Loki Sink

The Vector loki sink batches log events to Loki.

Configuration

vector.toml
[sinks.my_sink_id]
# General
type = "loki" # required
inputs = ["my-source-id"] # required
endpoint = "http://localhost:3100" # required
healthcheck = true # optional, default
# Encoding
encoding.codec = "json" # optional, default
# Labels
labels.key = "value" # example
labels.key = "{{ event_field }}" # example
12 items
tableoptional

auth

Options for the authentication strategy.

stringenumcommonrequired

strategy

The authentication strategy to use.

No default
Enum, must be one of: "basic"
View examples
stringcommonrequired*

password

The basic authentication password.If using GrafanaLab's hosted Loki then this must be setto your instanceId.

Only required when: strategy = "basic"
No default
View examples
stringcommonrequired*

user

The basic authentication user name.If using GrafanaLab's hosted Loki then this must be setto your Grafana.com api key.

Only required when: strategy = "basic"
No default
View examples
tableoptional

batch

Configures the sink batching behavior.

int (bytes)commonoptional

max_size

The maximum size of a batch, in bytes, before it is flushed.

See Buffers & Batches for more info.

Default: 10490000 (bytes)
View examples
int (seconds)commonoptional

timeout_secs

The maximum age of a batch before it is flushed.

See Buffers & Batches for more info.

Default: 1 (seconds)
View examples
tableoptional

buffer

Configures the sink specific buffer behavior.

int (events)commonoptional

max_events

The maximum number of events allowed in the buffer.

Only relevant when: type = "memory"
Default: 500 (events)
View examples
int (bytes)required*

max_size

The maximum size of the buffer on the disk.

See Buffers & Batches for more info.

Only required when: type = "disk"
No default
View examples
stringenumcommonoptional

type

The buffer's type and storage mechanism.

Default: "memory"
Enum, must be one of: "memory" "disk"
View examples
stringenumoptional

when_full

The behavior when the buffer becomes full.

Default: "block"
Enum, must be one of: "block" "drop_newest"
View examples
tablecommonoptional

encoding

Configures the encoding specific sink behavior.

stringenumcommonoptional

codec

The encoding codec used to serialize the events before outputting.

Default: "json"
Enum, must be one of: "json" "text"
View examples
[string]optional

except_fields

Prevent the sink from encoding the specified labels.

No default
View examples
[string]optional

only_fields

Limit the sink to only encoding the specified labels.

No default
View examples
stringenumoptional

timestamp_format

How to format event timestamps.

Default: "rfc3339"
Enum, must be one of: "rfc3339" "unix"
View examples
stringcommonrequired

endpoint

The endpoint used to ship logs to.

No default
View examples
boolcommonoptional

healthcheck

Enables/disables the sink healthcheck upon start.

See Health Checks for more info.

Default: true
View examples
tablecommonrequired

labels

A set of labels that will be attached to each batch of events. These valuesare also templateable to allow events to provide dynamic label values.Note: If the set of label values has high cardinality this can cause drasticperformance issues with Loki. To ensure this does not happen one should tryto reduce the amount of unique label values.

templateablestringcommonrequired

[label-name

A key-value pair for labels.

No default
View examples
booloptional

remove_label_fields

If this is set to true then when labels are collected from events those fields will also get removed from the event.

No default
View examples
booloptional

remove_timestamp

If this is set to true then the timestamp will be removed from the event. This is useful because loki uses the timestamp to index the event.

Default: true
View examples
tableoptional

request

Configures the sink request behavior.

int (requests)commonoptional

in_flight_limit

The maximum number of in-flight requests allowed at any given time.

See Rate Limits for more info.

Default: 5 (requests)
View examples
int (seconds)commonoptional

rate_limit_duration_secs

The time window, in seconds, used for the rate_limit_num option.

See Rate Limits for more info.

Default: 1 (seconds)
View examples
intcommonoptional

rate_limit_num

The maximum number of requests allowed within the rate_limit_duration_secs time window.

See Rate Limits for more info.

Default: 5
View examples
intoptional

retry_attempts

The maximum number of retries to make for failed requests.

See Retry Policy for more info.

Default: -1
View examples
int (seconds)optional

retry_initial_backoff_secs

The amount of time to wait before attempting the first retry for a failed request. Once, the first retry has failed the fibonacci sequence will be used to select future backoffs.

