Open source


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.


loki.write "LABEL" {
  endpoint {


loki.write supports the following arguments:

max_streamsintMaximum number of active streams.0 (no limit)no
external_labelsmap(string)Labels to add to logs sent over the


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

endpointendpointLocation to send logs
walwalWrite-ahead log
endpoint > basic_authbasic_authConfigure basic_auth for authenticating to the
endpoint > authorizationauthorizationConfigure generic authorization to the
endpoint > oauth2oauth2Configure OAuth2 for authenticating to the
endpoint > oauth2 > tls_configtls_configConfigure TLS settings for connecting to the
endpoint > tls_configtls_configConfigure TLS settings for connecting to the
endpoint > queue_configqueue_configWhen WAL is enabled, configures the queue

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:

urlstringFull URL to send logs to.yes
namestringOptional name to identify this endpoint
headersmap(string)Extra headers to deliver with the
batch_waitdurationMaximum amount of time to wait before sending a batch."1s"no
batch_sizestringMaximum batch size of logs to accumulate before sending."1MiB"no
remote_timeoutdurationTimeout for requests made to the URL."10s"no
tenant_idstringThe tenant ID used by default to push
min_backoff_perioddurationInitial backoff time between retries."500ms"no
max_backoff_perioddurationMaximum backoff time between retries."5m"no
max_backoff_retriesintMaximum number of retries.10no
bearer_tokensecretBearer token to authenticate
bearer_token_filestringFile containing a bearer token to authenticate
proxy_urlstringHTTP proxy to proxy requests
follow_redirectsboolWhether redirects returned by the server should be followed.trueno
enable_http2boolWhether HTTP2 is supported for requests.trueno
retry_on_http_429boolRetry when an HTTP 429 status code is received.trueno

At most one of the following can be provided:

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

password_filestringFile containing the basic auth
passwordsecretBasic auth
usernamestringBasic auth

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

authorization block

credentials_filestringFile containing the secret
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

client_idstringOAuth2 client
client_secret_filestringFile containing the OAuth2 client
client_secretsecretOAuth2 client
endpoint_paramsmap(string)Optional parameters to append to the token
proxy_urlstringOptional proxy URL for OAuth2
scopeslist(string)List of scopes to authenticate
token_urlstringURL to fetch the token

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.

tls_config block

ca_pemstringCA PEM-encoded text to validate the server
ca_filestringCA certificate to validate the server
cert_pemstringCertificate PEM-encoded text for client
cert_filestringCertificate file for client
insecure_skip_verifyboolDisables validation of the server
key_filestringKey file for client
key_pemsecretKey PEM-encoded text for client
min_versionstringMinimum acceptable TLS
server_namestringServerName extension to indicate the name of the

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)

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:

capacitystringControls 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.10MiBno
drain_timeoutdurationConfigures 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 Grafana Agent is configured to use. See the agent run documentation for how to change the storage path.

The following arguments are supported:

enabledboolWhether to enable the WAL.falseno
max_segment_agedurationMaximum time a WAL segment should be allowed to live. Segments older than this setting will be eventually deleted."1h"no
min_read_frequencydurationMinimum backoff time in the backup read mechanism."250ms"no
max_read_frequencydurationMaximum backoff time in the backup read mechanism."1s"no

Exported fields

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

receiverLogsReceiverA 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.


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 = ""
        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.