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Specify how tremor connects to the outside world in order to publish to external systems.

For example, the Elastic offramp pushes data to ElasticSearch via its bulk upload REST/HTTP API endpoint.

All offramps are specified of the form:

  - id: <unique offramp id>
    type: <offramp name>
    codec: <codec of the data>
    postprocessors: # can be omitted
      - <postprocessor 1>
      - <postprocessor 2>
      - ...
    preprocessors: # only for linked transport, can be omitted
      - <preprocessor 1>
      - <preprocessor 2>
      - ...
    linked: <true or false> # enable linked transport, default: false
      "<mime-type>": "<codec handling the given mime-type>"
      <key>: <value>

Delivery Properties

Each offramp is able to report events as being definitely sent off or as failed. It can also report itself as not functional anymore to the connected pipelines. How each offramp implements those abilities is described in the table below.

The column Delivery acknowledgements describes under what circumstanced the offramp considers an event delivered and acknowledges it to the connected pipelines and operators, onramps etc. therein. Acknowledgements, Failures or missing Acknowledgements take effect e.g. when using the operators or onramps that support those mechanisms (e.g. the WAL operator or the kafka onramp).

The column Disconnect events describes under which circumstances this offramp is not considered functional anymore.

Offramp Disconnect events Delivery acknowledgements
kafka see librdkafka see librdkafka
elastic connection loss on 200 replies
rest connection loss on non 4xx/5xx replies
ws connection loss on send
udp local socket loss on send
tcp connection loss on send
Postgres never always
file never always
blackhole never always
debug never always
exit never always
stdout never always
sderr never always

System Offramps

Each tremor runtime comes with some pre-configured offramps that can be used.


The offramp /offramp/system::stdout/system can be used to print to STDOUT. Data will be formatted as JSON.


The offramp /offramp/system::stderr/system can be used to print to STDERR. Data will be formatted as JSON.

Supported Offramps


The elastic offramp writes to one or more ElasticSearch hosts. This is currently tested with ES v6.

Supported configuration options are:

  • endpoints - A list of elastic search endpoints to send to.
  • concurrency - Maximum number of parallel requests (default: 4).

Used metadata variables:

  • index - The index to write to (required).
  • doc_type - The document type for elastic (required).
  • pipeline - The elastic search pipeline to use (optional).


  - id: es
    type: elastic
        - http://elastic:9200


The Kafka offramp connects sends events to Kafka topics. It uses librdkafka to handle connections and can use the full set of librdkaka 1.5.0 configuration options.

The default codec is json.

Supported configuration options are:

  • topic - The topic to send to.
  • brokers - Broker servers to connect to. (Kafka nodes)
  • hostname - Hostname to identify the client with. (default: the systems hostname)
  • key - Key to use for messages (default: none)
  • rdkafka_options - An optional map of option to value, where both sides need to be strings.

Used metadata variables:

  • $kafka_key - same as config key (optional. overrides related config param when present)


  - id: kafka-out
    type: kafka
        - kafka:9092
      topic: demo


Sends events over a WebSocket connection. Each event is a WebSocket message.

The default codec is json.

Supported configuration options are:

  • url - WebSocket endpoint to send data to.
  • binary - If data should be send as binary instead of text (default: false).

Used metadata variables:

  • $url - same as config url (optional. overrides related config param when present)
  • $binary - same as config binary (optional. overrides related config param when present)

Set metadata variables (for reply with linked transports):

  • $binary - true if the websocket message reply came as binary (false otherwise)

When used as a linked offramp, batched events are rejected by the offramp.


  - id: ws
    type: ws
      url: "ws://localhost:1234"


The UDP offramp sends data to a given host and port as UDP datagram.

The default codec is json.

When the UDP onramp gets a batch of messages it will send each element of the batch as an own UDP datagram.

Supported configuration options are:

  • host - the local host to send data from
  • port - the local port to send data from
  • dst_host - the destination host to send data to
  • dst_port - the destination port to send data to.


  - id: udp-out
    type: udp
      host: ""
      port: 1234
      dst_host: ""
      dst_port: 2345


The rest offramp is used to send events to the specified endpoint.

Supported configuration options are:

  • endpoint - Endpoint URL. Can be provided as string or as struct. The struct form is composed of the following standard URL fields:
    • scheme - String, required, typically http
    • username - String, optional
    • password - String, optional
    • host - String, required, hostname or ip address
    • port - Number, optional, defaults to 80
    • path - String, optional, defaults to /
    • query - String, optional
    • fragment - String, optional
  • method - HTTP method to use (default: POST)
  • headers - A map of headers to set for the requests, where both sides are strings
  • concurrency - Number of parallel in-flight requests (default: 4)

Used metadata variables:

Setting these metadata variables here allows users to dynamically change the behaviour of the rest offramp:

  • $endpoint - same format as config endpoint (optional. overrides related config param when present)
  • $request - A record capturing the HTTP request attributes. Available fields within:
    • method - same as config method (optional. overrides related config param when present)
    • headers - A map from header name (string) to header value (string or array of strings)(optional. overrides related config param when present)

These variables are aligned with the similar variables generated by the rest onramp. Note that $request.url is not utilized here -- instead the same can be configured by setting $endpoint (since enabling the former here can lead to request loops when events sourced from rest onramp are fed to the rest offramp, without overriding it from the pipeline. also, $endpoint can be separately configured as a URL string, which is convenient for simple offramp use).

