title: HandleHTTPRequest processor creating duplicate output flowfiles in nifi
body: <p>​Hi,
  I have created the handlehttprequest processor, on a standalone nifi instance which is timer driven, concurrent tasks set to 1 and run schedule is 0. I am hitting my web service with a request from postman or any browser. The output queue of the processor has one entry initially but it becomes 2 after around a minute. I have seen this issue on a single node as well as on a clustered nifi instance. Can someone give any pointers</p>
  
  <p>Nifi Version: 1.7.0</p>
  
  <p>Update 1: I have observed that in case the http response flow is not reached within a certain time a new http request is generated wit the same parameters. Is this expected?, if yes how can I avoid this?</p>
  
  <p>Update 2: We have seen that the second flow file gets generated after exactly 60 seconds. Not sure which configuration sets this.</p>
  
  <p>Update 3: I just saw that the StandardHttpContextMap that we use has a property: Request Expiration which is set to 1 min by default. The documentation states that "Specifies how long an HTTP Request should be left unanswered before being evicted from the cache and being responded to with a Service Unavailable status code". If I increase this value I can see that I dont see any other duplicate values. So now I know why this is happening, but not sure as to why this is acting like this. Why am I getting another entry in the forward queue.</p>