Reconnecting a WebSocket with a shared RxJS observable

Question

I have an observable like this:

const records$ =
    Rx.DOM.fromWebSocket('ws://192.168.2.4:9001/feed/', null)
    .map(ev => parseRecord(ev.data))
    .share();

I have many subscribers. When the connection is lost, all subscribers unsubscribe:

let records$Subscription;
records$Subscription = records$.subscribe(
    record => { ... },
    error => records$Subscription.dispose()
);

I verified that the call to dispose is indeed being made once for every subscription. Therefore, the share refcount has reached zero.

However, when I now subscribe to records$ again, no new WebSocket connection is set up. When I remove the call to share, however, it is. How come this doesn't work as expected with share?

which version of Rxjs are you using? – user3743222 Apr 17 '16 at 14:36 — user3743222, Apr 17 '16 at 14:36
@user3743222 RxJS v4.1.0 and RxJS-DOM v7.0.3 – Apr 17 '16 at 14:38 — , Apr 17 '16 at 14:38

score 1 · Accepted Answer · edited May 23 '17 at 10:28

I believe in rxjs v5, share does allow you to reconnect but not in Rxjs v4.

In Rxjs 4, share is bascially multicast.refCount and once the subject used for the multicast is completed, it cannot be reused (per Rxjs grammar rules, have a look at What are the semantics of different RxJS subjects? too), leading to the behaviour you observed.

In Rxjs 5, it uses a subject factory (something like multicast(() => new Rx.Suject().refCount())), so a subject is recreated when necessary.

See issues here and here for more details.

In short, if you can't do with the current behavior, you can switch to the v5 (note that it is still in beta and there are some breaking changes).

Reconnecting a WebSocket with a shared RxJS observable

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