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Re: [hono-dev] Agenda for face-to-face meeting

On 01/04/16 09:51, Hudalla Kai (INST/ESY) wrote:
-----Ursprüngliche Nachricht-----
Von: hono-dev-bounces@xxxxxxxxxxx [mailto:hono-dev-bounces@xxxxxxxxxxx] Im
Auftrag von Gordon Sim
Gesendet: Donnerstag, 31. März 2016 19:29
An: hono-dev@xxxxxxxxxxx
Betreff: Re: [hono-dev] Agenda for face-to-face meeting


* Is there likely to be a need to filter telemetry data for a given tenant in some way
(by device, by device type or grouping, by logical subject etc)

[KH] Personally, I would like to defer this to the consumer of the data, e.g. using Storm or any other framework for filtering, processing, forwarding the data. My concern is that we "re-build" a full-fledged message broker when we start to expose too many features of underlying MOM.

One issue there is that the abstraction that Hono exposes for telemetry is less capable than almost any of the protocols it may be adapting.

The other is a question of scaling. If there is no ability to filter/restrict the set of events other than identifying the tenant, then the maximum aggregate event rate for a tenant is limited by what a single subscriber can keep up with. Or would some form of shared subscriptions be supported?


* Would Hono store telemetry data for any length of time independent of any
active subscribers?

[KH] I would actually try to define a reasonable retention policy based on message age, e.g. all messages are removed after 10 (?) days regardless of whether any consumer has read the data or not. I guess this would also be consistent with the nature of "telemetry" data in that one value reported will be superseded by the next one anyways.

I shouldn't have said active. What I was asking was whether Hono would store telemetry data that is published when there are no subscriptions _registered_.

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