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Documentation Grafana Agent Grafana Agent Flow Reference Components loki.source.journal

loki.source.journal

loki.source.journal reads from the systemd journal and forwards them to other loki.* components.

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

Usage

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loki.source.journal "LABEL" {
  forward_to    = RECEIVER_LIST
}

Arguments

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

loki.source.journal supports the following arguments:

NOTE: A job label is added with the full name of the component loki.source.journal.LABEL.

Blocks

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

relabel_rules block

The rule block contains the definition of any relabeling rules that can be applied to an input metric. If more than one rule block is defined, the transformations are applied in top-down order.

The following arguments can be used to configure a rule. All arguments are optional. Omitted fields take their default values.

Here’s a list of the available actions, along with a brief description of their usage.

• replace - Matches regex to the concatenated labels. If there’s a match, it replaces the content of the target_label using the contents of the replacement field.
• keep - Keeps metrics where regex matches the string extracted using the source_labels and separator.
• drop - Drops metrics where regex matches the string extracted using the source_labels and separator.
• hashmod - Hashes the concatenated labels, calculates its modulo modulus and writes the result to the target_label.
• labelmap - Matches regex against all label names. Any labels that match are renamed according to the contents of the replacement field.
• labeldrop - Matches regex against all label names. Any labels that match are removed from the metric’s label set.
• labelkeep - Matches regex against all label names. Any labels that don’t match are removed from the metric’s label set.

Finally, note that the regex capture groups can be referred to using either the $CAPTURE_GROUP_NUMBER or ${CAPTURE_GROUP_NUMBER} notation.

Incoming messages have labels from the journal following the patten __journal_FIELDNAME

These labels are stripped unless a rule is created to retain the labels. An example rule is below.

river Copy

rule {
		action      = "labelmap"
		regex       = "__journal_(.*)"
		replacement = "journal_${1}"
	}

Component health

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

Debug Metrics

• agent_loki_source_journal_target_parsing_errors_total (counter): Total number of parsing errors while reading journal messages.
• agent_loki_source_journal_target_lines_total (counter): Total number of successful journal lines read.

Example

river Copy

loki.source.journal "read"  {
    forward_to = [loki.write.endpoint.receiver]
}

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