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Important: This documentation is about an older version. It's relevant only to the release noted, many of the features and functions have been updated or replaced. Please view the current version.

loki.write

Open source

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
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

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
`batch_wait`	`bool`	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
`bearer_token`	`secret`	Bearer token to authenticate with.		no
`bearer_token_file`	`string`	File containing a bearer token to authenticate with.		no
`proxy_url`	`string`	HTTP proxy to proxy requests through.		no
`follow_redirects`	`bool`	Whether redirects returned by the server should be followed.	`true`	no
`enable_http2`	`bool`	Whether HTTP2 is supported for requests.	`true`	no

At most one of the following can be provided:

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

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.

basic_auth block

Name	Type	Description	Required
`username`	`string`	Basic auth username.	no
`password`	`secret`	Basic auth password.	no
`password_file`	`string`	File containing the basic auth password.	no

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

authorization block

Name	Type	Description	Required
`type`	`string`	Authorization type, for example, “Bearer”.	no
`credentials`	`secret`	Secret value.	no
`credentials_file`	`string`	File containing the secret value.	no

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

oauth2 block

Name	Type	Description	Required
`client_id`	`string`	OAuth2 client ID.	no
`client_secret`	`secret`	OAuth2 client secret.	no
`client_secret_file`	`string`	File containing the OAuth2 client secret.	no
`scopes`	`list(string)`	List of scopes to authenticate with.	no
`token_url`	`string`	URL to fetch the token from.	no
`endpoint_params`	`map(string)`	Optional parameters to append to the token URL.	no
`proxy_url`	`string`	Optional proxy URL for OAuth2 requests.	no

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

The oauth2 block may also contain its own separate tls_config sub-block.

tls_config block

Name	Type	Description	Required
`ca_pem`	`string`	CA PEM-encoded text to validate the server with.	no
`ca_file`	`string`	CA certificate to validate the server with.	no
`cert_pem`	`string`	Certificate PEM-encoded text for client authentication.	no
`cert_file`	`string`	Certificate file for client authentication.	no
`key_pem`	`secret`	Key PEM-encoded text for client authentication.	no
`key_file`	`string`	Key file for client authentication.	no
`server_name`	`string`	ServerName extension to indicate the name of the server.	no
`insecure_skip_verify`	`bool`	Disables validation of the server certificate.	no
`min_version`	`string`	Minimum acceptable TLS version.	no

The following pairs of arguments are mutually exclusive and cannot 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

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.

Example

This example creates a loki.write component that sends received entries to a local Loki instance:

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

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loki.write

Usage

Arguments