Throttle transform

Rate limit logs passing through a topology

Rate limits one or more log streams to limit load on downstream services, or to enforce usage quotas on users.

Configuration

Example configurations

{
  "transforms": {
    "my_transform_id": {
      "type": "throttle",
      "inputs": [
        "my-source-or-transform-id"
      ]
    }
  }
}

[transforms.my_transform_id]
type = "throttle"
inputs = [ "my-source-or-transform-id" ]

transforms:
  my_transform_id:
    type: throttle
    inputs:
      - my-source-or-transform-id

{
  "transforms": {
    "my_transform_id": {
      "type": "throttle",
      "inputs": [
        "my-source-or-transform-id"
      ],
      "key_field": "{{ message }}"
    }
  }
}

[transforms.my_transform_id]
type = "throttle"
inputs = [ "my-source-or-transform-id" ]
key_field = "{{ message }}"

transforms:
  my_transform_id:
    type: throttle
    inputs:
      - my-source-or-transform-id
    key_field: "{{ message }}"

exclude

optional condition

A logical condition used to exclude events from sampling.

exclude.source

The text of the condition. The syntax of the condition depends on the value of type.

exclude.type

The type of condition to supply. See Available syntaxes below for a list of available types for this transform.

Available syntaxes

Syntax	Description	Example
`vrl`	A Vector Remap Language (VRL) Boolean expression.	`.status_code != 200 && !includes(["info", "debug"], .severity)`
`datadog_search`	A Datadog Search query string.	`*stack`
`is_log`	Whether the incoming event is a log.
`is_metric`	Whether the incoming event is a metric.
`is_trace`	Whether the incoming event is a trace.

Shorthand for VRL

If you opt for the vrl syntax for this condition, you can set the condition as a string via the condition parameter, without needing to specify both a source and a type. The table below shows some examples:

Config format	Example
YAML	`condition: .status == 200`
TOML	`condition = ".status == 200"`
JSON	`"condition": ".status == 200"`

Condition config examples

Standard VRL

exclude:
  type: "vrl"
  source: ".status == 500"

exclude = { type = "vrl", source = ".status == 500" }

"exclude": {
  "type": "vrl",
  "source": ".status == 500"
}

Datadog Search

exclude:
  type: "datadog_search"
  source: "*stack"

exclude = { type = "datadog_search", source = "*stack" }

"exclude": {
  "type": "datadog_search",
  "source": "*stack"
}

VRL shorthand

exclude: ".status == 500"

exclude = ".status == 500"

"exclude": ".status == 500"

graph

optional object

Extra graph configuration

Configure output for component when generated with graph command

graph.node_attributes

optional object

Node attributes to add to this component’s node in resulting graph

They are added to the node as provided

graph.node_attributes.*

required string literal

A single graph node attribute in graphviz DOT language.

Examples

{
  "color": "red",
  "name": "Example Node",
  "width": "5.0"
}

inputs

required [string]

A list of upstream source or transform IDs.

Wildcards (*) are supported.

See configuration for more info.

Array string literal

Examples

[
  "my-source-or-transform-id",
  "prefix-*"
]

internal_metrics

optional object

Configuration of internal metrics for the Throttle transform.

internal_metrics.emit_events_discarded_per_key

optional bool

Whether or not to emit the events_discarded_total internal metric with the key tag.

If true, the counter will be incremented for each discarded event, including the key value associated with the discarded event. If false, the counter will not be emitted. Instead, the number of discarded events can be seen through the component_discarded_events_total internal metric.

Note that this defaults to false because the key tag has potentially unbounded cardinality. Only set this to true if you know that the number of unique keys is bounded.

default: false

key_field

optional string template

The value to group events into separate buckets to be rate limited independently.

If left unspecified, or if the event doesn’t have key_field, then the event is not rate limited separately.

Note: This parameter supports Vector's template syntax, which enables you to use dynamic per-event values.

Examples

"{{ message }}"

"{{ hostname }}"

threshold

required uint

The number of events allowed for a given bucket per configured window_secs.

Each unique key has its own threshold.

window_secs

required float

The time window in which the configured threshold is applied, in seconds.

Outputs

<component_id>

Default output stream of the component. Use this component’s ID as an input to downstream transforms and sinks.

Telemetry

Metrics

link

component_discarded_events_total

counter

The number of events dropped by this component.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

host optional

The hostname of the system Vector is running on.

intentional

True if the events were discarded intentionally, like a filter transform, or false if due to an error.

pid optional

The process ID of the Vector instance.

component_errors_total

counter

The total number of errors encountered by this component.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

error_type

The type of the error

host optional

The hostname of the system Vector is running on.

pid optional

The process ID of the Vector instance.

stage

The stage within the component at which the error occurred.

component_received_event_bytes_total

counter

The number of event bytes accepted by this component either from tagged origins like file and uri, or cumulatively from other origins.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

container_name optional

The name of the container from which the data originated.

file optional

The file from which the data originated.

host optional

The hostname of the system Vector is running on.

mode optional

The connection mode used by the component.

peer_addr optional

The IP from which the data originated.

peer_path optional

The pathname from which the data originated.

pid optional

The process ID of the Vector instance.

pod_name optional

The name of the pod from which the data originated.

uri optional

The sanitized URI from which the data originated.

component_received_events_count

histogram

A histogram of the number of events passed in each internal batch in Vector’s internal topology.

