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Metrics

Nowadays, there are a lot of complex distributed systems, and every day their number is increasing. When developing such systems, it is important to strive for the highest possible performance. But how can we assess the performance of a system? There are special metrics for this.

Metrics are numerical data that are calculated or aggregated over a period of time. Metrics give us an idea of ​​the current and historical state of the system. They can be used for statistical analysis, to predict the future behavior of the system.

There are many types of metrics that can be used for monitoring the performance of distributed systems. For example, latency, bandwidth, error, saturation, traffic, etc. For each distributed system, we need to choose a list of metrics that suit it exactly.

For convenient graphical display and analysis of metrics, we should use monitoring systems such as Grafana, Prometheus. These systems allow us to create dashboards and display specific metrics over a given period of time. For each distributed system, it is necessary to be able to store metrics into monitoring systems for their further analysis.

Metrics in Proto.Actor

Proto.Actor is using metrics provided by OpenTelemetry. With simple Proto.Actor instrumentation from Proto.OpenTelemetry, it is possible to get insights how actor system is performing. Below it is possible to find more details regarding built in metrics.

Small remark, when using Prometheus exporter directly in the application then the metric names get postfixed with unit name, e.g. histogram protoactor_threadpool_latency_duration is renamed to protoactor_threadpool_latency_duration_seconds.

Proto.Actor Metrics

Name Type Labels
protoactor_threadpool_latency_duration Histogram id, address
protoactor_deadletter_count Count id, address, messagetype
protoactor_actor_spawn_count Count id, address, actortype
protoactor_actor_stopped_count Count id, address, actortype
protoactor_actor_restarted_count Count id, address, actortype
protoactor_actor_failure_count Count id, address, actortype
protoactor_actor_mailbox_length Gauge id, address, actortype
protoactor_actor_messagereceive_duration Histogram id, address, actortype, messagetype
protoactor_future_started_count Count id, address
protoactor_future_timedout_count Count id, address
protoactor_future_completed_count Count id, address

Proto.Remote Metrics

Name Type Labels
protoremote_message_serialize_count Count id, address, messagetype
protoremote_message_deserialize_count Count id, address, messagetype
protoremote_spawn_count Count id, address, kind
protoremote_endpoint_connected_count Count id, address, destinationaddress
protoremote_endpoint_disconnected_count Count id, address, destinationaddress

Proto.Cluster Metrics

Name Type Labels
protocluster_virtualactors Gauge id, address, clusterkind
protocluster_virtualactor_spawn_duration Histogram id, address, clusterkind
protocluster_virtualactor_requestasync_duration Histogram id, address, clusterkind, messagetype, pidsource
protocluster_virtualactor_requestasync_retry_count Count id, address, clusterkind, messagetype
protocluster_members_count Gauge id, address
protocluster_resolve_pid_duration Histogram id, address, clusterkind

Getting started

OpenTelemetry Exporter example

Realtime map is using Proto.OpenTelemetry and might be used as a working example. It uses OpenTelemetry exporter and also shows how to set it up locally.

Prometheus Exporter example

First what needs to be done is to register MeterProvider instance. It might be achieved with ready to use extension from OpenTelemetry.Extensions.Hosting nuget package. This extension is using builder pattern to properly configure MeterProvider with labels common for all metrics. Prometheus exporter built-in in the application is the easiest to setup and it will be shown as an example. It is needed to reference OpenTelemetry.Exporter.Prometheus nuget package and call AddPrometheusExporter() extension method. It adds /metrics endpoint from where Prometheus is able to scrape metrics. To make it work properly it is needed to call also app.UseOpenTelemetryPrometheusScrapingEndpoint() after building an application.

OpenTelemetry metrics in C# implementation use System.Diagnositcs.Metrics. AddProtoActorInstrumentation() extension shown in the example is adding Proto.Actor meter name. Method has additional parameter useRecommendedHistogramBoundaries which is true by default. It causes that default buckets used in OpenTelemetry implementation are changed to more preffered ones.

void ConfigureMetrics(WebApplicationBuilder builder) =>
    builder.Services.AddOpenTelemetryMetrics(b =>
        b.SetResourceBuilder(ResourceBuilder
                .CreateDefault()
                .AddAttributes(new KeyValuePair<string, object>[]
                {
                    new("someLabel", builder.Configuration["SomeLabel"]),
                    new("env", builder.Environment.EnvironmentName)
                })
                .AddService(builder.Configuration["Service:Name"])
            )
            .AddProtoActorInstrumentation()
            .AddPrometheusExporter()
    );

Using Prometheus and Grafana to store and visualize metrics

Another example of Prometheus metrics setup might be found in ActorMetrics example.

In this section, it will be presented how to run Prometheus and Grafana locally using Docker.

version: '3.7'

services:     
  grafana:
    image: grafana/grafana
    ports:
      - 3000:3000
      
  prometheus:
    image: prom/prometheus
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
    ports:
      - 9090:9090

prometheus.yml

scrape_configs:
- job_name: 'your-application'
  scrape_interval: 10s
  static_configs:
  - targets: ['host.docker.internal:5000']

A few words of exmplanation regarding docker-compose setup:

  • Grafana setup is bare minimum to run it, UI is available under 3000 port
  • Prometheus is available under 9090 port. Prometheus requires prometheus.yml config file to properly configure targets from where metrics are scraped. In this setup, file points only to application’s prometheus endpoint.

After running this docker-compose and some application that exposes metrics, it is possible to create some dashboard in Grafana do visualize it.

ActorMetrics example contains a sample dashboard that shows how to create a visualisation of metrics.

sample dashboard

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