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Remote Write (Push)

gnmic supports writing metrics to Prometheus using its remote write API.

gNMIc's prometheus remote write can be used to push metrics to a variety of monitoring systems like Prometheus, Mimir, CortexMetrics, VictoriaMetrics, Thanos...

A Prometheus write output can be defined using the below format in gnmic config file under outputs section:

    # required
    type: prometheus_write
    # url to push metrics towards, scheme is required
    url: http://<grafana-mimir-addr>:9009/api/v1/push
    # a map of string:string, 
    # custom HTTP headers to be sent along with each remote write request.
      # header: value
    # sets the `Authorization` header on every remote write request with the
    # configured username and password.
    # sets the `Authorization` header with type `.authorization.type` and the token value.
      type: Bearer
      credentials: <token string>
    # tls config
      # string, path to the CA certificate file,
      # this will be used to verify the clients certificates when `skip-verify` is false
      # string, client certificate file.
      # string, client key file.
      # boolean, if true, the client will not verify the server
      # certificate against the available certificate chain.
      skip-verify: false
    # duration, defaults to 10s, time interval between write requests
    interval: 10s
    # integer, defaults to 1000.
    # Buffer size for time series to be sent to the remote system.
    # metrics are sent to the remote system every `.interval` or when the buffer is full. Whichever one is reached first.
    buffer-size: 1000
    # integer, defaults to 500, sets the maximum number of timeSeries per write request to remote.
    max-time-series-per-write: 500
    # integer, defaults to 0
    # number of retries per write, retries will have a back off of 100ms.
    max-retries: 0
    # metadata configuration
      # boolean, 
      # if true, metrics metadata is sent.
      include: false
      # duration, defaults to 60s.
      # Applies if `metadata.include` is set to true
      # Interval after which all metadata entries are sent to the remote write address
      interval: 60s
      # integer, defaults to 500
      # applies if `metadata.include` is set to true
      # Max number of metadata entries per write request.
      max-entries-per-write: 500
    # string, to be used as the metric namespace
    metric-prefix: "" 
    # boolean, if true the subscription name will be appended to the metric name after the prefix
    append-subscription-name: false 
    # boolean, enables setting string type values as prometheus metric labels.
    strings-as-labels: false
    # duration, defaults to 10s
    # Push request timeout.
    timeout: 10s
    # boolean, defaults to false
    # Enables debug for prometheus write output.
    debug: false 
    # string, one of `overwrite`, `if-not-present`, ``
    # This field allows populating/changing the value of Prefix.Target in the received message.
    # if set to ``, nothing changes 
    # if set to `overwrite`, the target value is overwritten using the template configured under `target-template`
    # if set to `if-not-present`, the target value is populated only if it is empty, still using the `target-template`
    # string, a GoTemplate that allow for the customization of the target field in Prefix.Target.
    # it applies only if the previous field `add-target` is not empty.
    # if left empty, it defaults to:
    # {{- if index . "subscription-target" -}}
    # {{ index . "subscription-target" }}
    # {{- else -}}
    # {{ index . "source" | host }}
    # {{- end -}}`
    # which will set the target to the value configured under `subscription.$` if any,
    # otherwise it will set it to the target name stripped of the port number (if present)
    # list of processors to apply on the message before writing
    # an integer, sets the number of worker handling messages to be converted into Prometheus metrics
    num-workers: 1
    # an integer, sets the number of writers draining the buffer and writing to Prometheus
    num-writers: 1

gnmic creates the prometheus metric name and its labels from the subscription name, the gnmic path and the value name.

Metric Generation#

The below diagram shows an example of a prometheus metric generation from a gnmi update

Metric Naming#

The metric name starts with the string configured under metric-prefix.

Then if append-subscription-name is true, the subscription-name as specified in gnmic configuration file is appended.

The resulting string is followed by the gNMI path stripped of its keys if there are any.

All non-alphanumeric characters are replaced with an underscore "_"

The 3 strings are then joined with an underscore "_"

If further customization of the metric name is required, the processors can be used to transform the metric name.

For example, a gNMI update from subscription port-stats with path:


is exposed as a metric named:


Metric Labels#

The metrics labels are generated from the subscription metadata (e.g: subscription-name and source) and the keys present in the gNMI path elements.

For the previous example the labels would be:


Prometheus Write Metrics#

When a Prometheus server (gNMI API) is enabled, gnmic prometheus write output exposes 4 prometheus counters and 2 prometheus Gauges:

  • number_of_prometheus_write_msgs_sent_success_total: Number of msgs successfully sent by gnmic prometheus_write output.
  • number_of_prometheus_write_msgs_sent_fail_total: Number of failed msgs sent by gnmic prometheus_write output.
  • msg_send_duration_ns: gnmic prometheus_write output send duration in ns.

  • number_of_prometheus_write_metadata_msgs_sent_success_total: Number of metadata msgs successfully sent by gnmic prometheus_write output.

  • number_of_prometheus_write_metadata_msgs_sent_fail_total: Number of failed metadata msgs sent by gnmic prometheus_write output.
  • metadata_msg_send_duration_ns: gnmic prometheus_write output metadata send duration in ns.