astarte_flow
astarte_flow v0.1.0

http_source

  • type: producer
  • output: binary messages

This is a producer block that generates messages by polling HTTP URLs with a GET request.

It works by specifying a base_url and a list of target_paths to perform requests on. HttpSource will perform GET requests in a round robin fashion on all target_paths, waiting polling_interval_ms between two consecutive requests.

Properties

  • base_url: Target base URL. (required, string)
  • target_paths: Relative paths. (required, string array)
  • polling_interval_ms: Polling interval. (required, integer)
  • headers: Http request headers. (optional, object with string values)

base_url

 base_url

Target base URL such as "http://www.example.com".

target_paths

 target_paths

Relative paths to the base_url as a string array such as ["/first.json", "/second.json"].

polling_interval_ms

 polling_interval_ms

The time between two consecutive polling requests, expressed in milliseconds (e.g. 5000 for a 5 seconds interval).

headers

 headers

An optional object with additional headers such as {authorization: "Bearer <token>"}.

Output message

If the request succeeds, http_source produces a message containing these fields:

  • key: contains the target_path of the request
  • data: contains the body of the response
  • type: is always binary
  • subtype: is populated with the contents of the content-type HTTP header, defaulting to "application/octet-stream" if it's not found.
  • metadata: contains the "base_url" key with base_url as value. Moreover, it contains all the HTTP headers contained in the response with their keys prefixed with "Astarte.Flow.HttpSource.".
  • timestamp: contains the timestamp (in microseconds) the response was received.

If the request can't be performed or an error status (>= 400) is returned, no message is produced.

Examples

The following example uses http_source block for polling http://www.example.com/first.json and http://www.example.com/second.json every 5000 milliseconds (with a round robin policy on target paths /first.json and /second.json).

http_source
  .base_url("http://www.example.com")
  .target_paths(["/first.json", "/second.json"])
  .polling_interval_ms(5000)