http processors send body on GET

[mskarbek]

For:

pipeline:
  threads: -1
  processors:
    - branch:
        processors:
          - http:
              url: "https://REDACTED/service/rest/v1/components?repository=${! this.repo}"
              verb: GET
              headers:
                Accept: "application/json"
        result_map: "root.response = this"

I received 415 error from Sonatype Nexus server. Adding TRACE level of logging revealed that Benthos adds body to the request even if it is a GET which in turn upsets Nexus.
Is there a way to avoid sending body with GET requests?

[packman80]

From documentation:

A Bloblang mapping that describes how to create a request payload suitable for the child processors of this branch. If left empty then the branch will begin with an exact copy of the origin message (including metadata).

You need to get empty message without copy of original message. In this case you avoid sending body in GET request. Use it:

pipeline:
  threads: -1
  processors:
    - branch:
        request_map: root = "" 
        processors:
          - http:
              url: "https://REDACTED/service/rest/v1/components?repository=${! this.repo}"
              verb: GET
              headers:
                Accept: "application/json"
        result_map: "root.response = this"

[packman80]

it may be worth clarifying this in the documentation. In addition, the option to ignore sending the request body in the GET method might be useful, even if the message (and the request body, respectively) is not empty. In some cases, this would simplify the configs

[mihaitodor]

You don't necessarily need to use a branch processor. If you only wish to retain the response of the http processor, then placing a mapping processor before it with root = "" will suffice.

it may be worth clarifying this in the documentation.

From https://www.benthos.dev/docs/components/processors/http:

Performs an HTTP request using a message batch as the request body

The branch processor is a common utility which can be combined with any other processor, depending on the use case. Not sure how to help users discover it easier. It's definitely covered in the cookbooks, like for example this one: https://www.benthos.dev/cookbooks/enrichments

LE: Converted this to a discussion as per #2026.

[venatir]

The problem I'm facing is how do I pass any property to GET without then being forced to send it in the body?

[venatir]

Thanks @mihaitodor for answering on slack. Putting this here as I think it might help others
Slack chat excerpt:

---

@mihaitodor: The usual pattern is to use a mapping processor in which you set the metadata fields you need and then you can use interpolation in the http processor fields where you call the metadata() function to extract those metadata fields. Also, you can wrap it in a branch processor if you want to preserve the input message and then map the result of the http processor onto it (in the result_map)
@venatir: so using root="" is not affecting the metadata ?
@mihaitodor: Nope