alloy/docs/sources/reference/components/loki.write.md

canonical, description, title

canonical	description	title
https://grafana.com/docs/alloy/latest/reference/components/loki.write/	Learn about loki.write	loki.write

loki.write

loki.write receives log entries from other loki components and sends them over the network using Loki's logproto format.

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

Usage

loki.write "LABEL" {
  endpoint {
    url = REMOTE_WRITE_URL
  }
}

Arguments

loki.write supports the following arguments:

Name	Type	Description	Default	Required
max_streams	int	Maximum number of active streams.	0 (no limit)	no
external_labels	map(string)	Labels to add to logs sent over the network.		no

Blocks

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

Hierarchy	Block	Description	Required
endpoint	endpoint	Location to send logs to.	no
wal	wal	Write-ahead log configuration.	no
endpoint > basic_auth	basic_auth	Configure basic_auth for authenticating to the endpoint.	no
endpoint > authorization	authorization	Configure generic authorization to the endpoint.	no
endpoint > oauth2	oauth2	Configure OAuth2 for authenticating to the endpoint.	no
endpoint > oauth2 > tls_config	tls_config	Configure TLS settings for connecting to the endpoint.	no
endpoint > tls_config	tls_config	Configure TLS settings for connecting to the endpoint.	no
endpoint > queue_config	queue_config	When WAL is enabled, configures the queue client.	no

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

endpoint block

The endpoint block describes a single location to send logs to. Multiple endpoint blocks can be provided to send logs to multiple locations.

The following arguments are supported:

Name	Type	Description	Default	Required
url	string	Full URL to send logs to.		yes
name	string	Optional name to identify this endpoint with.		no
headers	map(string)	Extra headers to deliver with the request.		no
batch_wait	duration	Maximum amount of time to wait before sending a batch.	"1s"	no
batch_size	string	Maximum batch size of logs to accumulate before sending.	"1MiB"	no
remote_timeout	duration	Timeout for requests made to the URL.	"10s"	no
tenant_id	string	The tenant ID used by default to push logs.		no
min_backoff_period	duration	Initial backoff time between retries.	"500ms"	no
max_backoff_period	duration	Maximum backoff time between retries.	"5m"	no
max_backoff_retries	int	Maximum number of retries.	10	no
retry_on_http_429	bool	Retry when an HTTP 429 status code is received.	true	no
bearer_token_file	string	File containing a bearer token to authenticate with.		no
bearer_token	secret	Bearer token to authenticate with.		no
enable_http2	bool	Whether HTTP2 is supported for requests.	true	no
follow_redirects	bool	Whether redirects returned by the server should be followed.	true	no
proxy_url	string	HTTP proxy to send requests through.		no
no_proxy	string	Comma-separated list of IP addresses, CIDR notations, and domain names to exclude from proxying.		no
proxy_from_environment	bool	Use the proxy URL indicated by environment variables.	false	no
proxy_connect_header	map(list(secret))	Specifies headers to send to proxies during CONNECT requests.		no

At most, one of the following can be provided:

• bearer_token argument.
• bearer_token_file argument.
• basic_auth block.
• authorization block.
• oauth2 block.

{{< docs/shared lookup="reference/components/http-client-proxy-config-description.md" source="alloy" version="<ALLOY_VERSION>" >}}

If no tenant_id is provided, the component assumes that the Loki instance at endpoint is running in single-tenant mode and no X-Scope-OrgID header is sent.

When multiple endpoint blocks are provided, the loki.write component creates a client for each. Received log entries are fanned-out to these clients in succession. That means that if one client is bottlenecked, it may impact the rest.

Endpoints can be named for easier identification in debug metrics by using the name argument. If the name argument isn't provided, a name is generated based on a hash of the endpoint settings.

