Collects Cowboy metrics using metrics stream handler

Exported metrics

• cowboy_early_errors_total: Total number of Cowboy early errors, i.e. errors that occur before a request is received.
  • Type: counter.
  • Labels: default - [], configured via early_errors_labels.
• cowboy_protocol_upgrades_total: Total number of protocol upgrades, i.e. when http connection upgraded to websocket connection.
  • Type: counter.
  • Labels: default - [], configured via protocol_upgrades_labels.
• cowboy_requests_total: Total number of Cowboy requests.
  • Type: counter.
  • Labels: default - [method, reason, status_class], configured via request_labels.
• cowboy_spawned_processes_total: Total number of spawned processes.
  • Type: counter.
  • Labels: default - [method, reason, status_class], configured via request_labels.
• cowboy_errors_total: Total number of Cowboy request errors.
  • Type: counter.
  • Labels: default - [method, reason, error], configured via error_labels.
• cowboy_request_duration_seconds: Cowboy request duration.
  • Type: histogram.
  • Labels: default - [method, reason, status_class], configured via request_labels.
  • Buckets: default - [0.01, 0.1, 0.25, 0.5, 0.75, 1, 1.5, 2, 4], configured via duration_buckets.
• cowboy_receive_body_duration_seconds: Request body receiving duration.
  • Type: histogram.
  • Labels: default - [method, reason, status_class], configured via request_labels.
  • Buckets: default - [0.01, 0.1, 0.25, 0.5, 0.75, 1, 1.5, 2, 4], configured via duration_buckets.
• cowboy_request_body_size_bytes: Request body size in bytes.
  • Type: histogram.
  • Labels: default - [method, reason, status_class], configured via request_labels.

  • Buckets: default - [0 | prometheus_buckets:exponential(1, 8.0, 9)] (0 KiB - 16 MiB), configured via body_size_buckets.

• cowboy_response_body_size_bytes: Response body size in bytes.
  • Type: histogram.
  • Labels: default - [method, reason, status_class], configured via request_labels.

  • Buckets: default - [0 | prometheus_buckets:exponential(1, 8.0, 9)] (0 KiB - 16 MiB), configured via body_size_buckets.

Configuration

Prometheus Cowboy2 instrumenter configured via cowboy_instrumenter key of prometheus app environment.

Default configuration:

{prometheus, [
    ...
    {cowboy_instrumenter, [{duration_buckets, [0.01, 0.1, 0.25, 0.5,
                                               0.75, 1, 1.5, 2, 4]},
                           {early_error_labels,  []},
                           {request_labels, [method, reason, status_class]},
                           {error_labels, [method, reason, error]},
                           {registry, default}]}
    ...
]}

Labels

Builtin:

• host,
• port,
• method,
• status,
• status_class,
• reason,
• error.

Custom labels

Can be implemented via module exporting label_value/2 function. First argument will be label name, second is Metrics data from metrics stream handler Set this module to labels_module configuration option.