[Observability] Integrate OpenTelemetry (#17627)

api/.env.example

@@ -463,3 +463,16 @@ CREATE_TIDB_SERVICE_JOB_ENABLED=false
 MAX_SUBMIT_COUNT=100
 # Lockout duration in seconds
 LOGIN_LOCKOUT_DURATION=86400
+
+# Enable OpenTelemetry
+ENABLE_OTEL=false
+OTLP_BASE_ENDPOINT=http://localhost:4318
+OTLP_API_KEY=
+OTEL_EXPORTER_TYPE=otlp
+OTEL_SAMPLING_RATE=0.1
+OTEL_BATCH_EXPORT_SCHEDULE_DELAY=5000
+OTEL_MAX_QUEUE_SIZE=2048
+OTEL_MAX_EXPORT_BATCH_SIZE=512
+OTEL_METRIC_EXPORT_INTERVAL=60000
+OTEL_BATCH_EXPORT_TIMEOUT=10000
+OTEL_METRIC_EXPORT_TIMEOUT=30000