The retry_on_http_429 argument specifies whether HTTP 429 status code responses should be treated as recoverable errors; other HTTP 4xx status code responses are never considered recoverable errors. When retry_on_http_429 is enabled, the retry mechanism will be governed by the backoff configuration specified through min_backoff_period, max_backoff_period and max_backoff_retries attributes.

basic_auth block

{{< docs/shared lookup="reference/components/basic-auth-block.md" source="alloy" version="<ALLOY_VERSION>" >}}

authorization block

{{< docs/shared lookup="reference/components/authorization-block.md" source="alloy" version="<ALLOY_VERSION>" >}}

oauth2 block

{{< docs/shared lookup="reference/components/oauth2-block.md" source="alloy" version="<ALLOY_VERSION>" >}}

tls_config block

{{< docs/shared lookup="reference/components/tls-config-block.md" source="alloy" version="<ALLOY_VERSION>" >}}

queue_config block (experimental)

The optional queue_config block configures, when WAL is enabled (see Write-Ahead block), how the underlying client queues batches of logs to be sent to Loki.

The following arguments are supported:

Name	Type	Description	Default	Required
capacity	string	Controls the size of the underlying send queue buffer. This setting should be considered a worst-case scenario of memory consumption, in which all enqueued batches are full.	10MiB	no
drain_timeout	duration	Configures the maximum time the client can take to drain the send queue upon shutdown. During that time, it will enqueue pending batches and drain the send queue sending each.	"1m"	no

wal block (experimental)

The optional wal block configures the Write-Ahead Log (WAL) used in the Loki remote-write client. To enable the WAL, you must include the wal block in your configuration. When the WAL is enabled, the log entries sent to the loki.write component are first written to a WAL under the dir directory and then read into the remote-write client. This process provides durability guarantees when an entry reaches this component. The client knows when to read from the WAL using the following two mechanisms:

• The WAL-writer side of the loki.write component notifies the reader side that new data is available.
• The WAL-reader side periodically checks if there is new data, increasing the wait time exponentially between min_read_frequency and max_read_frequency.

The WAL is located inside a component-specific directory relative to the storage path {{< param "PRODUCT_NAME" >}} is configured to use. See the alloy run documentation for how to change the storage path.

The following arguments are supported:

Name	Type	Description	Default	Required
enabled	bool	Whether to enable the WAL.	false	no
max_segment_age	duration	Maximum time a WAL segment should be allowed to live. Segments older than this setting will be eventually deleted.	"1h"	no
min_read_frequency	duration	Minimum backoff time in the backup read mechanism.	"250ms"	no
max_read_frequency	duration	Maximum backoff time in the backup read mechanism.	"1s"	no
drain_timeout	duration	Maximum time the WAL drain procedure can take, before being forcefully stopped.	"30s"	no

Exported fields

The following fields are exported and can be referenced by other components:

Name	Type	Description
receiver	LogsReceiver	A value that other components can use to send log entries to.

Component health

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

Debug information

loki.write does not expose any component-specific debug information.

Debug metrics

• loki_write_encoded_bytes_total (counter): Number of bytes encoded and ready to send.
• loki_write_sent_bytes_total (counter): Number of bytes sent.
• loki_write_dropped_bytes_total (counter): Number of bytes dropped because failed to be sent to the ingester after all retries.
• loki_write_sent_entries_total (counter): Number of log entries sent to the ingester.
• loki_write_dropped_entries_total (counter): Number of log entries dropped because they failed to be sent to the ingester after all retries.
• loki_write_request_duration_seconds (histogram): Duration of sent requests.
• loki_write_batch_retries_total (counter): Number of times batches have had to be retried.
• loki_write_stream_lag_seconds (gauge): Difference between current time and last batch timestamp for successful sends.

Examples

The following examples show you how to create loki.write components that send log entries to different destinations.

Send log entries to a local Loki instance

You can create a loki.write component that sends your log entries to a local Loki instance:

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

Send log entries to a managed service

You can create a loki.write component that sends your log entries to a managed service, for example, Grafana Cloud. The Loki username and Grafana Cloud API Key are injected in this example through environment variables.

loki.write "default" {
    endpoint {
        url = "https://logs-xxx.grafana.net/loki/api/v1/push"
        basic_auth {
            username = env("LOKI_USERNAME")
            password = env("GRAFANA_CLOUD_API_KEY")
        }
    }
}

Technical details

loki.write uses snappy for compression.

Any labels that start with __ will be removed before sending to the endpoint.

Compatible components

loki.write has exports that can be consumed by the following components:

• Components that consume Loki LogsReceiver

{{< admonition type="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. {{< /admonition >}}