NiFi InvokeHTTP POST invalid request - apache-nifi

Question

I am trying to execute a simple POST request from nifi using the InvokeHTTP processor. The target server responds with the response "error: invalid request". I am able to POST successfully with curl from nifi's host.
I have set the processor's HTTP method to "POST", and the URL to "http://myhost:1234", other fields are set to the defaults. The incoming flowfile's mime.type is application/json and the flowfile content is valid json.
Here's what I tried (server names etc. were replaced with fake names):
I confirmed that the target server is ok with curl using seemingly equal parameters to the InvokeHTTP processor (with and without the --http2 flag, equally on the InvokeHTTP processor I tried with the "HTTP/2 Disabled" property on true and false):
curl -v --http2 -POST -H "content-type: application/json" http://myhost:1234/ -d '\[{"key":"value"\]'
For the data I used the actual content of the flowfile used by InvokeHTTP.
* Trying <ip>...
* TCP_NODELAY set
* Connected to myhost (<ip>) port 1234 (#0)
> POST / HTTP/1.1
> Host: myhost:1234
> User-Agent: curl/7.61.1
> Accept: */*
> Connection: Upgrade, HTTP2-Settings
> Upgrade: h2c
> HTTP2-Settings: AAMAAABkAARAAAAAAAIAAAAA
> content-type: application/json
> Content-Length: 17
>
* upload completely sent off: 17 out of 17 bytes
< HTTP/1.1 201 Created
< Server: <servername>
< Content-Length: 0
<
* Connection #0 to host myhost left intact
With InvokeHTTP, the response is routed to the NoRetry output with the following attributes added to the flowfile:
invokehttp.response.body
error: invalid request
invokehttp.response.url
http://myhost:1234/
invokehttp.status.code
400
invokehttp.status.message
Forbidden
I tried logging the request by setting the org.apache.nifi.processors.standard.InvokeHTTP logger to DEBUG. The resulting logs:
2022-11-17 11:22:03,384 DEBUG [Timer-Driven Process Thread-4] o.a.nifi.processors.standard.InvokeHTTP InvokeHTTP[id=<guid>]
Request to remote service:
http://myhost:1234/
date: Thu, 17 Nov 2022 11:22:03 GMT
user-agent:
2022-11-17 11:22:03,384 DEBUG [Timer-Driven Process Thread-4] o.a.nifi.processors.standard.InvokeHTTP InvokeHTTP[id=<guid>]
Request to remote service:
http://myhost:1234/
date: Thu, 17 Nov 2022 11:22:03 GMT
user-agent:
2022-11-17 11:22:03,391 DEBUG [Timer-Driven Process Thread-4] o.a.nifi.processors.standard.InvokeHTTP InvokeHTTP[id=<guid>]
Response from remote service:
http://myhost:1234/
content-length: 23
server: <servername>
2022-11-17 11:22:03,391 DEBUG [Timer-Driven Process Thread-4] o.a.nifi.processors.standard.InvokeHTTP InvokeHTTP[id=<guid>]
Response from remote service:
http://myhost:1234/
content-length: 23
server: <servername>
At this point I don't know what to do. I don't know if the logged requests are purposefully limited to these fields or if there's actually a lot of information missing from the requests themselves such as the payload and the content type. I'm also wondering why the requests are logged twice, or whether they're actually sent twice (I'm on a single node environment).
I expect this processor to be able to perform such a simple request without much trouble, and have confirmed that the target server is not the issue. Did I miss something? How can I debug this further (e.g. see the actual raw request sent by InvokeHTTP)?
Thank you.

Answer 1

Check the mime.type attribute. That is automatically translated to a header for you, and you could be sending form-encoded parameters as the mime type or something like that instead of the expected json.