Splunk HEC metrics

Deliver metric data to Splunk’s HTTP Event Collector

status: stable delivery: at-least-once acknowledgements: yes egress: batch state: stateless
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Configuration

Example configurations 

{
  "sinks": {
    "my_sink_id": {
      "type": "splunk_hec_metrics",
      "inputs": [
        "my-source-or-transform-id"
      ],
      "default_token": "${SPLUNK_HEC_TOKEN}",
      "endpoint": "https://http-inputs-hec.splunkcloud.com"
    }
  }
}
[sinks.my_sink_id]
type = "splunk_hec_metrics"
inputs = [ "my-source-or-transform-id" ]
default_token = "${SPLUNK_HEC_TOKEN}"
endpoint = "https://http-inputs-hec.splunkcloud.com"

sinks:
  my_sink_id:
    type: splunk_hec_metrics
    inputs:
      - my-source-or-transform-id
    default_token: ${SPLUNK_HEC_TOKEN}
    endpoint: https://http-inputs-hec.splunkcloud.com

{
  "sinks": {
    "my_sink_id": {
      "type": "splunk_hec_metrics",
      "inputs": [
        "my-source-or-transform-id"
      ],
      "compression": "none",
      "default_namespace": "service",
      "default_token": "${SPLUNK_HEC_TOKEN}",
      "endpoint": "https://http-inputs-hec.splunkcloud.com",
      "host_key": "host",
      "index": "{{ host }}",
      "source": "{{ file }}",
      "sourcetype": "{{ sourcetype }}"
    }
  }
}
[sinks.my_sink_id]
type = "splunk_hec_metrics"
inputs = [ "my-source-or-transform-id" ]
compression = "none"
default_namespace = "service"
default_token = "${SPLUNK_HEC_TOKEN}"
endpoint = "https://http-inputs-hec.splunkcloud.com"
host_key = "host"
index = "{{ host }}"
source = "{{ file }}"
sourcetype = "{{ sourcetype }}"

sinks:
  my_sink_id:
    type: splunk_hec_metrics
    inputs:
      - my-source-or-transform-id
    compression: none
    default_namespace: service
    default_token: ${SPLUNK_HEC_TOKEN}
    endpoint: https://http-inputs-hec.splunkcloud.com
    host_key: host
    index: "{{ host }}"
    source: "{{ file }}"
    sourcetype: "{{ sourcetype }}"

acknowledgements

optional object
Splunk HEC acknowledgement configuration.

acknowledgements.enabled

optional bool

Whether or not end-to-end acknowledgements are enabled.

When enabled for a sink, any source connected to that sink, where the source supports end-to-end acknowledgements as well, waits for events to be acknowledged by all connected sinks before acknowledging them at the source.

Enabling or disabling acknowledgements at the sink level takes precedence over any global acknowledgements configuration.

acknowledgements.indexer_acknowledgements_enabled

optional bool
Controls if the sink integrates with Splunk HEC indexer acknowledgements for end-to-end acknowledgements.
default: true

acknowledgements.max_pending_acks

optional uint

The maximum number of pending acknowledgements from events sent to the Splunk HEC collector.

Once reached, the sink begins applying backpressure.

default: 1e+06

acknowledgements.query_interval

optional uint
The amount of time to wait between queries to the Splunk HEC indexer acknowledgement endpoint.
default: 10 (seconds)

acknowledgements.retry_limit

optional uint
The maximum number of times an acknowledgement ID is queried for its status.
default: 30

batch

optional object
Event batching behavior.

batch.max_bytes

optional uint

The maximum size of a batch that is processed by a sink.

This is based on the uncompressed size of the batched events, before they are serialized/compressed.

default: 1e+06 (bytes)

batch.max_events

optional uint
The maximum size of a batch before it is flushed.

batch.timeout_secs

optional float
The maximum age of a batch before it is flushed.
default: 1 (seconds)

buffer

optional object

Configures the buffering behavior for this sink.

More information about the individual buffer types, and buffer behavior, can be found in the Buffering Model section.

buffer.max_events

optional uint
The maximum number of events allowed in the buffer.
Relevant when: type = "memory"
default: 500

buffer.max_size

required uint

The maximum size of the buffer on disk.

Must be at least ~256 megabytes (268435488 bytes).

Relevant when: type = "disk"

buffer.type

optional string literal enum
The type of buffer to use.
Enum options
OptionDescription
disk

Events are buffered on disk.

This is less performant, but more durable. Data that has been synchronized to disk will not be lost if Vector is restarted forcefully or crashes.

Data is synchronized to disk every 500ms.

memory

Events are buffered in memory.

This is more performant, but less durable. Data will be lost if Vector is restarted forcefully or crashes.

default: memory

buffer.when_full

optional string literal enum
Event handling behavior when a buffer is full.
Enum options
OptionDescription
block

Wait for free space in the buffer.

