What exactly is the cloud term 'a Firehose'?
The fire hose is a reference to an old Weird Al Yankovick movie, UHF (1989). In this movie, George Newman (portrayed by Yankovick) starts a local TV channel in the UHF band and is responsible for programming on the channel. After befriending the Station's Janitor, Stanley Spadowski, (portrayed by Michael Richards) George gives the Janitor a slot to run a show of his own making. The show, entitled "Stanley Spadowski's clubhouse" becomes an overnight sensation due to Spadowski's zany antics.

During a gameshow segment on the show, (video) Spadowski announces that a little boy, Joel Miller has "won" a contest by finding a marble in a wading pool of oatmeal and "gets to drink from the firehose!" - and this seems to be the likely origin of the term.



An oft-repeated sentiment in IT is that trying to comprehend a vast amount of material in a short amount of time (such as is the case when starting a new job, taking a training course or seminar on a technological subject or learning about a new product or device) is like "attempting to drink from a firehose" - it is nearly impossible to consume the entirety of such a large volume of information that is directed at you with such a rapid flow - a direct reference to the above scene.

It appears that in an attempt at humor, Cloudfoundry has chosen to call their Websocket "The Firehose" because websockets are used to "stream all application event data" (which they apparently regard as voluminous) most likely in reference to this sentiment/saying and scene.