Sample transform

Sample events from an event stream based on supplied criteria and at a configurable rate

Samples events at a configurable rate.

Configuration

Example configurations

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

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

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

{
  "transforms": {
    "my_transform_id": {
      "type": "sample",
      "inputs": [
        "my-source-or-transform-id"
      ],
      "group_by": "{{ service }}",
      "key_field": "message",
      "rate": 1500,
      "ratio": 0.13,
      "sample_rate_key": "sample_rate"
    }
  }
}

[transforms.my_transform_id]
type = "sample"
inputs = [ "my-source-or-transform-id" ]
group_by = "{{ service }}"
key_field = "message"
rate = 1_500
ratio = 0.13
sample_rate_key = "sample_rate"

transforms:
  my_transform_id:
    type: sample
    inputs:
      - my-source-or-transform-id
    group_by: "{{ service }}"
    key_field: message
    rate: 1500
    ratio: 0.13
    sample_rate_key: sample_rate

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"
}

group_by

optional string template

The value to group events into separate buckets to be sampled independently.

If left unspecified, or if the event doesn’t have group_by, then the event is not sampled separately.

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

Examples

"{{ service }}"

"{{ hostname }}-{{ service }}"

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-*"
]

key_field

optional string literal

The name of the field whose value is hashed to determine if the event should be sampled.

Each unique value for the key creates a bucket of related events to be sampled together and the rate is applied to the buckets themselves to sample 1/N buckets. The overall rate of sampling may differ from the configured one if values in the field are not uniformly distributed. If left unspecified, or if the event doesn’t have key_field, then the event is sampled independently.

This can be useful to, for example, ensure that all logs for a given transaction are sampled together, but that overall 1/N transactions are sampled.

Examples

"message"

rate

optional uint

The rate at which events are forwarded, expressed as 1/N.

For example, rate = 1500 means 1 out of every 1500 events are forwarded and the rest are dropped. This differs from ratio which allows more precise control over the number of events retained and values greater than 1/2. It is an error to provide a value for both rate and ratio.

Examples

ratio

optional float

The rate at which events are forwarded, expressed as a percentage

For example, ratio = .13 means that 13% out of all events on the stream are forwarded and the rest are dropped. This differs from rate allowing the configuration of a higher precision value and also the ability to retain values of greater than 50% of all events. It is an error to provide a value for both rate and ratio.

Examples

0.13

sample_rate_key

optional string literal

The event key in which the sample rate is stored. If set to an empty string, the sample rate will not be added to the event.

Examples

"sample_rate"

default: sample_rate

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.

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.

How it works

State

This component is stateless, meaning its behavior is consistent across each input.