o11y: Implement tracing/metrics via OpenCensus

gcp/observability/config.go

@@ -82,6 +82,9 @@ func parseObservabilityConfig() (*configpb.ObservabilityConfig, error) {
 		if err := validateFilters(&config); err != nil {
 			return nil, fmt.Errorf("error parsing observability config: %v", err)
 		}
+		if config.GlobalTraceSamplingRate > 1 || config.GlobalTraceSamplingRate < 0 {
+			return nil, fmt.Errorf("error parsing observability config: invalid global trace sampling rate %v", config.GlobalTraceSamplingRate)
+		}
 		logger.Infof("Parsed ObservabilityConfig: %+v", &config)
 		return &config, nil
 	}

gcp/observability/go.mod

@@ -4,8 +4,10 @@ go 1.14
 
 require (
 	cloud.google.com/go/logging v1.4.2
+	contrib.go.opencensus.io/exporter/stackdriver v0.13.12
 	github.com/golang/protobuf v1.5.2
 	github.com/google/uuid v1.3.0
+	go.opencensus.io v0.23.0
 	golang.org/x/oauth2 v0.0.0-20211104180415-d3ed0bb246c8
 	google.golang.org/grpc v1.46.0
 	google.golang.org/protobuf v1.27.1

gcp/observability/internal/config/config.proto

@@ -1,16 +1,16 @@
 // Copyright 2022 The gRPC Authors
 //
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
 
 // Observability Config is used by gRPC Observability plugin to control provided
 // observability features. It contains parameters to enable/disable certain
@@ -34,8 +34,14 @@ option go_package = "google.golang.org/grpc/gcp/observability/internal/config";
 // most common knobs for gRPC users. It's always possible to override with
 // explicit config in code.
 message ObservabilityConfig {
-    // Whether the logging data uploading to CloudLogging should be enabled or
-    // not. The default value is true.
+    // Whether the tracing data upload to CloudTrace should be enabled or not.
+    bool enable_cloud_trace = 4;
+
+    // Whether the metrics data upload to CloudMonitoring should be enabled or
+    // not.
+    bool enable_cloud_monitoring = 5;
+
+    // Whether the logging data upload to CloudLogging should be enabled or not.
     bool enable_cloud_logging = 1;
 
     // The destination GCP project identifier for the uploading log entries. If
@@ -75,4 +81,9 @@ message ObservabilityConfig {
     // the LogFilter. Any other LogFilter that also matches that comes later
     // will be ignored. So a LogFilter of "*/*" should appear last in this list.
     repeated LogFilter log_filters = 3;
+
+    // The global setting that controls the probability of a RPC being traced.
+    // For example, 0.05 means there is a 5% chance for a RPC to be traced, 1.0
+    // means trace every call, 0 means don’t start new traces.
+    double global_trace_sampling_rate = 6;
 }

gcp/observability/observability.go

@@ -65,6 +65,11 @@ func Start(ctx context.Context) error {
 		return err
 	}
 
+	// Enabling tracing and metrics via OpenCensus
+	if err := startOpenCensus(config, nil); err != nil {
+		return err
+	}
+
 	// Logging is controlled by the config at methods level.
 	return defaultLogger.Start(ctx, config)
 }