feat: Migrate PipelineRun and TaskRun metrics to OpenTelemetry

This commit migrates the metrics for PipelineRuns and TaskRuns from
OpenCensus to OpenTelemetry.

  The following changes are included:
   - Updated the observability config to support OpenTelemetry.
   - Migrated the implementation of PipelineRun and TaskRun metrics to use
    the OpenTelemetry Go SDK.
   - Updated the tests to work with the new OpenTelemetry-based
    implementation.

Add comprehensive migration documentation for the OpenCensus to OpenTelemetry
metrics transition. Provides breaking change details, configuration examples,
query migration patterns, and troubleshooting guidance for users upgrading
to the new metrics implementation.
Assisted in Test: Gemini
Docs-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: khrm

config/config-observability.yaml

@@ -21,6 +21,7 @@ metadata:
     app.kubernetes.io/instance: default
     app.kubernetes.io/part-of: tekton-pipelines
 data:
+  metrics-protocol: prometheus
   _example: |
     ################################
     #                              #
@@ -37,23 +38,46 @@ data:
     # this example block and unindented to be in the data block
     # to actually change the configuration.
 
-    # metrics.backend-destination field specifies the system metrics destination.
-    # It supports either prometheus (the default) or stackdriver.
-    # Note: Using Stackdriver will incur additional charges.
-    metrics.backend-destination: prometheus
-
-    # metrics.stackdriver-project-id field specifies the Stackdriver project ID. This
-    # field is optional. When running on GCE, application default credentials will be
-    # used and metrics will be sent to the cluster's project if this field is
-    # not provided.
-    metrics.stackdriver-project-id: "<your stackdriver project id>"
-
-    # metrics.allow-stackdriver-custom-metrics indicates whether it is allowed
-    # to send metrics to Stackdriver using "global" resource type and custom
-    # metric type. Setting this flag to "true" could cause extra Stackdriver
-    # charge.  If metrics.backend-destination is not Stackdriver, this is
-    # ignored.
-    metrics.allow-stackdriver-custom-metrics: "false"
+    # OpenTelemetry Metrics Configuration
+    # Protocol for metrics export (prometheus, grpc, http/protobuf, none)
+    # Default if not specified: "none"
+    metrics-protocol: prometheus
+
+    # Metrics endpoint (for grpc/http protocols)
+    # Default: empty (uses default OTLP endpoint)
+    metrics-endpoint: ""
+
+    # Metrics export interval (e.g., "30s", "1m")
+    # Default: empty (uses default interval)
+    metrics-export-interval: ""
+
+    # OpenTelemetry Tracing Configuration
+    # Protocol for tracing export (grpc, http/protobuf, none, stdout)
+    # Default: none
+    tracing-protocol: none
+
+    # Tracing endpoint (for grpc/http protocols)
+    # Default: empty
+    tracing-endpoint: ""
+
+    # Tracing sampling rate (0.0 to 1.0)
+    # Default: 1.0 (100% sampling)
+    tracing-sampling-rate: "1.0"
+
+    # Runtime Configuration
+    # Enable profiling (enabled, disabled)
+    # Default: disabled
+    runtime-profiling: disabled
+
+    # Runtime export interval (e.g., "15s")
+    # Default: 15s
+    runtime-export-interval: "15s"
+
+    # Note: Legacy OpenCensus configuration (metrics.backend-destination, etc.) has been
+    # removed as OpenCensus support is no longer provided by the underlying infrastructure.
+    # Please use the OpenTelemetry configuration options above.
+
+    # Tekton-specific metrics configuration
     metrics.taskrun.level: "task"
     metrics.taskrun.duration-type: "histogram"
     metrics.pipelinerun.level: "pipeline"

config/resolvers/config-observability.yaml

@@ -1,4 +1,4 @@
-# Copyright 2022 The Tekton Authors
+# Copyright 2019 The Tekton Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -16,13 +16,12 @@ apiVersion: v1
 kind: ConfigMap
 metadata:
   name: config-observability
-  namespace: tekton-pipelines-resolvers
+  namespace: tekton-pipelines
   labels:
-    app.kubernetes.io/component: resolvers
     app.kubernetes.io/instance: default
     app.kubernetes.io/part-of: tekton-pipelines
-
 data:
+  metrics-protocol: prometheus
   _example: |
     ################################
     #                              #
@@ -39,24 +38,41 @@ data:
     # this example block and unindented to be in the data block
     # to actually change the configuration.
 
-    # metrics.backend-destination field specifies the system metrics destination.
-    # It supports either prometheus (the default) or stackdriver.
-    # Note: Using stackdriver will incur additional charges
-    metrics.backend-destination: prometheus
-
-    # metrics.request-metrics-backend-destination specifies the request metrics
-    # destination. If non-empty, it enables queue proxy to send request metrics.
-    # Currently supported values: prometheus, stackdriver.
-    metrics.request-metrics-backend-destination: prometheus
-
-    # metrics.stackdriver-project-id field specifies the stackdriver project ID. This
-    # field is optional. When running on GCE, application default credentials will be
-    # used if this field is not provided.
-    metrics.stackdriver-project-id: "<your stackdriver project id>"
-
-    # metrics.allow-stackdriver-custom-metrics indicates whether it is allowed to send metrics to
-    # Stackdriver using "global" resource type and custom metric type if the
-    # metrics are not supported by "knative_revision" resource type. Setting this
-    # flag to "true" could cause extra Stackdriver charge.
-    # If metrics.backend-destination is not Stackdriver, this is ignored.
-    metrics.allow-stackdriver-custom-metrics: "false"
+    # OpenTelemetry Metrics Configuration
+    # Protocol for metrics export (prometheus, grpc, http/protobuf, none)
+    # Default if not specified: "none"
+    metrics-protocol: prometheus
+
+    # Metrics endpoint (for grpc/http protocols)
+    # Default: empty (uses default OTLP endpoint)
+    metrics-endpoint: ""
+
+    # Metrics export interval (e.g., "30s", "1m")
+    # Default: empty (uses default interval)
+    metrics-export-interval: ""
+
+    # OpenTelemetry Tracing Configuration
+    # Protocol for tracing export (grpc, http/protobuf, none, stdout)
+    # Default: none
+    tracing-protocol: none
+
+    # Tracing endpoint (for grpc/http protocols)
+    # Default: empty
+    tracing-endpoint: ""
+
+    # Tracing sampling rate (0.0 to 1.0)
+    # Default: 1.0 (100% sampling)
+    tracing-sampling-rate: "1.0"
+
+    # Runtime Configuration
+    # Enable profiling (enabled, disabled)
+    # Default: disabled
+    runtime-profiling: disabled
+
+    # Runtime export interval (e.g., "15s")
+    # Default: 15s
+    runtime-export-interval: "15s"
+
+    # Note: Legacy OpenCensus configuration (metrics.backend-destination, etc.) has been
+    # removed as OpenCensus support is no longer provided by the underlying infrastructure.
+    # Please use the OpenTelemetry configuration options above.