Documentation Grafana Cloud Instrument and send data Grafana Alloy Reference Components loki loki.source.api

loki.source.api

loki.source.api receives log entries over HTTP and forwards them to other loki.* components.

The HTTP API exposed is compatible with Loki push API and the logproto format. This means that other loki.write components can be used as a client and send requests to loki.source.api which enables using Alloy as a proxy for logs.

Usage

alloy Copy

loki.source.api "LABEL" {
    http {
        listen_address = "LISTEN_ADDRESS"
        listen_port = PORT
    }
    forward_to = RECEIVER_LIST
}

The component will start an HTTP server on the configured port and address with the following endpoints:

• /loki/api/v1/push - accepting POST requests compatible with Loki push API, for example, from another Alloy’s loki.write component.
• /loki/api/v1/raw - accepting POST requests with newline-delimited log lines in body. This can be used to send NDJSON or plain text logs. This is compatible with the Promtail push API endpoint. Refer to the Promtail documentation for more information. When this endpoint is used, the incoming timestamps can’t be used and the use_incoming_timestamp = true setting will be ignored.
• /ready - accepting GET requests. Can be used to confirm the server is reachable and healthy.
• /api/v1/push - internally reroutes to /loki/api/v1/push.
• /api/v1/raw - internally reroutes to /loki/api/v1/raw.

Arguments

loki.source.api supports the following arguments:

The relabel_rules field can make use of the rules export value from a loki.relabel component to apply one or more relabeling rules to log entries before they’re forwarded to the list of receivers in forward_to.

Blocks

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

http

The http block configures the HTTP server.

You can use the following arguments to configure the http block. Any omitted fields take their default values.

Exported fields

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

Component health

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

Debug metrics

The following are some of the metrics that are exposed when this component is used. Note that the metrics include labels such as status_code where relevant, which can be used to measure request success rates.

• loki_source_api_request_duration_seconds (histogram): Time (in seconds) spent serving HTTP requests.
• loki_source_api_request_message_bytes (histogram): Size (in bytes) of messages received in the request.
• loki_source_api_response_message_bytes (histogram): Size (in bytes) of messages sent in response.
• loki_source_api_tcp_connections (gauge): Current number of accepted TCP connections.

Example

This example starts an HTTP server on 0.0.0.0 address and port 9999. The server receives log entries and forwards them to a loki.write component while adding a forwarded="true" label. The loki.write component will send the logs to the specified loki instance using basic auth credentials provided.

alloy Copy

loki.write "local" {
    endpoint {
        url = "http://loki:3100/api/v1/push"
        basic_auth {
            username = "<your username>"
            password_file = "<your password file>"
        }
    }
}

loki.source.api "loki_push_api" {
    http {
        listen_address = "0.0.0.0"
        listen_port = 9999
    }
    forward_to = [
        loki.write.local.receiver,
    ]
    labels = {
        forwarded = "true",
    }
}

Technical details

loki.source.api filters out all labels that start with __, for example, __tenant_id__.

If you need to be able to set the tenant ID, you must either make sure the X-Scope-OrgID header is present or use the loki.process component.

Compatible components

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

• Components that export Loki LogsReceiver