Monitoring replication iOS

Mobile
1

I’m trying to get notified when my continuous replication changes state. I’ve tried the code below, but I only ever get 1 notification (when it starts). What am I doing wrong please?

[[NSNotificationCenter defaultCenter] addObserverForName:kCBLReplicationChangeNotification object:repl queue:nil usingBlock:^(NSNotification *notification) {

    NSString *status;
    if (repl.status == kCBLReplicationActive) {
        NSLog(@"Repication in progress");
        status = @"in-progrss";
    } else if (repl.status == kCBLReplicationOffline) {
        NSLog(@"Sync in offline");
        status = @"offline";
    } else if (repl.status == kCBLReplicationStopped) {
        NSLog(@"Sync in stopped");
        status = @"in-stopped";
    } else if (repl.status == kCBLReplicationIdle) {
        NSLog(@"Sync in idle");
        status = @"in-idle";
    }

    NSError *error = repl.lastError;
    if(error) {
        status = @"error";
        NSLog(@"replication error %ld", (long)error.code);
    }

    NSDictionary *dictionary = @{
                                 @"type": type,
                                 @"changesCount": @(repl.changesCount),
                                 @"completedChangesCount": @(repl.completedChangesCount),
                                 @"running": @(repl.running),
                                 @"status": status,
                                 @"suspended": @(repl.suspended),
                                 };

    [self sendEventWithName:@"replicationChanged" body:dictionary];

}];
2

Usually when this problem occurs it’s because the object registered as the observer got dealloced. However, you’re using the new-ish API that registers a block as the observer; I’m not entirely sure how ref-counting works with that.

Maybe try changing this to the traditional object/selector style, then make sure the object has strong references to it so it doesn’t get dealloced.

3

Thanks for the reply Jens.

I have tried doing it the other way, but get the same result. Just a single callback per continuous replication, with status kCBLReplicationOffline, and never anything else.

[[NSNotificationCenter defaultCenter] addObserver: self
                                         selector: @selector(replicationChanged:)
                                             name: kCBLReplicationChangeNotification
                                           object: repl];

...

- (void) replicationChanged: (NSNotification*)notification {
CBLReplication *repl = notification.object;

NSString *status;
if (repl.status == kCBLReplicationActive) {
    NSLog(@"Repication in progress");
    status = @"in-progrss";
} else if (repl.status == kCBLReplicationOffline) {
    NSLog(@"Sync in offline");
    status = @"offline";
} else if (repl.status == kCBLReplicationStopped) {
    NSLog(@"Sync in stopped");
    status = @"in-stopped";
} else if (repl.status == kCBLReplicationIdle) {
    NSLog(@"Sync in idle");
    status = @"in-idle";
}

NSError *error = repl.lastError;
if(error) {
    status = @"error";
    NSLog(@"replication error %ld", (long)error.code);
}

NSDictionary *dictionary = @{
                             @"changesCount": @(repl.changesCount),
                             @"completedChangesCount": @(repl.completedChangesCount),
                             @"running": @(repl.running),
                             @"status": status,
                             @"suspended": @(repl.suspended),
                             };

[self sendEventWithName:@"replicationChanged" body:dictionary];
}

Replication is working fine though.

4

Any more ideas? Is there a working example out there somewhere? I simply can’t get it to work with CBL 1.4 - there’s only ever one event.

Here’s my code.

5

Oh, you didn’t say that this is in React Native, not in a normal app!

What thread does this object get called on? Is the thread running a runloop? Couchbase Lite notifications are scheduled via the runloop, so without that you won’t get them.

Alternatively you can set the Manager’s dispatchQueue property to a serial queue, and notifications will be delivered there. But then you need to always call Couchbase Lite methods from that queue, to avoid threading problems.

6

Ha, that’s a good question, thanks for the reply.

Why method do you mean? startContinuousReplication or replicationChanged?

startContinuousReplication gets called by RN, i don’t know which thread, I don’t even know how to find out at the moment. And replicationChanged, well, doesn’t get called at all al the moment which is the problem i’m trying to sort out.

7

Well, that’s your problem then. React’s thread probably doesn’t run a runloop.

In your case I would use a dispatch queue. Create your own, and then wrap dispatch_sync around the calls to Couchbase Lite.

Then you’ll have to be careful calling in the other direction, since callbacks from Couchbase Lite will occur on that queue (I.e. On a random background thread) and it might not be safe to call into React from there.

8

I had a look around the react-native docs and found this. Specifically it says

The - (dispatch_queue_t)methodQueue method allows the native module to specify which queue its methods should be run on

So I added one to my RN module here, and I can see at least form the logging that it looks like all method are now invoked on my new thread (called RNCBL.Queue), for example:

[info][tid:RNCBL.Queue][ReactCBLite.m:38] Launching Couchbase Lite...

It works if I specify the main thread. Thanks for your help.