[Ops] Note draft: "Operational Identification"

[Pierre Fernique]

Dear Ops IG,

The idea of encouraging VO customers to use a sufficiently 
discriminating User-Agent is an excellent initiative. And at CDS, we are 
particularly in favour of such a evolution. Many thanks for all people 
involve in this effort,

Concerning the "pre-note" itself, it seems very clear to me.

I have noted a technical point that I raise. The document mentions three 
types of op-purpose: validate, monitor, harvest.I think the first two 
will be not so easy to differentiate. In practice, they are usually the 
same tools that perform both functions, and it is unlikely that 
developers will modify the User-agent to suit the use that the user will 
be made of it. Maybe keep only one term: "check" ? Also, the notion of 
"harvest" may be too "VO registry" oriented and very limited in 
practice. I'm afraid it won't be used for other inter-center data 
synchronization operations. It would probably be interesting to enlarge 
its usage by giving some other examples for the use of this 
"op-purpose": Synchronizing data from one server to another server => 
notably Hipsgen MIRROR could use this term, or Simbad's recurring global 
queries for populating partner DBs. I was also wondering about the 
possibility of adding a term such as "proxy" to list clients acting only 
as relays - usually to bypass a technical access restriction (ie: 
javascript)

Concerning the identification of servers (section 3), I was wondering 
about the ease/difficulty of its application. Very concretely, it would 
imply that each data provider in the IVOA would have to modify their 
servers in order to generate the appropriate header. In the case of the 
CDS, some HTTP servers have multiple functions and this will require 
intervention on each component (CGI level, library level, tomcat level, 
etc.). A probably delicate operation to plan for the long term - 
probably following the upgrades of these different components.

This is why I think that we should stay at the level of suggestion as 
mentioned in the document, and not be tempted to go towards a strict 
recommendation that might in practice be very constraining for some IVOA 
members.

Finally, I draw attention to the fact that modifying existing 
User-agents will necessarily require an adjustment of the tools 
(filters/scripts/...) used by the different centers to perform their 
statistics. In the case of the CDS (server side), such a unilateral 
modification will cause a lack of measurements, the time to identify the 
modifications and to adapt the processing tools. Symmetrically, I 
suppose that the modification of the User-agents used by our clients and 
CDS libraries could not be done without warning the different known 
actors. I suggest that in the note, modalities to warn the different 
actors should be indicated: planned date for the modification, old 
User-agent and new User-agent. Possibly by using IVOA mailing list, or a 
dedicated page in the IVOA twiki, or other adapted channels.

Cheers
Pierre

Le 23/02/2021 à 13:54, Markus Demleitner a écrit :
> Dear Ops IG,
>
> A while ago Mark Taylor created the wiki page
> https://wiki.ivoa.net/twiki/bin/view/IVOA/UserAgentUsage on how to
> use HTTP Server and User-Agent headers in the VO, and when last I had
> wished these things to be more widely adopted, I managed to talk Mark
> into letting me convert it into a proper IVOA note.  I personally
> would hope that will make the recommendations a bit more visible and
> hence implemented.
>
> The current result is at https://github.com/msdemlei/softid (until it
> perhaps finds a place below ivoa-std).  A pre-rendered copy is
> available (temporarily) at http://docs.g-vo.org/softid.pdf.
>
> I would be grateful if people here could have a look at it before we
> submit it as a note -- any sort of feedback would be most
> appreciated, almost as much as takeup...
>
> Thanks,
>
>            Markus
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