Invoke HTTP directive

The INVOKE-HTTP directive is an experimental directive to trigger an HTTP POST request with a body composed from specified fields.

Syntax

invoke-http 'url' :column [,:column:]* [<header>]

The columns specify the value to be sent to the service 'url' in the POST request as the body.

Usage Notes

The INVOKE-HTTP directive is used to apply a transformation on data using an existing REST service. This directive passes the specified columns as the POST body in the form of a JSON Object. The keys in the JSON object are the column names, with the values and their types derived from the objects stored in the column.

Upon processing of request by the service, the INVOKE-HTTP directive expects the data to be written back as a JSON object. The JSON object is then added to the record with its keys being the column names and the values being the values returned for the keys. The types are all valid JSON types.

Currently, the JSON response has to be simple types. Nested JSONs are not currently supported.

Note: There is a significant cost associated with making an HTTP call and this directive should not be used in an environment which would use it to process large quantities of data.

When an HTTP service requires more than one header to be passed, they can be specified as key-value pairs. For example:

X-Proxy-Server=0.0.0.0,X-Auth-Type=Basic

Note: The key and value are separated by an equals sign (=) and headers are separated by commas (,).

Examples

Using this record as an example:

{
    "latitude": 24.56,
    "longitude": -65.23,
    "IMEI": 212332321313,
    "location": "Mars City"
}

Assume that a service to locate a postal code, given a latitude and longitude, is available at an address such as http://hostname/v3/api/geo-find.

Applying this directive:

This would be translated into a POST call:

with a body of:

Note that only the two fields specified as parameters to the directive are sent to the service.

In case of a failure, the input record is passed to the error collector so that it can be re-processed later.