Migrate metrics from OpenCensus to OpenTelemetry

[infernus01]

Changes

Migrates Operator metrics from the deprecated OpenCensus library to OpenTelemetry.

• Replace OpenCensus imports (go.opencensus.io/stats, stats/view, tag) with OpenTelemetry (go.opentelemetry.io/otel, otel/attribute, otel/metric) in tektonpipeline/metrics.go, tektontrigger/metrics.go, tektonchain/metrics.go, and tektonresult/metrics.go
• Convert counter metrics to metric.Int64Counter and gauge metric to metric.Float64Gauge
• Rewrite tektonresult/metrics_test.go to use sdkmetric.ManualReader for asserting actual collected metric values
• Update config-observability.yaml to use OTel configuration keys (metrics-protocol, tracing-protocol) and remove legacy OpenCensus keys
• Bump knative.dev/pkg to v0.0.0-20260318013857-98d5a706d4fd (OTel observability stack)
• Regenerate client code via ./hack/update-codegen.sh
  /kind feature

closes : #3307
fixes : #3331

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Run make test lint before submitting a PR
• Includes tests (if functionality changed/added)
• Includes docs (if user facing)
• Commit messages follow commit message best practices

See the contribution guide for more details.

Release Notes

Migrated operator metrics from OpenCensus to OpenTelemetry.

ACTION REQUIRED:

1. Configuration key change
   Replace metrics.backend-destination with metrics-protocol in your tekton-config-observability ConfigMap.

2. Infrastructure metric renaming

   ┌──────────────────────────────────────────────────────────────────┬────────────────────────────────────────────────────┐
   │ Old Metric Name (OpenCensus)                                     │ New Metric Name (OpenTelemetry)                    │
   ├──────────────────────────────────────────────────────────────────┼────────────────────────────────────────────────────┤
   │ tekton_operator_lifecycle_workqueue_adds_total                   │ kn_workqueue_adds_total                            │
   │ tekton_operator_lifecycle_workqueue_depth                        │ kn_workqueue_depth                                 │
   │ tekton_operator_lifecycle_workqueue_queue_latency_seconds        │ kn_workqueue_queue_duration_seconds                │
   │ tekton_operator_lifecycle_workqueue_work_duration_seconds        │ kn_workqueue_process_duration_seconds              │
   │ tekton_operator_lifecycle_workqueue_unfinished_work_seconds      │ kn_workqueue_unfinished_work_seconds               │
   │ tekton_operator_lifecycle_client_latency                         │ http_client_request_duration_seconds               │
   │ tekton_operator_lifecycle_client_results                         │ kn_k8s_client_http_response_status_code_total      │
   │ tekton_operator_lifecycle_go_*                                   │ go_*                                               │
   │ tekton_operator_lifecycle_reconcile_count                        │ removed (use kn_workqueue_adds_total)              │
   │ tekton_operator_lifecycle_reconcile_latency                      │ removed (use kn_workqueue_process_duration_seconds)│
   └──────────────────────────────────────────────────────────────────┴────────────────────────────────────────────────────┘

[infernus01]

I don't see we are consuming eventing pkg anywhere in the code.

[khrm]

I think we should remove metrics in the operator. These aren't used by customers or users. It was for some telemetry, but it's not working properly for that also.

If I get time, I would write more on that.

[jkhelil]

I think we should remove metrics in the operator. These aren't used by customers or users. It was for some telemetry, but it's not working properly for that also.

If I get time, I would write more on that.

We have stories to enhance overall metrics on operator, to move to olm level 3 and for 4, i didnt dig into details for these levels, but lets not remove metrics for now, until we tackle properly those stories please

[jkhelil]

@khrm would like to move forward with this, do you lgtm , or do you still think we need antoher approch removing metrics in operator ?

[jkhelil]

@anithapriyanatarajan given you work on opentelemetry assessment, would like your review in this one please, would like to move froward on it

[khrm]

We have stories to enhance overall metrics on operator, to move to olm level 3 and for 4, i didnt dig into details for these levels, but lets not remove metrics for now, until we tackle properly those stories please

I was talking of removing the custom metrics which we added to the operator.
Other metrics from Knative would surface anyway. We don't use former custom metrics anywhere, and they aren't that usable. They were added for telemetry purposes, but it couldn't fulfil that either. We never documented those metrics. So documenting those now as part of the release notes doesn't make sense.

Even if we don't remove them, why should we surface those in release notes? It will confuse users.

[infernus01]

@khrm For now I have updated the release notes sectino to not include those custom metrics.
Do you want me to remove those metrics from operator in this PR, or we can raise a follow-up issue to do so?

[jkhelil]

@khrm understood now, @infernus01 would you be able to update the PR then, i think it make sense to remove those to start with clean metrics list

[anithapriyanatarajan]

@infernus01 Please consider metioning the metrics that were removed as part of release notes. Also remove the metrics.go file if no metrics are recorded.

[tekton-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
To complete the pull request process, please assign puneetpunamiya after the PR has been reviewed.
You can assign the PR to them by writing /assign @puneetpunamiya in a comment when ready.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[infernus01]

@infernus01 Please consider metioning the metrics that were removed as part of release notes. Also remove the metrics.go file if no metrics are recorded.

Wouldn't that conflict with @khrm's comment, that it was not even documented before why we should even write that in release notes.?