This applies backpressure up the topology, signalling that sources should slow down the acceptance/consumption of events. This means that while no data is lost, data will pile up at the edge.

drop_newest

Drops the event instead of waiting for free space in buffer.

The event will be intentionally dropped. This mode is typically used when performance is the highest priority, and it is preferable to temporarily lose events rather than cause a slowdown in the acceptance/consumption of events.

default: block

compression

optional string literal enum

Compression configuration.

All compression algorithms use the default compression level unless otherwise specified.

Enum options string literal
OptionDescription
gzipGzip compression.
noneNo compression.
snappySnappy compression.
zlibZlib compression.
zstdZstandard compression.
default: none

default_namespace

optional string literal

Sets the default namespace for any metrics sent.

This namespace is only used if a metric has no existing namespace. When a namespace is present, it is used as a prefix to the metric name, and separated with a period (.).

Examples 
"service"

default_token

required string literal

Default Splunk HEC token.

If an event has a token set in its metadata, it prevails over the one set here.

Examples 
"${SPLUNK_HEC_TOKEN}"
"A94A8FE5CCB19BA61C4C08"

endpoint

required string literal

The base URL of the Splunk instance.

The scheme (http or https) must be specified. No path should be included since the paths defined by the Splunk API are used.

Examples 
"https://http-inputs-hec.splunkcloud.com"
"https://hec.splunk.com:8088"
"http://example.com"

healthcheck

optional object
Healthcheck configuration.

healthcheck.enabled

optional bool
Whether or not to check the health of the sink when Vector starts up.
default: true

host_key

optional string literal

Overrides the name of the log field used to retrieve the hostname to send to Splunk HEC.

By default, the global log_schema.host_key option is used.

default: host

index

optional string template

The name of the index where to send the events to.

If not specified, the default index defined within Splunk is used.

Note: This parameter supports Vector's template syntax, which enables you to use dynamic per-event values.
Examples 
"{{ host }}"
"custom_index"

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-*"
]

proxy

optional object

Proxy configuration.

Configure to proxy traffic through an HTTP(S) proxy when making external requests.

Similar to common proxy configuration convention, you can set different proxies to use based on the type of traffic being proxied. You can also set specific hosts that should not be proxied.

proxy.enabled

optional bool
Enables proxying support.
default: true

proxy.http

optional string literal

Proxy endpoint to use when proxying HTTP traffic.

Must be a valid URI string.

Examples 
"http://foo.bar:3128"

proxy.https

optional string literal

Proxy endpoint to use when proxying HTTPS traffic.

Must be a valid URI string.

Examples 
"http://foo.bar:3128"

proxy.no_proxy

optional [string]

A list of hosts to avoid proxying.

Multiple patterns are allowed:

PatternExample match
Domain namesexample.com matches requests to example.com
Wildcard domains.example.com matches requests to example.com and its subdomains
IP addresses127.0.0.1 matches requests to 127.0.0.1
CIDR blocks192.168.0.0/16 matches requests to any IP addresses in this range
Splat* matches all hosts

request

optional object

Middleware settings for outbound requests.

Various settings can be configured, such as concurrency and rate limits, timeouts, retry behavior, etc.

Note that the retry backoff policy follows the Fibonacci sequence.

request.adaptive_concurrency

optional object

Configuration of adaptive concurrency parameters.

These parameters typically do not require changes from the default, and incorrect values can lead to meta-stable or unstable performance and sink behavior. Proceed with caution.

request.adaptive_concurrency.decrease_ratio
optional float

The fraction of the current value to set the new concurrency limit when decreasing the limit.

Valid values are greater than 0 and less than 1. Smaller values cause the algorithm to scale back rapidly when latency increases.

Note that the new limit is rounded down after applying this ratio.

default: 0.9
request.adaptive_concurrency.ewma_alpha
optional float

The weighting of new measurements compared to older measurements.

Valid values are greater than 0 and less than 1.

ARC uses an exponentially weighted moving average (EWMA) of past RTT measurements as a reference to compare with the current RTT. Smaller values cause this reference to adjust more slowly, which may be useful if a service has unusually high response variability.

default: 0.4
request.adaptive_concurrency.initial_concurrency
optional uint

The initial concurrency limit to use. If not specified, the initial limit will be 1 (no concurrency).

It is recommended to set this value to your service’s average limit if you’re seeing that it takes a long time to ramp up adaptive concurrency after a restart. You can find this value by looking at the adaptive_concurrency_limit metric.

default: 1
request.adaptive_concurrency.max_concurrency_limit
optional uint

The maximum concurrency limit.

