Previously, if a subscriber received the OTA migration before the host,
then it would attempt to subscribe to a non-existent resource, and
receive a nack, thus unsubscribing the ship from the notebook. To
rectify this, the tombstoned publish has been changed to resubscribe in
a loop with exponential back off. Once it receives a positive watch-ack
(i.e. the host completed the OTA), it will then migrate the notebook to
graph-store by adding it to graph-pull-hook
In order to curb event queue growth when a client for whatever reason
isn't acking the events we send out, we implement a mechanism for
detecting such "clogging", and proactively kick subscriptions which are
adding too many events to the queue.
If the client hasn't sent an ack for ~s30, any subscription that accrues
more than 50 unacked %facts gets closed to prevent further buildup.
Upon reconnecting, the client will see %kick for the relevant
subscriptions and can open a new subscription as appropriate.
Includes a simple test for this behavior, and updates /app/dbug to be
able to display the newly tracked statistics.
By doing a %watch instead of %watch-as %json for channel subscriptions,
we can hopefully make better use of noun deduplication, when storing
events in a channel's event queue until they get acked.
Store the gall events from channel subscriptions as (vaseless) signs,
instead of serialized events. This should be smaller in memory, and
makes it more likely for noun deduplication to happen.
The cost is needing to reserialize upon channel reconnect, but this is
the less common case, and we don't expect it to be particularly slow.
In certain cases +find-merge-points was very slow. Specifically, the
`done` set was meant to avoid checking the same commit repeatedly, but
it didn't catch the case where a commit was added to the worklist that
was already in that worklist.
Secondly, the worklist was stored as a list but used as a queue, which
resulted in a lot of unnecessary welding. We change it to a qeu.
Fixes#3735
