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Open source

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.

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

Usage

Alloy 
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.

loki.source.docker supports the following arguments:

NameTypeDescriptionDefaultRequired
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

Blocks

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

HierarchyBlockDescriptionRequired
clientclientHTTP client settings when connecting to the endpoint.no
client > basic_authbasic_authConfigure basic_auth for authenticating to the endpoint.no
client > authorizationauthorizationConfigure generic authorization to the endpoint.no
client > oauth2oauth2Configure OAuth2 for authenticating to the endpoint.no
client > oauth2 > tls_configtls_configConfigure TLS settings for connecting to the endpoint.no
client > tls_configtls_configConfigure TLS settings for connecting to the endpoint.no

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.

NameTypeDescriptionDefaultRequired
bearer_token_filestringFile containing a bearer token to authenticate with.no
bearer_tokensecretBearer token to authenticate with.no
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 through.no
no_proxystringComma-separated list of IP addresses, CIDR notations, and domain names to exclude from proxying.no
proxy_from_environmentboolUse the proxy URL indicated by environment variables.falseno
proxy_connect_headermap(list(secret))Specifies headers to send to proxies during CONNECT requests.no

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.

no_proxy can contain IPs, CIDR notations, and domain names. IP and domain names can contain port numbers. proxy_url must be configured if no_proxy is configured.

proxy_from_environment uses the environment variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY (or the lowercase versions thereof). Requests use the proxy from the environment variable matching their scheme, unless excluded by NO_PROXY. proxy_url and no_proxy must not be configured if proxy_from_environment is configured.

proxy_connect_header should only be configured if proxy_url or proxy_from_environment are configured.

basic_auth block

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

NameTypeDescriptionDefaultRequired
password_filestringFile containing the basic auth password.no
passwordsecretBasic auth password.no
usernamestringBasic auth username.no

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.

NameTypeDescriptionDefaultRequired
credentials_filestringFile containing the secret value.no
credentialssecretSecret value.no
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.

NameTypeDescriptionDefaultRequired
client_idstringOAuth2 client ID.no
client_secret_filestringFile containing the OAuth2 client secret.no
client_secretsecretOAuth2 client secret.no
endpoint_paramsmap(string)Optional parameters to append to the token URL.no
proxy_urlstringHTTP proxy to send requests through.no
no_proxystringComma-separated list of IP addresses, CIDR notations, and domain names to exclude from proxying.no
proxy_from_environmentboolUse the proxy URL indicated by environment variables.falseno
proxy_connect_headermap(list(secret))Specifies headers to send to proxies during CONNECT requests.no
scopeslist(string)List of scopes to authenticate with.no
token_urlstringURL to fetch the token from.no

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.

no_proxy can contain IPs, CIDR notations, and domain names. IP and domain names can contain port numbers. proxy_url must be configured if no_proxy is configured.

proxy_from_environment uses the environment variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY (or the lowercase versions thereof). Requests use the proxy from the environment variable matching their scheme, unless excluded by NO_PROXY. proxy_url and no_proxy must not be configured if proxy_from_environment is configured.

proxy_connect_header should only be configured if proxy_url or proxy_from_environment are configured.

tls_config block

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

NameTypeDescriptionDefaultRequired
ca_pemstringCA PEM-encoded text to validate the server with.no
ca_filestringCA certificate to validate the server with.no
cert_pemstringCertificate PEM-encoded text for client authentication.no
cert_filestringCertificate file for client authentication.no
insecure_skip_verifyboolDisables validation of the server certificate.no
key_filestringKey file for client authentication.no
key_pemsecretKey PEM-encoded text for client authentication.no
min_versionstringMinimum acceptable TLS version.no
server_namestringServerName extension to indicate the name of the server.no

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 is used to store read offsets, so that if a component or Grafana Agent 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 will deduplicate them, and only keep 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 will be 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 
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"
  }
}

Compatible components

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

Note

Connecting some components may not be sensible or components may require further configuration to make the connection work correctly. Refer to the linked documentation for more details.