Cromwell's instrumentation support can be useful to collect utilization data in long-running, high-volume production environments. The default implementation of this ignores these metrics, but Cromwell includes alternate implementations that can forward metrics to a specific server.


While this instrumentation support can be used in smaller environments it will still require setting up a StatsD server outside of Cromwell and it's possible not enough data would be produced to be useful. Cromwell collects metrics while running and sends them to an internal service.

Make sure to configure your StatsD service:

services.Instrumentation {
    class = "cromwell.services.instrumentation.impl.statsd.StatsDInstrumentationServiceActor"

    config {
        hostname = "localhost" # Replace with your host
        port = 8125 # Replace with your port
        # prefix = "my_prefix" # All metrics will be prefixed by this value if present.
        flush-rate = 1 second # Rate at which metrics are sent to the StatsD server

There is also an additional configuration value that can be set:

# Rate at which Cromwell updates its gauge values (number of workflows running, queued, etc...)
system.instrumentation-rate = 5 seconds

If you have multiple Cromwell instances, and would like to separate the instrumentation path for each instance, set the system.cromwell_id with the unique identifier for each Cromwell instance. For example,

system.cromwell_id = "cromwell-instance-1"

will prepend all the metrics with path cromwell.cromwell-instance-1... for that instance.


The current StatsD implementation uses metrics-statsd to report instrumentation values. metrics-statsd reports all metrics with a gauge type. This means all metrics will be under the gauge section. We might add or remove metrics in the future depending on need and usage. These are the current high level categories:

  • backend
  • rest-api
  • job
  • workflow
  • io


Cromwell now supports sending metrics to Google's Stackdriver API. To use the Stackdriver instrumentation specify this in your config:

services.Instrumentation {
    class = "cromwell.services.instrumentation.impl.stackdriver.StackdriverInstrumentationServiceActor"

    config {
        # auth scheme can be `application_default` or `service_account`
        auth = "service-account"
        google-project = "my-project"
        # rate at which aggregated metrics will be sent to Stackdriver. It needs to be equal or greater than 1 minute.
        # Google's Stackdriver API needs each metric to be sent not more than once per minute.
        flush-rate = 1 minute
        # below 3 keys are attached as labels to each metric. `cromwell-perf-test-case` is specifically meant for perf env.
        cromwell-instance-role = "role"
        cromwell-perf-test-case = "perf-test-1"

The 2 label keys are optional. If specified, each metric will have label(s) added in the form of a (key, value) pair. So for example, if cromwell-instance-role = "backend" is mentioned in config, each metric data point sent to Stackdriver will have a label (cromwell_instance_role, backend) added to it.

There is another optional label that can be added to each metric. cromwell_id represents the identifier for different Cromwell instances.

# Unique Cromwell instance identifier
system.cromwell_id = "cromwell-instance-1"
Metric type and Label keys naming convention

More details on the this can be found here.

You must adhere to the following spelling rules for metric type names: - You can use upper and lower-case letters, digits, and underscores (_) in the names. - You can use periods (.) in the domain part of the names. - You can use forward slashes (/) to separate path elements. - You can start each path element with a letter or digit. - The maximum length of a metric type name is 200 characters.

You must adhere to the following spelling rules for metric label names: - You can use upper and lower-case letters, digits, underscores (_) in the names. - You can start names with a letter or digit. - The maximum length of a metric label name is 100 characters.