android - Firebase Cloud Messaging issue with subscribe//unsubscribe from topic -

firebase cloud messaging (fcm) subscribetotopic(topic) , unsubscribefromtopic(topic) functions have backoff timer until work or timeout.

if call subscribe (and wasn't successful) call unsubscribe (immediately successful) firebase handle them queued , end unsubscribe, or possible end subscribe because of backoff if called unsubscribe after?

hope made sense.

currently (v 9.2.0) fcm doesn't try cancel local operations when 2 opposite actions queued locally.

that said, backoff mention not per single operation, whole queue sync task. means when device connected , backoff time trigger, fcm try perform queued operations possible, it's difficult device end in situation out of 2 queued operations, 1 succeeded while other got delayed.

please note implementation detail valid in current release (v9.2.0). might change approach in future, if compatible other improvements have in pipeline.