The adaptive request concurrency limit will not go above this bound. This is put in place as a safeguard.

default: 200
request.adaptive_concurrency.rtt_deviation_scale
optional float

Scale of RTT deviations which are not considered anomalous.

Valid values are greater than or equal to 0, and we expect reasonable values to range from 1.0 to 3.0.

When calculating the past RTT average, we also compute a secondary “deviation” value that indicates how variable those values are. We use that deviation when comparing the past RTT average to the current measurements, so we can ignore increases in RTT that are within an expected range. This factor is used to scale up the deviation to an appropriate range. Larger values cause the algorithm to ignore larger increases in the RTT.

default: 2.5

request.concurrency

optional string literal enum uint

Configuration for outbound request concurrency.

This can be set either to one of the below enum values or to a positive integer, which denotes a fixed concurrency limit.

Enum options
OptionDescription
adaptiveConcurrency will be managed by Vector’s Adaptive Request Concurrency feature.
none

A fixed concurrency of 1.

Only one request can be outstanding at any given time.

default: adaptive

request.rate_limit_duration_secs

optional uint
The time window used for the rate_limit_num option.
default: 1 (seconds)

request.rate_limit_num

optional uint
The maximum number of requests allowed within the rate_limit_duration_secs time window.
default: 9.223372036854776e+18 (requests)

request.retry_attempts

optional uint
The maximum number of retries to make for failed requests.
default: 9.223372036854776e+18 (retries)

request.retry_initial_backoff_secs

optional uint

The amount of time to wait before attempting the first retry for a failed request.

After the first retry has failed, the fibonacci sequence is used to select future backoffs.

default: 1 (seconds)

request.retry_jitter_mode

optional string literal enum
The jitter mode to use for retry backoff behavior.
Enum options
OptionDescription
Full

Full jitter.

The random delay is anywhere from 0 up to the maximum current delay calculated by the backoff strategy.

Incorporating full jitter into your backoff strategy can greatly reduce the likelihood of creating accidental denial of service (DoS) conditions against your own systems when many clients are recovering from a failure state.

NoneNo jitter.
default: Full

request.retry_max_duration_secs

optional uint
The maximum amount of time to wait between retries.
default: 30 (seconds)

request.timeout_secs

optional uint

The time a request can take before being aborted.

Datadog highly recommends that you do not lower this value below the service’s internal timeout, as this could create orphaned requests, pile on retries, and result in duplicate data downstream.

default: 60 (seconds)

source

optional string template

The source of events sent to this sink.

This is typically the filename the logs originated from.

If unset, the Splunk collector sets it.

Note: This parameter supports Vector's template syntax, which enables you to use dynamic per-event values.
Examples 
"{{ file }}"
"/var/log/syslog"
"UDP:514"

sourcetype

optional string template

The sourcetype of events sent to this sink.

If unset, Splunk defaults to httpevent.

Note: This parameter supports Vector's template syntax, which enables you to use dynamic per-event values.
Examples 
"{{ sourcetype }}"
"_json"

tls

optional object
TLS configuration.

tls.alpn_protocols

optional [string]

Sets the list of supported ALPN protocols.

Declare the supported ALPN protocols, which are used during negotiation with peer. They are prioritized in the order that they are defined.

tls.ca_file

optional string literal

Absolute path to an additional CA certificate file.

The certificate must be in the DER or PEM (X.509) format. Additionally, the certificate can be provided as an inline string in PEM format.

Examples 
"/path/to/certificate_authority.crt"

tls.crt_file

optional string literal

Absolute path to a certificate file used to identify this server.

The certificate must be in DER, PEM (X.509), or PKCS#12 format. Additionally, the certificate can be provided as an inline string in PEM format.

If this is set, and is not a PKCS#12 archive, key_file must also be set.

Examples 
"/path/to/host_certificate.crt"

tls.key_file

optional string literal

Absolute path to a private key file used to identify this server.

The key must be in DER or PEM (PKCS#8) format. Additionally, the key can be provided as an inline string in PEM format.

Examples 
"/path/to/host_certificate.key"

tls.key_pass

optional string literal

Passphrase used to unlock the encrypted key file.

This has no effect unless key_file is set.

Examples 
"${KEY_PASS_ENV_VAR}"
"PassWord1"

tls.server_name

optional string literal

Server name to use when using Server Name Indication (SNI).

Only relevant for outgoing connections.

Examples 
"www.example.com"

tls.verify_certificate

optional bool

Enables certificate verification. For components that create a server, this requires that the client connections have a valid client certificate. For components that initiate requests, this validates that the upstream has a valid certificate.

If enabled, certificates must not be expired and must be issued by a trusted issuer. This verification operates in a hierarchical manner, checking that the leaf certificate (the certificate presented by the client/server) is not only valid, but that the issuer of that certificate is also valid, and so on until the verification process reaches a root certificate.

Do NOT set this to false unless you understand the risks of not verifying the validity of certificates.

tls.verify_hostname

optional bool

Enables hostname verification.

If enabled, the hostname used to connect to the remote host must be present in the TLS certificate presented by the remote host, either as the Common Name or as an entry in the Subject Alternative Name extension.

Only relevant for outgoing connections.

Do NOT set this to false unless you understand the risks of not verifying the remote hostname.

Telemetry

Metrics

link

buffer_byte_size

gauge
The number of bytes current in the buffer.
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.

buffer_discarded_events_total

counter
The number of events dropped by this non-blocking buffer.
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.

buffer_events

gauge
The number of events currently in the buffer.
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.

buffer_received_event_bytes_total

counter
The number of bytes received by this buffer.
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.

buffer_received_events_total

counter
The number of events received by this buffer.
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.

buffer_sent_event_bytes_total

counter
The number of bytes sent by this buffer.
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.

buffer_sent_events_total

counter
The number of events sent by this buffer.
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.

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_bytes_total

counter
The number of raw bytes sent by this component to destination sinks.
component_id
The Vector component ID.
component_kind
The Vector component kind.
component_type
The Vector component type.
endpoint optional
The endpoint to which the bytes were sent. For HTTP, this will be the host and path only, excluding the query string.
file optional
The absolute path of the destination file.
host optional
The hostname of the system Vector is running on.
pid optional
The process ID of the Vector instance.
protocol
The protocol used to send the bytes.
region optional
The AWS region name to which the bytes were sent. In some configurations, this may be a literal hostname.

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.

http_client_response_rtt_seconds

histogram
The round-trip time (RTT) of HTTP requests, tagged with the response code.
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.
status optional
The HTTP status code of the request.

http_client_responses_total

counter
The total number of HTTP requests, tagged with the response code.
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.
status optional
The HTTP status code of the request.

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

Buffers and batches

This component 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_bytes or max_events.

Buffers are controlled via the buffer.* options.

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.yaml --require-healthy

Disable health checks

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

Indexer Acknowledgements

To provide more accurate end-to-end acknowledgements, this sink will automatically integrate (unless explicitly disabled) with Splunk HEC indexer acknowledgements if the provided Splunk HEC token has the feature enabled. In other words, if ackID’s are present in Splunk HEC responses, this sink will store and query for the status of said ackID’s to confirm that data has been successfully delivered. Upstream sources with the Vector end-to-end acknowledgements feature enabled will wait for this sink to confirm delivery of events before acknowledging receipt.

The Splunk channel required for indexer acknowledgements is created using a randomly generated UUID. By default, this sink uses the recommended Splunk indexer acknowledgements client behavior: querying for ack statuses every 10 seconds for a maximum of 30 attempts (5 minutes) per ackID.

Multivalue Tags

If Splunk receives a tag with multiple values it will only take the last value specified, so Vector only sends this last value.

Rate limits & adaptive concurrency

Adaptive Request Concurrency (ARC)

Adaptive Request Concurrency is a feature of Vector that does away with static concurrency limits and automatically optimizes HTTP concurrency based on downstream service responses. The underlying mechanism is a feedback loop inspired by TCP congestion control algorithms. Checkout the announcement blog post,

We highly recommend enabling this feature as it improves performance and reliability of Vector and the systems it communicates with. As such, we have made it the default, and no further configuration is required.

Static concurrency

If Adaptive Request Concurrency is not for you, you can manually set static concurrency limits by specifying an integer for request.concurrency:

sinks:
	my-sink:
		request:
			concurrency: 10

Rate limits

In addition to limiting request concurrency, you can also limit the overall request throughput via the request.rate_limit_duration_secs and request.rate_limit_num options.

sinks:
	my-sink:
		request:
			rate_limit_duration_secs: 1
			rate_limit_num: 10

These will apply to both adaptive and fixed request.concurrency values.

Retry policy

Vector will retry failed requests (status in [408, 429], >= 500, and != 501). Other responses will not be retried. You can control the number of retry attempts and backoff rate with the request.retry_attempts and request.retry_backoff_secs options.

Splunk HEC Channel Header

Splunk HEC requests will include the X-Splunk-Request-Channel header with a randomly generated UUID as the channel value. Splunk requires a channel value when using indexer acknowledgements, but also accepts channel values when indexer acknowledgements is disabled. Thus, this channel value is included regardless of indexer acknowledgement settings.

State

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

Transport Layer Security (TLS)

Vector uses OpenSSL for TLS protocols due to OpenSSL’s maturity. You can enable and adjust TLS behavior via the tls.* options and/or via an OpenSSL configuration file. The file location defaults to /usr/local/ssl/openssl.cnf or can be specified with the OPENSSL_CONF environment variable.
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