alsonkemp
commented
3 years ago Argh. Sure enough this likely turned out to be a dangling or misunderstood Future. async/await in Dart doesn't seem to work the same as in JS/TS:
I switched the code around to use .then() and it seems to be working now. In the code below PubNub is my wrapper for PubNub (basically, just the stock client with some helpers). .subscribeAll() subscribes to a few of our channels (but otherwise is pretty standard). Our .publish() is fairly specialized because it takes a closure as an argument and synthesizes a request/response cycle (via requestId/responseId). The original PubNub library is imported as original.
Working:
PubNub pnClient = PubNub(pubKey, subKey, secKey, null);
PubNub pnServer = PubNub(pubKey, subKey, secKey, null);
return await pnServer.subscribeAll().then((_) async {
return pnClient.subscribeAll();
}).then((_) async {
return Future<void>.delayed(Duration(seconds: 1));
}).then((_) async {
Ping ping = Ping('This is a ping...');
Completer completer = Completer<bool>();
original.PublishResult pr = await pnClient.publish('ping', ping, (BaseMessage m) async {
// The server's response comes in here...
print("--- Response received: ${m.toMap()}");
expect(m.envelope.payload['kind'], equals('pong'));
completer.complete(true);
return true;
});
return completer.future;
});Not working (it looks as though the messages is being published by the client before the server is subscribed::
PubNub pnClient = PubNub(pubKey, subKey, secKey, null);
PubNub pnServer = PubNub(pubKey, subKey, secKey, null);
await pnClient.subscribeAll();
await pnServer.subscribeAll();
sleep(Duration(seconds: 1));
Ping ping = Ping('This is a ping...');
Completer completer = Completer<bool>();
original.PublishResult pr = await pnClient.publish('ping', ping, (BaseMessage m) async {
// The server's response SOMETIMES comes in here.
print("--- Response received: ${m.toMap()}");
expect(m.envelope.payload['kind'], equals('pong'));
completer.complete(true);
return true;
});
return completer.future;
are
I've written a simple client/server implementation to do ping/pong with synthesized request/response and occasionally see missing messages. I know this is not a lot to go on but I'm a bit new to Dart and its async implementation and didn't know if there were any quick gotchas that I was missing. (The code is proprietary so it'll take me a good amount of time to put together a minimal, replicating sample...)
This is a good test session:
Once every 5-10 test runs, I get:
In this case, the test sent out a "Ping" message but only got presence type messages (which aren't decoded in the system (hence the "MSG was null")) back. Is there some way that the presence messages could be disrupting the PubNub library? I've run through the code to see if I have any missing/messed-up async. Any suggestions?
Ah, got debug logging going. This is the failing log:
This is the good log: