Lagom configuration

Lagom endpoints need to be selected for Telemetry using configuration. Cinnamon accesses the same configuration as used to configure an ActorSystem. The default configuration is in application.conf.

Server metrics

Server metrics are automatically enabled when Cinnamon’s Lagom dependency is on the classpath.

It is possible to turn server-metrics off for a server with configuration, see override and disable server metrics below.

Server metrics configuration

Endpoint metrics are not enabled by default. In other words, without any specific configuration, there will be no metrics for the endpoints.

Endpoint configuration settings are grouped per “host:port.” Cinnamon will inquire the configuration to determine how to set things up.

The configuration should define the following settings:

Each endpoint in the paths section should define the following:

Server endpoint naming

By default, endpoint metrics created use the endpoint path as name for the metric. Let’s look at an example to clarify this feature:

Configuration conflict resolution

If there are several HTTP related configuration settings available on the classpath, e.g. Lagom and Akka HTTP, Lightbend Telemetry will merge all settings if possible. Should there be conflicting settings, the following order is applied: Lagom > Play > Akka HTTP.

Example configurations

Simple server configuration

The simplest configuration possible is the one that matches all paths, hosts and ports:

copycinnamon.lagom.http.servers {
  "*:*" {
    paths {
      "*" {
        metrics = on
      }
    }
  }
}

Configure specific endpoint paths

Below is an example configuration that is more specific than the simple server configuration:

copycinnamon.lagom.http.servers {
  "192.168.10.1:8080" {
    paths {
      "users/us/*" {
        metrics = on
      }
      "users/se/*" {
        metrics = on
      }
      "users/nz/*" {
        metrics = on
      }
    }
  }
}

The above configuration will create metrics for paths that map to users in us, se, or nz. Notice that all users in these domains are valid since we use * as part of the paths. Furthermore, this configuration is only valid for a server started on IP 192.168.10.1 and port 8080.

Override and disable server metrics

HTTP server configuration is selected from most specific to least specific port and host combination. This means that you can override wildcard configurations by having a more specific configuration section that have different settings.

Turn off all metrics for a particular host while still having them turned on for all other hosts:

copycinnamon.lagom.http.servers {
  "*:*" {
    paths {
      "*" {
        metrics = on
      }
    }
  },
  "192.168.0.1:*" {
    server-metrics = off
  }
}

The server-metrics setting is optional and if not present it will automatically be set to on.

Enable endpoint metrics per status code class

Like overall server metrics, endpoint metrics (response rate and response time) can be recorded for each status code class (2xx, 3xx, 4xx, or 5xx). Use the status-code-classes setting to enable these additional metrics for matching endpoint paths:

copycinnamon.lagom.http.servers {
  "*:*" {
    paths {
      "a/*" {
        metrics = on
      }
      "b/*" {
        metrics = on
        status-code-classes = on
      }
    }
  }
}

Client metrics configuration

Client metrics configuration settings are grouped per “host:port”. In the context of a Lagom service client we refer to “host:port” as a service. Each service can define which “paths” should generate metrics.

Let us look at a couple of client metrics configuration examples.

Simple client configuration

The simplest configuration possible is the one that matches all paths, hosts and ports:

copycinnamon.lagom.http.clients {
  "*:*" {
    paths {
      "*" {
        metrics = on
      }
    }
  }
}

With the above configuration all service calls will be monitored and metrics generated will be under the service name “:”.

Configure client service name

In the configuration below we use the setting service-name which means that metrics will be generated in the context of “accountService” and “customerService”.

copycinnamon.lagom.http.clients {
  "192.168.10.1:*" {
    service-name = "accountService"
    paths {
      "*" {
        metrics = on
      }
    }
  },
  "192.168.10.10:8080" {
    service-name = "customerService"
    paths {
      "*" {
        metrics = on
      }
    }
  }
}

Configure specific client paths

It is also possible to define what paths of a service that should generate and contribute to the metrics.

copycinnamon.lagom.http.clients {
  "192.168.10.1:8080" {
    paths {
      "customer/address/*" {
        metrics = on
      }
    }
  }
}

Circuit breaker configuration

To wire up Lagom circuit breakers telemetry in your Java application you must add the following line to the configuration file:

lagom.spi.circuit-breaker-metrics-class = "cinnamon.lagom.CircuitBreakerInstrumentation"

For Scala, cinnamon.lagom.CircuitBreakerInstrumentation should be wired in your application. See the Scala example for details.

This instructs Lagom to provide data to Lightbend Telemetry rather than the default behavior. The information gathered include:

• State of circuit breaker — closed, open, half-open

• Latency

• Throughput

• Success and failure counts

Lagom circuit breakers

It is important to have an understanding of the circuit breakers in Lagom in order to interpret the data that is gathered. In Lagom each client talking to another service uses a circuit breaker. This basically means that the circuit breaker is on the client instead of the server (in a traditional sense). This means that if your code calls a service directly there will not be any information gathered about this call. Currently only service to service calls are instrumented. See the Lagom documentation for more information on service clients and circuit breakers.

The state of a circuit breaker is one of:

The Data Representation in the above table is the number associated with a certain state, i.e. this is what comes out of Lightbend Telemetry to any reporter listening to the data.