Note that this is separate than sink-level batching. It is mostly useful for low level debugging performance issues in Vector due to small internal batches.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

container_name optional

The name of the container from which the data originated.

file optional

The file from which the data originated.

host optional

The hostname of the system Vector is running on.

mode optional

The connection mode used by the component.

peer_addr optional

The IP from which the data originated.

peer_path optional

The pathname from which the data originated.

pid optional

The process ID of the Vector instance.

pod_name optional

The name of the pod from which the data originated.

uri optional

The sanitized URI from which the data originated.

component_received_events_total

counter

The number of events accepted by this component either from tagged origins like file and uri, or cumulatively from other origins.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

container_name optional

The name of the container from which the data originated.

file optional

The file from which the data originated.

host optional

The hostname of the system Vector is running on.

mode optional

The connection mode used by the component.

peer_addr optional

The IP from which the data originated.

peer_path optional

The pathname from which the data originated.

pid optional

The process ID of the Vector instance.

pod_name optional

The name of the pod from which the data originated.

uri optional

The sanitized URI from which the data originated.

component_sent_event_bytes_total

counter

The total number of event bytes emitted by this component.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

host optional

The hostname of the system Vector is running on.

output optional

The specific output of the component.

pid optional

The process ID of the Vector instance.

component_sent_events_total

counter

The total number of events emitted by this component.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

host optional

The hostname of the system Vector is running on.

output optional

The specific output of the component.

pid optional

The process ID of the Vector instance.

events_discarded_total

counter

The total number of events discarded by this component.

host optional

The hostname of the system Vector is running on.

pid optional

The process ID of the Vector instance.

reason

The type of the error

utilization

gauge

A ratio from 0 to 1 of the load on a component. A value of 0 would indicate a completely idle component that is simply waiting for input. A value of 1 would indicate a that is never idle. This value is updated every 5 seconds.

component_id

The Vector component ID.

component_kind

The Vector component kind.

component_type

The Vector component type.

host optional

The hostname of the system Vector is running on.

pid optional

The process ID of the Vector instance.

Examples

Rate limiting

Given this event...

[{"log":{"host":"host-1.hostname.com","message":"First message","timestamp":"2020-10-07T12:33:21.223543Z"}},{"log":{"host":"host-1.hostname.com","message":"Second message","timestamp":"2020-10-07T12:33:21.223543Z"}}]

...and this configuration...

transforms:
  my_transform_id:
    type: throttle
    inputs:
      - my-source-or-transform-id
    threshold: 1
    window_secs: 60

[transforms.my_transform_id]
type = "throttle"
inputs = [ "my-source-or-transform-id" ]
threshold = 1
window_secs = 60

{
  "transforms": {
    "my_transform_id": {
      "type": "throttle",
      "inputs": [
        "my-source-or-transform-id"
      ],
      "threshold": 1,
      "window_secs": 60
    }
  }
}

...this Vector event is produced:

[{"log":{"host":"host-1.hostname.com","message":"First message","timestamp":"2020-10-07T12:33:21.223543Z"}}]

How it works

Rate Limiting

The throttle transform will spread load across the configured window_secs, ensuring that each bucket’s throughput averages out to the threshold per window_secs. It utilizes a Generic Cell Rate Algorithm to rate limit the event stream.

Buckets

The throttle transform buckets events into rate limiters based on the provided key_field, or a single bucket if not provided. Each bucket is rate limited separately.

Quotas

Rate limiters use “cells” to determine if there is sufficient capacity for an event to successfully pass through a rate limiter. Each event passing through the transform consumes an available cell, if there is no available cell the event will be rate limited.

A rate limiter is created with a maximum number of cells equal to the threshold, and cells replenish at a rate of window_secs divided by threshold. For example, a window_secs of 60 with a threshold of 10 replenishes a cell every 6 seconds and allows a burst of up to 10 events.

Rate Limited Events

The rate limiter will allow up to threshold number of events through and drop any further events for that particular bucket when the rate limiter is at capacity. Any event passed when the rate limiter is at capacity will be discarded and tracked by an events_discarded_total metric tagged by the bucket’s key.

State

This component is stateful, meaning its behavior changes based on previous inputs (events). State is not preserved across restarts, therefore state-dependent behavior will reset between restarts and depend on the inputs (events) received since the most recent restart.