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Reporting Metrics to Datadog

Datadog is a monitoring service for IT, Operations and Development teams who write and run applications at scale, and want to turn the massive amounts of data produced by their apps, tools and services into actionable insight.


Add the kamon-datadog dependency to your project and ensure that it is in your classpath at runtime, that’s it. Kamon’s module loader will detect that the Datadog module is in the classpath and automatically start it.


By default, this module assumes that you have an instance of the Datadog Agent running in localhost and listening on port 8125. If that is not the case the you can use the kamon.datadog.hostname and kamon.datadog.port configuration keys to point the module at your Datadog Agent installation.

The Datadog module subscribes itself to the entities included in the kamon.datadog.subscriptions key. By default, the following subscriptions are included:

kamon.datadog {
  subscriptions {
    histogram       = [ "**" ]
    min-max-counter = [ "**" ]
    gauge           = [ "**" ]
    counter         = [ "**" ]
    trace           = [ "**" ]
    trace-segment   = [ "**" ]
    akka-actor      = [ "**" ]
    akka-dispatcher = [ "**" ]
    akka-router     = [ "**" ]
    system-metric   = [ "**" ]
    http-server     = [ "**" ]

If you are interested in reporting additional entities to Datadog please ensure that you include the categories and name patterns accordingly.

Metric Naming Conventions

For all single instrument entities (those tracking counters, histograms, gaugues and min-max-counters) the generated metric key will follow the application.instrument-type.entity-name pattern. Additionaly all tags supplied when creating the instrument will also be reported.

For all other entities the pattern is a little different: application.entity-category.entity-name and a identification tag using the category and entity name will be used. For example, all mailbox size measurements for Akka actors are reported under the application.akka-actor.mailbox-size metric and a identification tag similar to actor:/user/example-actor is included as well.

Finally, the application name can be changed by setting the kamon.datadog.application-name configuration key.

Metric Units

Kamon keeps all timing measurements in nanoseconds and memory measurements in bytes. In order to scale those to other units before sending to datadog, set time-units and memory-units config keys to desired units. Supported units are:

n  - nanoseconds
µs - microseconds
ms - milliseconds
s  - seconds

b  - bytes
kb - kilobytes
mb - megabytes
gb - gigabytes

For example,

kamon.datadog.time-units = "ms"

will scale all timing measurements to milliseconds right before sending to datadog. Note that if timing measurements are below 1 millisecond when you set time-units="ms", the measurements are reported to Datadog as zero values by dropping everything below the decimal point, because Kamon holds all timing measurements in Long internally.

Integration Notes

  • Contrary to other Datadog client implementations, we don’t flush the metrics data as soon as the measurements are taken but instead, all metrics data is buffered by the kamon-datadog module and flushed periodically using the configured kamon.datadog.flush-interval and kamon.datadog.max-packet-size settings.
  • It is advisable to experiment with the kamon.datadog.flush-interval and kamon.datadog.max-packet-size settings to find the right balance between network bandwidth utilisation and granularity on your metrics data.

Visualization and Fun

Creating a dashboard in the Datadog user interface is really simple, just start typing the application name (“kamon” by default) in the metric selector and all metric names will start to show up. You can also break it down based on the entity names. Here is a very simple example of a dashboard created with metrics reported by Kamon: