Datasource Fallbacks (simplestreams)

[John Meinel]

So there is a difference between there not being a simplestream source at a
location and there not being a matching entry in an existing file. If
someone sets up a private stream falling back might not be expected.

John
=:->
On Oct 10, 2013 11:16 AM, "Andrew Wilkins" <andrew.wilkins at canonical.com>
wrote:

> On Fri, Oct 4, 2013 at 9:24 PM, Curtis Hovey-Canonical <
> curtis at canonical.com> wrote:
>
>> Do we place a specific warning in the log. If I bootstrap with
>> --show-log, do I see a message that clearly states the image cannot be
>> found and and that Juju is falling back? I want to know if I have
>> misconfigured something.
>>
>
> Not a warning, because it's not necessarily unexpected. The code currently
> logs a DEBUG level message if it can't find product (image, tools)
> information from a source.
>
> Cheers,
> Andrew
>
>
>>
>> On Fri, Oct 4, 2013 at 6:24 AM, William Reade
>> <william.reade at canonical.com> wrote:
>> > Yeah, let's go with always-fall-back. Much more likely to be useful in
>> > general, and we can worry about masking off the rest of the world if
>> there's
>> > a clear need for it that can't be easily addressed outside juju (if the
>> > environment can't see a stream, it won't be able to fall back to it ;)).
>> >
>> >
>> > On Fri, Oct 4, 2013 at 11:26 AM, Jeroen Vermeulen
>> > <jeroen.vermeulen at canonical.com> wrote:
>> >>
>> >> On 04/10/13 12:26, John Arbash Meinel wrote:
>> >>
>> >>> We came to this because the Azure provider was adding the "daily"
>> >>> stream to the search path. Which meant that we would find the daily
>> >>> stream, parse it, not find anything and then stop. Without falling
>> >>> back to the releases stream which has the actual entries we are
>> >>> looking for. (We "solved" this by just removing the daily stream,
>> >>> which was also for other reasons.)
>> >>
>> >>
>> >> I did that, IIRC at a time when only the daily images worked yet but
>> >> releases were the obvious long-term way to go.
>> >>
>> >> The implied contract for the imagemetadata package seemed to be that it
>> >> would consider only the selected stream, and ignore any other streams
>> it
>> >> found in the search path.  From what you say, that's what Andrew
>> >> implemented.  Otherwise, what's the point of supporting a search path
>> >> consisting of multiple URLs?
>> >>
>> >> With the fallback, having both the daily and the release stream in the
>> >> path allows users to select one or the other by setting just a stream
>> name —
>> >> no messing with simplestreams URLs in the most common case.
>> >>
>> >>
>> >>
>> >> Jeroen
>> >>
>> >>
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>> >
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>>
>>
>> --
>> Curtis Hovey
>> Canonical Cloud Development and Operations
>> http://launchpad.net/~sinzui
>>
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>
>
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