This is documentation for the next version of Agent. For the latest stable release, go to the latest version.

Open source


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.

Multiple loki.source.docker components can be specified by giving them different labels.


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


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.

loki.source.file supports the following arguments:

hoststringAddress of the Docker daemon.yes
targetslist(map(string))List of containers to read logs from.yes
forward_tolist(LogsReceiver)List of receivers to send log entries to.yes
labelsmap(string)The default set of labels to apply on entries."{}"no
relabel_rulesRelabelRulesRelabeling rules to apply on log entries."{}"no
refresh_intervaldurationThe refresh interval to use when connecting to the Docker daemon over HTTP(S)."60s"no


The following blocks are supported inside the definition of loki.source.docker:

clientclientHTTP client settings when connecting to the
client > basic_authbasic_authConfigure basic_auth for authenticating to the
client > authorizationauthorizationConfigure generic authorization to the
client > oauth2oauth2Configure OAuth2 for authenticating to the
client > oauth2 > tls_configtls_configConfigure TLS settings for connecting to the
client > tls_configtls_configConfigure TLS settings for connecting to the

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 block

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

bearer_token_filestringFile containing a bearer token to authenticate
bearer_tokensecretBearer token to authenticate
enable_http2boolWhether HTTP2 is supported for requests.trueno
follow_redirectsboolWhether redirects returned by the server should be followed.trueno
proxy_urlstringHTTP proxy to send requests

bearer_token, bearer_token_file, basic_auth, authorization, and oauth2 are mutually exclusive, and only one can be provided inside of a http_client_config block.

basic_auth block

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

password_filestringFile containing the basic auth
passwordsecretBasic auth
usernamestringBasic auth

password and password_file are mutually exclusive, and only one can be provided inside a basic_auth block.

authorization block

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

credentials_filestringFile containing the secret
typestringAuthorization type, for example, “Bearer”.no

credential and credentials_file are mutually exclusive, and only one can be provided inside an authorization block.

oauth2 block

The oauth2 block configures OAuth2 authorization to use for the Docker daemon.

client_idstringOAuth2 client
client_secret_filestringFile containing the OAuth2 client
client_secretsecretOAuth2 client
endpoint_paramsmap(string)Optional parameters to append to the token
proxy_urlstringOptional proxy URL for OAuth2
scopeslist(string)List of scopes to authenticate
token_urlstringURL to fetch the token

client_secret and client_secret_file are mutually exclusive, and only one can be provided inside an oauth2 block.

The oauth2 block may also contain a separate tls_config sub-block.

tls_config block

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

ca_pemstringCA PEM-encoded text to validate the server
ca_filestringCA certificate to validate the server
cert_pemstringCertificate PEM-encoded text for client
cert_filestringCertificate file for client
insecure_skip_verifyboolDisables validation of the server
key_filestringKey file for client
key_pemsecretKey PEM-encoded text for client
min_versionstringMinimum acceptable TLS
server_namestringServerName extension to indicate the name of the

The following pairs of arguments are mutually exclusive and can’t both be set simultaneously:

  • ca_pem and ca_file
  • cert_pem and cert_file
  • key_pem and key_file

When configuring client authentication, both the client certificate (using cert_pem or cert_file) and the client key (using key_pem or key_file) must be provided.

When min_version is not provided, the minimum acceptable TLS version is inherited from Go’s default minimum version, TLS 1.2. If min_version is provided, it must be set to one of the following strings:

  • "TLS10" (TLS 1.0)
  • "TLS11" (TLS 1.1)
  • "TLS12" (TLS 1.2)
  • "TLS13" (TLS 1.3)

Exported fields

loki.source.docker does not 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 stores the read offsets so that if there is a component or Agent restart, loki.source.docker can pick up tailing from the same spot.


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.

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

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

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