Simultaneous failures cause circuit to never move into the halfOpened state

[mnutt]

Node.js Version:

10.17.0

Operating System:

MacOS 10.14.6

Steps to Produce Error:

I'm seeing an issue that started happening in 4.2.0 (#383) where the circuit never enters the halfOpened state.

If you have a circuit that automatically opens after 5 requests and you concurrently launch 6 simultaneous requests that each eventually error:

• The first 4 requests will fail() but not call open()
• The 5th request will call open() which will emit the open event and start the timer to later move into the halfOpened state
• The 6th request will call open() again which will cancel the timer, but since it is already in the opened state, will not emit the open event and thus not restart the timer.
• The circuit stays in the opened state and never enters the halfOpened state, so all further requests are rejected.

I think that the correct behavior might be for open() to cancel the current timer and immediately re-add it, so that it pushes the timer end date out regardless of whether or not the state change happens?

[tjenkinson]

Oops sorry about that I didn’t realise open() was the same thing that was called internally. I thought for the public api it would be strange for an open call to later be undone

[tjenkinson]

Another solution could be to check the state before calling open(), and only call it if it’s not already OPEN. This makes it still possible from the api to permanently open and close

[lholmquist]

Just released this as 4.2.1