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On Thu, Nov 3, 2016 at 1:04 PM, Amrith Kumar <amrith at tesora.com> wrote:

> Gordon,
>
> You can see a very quick-and-dirty prototype of the kind of thing I'm
> looking to do in Trove at
> https://gist.github.com/amrith/6a89ff478f81c2910e84325923eddebe
>
> Uncommenting line 51 would simulate a bad hash.
>
> I'd be happy to propose something similar in oslo.messaging if you think
> that would pass muster there.
>
> -amrith
>
> -----Original Message-----
> From: gordon chung [mailto:gord at live.ca]
> Sent: Thursday, November 3, 2016 3:09 PM
> To: openstack-dev at lists.openstack.org
> Subject: Re: [openstack-dev] [all][dev][python] constructing a
> deterministic
> representation of a python data structure
>
>
>
> On 03/11/16 02:24 PM, Amrith Kumar wrote:
>
> >
> > So, just before calling call() or cast(), I could compute the hash and
> > stuff it into the dictionary that is being sent over, and I can do the
> > same on the receiving side. But since I cannot guarantee that the
> > representation on the receiving side is necessarily identical to the
> > representation on the sending side, I have issues computing the hash.
> >
> >
>
> based on description, you're trying to sign the messages? there was some
> effort done in oslo.messaging[1]
>
> we do something similar in Ceilometer to sign IPC messages[2]. it does add
> overhead though.
>
> [1] https://review.openstack.org/#/c/205330/
> [2]
> https://github.com/openstack/ceilometer/blob/
> ffc9ee99c10ede988769907fdb0594a
> 512c890cd/ceilometer/publisher/utils.py#L43-L58
>
> cheers,
> --
> gord
>
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>
I had to solve a similar issue for deterministic key generation in dogpile
(key for memcache/etc) when memoizing methods/functions with kwargs. There
are a couple issues you run into, default args are not represented in
**kwargs, and non-positional args can come in any order.

If you want an example of what we did to generate the cache-key
programatically you can look here:

https://bitbucket.org/zzzeek/dogpile.cache/src/669582c2e5bf12b1303f50c4b7ba3dad308eb1cc/dogpile/cache/util.py?at=master&fileviewer=file-view-default#util.py-67:118

You don't need all the namespace and probably not fn/module info, but this
can look at the call and handle / ensure defaults also match (or be used to
extract default kwargs if needed) for passing down to RPC.

--Morgan
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