Migrate from OpenCensus library #1881

tiffanny29631 · 2025-09-22T18:52:32Z

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 · 2025-09-22T18:52:35Z

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

google-oss-prow · 2025-09-22T18:52:49Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

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sdowell · 2025-10-20T17:27:28Z

pkg/applier/applier_test.go

 }

 func TestApply(t *testing.T) {
+	_ = testmetrics.NewTestExporter()


What is this line doing? Consider adding a comment explaining the purpose

Refactored testexporter.go in #1909 for readability and using ResetGlobalMetrics when no exporter is needed. Comment is added to the func signature. ResetGlobalMetrics does the similar to NewTestExporter expects not returning an exporter, only initializing metrics and meter provider. The function needs to be explicitly invoked to respect the nature of how metrics are initialized in OtelSDK.

pkg/kmetrics/register.go

sdowell · 2025-10-20T20:53:38Z

pkg/declared/resources_test.go

-			Tags: []tag.Tag{
-				{Key: metrics.KeyInternalErrorSource, Value: "parser"},
-			},
+			Name:   "declared_resources",


Is this a change in behavior?

Not quite, declared_resources is part of the metric entries that are recorded in this test, the validateMetrics checks if the expectedMetrics is a subset of the entire metric storage, so it's additional coverage. But since it's irrelevant to the specific test, I removed it in #1909 for reduced confusion.

pkg/kmetrics/record.go

pkg/metrics/record.go

pkg/testing/testmetrics/testexporter.go

sdowell · 2025-10-20T21:11:38Z

pkg/testing/testmetrics/testexporter.go

+}
+
+// Global test reader to capture metrics
+var globalTestReader sdkmetric.Reader


Is the global reader necessary? The previous scaffolding seems to have been able to do this without a global

testexporter.go is refactored in #1909 and global reader is no longer needed.

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.

tiffanny29631 · 2025-10-21T17:05:42Z

/gemini summary
/gemini review

gemini-code-assist · 2025-10-21T17:10:30Z

Pull Request Summary

This pull request migrates the project's metrics implementation from OpenCensus to OpenTelemetry SDK. The migration is comprehensive, ensuring that existing metric names, types, descriptions, recording patterns, pipeline architecture, data flow, sidecar configurations, and export destinations (Prometheus, Cloud Monitoring, Cloud Monarch) are preserved.

Key changes include:

Dependency Updates: Replaced OpenCensus libraries (go.opencensus.io) with OpenTelemetry SDK (go.opentelemetry.io/otel) across the codebase and in go.mod/go.sum.
Metric Instrument Types: OpenCensus stats.Int64 and stats.Float64 are now mapped to OpenTelemetry metric.Int64Counter, metric.Int64Gauge, and metric.Float64Histogram.
Recording Patterns: Updated metric recording calls from stats.Record(ctx, measurement) to OpenTelemetry's instrument.Record(ctx, value, metric.WithAttributes(attrs...)).
Tag/Attribute System: Migrated from OpenCensus tag.New to OpenTelemetry attribute.Key and attribute.String for defining and using metric attributes.
Exporter Configuration: Switched from OpenCensus Agent Exporter (ocagent.NewExporter) to OTLP gRPC Exporter (otlpmetricgrpc.New).
Configuration Files: Updated various YAML configuration files (e.g., docs/custom-metric-filter.md, manifests/*.yaml, e2e/testdata/*.yaml) to use otlp receivers and corresponding port numbers (e.g., 4317 for gRPC, 4318 for HTTP) instead of opencensus and its default ports.
Testing Infrastructure: Refactored pkg/testing/testmetrics/testexporter.go and numerous test files to use OpenTelemetry SDK's sdk/metric.NewManualReader and metricdata.ResourceMetrics for metric collection and validation, replacing OpenCensus stats/view.

This migration ensures the project aligns with the latest observability standards and best practices provided by the OpenTelemetry ecosystem.

Code Review

Overall, this is a well-executed and comprehensive migration from OpenCensus to OpenTelemetry. The changes are consistent across the codebase, addressing all necessary aspects from dependency management to metric instrumentation, recording, exporting, and testing. The adherence to OpenTelemetry's API and best practices is evident throughout the modified files.

I recommend merging this pull request.

mikebz · 2025-10-21T20:16:00Z

this is closed, but is there a follow up? Are we giving up on this project?

tiffanny29631 · 2025-10-21T22:45:07Z

The PR was opened on a wrong branch. Will reopen new one from fork and address comments from there.

google-oss-prow bot added the do-not-merge/work-in-progress label Sep 22, 2025

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google-oss-prow bot requested review from Camila-B and mikebz September 22, 2025 18:52

tiffanny29631 force-pushed the oc-migration branch 2 times, most recently from aa7bce5 to 6703484 Compare September 22, 2025 19:03

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tiffanny29631 marked this pull request as ready for review October 8, 2025 00:09

google-oss-prow bot removed the do-not-merge/work-in-progress label Oct 8, 2025

google-oss-prow bot requested review from Camila-B and janetkuo October 8, 2025 00:09

tiffanny29631 force-pushed the oc-migration branch 2 times, most recently from 9b6aeca to 8544c2f Compare October 9, 2025 22:05

sdowell reviewed Oct 20, 2025

View reviewed changes

tiffanny29631 force-pushed the oc-migration branch from 8544c2f to ac1af18 Compare October 20, 2025 22:08

tiffanny29631 closed this Oct 21, 2025

tiffanny29631 deleted the oc-migration branch October 21, 2025 20:02

sdowell mentioned this pull request Oct 21, 2025

Migrate from OpenCensus library #1909

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Migrate from OpenCensus library #1881

Migrate from OpenCensus library #1881

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tiffanny29631 commented Sep 22, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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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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Pull Request Summary

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tiffanny29631 commented Sep 22, 2025 •

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