GetHTTP: Downloads the contents of a remote HTTP- or HTTPS-based URL into NiFi. The Processor will remember the ETag and Last-Modified Date in order to ensure that the data is not continually ingested.

ListenHTTP: Starts an HTTP (or HTTPS) Server and listens for incoming connections. For any incoming POST request, the contents of the request are written out as a FlowFile, and a 200 response is returned.

InvokeHTTP: Performs an HTTP Request that is configured by the user. This Processor is much more versatile than the GetHTTP and PostHTTP but requires a bit more configuration. This Processor cannot be used as a Source Processor and is required to have incoming FlowFiles in order to be triggered to perform its task.

PostHTTP: Performs an HTTP POST request, sending the contents of the FlowFile as the body of the message. This is often used in conjunction with ListenHTTP in order to transfer data between two different instances of NiFi in cases where Site-to-Site cannot be used (for instance, when the nodes cannot access each other directly and are able to communicate through an HTTP proxy). Note: HTTP is available as a Site-to-Site transport protocol in addition to the existing RAW socket transport. It also supports HTTP Proxy. Using HTTP Site-to-Site is recommended since it's more scalable, and can provide bi-directional data transfer using input/output ports with better user authentication and authorization.

HandleHttpRequest / HandleHttpResponse: The HandleHttpRequest Processor is a Source Processor that starts an embedded HTTP(S) server similarly to ListenHTTP. However, it does not send a response to the client. Instead, the FlowFile is sent out with the body of the HTTP request as its contents and attributes for all of the typical Servlet parameters, headers, etc. as Attributes. The HandleHttpResponse then is able to send a response back to the client after the FlowFile has finished being processed. These Processors are always expected to be used in conjunction with one another and allow the user to visually create a Web Service within NiFi. This is particularly useful for adding a front-end to a non-web- based protocol or to add a simple web service around some functionality that is already performed by NiFi, such as data format conversion.