Cowboy/Ranch Exits with vague error message. Why?

[scottmessinger]

Just wanted to followup and say my problem is I was calling render two times in the controller (result of a bad merge):

Getting this strange undecipherable error on a get request using the API passthrough

json/2 executes send_resp/3 under the hood (see code), so your code is attempting to send 2 responses. Why it’s erroring out is explained in Plug.Conn.send_resp/1 Note that this function does not halt the connection, so if subsequent plugs try to send another response, it will error out. Use halt/1 after this function if you want to halt the plug pipeline. Since json/2 is executing send_resp/3 but doesn’t implicitly halt the connect, your code is trying to send another response on a connect…