origin

The origin module contains functions for retrieving relevant origin metadata about events (eg: host sending the event).

The metadata is generated by onramps and is passed down to the tremor pipeline as a URI. Internally, the URI is composed of these basic fields:

• scheme

• host

• port

• path

  The URI format was chosen so that onramps can expose origin information in a structured manner, without sacrificing the ability to encode information that can vary from onramp to onramp.

  Since the kind and amount of origin information varies based on onramp (especially for the path field), the specifics of what each onramp exposes is documented in the onramps page.

Functions

as_uri_string()

Returns the full origin URI as a string, or null value if URI is not set. The string is of the following standard form (with port as optional):

<scheme>://<host>[:<port>]/<path>

For example, with udp onramp receiving events on port 12202 from the same host as tremor:

use tremor::system::origin;
origin::as_uri_string() # returns "tremor-udp://127.0.0.1:41371/12202",
                       # where 41371 is the ephemeral port on the sending
                       # side

port()

Returns the origin URI port, or null value if not set (either the whole URI or just the port). Encodes the source port on the host that sent the event.

For example, with udp onramp:

use tremor::system::origin;
origin::port() # returns an ephemeral port on the sender host (eg: 41371)

Returns integer or null

host()

Returns the origin URI host, or null value if URI is not set. Encodes the source host (usually IP) that sent the event.

For example, with udp onramp and for a test event sent from the same host as tremor:

use tremor::system::origin;
origin::host() # returns "127.0.0.1"

Returns string or null

path()

Returns the origin URI path as an array (with path segments constituting the array members), or null value if URI is not set. Encodes information specific to the onramp.

The array structure here allows for capturing multiple details about the origin, in a manner that's easily accessible from tremor-script (position-based retrieval).

For example, with udp onramp receiving events on port 12202:

use tremor::system::origin;
origin::path() # returns ["12202"]

scheme()

Returns the origin URI scheme, or null value if URI is not set. Encodes the source of events within tremor (i.e. onramp name).

For example, with udp onramp:

use tremor::system::origin;
origin::scheme() == "tremor-udp"

Returns string or null

as_uri_record()

Returns the full origin URI as a record, or null value if URI is not set. For example, with udp onramp receiving events on port 12202 from the same host as tremor:

use tremor::system::origin;
origin::as_uri_record() == {
  "scheme": "tremor-udp",
  "host":"127.0.0.1",
  "port":41371, # where 41371 is the ephemeral port on the sending side
  "path":["12202"]
}