Documentation Grafana Alloy Reference Components loki loki.source.docker

loki.source.docker

loki.source.docker reads log entries from Docker containers and forwards them to other loki.* components. Each component can read from a single Docker daemon.

You can specify multiple loki.source.docker components by giving them different labels.

Usage

alloy Copy

loki.source.docker "LABEL" {
  host       = HOST
  targets    = TARGET_LIST
  forward_to = RECEIVER_LIST
}

Arguments

The component starts a new reader for each of the given targets and fans out log entries to the list of receivers passed in forward_to.

You can use the following arguments with loki.source.docker:

Blocks

You can use the following blocks with loki.source.docker:

The > symbol indicates deeper levels of nesting. For example, client > basic_auth refers to an basic_auth block defined inside a client block.

These blocks are only applicable when connecting to a Docker daemon over HTTP or HTTPS and has no effect when connecting via a unix:/// socket

client

The client block configures settings used to connect to HTTP(S) Docker daemons.

authorization

The authorization block configures custom authorization to use for the Docker daemon.

basic_auth

The basic_auth block configures basic authentication for HTTP(S) Docker daemons.

oauth2

The oauth2 block configures OAuth 2.0 authorization to use for the Docker daemon.

tls_config

The tls_config block configures TLS settings for connecting to HTTPS Docker daemons.

Exported fields

loki.source.docker doesn’t export any fields.

Component health

loki.source.docker is only reported as unhealthy if given an invalid configuration.

Debug information

loki.source.docker exposes some debug information per target:

• Whether the target is ready to tail entries.
• The labels associated with the target.
• The most recent time a log line was read.

Debug metrics

• loki_source_docker_target_entries_total (gauge): Total number of successful entries sent to the Docker target.
• loki_source_docker_target_parsing_errors_total (gauge): Total number of parsing errors while receiving Docker messages.

Component behavior

The component uses its data path, a directory named after the domain’s fully qualified name, to store its positions file. The positions file is used to store read offsets, so that if a component or Alloy restarts, loki.source.docker can pick up tailing from the same spot.

If the target’s argument contains multiple entries with the same container ID, for example, as a result of discovery.docker picking up multiple exposed ports or networks, loki.source.docker deduplicates them, and only keeps the first of each container ID instances, based on the __meta_docker_container_id label. As such, the Docker daemon is queried for each container ID only once, and only one target is available in the component’s debug info.

Example

This example collects log entries from the files specified in the targets argument and forwards them to a loki.write component to be written to Loki.

alloy Copy

discovery.docker "linux" {
  host = "unix:///var/run/docker.sock"
}

loki.source.docker "default" {
  host       = "unix:///var/run/docker.sock"
  targets    = discovery.docker.linux.targets
  labels     = {"app" = "docker"}
  forward_to = [loki.write.local.receiver]
}

loki.write "local" {
  endpoint {
    url = "http://loki:3100/loki/api/v1/push"
  }
}

Compatible components

loki.source.docker can accept arguments from the following components:

• Components that export Targets
• Components that export Loki LogsReceiver