Enable exemplar export/display support (open-telemetry#704)

* Enable exemplar export/display support

Ensure the collector's prometheus endpoint produces exemplars
Ensure that prometheus collects and stores exemplar data
Ensure that grafana will display links to exemplars from dashboards/the explore tab

* Enable exemplars for latency histogram in demo dashboard

CHANGELOG.md

@@ -206,3 +206,5 @@ significant modifications will be credited to OpenTelemetry Authors.
 ([#703](https://github.com/open-telemetry/opentelemetry-demo/pull/703))
 * Update dockerfile for adservice to use different base images
 ([#705](https://github.com/open-telemetry/opentelemetry-demo/pull/705))
+* Enable exemplar support in the metrics exporter, Prometheus, and Grafana
+([#704](https://github.com/open-telemetry/opentelemetry-demo/pull/704))

docker-compose.yml

@@ -625,7 +625,7 @@ services:
 
   # OpenTelemetry Collector
   otelcol:
-    image: otel/opentelemetry-collector-contrib:0.61.0
+    image: otel/opentelemetry-collector-contrib:0.69.0
     container_name: otel-col
     deploy:
       resources:
@@ -657,6 +657,7 @@ services:
       - --storage.tsdb.path=/prometheus
       - --web.enable-lifecycle
       - --web.route-prefix=/
+      - --enable-feature=exemplar-storage
     volumes:
       - ./src/prometheus/prometheus-config.yaml:/etc/prometheus/prometheus-config.yaml
     ports:

docs/demo_features.md

@@ -17,14 +17,14 @@ be added as the relevant SDKs are released.
   Collector](https://opentelemetry.io/docs/collector/getting-started)**: all
   services are instrumented and sending the generated traces and metrics to the
   OpenTelemetry Collector via gRPC. The received traces are then exported to the
-  logs and to Jaeger.
+  logs and to Jaeger; received metrics and exemplars are exported to logs and Prometheus.
 - **[Jaeger](https://www.jaegertracing.io)**: all generated traces are being
   sent to Jaeger.
 - **Synthetic Load Generation**: the application demo comes with a background
   job that creates realistic usage patterns on the website using
   [Locust](https://locust.io/) load generator.
-- **[Prometheus](https://prometheus.io/)**: all generated metrics are scraped by
-  Prometheus.
+- **[Prometheus](https://prometheus.io/)**: all generated metrics and exemplars
+  are scraped by Prometheus.
 - **[Grafana](https://grafana.com/)**: all metric dashboards are stored in
   Grafana.
 - **[Envoy](https://www.envoyproxy.io/)**: Envoy is used as a reverse proxy for

docs/metric_service_features.md

@@ -9,15 +9,15 @@ Emoji Legend
 | Service         | Language        | Auto-instrumentation | Manual Instrumentation | Multiple Instruments | Views          | Custom Attributes | Resource Detection | Trace Exemplars |
 |-----------------|-----------------|----------------------|------------------------|----------------------|----------------|-------------------|--------------------|-----------------|
 | Accounting      | Go              | :construction:       | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
-| Ad              | Java            | :100:                | :100:                  | :construction:       | :construction: | :100:             | :100:              | :construction:  |
+| Ad              | Java            | :100:                | :100:                  | :construction:       | :construction: | :100:             | :100:              | :100:           |
 | Cart            | .NET            | :100:                | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
 | Checkout        | Go              | :100:                | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
 | Currency        | C++             | :no_bell:            | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
 | Email           | Ruby            | :construction:       | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
 | Feature Flag    | Erlang / Elixir | :construction:       | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
 | Fraud Detection | Kotlin          | :100:                | :construction:         | :construction:       | :construction: | :construction:    | :100:              | :construction:  |
 | Frontend        | TypeScript      | :construction:       | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
-| Payment         | JavaScript      | :construction:       | :construction:         | :construction:       | :construction: | :construction:    | :100:              | :construction:  |
+| Payment         | JavaScript      | :construction:       | :100:                  | :construction:       | :construction: | :construction:    | :100:              | :construction:  |
 | Product Catalog | Go              | :construction:       | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
 | Quote           | PHP             | :construction:       | :construction:         | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |
 | Recommendation  | Python          | :100:                | :100:                  | :construction:       | :construction: | :construction:    | :construction:     | :construction:  |