Default: 1 (seconds)
View examples
int (seconds)optional

retry_max_duration_secs

The maximum amount of time, in seconds, to wait between retries.

Default: 10 (seconds)
View examples
int (seconds)commonoptional

timeout_secs

The maximum time a request can take before being aborted. It is highly recommended that you do not lower value below the service's internal timeout, as this could create orphaned requests, pile on retries, and result in duplicate data downstream.

See Buffers & Batches for more info.

Default: 60 (seconds)
View examples
stringoptional

tenant_id

The tenant id that will be sent with every request, by default this is not required since a proxy should set this header. When running loki locally a tenant id is not required either.

You can read more about tenant id's here

No default
View examples
tableoptional

tls

Configures the TLS options for connections from this sink.

stringoptional

ca_path

Absolute path to an additional CA certificate file, in DER or PEM format (X.509).

No default
View examples
stringcommonoptional

crt_path

Absolute path to a certificate file used to identify this connection, in DER or PEM format (X.509) or PKCS#12. If this is set and is not a PKCS#12 archive, key_path must also be set.

No default
View examples
stringoptional

key_pass

Pass phrase used to unlock the encrypted key file. This has no effect unless key_path is set.

No default
View examples
stringcommonoptional

key_path

Absolute path to a certificate key file used to identify this connection, in DER or PEM format (PKCS#8). If this is set, crt_path must also be set.

No default
View examples
booloptional

verify_certificate

If true (the default), Vector will validate the TLS certificate of the remote host. Do NOT set this to false unless you understand the risks of not verifying the remote certificate.

Default: true
View examples
booloptional

verify_hostname

If true (the default), Vector will validate the configured remote host name against the remote host's TLS certificate. Do NOT set this to false unless you understand the risks of not verifying the remote hostname.

Default: true
View examples

How It Works

Buffers & Batches

The loki sink buffers & batches data as shown in the diagram above. You'll notice that Vector treats these concepts differently, instead of treating them as global concepts, Vector treats them as sink specific concepts. This isolates sinks, ensuring services disruptions are contained and delivery guarantees are honored.

Batches are flushed when 1 of 2 conditions are met:

  1. The batch age meets or exceeds the configured timeout_secs.
  2. The batch size meets or exceeds the configured max_size.

Buffers are controlled via the buffer.* options.

Decentralized Deployments

Loki currently does not support out-of-order inserts. If Vector is deployed in a decentralized setup then there is the possiblity that logs might get rejected due to data races between Vector instances. To avoid this we suggest either assigning each Vector instance with a unique label or deploying a centralized Vector which will ensure no logs will get sent out-of-order.

Environment Variables

Environment variables are supported through all of Vector's configuration. Simply add ${MY_ENV_VAR} in your Vector configuration file and the variable will be replaced before being evaluated.

You can learn more in the Environment Variables section.

Event Ordering

The loki sink will ensure that all logs are sorted via their timestamp. This is to ensure that logs will be accepted by Loki. If no timestamp is supplied with events then the Loki sink will supply its own monotonically increasing timestamp.

Health Checks

Health checks ensure that the downstream service is accessible and ready to accept data. This check is performed upon sink initialization. If the health check fails an error will be logged and Vector will proceed to start.

Require Health Checks

If you'd like to exit immediately upon a health check failure, you can pass the --require-healthy flag:

vector --config /etc/vector/vector.toml --require-healthy

Disable Health Checks

If you'd like to disable health checks for this sink you can set the healthcheck option to false.

Rate Limits

Vector offers a few levers to control the rate and volume of requests to the downstream service. Start with the rate_limit_duration_secs and rate_limit_num options to ensure Vector does not exceed the specified number of requests in the specified window. You can further control the pace at which this window is saturated with the in_flight_limit option, which will guarantee no more than the specified number of requests are in-flight at any given time.

Please note, Vector's defaults are carefully chosen and it should be rare that you need to adjust these. If you found a good reason to do so please share it with the Vector team by opening an issie.

Retry Policy

Vector will retry failed requests (status == 429, >= 500, and != 501). Other responses will not be retried. You can control the number of retry attempts and backoff rate with the retry_attempts and retry_backoff_secs options.