Programmatically provide NiFi InvokeHTTP different certificates - ssl-certificate

Question

I have a requirement in Nifi where I have cycle through different HTTPS REST Endpoints and provide different certificates for some endpoints and different username / password for some other endpoints.
I used InvokeHTTP processor to send the requests, although URL takes an expression language, I cannot setup SSLContextService with an expression.
Alternatively, I thought on using ExecuteScript to call those Endpoints, however as listed here in StackOverflow post; I still don't know how to programmatically call an external service through a script.
Any help appreciated.

Answer 1

just for fun created the groovy script that calls http.
for sure you can avoid using it. and I believe InvokeHTTP processor covers almost all needs.
However.. going to call test rest service: /post at https://httpbin.org
the flow: GenerateFlowFile (generates body) -> EcecuteGroovyScript (call service)
The body generated by GenerateFlowFile : {"id":123, "txt":"aaabbbccc"}
In ExecuteGroovyScript 1.5.0 declare the CTL.ssl1 property and link it to StandardSSLContextService
and now the script:
#Grab(group='acme.groovy', module='acmehttp', version='20180301', transitive=false)
import groovyx.acme.net.AcmeHTTP
import org.apache.nifi.ssl.SSLContextService.ClientAuth
def ff=session.get()
if(!ff)return
def http
ff.write{ffIn, ffOut->
http = AcmeHTTP.post(
url: "https://httpbin.org/post", //base url
query: [aaa:"hello", bbb:"world!"], //query parameters
// send flowfile content (stream) as a body
body: ffIn,
headers:[
//assign content-type from flowfile `mime.type` attribute
"content-type":ff.'mime.type'
],
// you can declare `CTX.ssl1`, `CTX,.ssl2`,... processor properties and map them to SSLContextService
// then depending on some condition create different SSLContext
// in this case let's take `CTL.ssl1` service to create context
ssl: CTL["ssl"+1].createSSLContext(ClientAuth.WANT),
// the next commented line creates trust all ssl context:
//ssl: AcmeHTTP.getNaiveSSLContext(),
// the receiver that transfers url response stream to flowfile stream
receiver:{respStream, httpCtx-> ffOut << respStream }
)
}
//set response hesders as flow file attributes with 'http.header.' prefix
http.response.headers.each{ k,v-> ff['http.header.'+k]=v }
//status code and message
ff.'http.status.code' = http.response.code
ff.'http.status.message' = http.response.message
if( http.response.code < 400){
//transfer to success if response was ok
REL_SUCCESS << ff
}else{
//transfer to failure when response code is 400+
REL_FAILURE << ff
}