Proxy Metrics

request_total: A counter of the number of requests the proxy has received. This is incremented when the request stream begins.
response_total: A counter of the number of responses the proxy has received. This is incremented when the response stream ends.
response_latency_ms: A histogram of response latencies. This measurement reflects the time-to-first-byte (TTFB) by recording the elapsed time between the proxy processing a request’s headers and the first data frame of the response. If a response does not include any data, the end-of-stream event is used. The TTFB measurement is used so that Linkerd accurately reflects application behavior when a server provides response headers immediately but is slow to begin serving the response body.
route_request_total, route_response_latency_ms, and route_response_total: These metrics are analogous to request_total, response_latency_ms, and response_total except that they are collected at the route level. This means that they do not have authority, tls, grpc_status_code or any outbound labels but instead they have:
- dst: The authority of this request.
- rt_route: The name of the route for this request.
control_request_total, control_response_latency_ms, and control_response_total: These metrics are analogous to request_total, response_latency_ms, and response_total but for requests that the proxy makes to the Linkerd control plane. Instead of authority, direction, or any outbound labels, instead they have:
- addr: The address used to connect to the control plane.

Each of these metrics has the following labels:

authority: The value of the :authority (HTTP/2) or Host (HTTP/1.1) header of the request.
direction: inbound if the request originated from outside of the pod, outbound if the request originated from inside of the pod.

Response Labels

The following labels are only applicable on response_* metrics.

classification: success if the response was successful, or failure if a server error occurred. This classification is based on the gRPC status code if one is present, and on the HTTP status code otherwise. Only applicable to response metrics.
grpc_status_code: The value of the grpc-status trailer. Only applicable for gRPC responses.
status_code: The HTTP status code of the response.

Outbound labels

The following labels are only applicable if direction=outbound.

dst_deployment: The deployment to which this request is being sent.
dst_k8s_job: The job to which this request is being sent.
dst_replicaset: The replica set to which this request is being sent.
dst_daemonset: The daemon set to which this request is being sent.
dst_statefulset: The stateful set to which this request is being sent.
dst_replicationcontroller: The replication controller to which this request is being sent.
dst_namespace: The namespace to which this request is being sent.
dst_service: The service to which this request is being sent.
dst_pod_template_hash: The of the pod to which this request is being sent. This label selector roughly approximates a pod’s ReplicaSet or ReplicationController.

Prometheus Collector labels

The following labels are added by the Prometheus collector.

instance: ip:port of the pod.
job: The Prometheus job responsible for the collection, typically linkerd-proxy.

Kubernetes labels added at collection time

Kubernetes namespace, pod name, and all labels are mapped to corresponding Prometheus labels.

namespace: Kubernetes namespace that the pod belongs to.
pod: Kubernetes pod name.
pod_template_hash: Corresponds to the pod-template-hash Kubernetes label. This value changes during redeploys and rolling restarts. This label selector roughly approximates a pod’s ReplicaSet or ReplicationController.

Linkerd labels added at collection time

daemonset: The daemon set that the pod belongs to (if applicable).
: The deployment that the pod belongs to (if applicable).
k8s_job: The job that the pod belongs to (if applicable).
replicaset: The replica set that the pod belongs to (if applicable).
statefulset: The stateful set that the pod belongs to (if applicable).

Here’s a concrete example, given the following pod snippet:

The resulting Prometheus labels will look like this:

request_total{
  pod="vote-bot-5b7f5657f6-xbjjw",
  namespace="emojivoto",
  app="vote-bot",
  control_plane_ns="linkerd",
  deployment="vote-bot",
  pod_template_hash="3957278789",
  test="vote-bot-test",
  instance="10.1.3.93:4191",
  job="linkerd-proxy"
}

Transport-Level Metrics

The following metrics are collected at the level of the underlying transport layer.

tcp_open_total: A counter of the total number of opened transport connections.
tcp_close_total: A counter of the total number of transport connections which have closed.
tcp_open_connections: A gauge of the number of transport connections currently open.
tcp_write_bytes_total: A counter of the total number of sent bytes. This is updated when the connection closes.
tcp_read_bytes_total: A counter of the total number of received bytes. This is updated when the connection closes.
tcp_connection_duration_ms: A histogram of the duration of the lifetime of a connection, in milliseconds. This is updated when the connection closes.

Each of these metrics has the following labels:

direction: inbound if the connection was established either from outside the pod to the proxy, or from the proxy to the application, outbound if the connection was established either from the application to the proxy, or from the proxy to outside the pod.
peer: src if the connection was accepted by the proxy from the source, dst if the connection was opened by the proxy to the destination.

Note that the labels described above under the heading “Prometheus Collector labels” are also added to transport-level metrics, when applicable.

Connection Close Labels

classification: success if the connection terminated cleanly, if the connection closed due to a connection failure.