Enable a more efficient polling of catalog

[duglin]

What do people think about supporting an ETag type of mechanism for /v2/catalog so that a broker can return "304 Not Modified" if nothing has changed since the last time the Platform queried the catalog? It would save the broker the time of regenerating the result, and it will save the platform the time of diff'ing it.

[dotchev]

Most of our brokers use a static catalog, so it is not an issue on the broker side.

It would be nice if a broker could specify the period when the platform should refresh the catalog, e.g. via Cache-Control: max-age=... response header. Then different brokers might use different intervals.

[duglin]

@mattmcneeney was this discussed during the call this week? Any feedback?

[pmorie]

I'm not sure what an etag is exactly, but I agree with the goal described here

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[duglin]

@pmorie https://en.wikipedia.org/wiki/HTTP_ETag

[mattmcneeney]

@duglin This was discussed briefly though we had low attendance on yesterday's call. @fmui mentioned that since ETags are just part of the HTTP spec, why do we have to add something to the spec? (I think - correct me if I'm wrong Florian!)

[duglin]

While true its part of the HTTP spec, given not everyone knows about it (as shown by Paul's comment), I suspect that unless we call it out people will not consider supporting this optional feature. So, a PR on this wouldn't require people to use it, but rather make people aware of it and explain any implications of its use. I know that some uses of OSBAPI will ping the catalog quite often, so I think highlighting this to help performance would be nice.

[mattmcneeney]

@jberkhahn is this still something that may be of use to the svc-cat community?

[jberkhahn]

sure

[mattmcneeney]

@jberkhahn Cool - do you want to own opening the PR for this one? :)

[jberkhahn]

i'll try to get around to it this week