Bacon zipped Stream not ending when matches complete causing test suite to hang

Question

I have been trying to use Bacon's zip...() operations to create a Mocha test-suite, where a sequence of values from actual asynchronous networked events could be compared to a sequence of target values to verify correct behaviour.

However, the zipped stream in the test case never terminates.

I have a successful Bacon test case where two streams are 'faked' by creating both streams from arrays. This test case successfully terminates, with toPromise() for the stream returning without error. https://gist.github.com/cefn/7fd3504a0b29575f3b6f

However, in the case where one of the streams is actually wired to the asynchronous networked events, the toPromise() call never completes and the test suite hangs, even though I can tell through the V8 debugger that the final array entry in the target sequence is indeed matched.

I don't understand what causes the streams to end in one case and not end in the other. Is there a configuration change that I can make, or an explicit declaration of the number of events in the stream, or something else, to force the stream end event to be fired from the zipped stream.

            it("Sends branch keys then leaf values", function(){

                var sniffer = mqtt.connect(conf.mqttWsAddr);

                var subscribeAndSendPromise = util.createSubscriptionPromise(sniffer, '#')
                    .then(function(){
                        writer.setItem('oldmacdonald/farm', {
                            sheep:"Baa",
                            pig:"Oink",
                            cow:"Moo",
                            duck:"Quack",
                        });
                    });

                var actualStream = Bacon.fromEvent(sniffer, "message", function(topic,payload,packet){
                    packet.message = payload.toString();
                    return packet;
                });

                var targetStream = Bacon.sequentially(0,[
                    ["the_workshop/oldmacdonald", "[]" ] , //originally empty
                    // ["the_workshop/oldmacdonald", JSON.stringify(['farm']) , // TODO somehow missing
                    // ["the_workshop/oldmacdonald/farm", JSON.stringify([]) ] , // TODO somehow missing
                    ["the_workshop/oldmacdonald/farm", JSON.stringify(['sheep','pig','cow','duck']) ] , //n.b. JSON array
                    ["the_workshop/oldmacdonald/farm" + "/sheep", JSON.stringify("Baa")] , //n.b. quoted JSON strings
                    ["the_workshop/oldmacdonald/farm" + "/pig", JSON.stringify("Oink")] ,
                    ["the_workshop/oldmacdonald/farm" + "/cow", JSON.stringify("Moo")] ,
                    ["the_workshop/oldmacdonald/farm" + "/duck", JSON.stringify("Quack")] ,
                ]);

                var deepEqual = function(targetValues, actualPacket){
                    var actualTopic = actualPacket.topic;
                    var actualMessage = actualPacket.message;
                    var targetTopic = targetValues[0];
                    var targetMessage = targetValues[1];
                    assert(actualTopic == targetTopic);
                    assert(actualMessage == targetMessage);
                    return true;
                };

                var zippedStream = Bacon.zipAsArray(targetStream, actualStream);
                zippedStream.onValues(deepEqual);

                var receivePromise = zippedStream.toPromise();
                receivePromise.finally(function(){
                    sniffer.end();
                });

                return Q.all([subscribeAndSendPromise, receivePromise]);

            })

Can you reduce this to a point where no external code is called? — Benjamin Gruenbaum, Jun 23 '15 at 14:25

score 0 · Accepted Answer · answered Jun 25 '15 at 08:29

0

The problem is that the actualStream never ends: it is created with fromEvent and listens to the EventEmitter forever.

The zippedStream only ends when both targetStream and actualStream have ended.

You could add a timeout to the actualStream with:

var actualStreamWithTimeout = actualStream.takeUntil(Bacon.later(1000))

answered Jun 25 '15 at 08:29

OlliM

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I can confirm this behaviour in the gist at https://gist.github.com/anonymous/b053aa54750db5c5fd01 which uses sequentially(0, arr) alongside repeatedly(0, arr). However this is contrary to the bacon documentation which claims "A zipped stream will publish only when it has a value from each stream and will only produce values up to when any single stream ends." as the sequentially stream ends, but the zipped stream does not. Surely zipped streams can't be intended to hang forever even though they will never produce any future values. Seems like a bug to me. – cefn Jun 26 '15 at 17:27
That is true, it would make sense for the zipped stream to end when one of the streams ends, as it no longer produces values. I recommend filing an issue on github. – OlliM Jun 27 '15 at 06:36
Understood. Filed [this issue](https://github.com/baconjs/bacon.js/issues/610) at github. – cefn Jun 27 '15 at 10:29

Bacon zipped Stream not ending when matches complete causing test suite to hang

1 Answers1