observability: add custom tags and location tags

observability/exporting.go

@@ -53,11 +53,11 @@ func newCloudLoggingExporter(ctx context.Context, projectID string) (*cloudLoggi
 	if err != nil {
 		return nil, fmt.Errorf("failed to create cloudLoggingExporter: %v", err)
 	}
-	logger.Infof("successfully created cloudLoggingExporter")
+	defer logger.Infof("successfully created cloudLoggingExporter")
 	return &cloudLoggingExporter{
 		projectID: projectID,
 		client:    c,
-		logger:    c.Logger("grpc"),
+		logger:    c.Logger("grpc", gcplogging.CommonLabels(getCustomTags())),
 	}, nil
 }
 

observability/tags.go

@@ -0,0 +1,39 @@
+/*
+ *
+ * Copyright 2022 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
+ *
+ *     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.
+ *
+ */
+
+package observability
+
+import (
+	"os"
+	"strings"
+)
+
+const envPrefixCustomTags = "GRPC_OBSERVABILITY_"
+
+func getCustomTags() map[string]string {
+	m := make(map[string]string)
+	for _, e := range os.Environ() {
+		if !strings.HasPrefix(e, envPrefixCustomTags) {
+			continue
+		}
+		if i := strings.Index(e, "="); i >= 0 {
+			m[e[:i]] = e[i+1:]
+		}
+	}
+	return m
+}