nothize / ib Goto Github PK

Procedure:

GATEWAY_URL=localhost:4002 go test -run TestInstrumentManager -v

Expected result:

Test should complete and success.

Actual result (the test is not end and the message is showed repeatedly):

=== RUN TestInstrumentManager
2017/06/13 22:45:56 Waited 5 seconds for reply channel 0xc42006d200

Findings:

1. 8a68c49 tries to fix the infinity loop when the errors channel is being closed. (Reading from a closed channel will return immediately with ok as false, so it prevents other cases from being processed)
2. However, the defer block will only execute after errors being set to nil and reading from a nil channel will wait forever thus the EngineState observer is never unsubscribed from the Engine which cause infinity loop in the defer block of Engine's main loop.

Solution:

1. Setting nil to the closed channel errors to prevent the case from preempting the select block is correct, though can be done right after close(errors).
2. Reading from errors from the defer block works if errors is not nil, so a better alternative is to add a new channel to synchronise between the preLoop goroutine and defer block.