Hi Darren,
Am 16.03.19 um 13:35 schrieb Darren Smith:
>
> Hi
>
> According to the spec, the Publication ID is a Global Scope ID
> and so "MUST be drawn randomly from a uniform distribution".
yes, correct!
>
> What is the reason for drawing it randomly, rather than, say,
> an increment by 1 approach (e.g. a Session Scope ID) ?
globally scoped IDs need to be, well, "globally unique". global here
means within a routing realm of WAMP - and across potentially all
physical WAMP routers clustered or federated.
the latter is important (not with a single node router, but beyond ..)
in a distributed system (the presumed cluster/federation of physical
WAMP routers), stuff can fail .. in many ways.
coming up with a requirement of a "globally unique sequence" for eg WAMP
registrations or subscriptions would make above quite hard: you need a
strictly consistent store for the sequence.
ultimately, random numbers are super cheap at achieving the same goal:
globally unique - practically.
>
> I think it would be more natural to act like a Session Scope
> ID since it is the broker that establishes the ordered history
> of Events, and so each successive Event could be incremented
> by 1. It is also computationally cheaper. There is less
> likelihood of duplicate IDs being used (unique to individual
> topics).
>
> If a broker implementation were instead to generate these ID
> via increment-by-1 approach, what problems might this cause
> for subscriber-clients that expected randomly drawn IDs?
I'm afraid, rgd the "ID question": the discussion on this is closed and
the protocol is fixed in the WAMP spec. However, we should absolutely
explain the why and reasoning;)
I took the chance and added this post to he following tracking issue on
above:
https://github.com/wamp-proto/wamp-proto/issues/231
Anyways, hope above helps already on that! Cheers,
/Tobias
>
> Thanks,
>
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