The rest offramp encodes the event as request body using the Content-Type header if present, using the customizable builtin codec_map to determine a matching coded. It falls back to use the configured codec if no Content-Type header is available.

When used as Linked Transport the same handling is applied to the incoming HTTP response, giving precedence to the Content-Type header and only falling back to the configured codec.

Set metadata variables:

These metadata variables are used for HTTP response events emitted through the OUT port:

  • $response - A record capturing the HTTP response attributes. Available fields within:
    • status - Numeric HTTP status code
    • headers - A record that maps header name (lowercase string) to value (array of strings)

When used as a linked offramp, batched events are rejected by the offramp.

Example 1:

  - id: rest-offramp
    type: rest
    codec: json
      - gzip
    linked: true
        port: 80
        path: /anything
        query: "q=search"
        "Accept": "application/json"
        "Transfer-Encoding": "gzip"

Example 2:

  - id: rest-offramp-2
    type: rest
    codec: json
      "text/html": "string"
      "application/vnd.stuff": "string"
      endpoint: ""
      method: PATCH

rest offramp example for InfluxDB

The structure is given for context.

  - id: influxdb
    type: rest
    codec: influx
      - lines
      endpoint: http://influx/write?db=metrics
        "Client": "Tremor"


PostgreSQL offramp.

Supported configuration options are:

  • host - PostgreSQL database hostname
  • port - PostgresSQL database port
  • user - Username for authentication
  • password - Password for authentication
  • dbname - Database name
  • table - Database table name

Data that comes in will be used to run an INSERT statement. It is required that data comes in objects representing columns. The object key must represent field name in the database and must contain following fields:

  • fieldType - a PostgreSQL field type (e.g. VARCHAR, INT4, TIMESTAMPTZ, etc.)
  • name - field name as represented by database table schema
  • value - the value of the field


id: db
type: postgres
codec: json
  host: localhost
  port: 5432
  user: postgres
  password: example
  dbname: sales
  table: transactions


The file offramp writes events to a file, one event per line. The file is overwritten if it exists.

The default codec is json.

Supported configuration options are:

  • file - The file to write to.


  - id: in
    type: file
      file: /my/path/to/a/file.json


The standard out offramp prints each event to the stdout output.

This operator does not support configuration.


  - id: console
    type: stdout


The blackhole offramp is used for benchmarking it takes measurements of the end to end times of each event traversing the pipeline and at the end prints an HDR ( High Dynamic Range ) histogram.

Supported configuration options are:

  • warmup_secs - Number of seconds after startup in which latency won't be measured to allow for a warmup delay.
  • stop_after_secs - Stop tremor after a given number of seconds and print the histogram.
  • significant_figures - Significant figures for the HDR histogram. (the first digits of each measurement that are kept as precise values)


  - id: bh
    type: blackhole
      warmup_secs: 10
      stop_after_secs: 40


The debug offramp is used to get an overview of how many events are put in wich classification.

This operator does not support configuration.

Used metadata variables:

  • $class - Class of the event to count by. (optional)


  - id: dbg
    type: debug


This connects on a specified port for distributing outbound TCP data.

The offramp can leverage postprocessors to frame data after codecs are applied and events are forwarded to external TCP protocol distribution endpoints.

The default codec is json.

Supported configuration options are:

  • host - The host to advertise as
  • port - The TCP port to listen on
  • is_non_blocking - Is the socket configured as non-blocking ( default: false )
  • ttl - Set the socket's time-to-live ( default: 64 )
  • is_no_delay - Set the socket's nagle ( delay ) algorithm to off ( default: true )


  - id: tcp
    type: tcp
    codec: json
      - gzip
      - base64
      - lines
      host: "localhost"
      port: 9000


The exit offramp terminates the runtime with a system exit status.

The offramp accepts events via its standard input port and responds to events with a record structure containing a numeric exit field.

To indicate successful termination, an exit status of zero may be used:

{ "exit": 0 }

To indicate non-succesful termination, a non-zero exit status may be used:

{ "exit": 1 }

Exit codes should follow standard UNIX/Linux guidelines when being integrated with bash or other shell-based environments, as follows:

Code Meaning
0 Success
1 General errors
2 Misuse of builtins
126 Command invoked cannot run due to credentials/auth constraints
127 Command not understood, not well-formed or illegal

To delay the exit (to allow flushing of other offramps) the delay key can be used to delay the exit by a number of milliseconds:

  "exit": 1,
  "delay": 1000


  - id: terminate
    type: exit


Send events to New Relic platform, using it's log apis (variable by region).

The default codec is json.

Supported configuration options are:

  • license_key - New Relic's license (or insert only) key
  • compress_logs - Whther logs should be compressed before sending to New Relic (avoids extra egress costs but at the cost of more cpu usage by tremor) (default: false)
  • region - Region to use to send logs. Available choices: usa, europe (default: usa)


  - id: newrelic
    type: newrelic
      license_key: keystring
      compress_logs: true
      region: europe