Send SIGQUIT when cancelling an execution

When the context passed to Nomad Allocation Exec is cancelled, the
process is not terminated. Instead, just the WebSocket connection is
closed. In order to terminate long-running processes, a special
character is injected into the standard input stream. This character is
parsed by the tty line discipline (tty has to be true). The line
discipline sends a SIGQUIT signal to the process, terminating it and
producing a core dump (in a file called 'core'). The SIGQUIT signal can
be caught but isn't by default, which is why the runner is destroyed if
the program does not terminate during a grace period after the signal
was sent.

internal/api/websocket_test.go

@@ -223,7 +223,7 @@ func (s *WebSocketTestSuite) TestWebsocketError() {
 	s.True(websocket.IsCloseError(err, websocket.CloseNormalClosure))
 
 	_, _, errMessages := helpers.WebSocketOutputMessages(messages)
-	s.Equal(1, len(errMessages))
+	s.Require().Equal(1, len(errMessages))
 	s.Equal("Error executing the request", errMessages[0])
 }
 
@@ -370,10 +370,12 @@ func TestCodeOceanToRawReaderReturnsOnlyAfterOneByteWasReadFromConnection(t *tes
 
 // --- Test suite specific test helpers ---
 
-func newNomadAllocationWithMockedAPIClient(runnerID string) (r runner.Runner, executorAPIMock *nomad.ExecutorAPIMock) {
-	executorAPIMock = &nomad.ExecutorAPIMock{}
-	r = runner.NewNomadJob(runnerID, nil, executorAPIMock, nil)
-	return
+func newNomadAllocationWithMockedAPIClient(runnerID string) (runner.Runner, *nomad.ExecutorAPIMock) {
+	executorAPIMock := &nomad.ExecutorAPIMock{}
+	manager := &runner.ManagerMock{}
+	manager.On("Return", mock.Anything).Return(nil)
+	r := runner.NewNomadJob(runnerID, nil, executorAPIMock, manager)
+	return r, executorAPIMock
 }
 
 func webSocketURL(scheme string, server *httptest.Server, router *mux.Router,
@@ -429,14 +431,21 @@ func mockAPIExecuteHead(api *nomad.ExecutorAPIMock) {
 
 var executionRequestSleep = dto.ExecutionRequest{Command: "sleep infinity"}
 
-// mockAPIExecuteSleep mocks the ExecuteCommand method of an ExecutorAPI to sleep until the execution is canceled.
+// mockAPIExecuteSleep mocks the ExecuteCommand method of an ExecutorAPI to sleep
+// until the execution receives a SIGQUIT.
 func mockAPIExecuteSleep(api *nomad.ExecutorAPIMock) <-chan bool {
 	canceled := make(chan bool, 1)
 	mockAPIExecute(api, &executionRequestSleep,
 		func(_ string, ctx context.Context, _ []string, _ bool,
 			stdin io.Reader, stdout io.Writer, stderr io.Writer,
 		) (int, error) {
-			<-ctx.Done()
+			var err error
+			buffer := make([]byte, 1) //nolint:makezero // if the length is zero, the Read call never reads anything
+			for n := 0; !(n == 1 && buffer[0] == runner.SIGQUIT); n, err = stdin.Read(buffer) {
+				if err != nil {
+					return 0, fmt.Errorf("error while reading stdin: %w", err)
+				}
+			}
 			close(canceled)
 			return 0, ctx.Err()
 		})