Oct 21, 2025 •

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Key Changes

1. Library Dependencies

2. Metric Instrument Types

3. Recording Patterns

4. Tag/Attribute System

5. Exporter Configuration

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tiffanny29631 commented Oct 21, 2025 •

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