PubSub : repeatedly extend the acknowledgement deadline for backlogged pull messages

[dhoard]

For the asynchronous subscriber, backlogged messages have automatic acknowledgement deadline processing.

" Because the client library repeatedly extends the acknowledgement deadline for backlogged messages "

This feature would be useful for messages that are being processed via synchronous (pull.)

[yuri-sergiichuk]

We've implemented our own wrapper around PubSub sync functionality that starts ScheduledExecutorService and performs automatic ack prolong action if the task is not yet acknowledged.

[dhoard]

@yuri-sergiichuk We have done the same. It seems like core functionality that should be in the library ... at least from an optional / configurable basis.

[ajaaym]

closing this and will track in #3500