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From Kay Schenk <kay.sch...@gmail.com>
Subject Re: [DL LOGIC] How to choose a mirror when more than 1 is available?
Date Sat, 14 Apr 2012 16:21:00 GMT


On 04/07/2012 09:45 PM, Dennis E. Hamilton wrote:
> I agree that it is far more appealing to do this server side rather
> than have the client user agent have to fire up only to do a
> redirect.
>
> It also leaves open the prospect of handling the failure modes more
> effectively.
>
> Of course, that change can be done at any time, perhaps when there is
> no peak load on the horizon?
>
> - Dennis

I'll take a look at this when I get a moment this weekend. I understand 
Dennis's concern about the scarey aspects of changing mirror sites in 
the JS we currently use especially given the number of committers we 
have now with access to the entire web tree.

I'm assuming if we did use server-side mirror selection logic, we would 
just specify the Apache mirror for ooo --- 
http://apache.tradebit.com/pub/incubator/ooo/ -- and let server side 
logic figure it out from there.


>
> -----Original Message----- From: Dave Fisher
> [mailto:dave2wave@comcast.net] Sent: Saturday, April 07, 2012 20:02
> To: ooo-dev@incubator.apache.org Subject: Re: [DL LOGIC] How to
> choose a mirror when more than 1 is available?
>
> Hi Joe,
>
> While everyone else might be ignoring the distinction between the
> Apache closer cgi/ezt and the current OOo javascript methods, I
> haven't missed the difference. One is server and the other client.
>
> You've mentioned where the various example pieces are, but to make it
> really easy would you mind providing the two or three key urls into
> the svn repos? I'm interested, but not in a hurry.
>
> Thanks, Dave
>
> On Apr 7, 2012, at 1:09 PM, Joe Schaefer wrote:
>
>> If you're really paranoid about the ASF mirrors you can use ezt to
>> embed the [preferred] mirror inside some javascript within the page
>> and run a test HEAD request on the url to ensure it exists.
>>
>> I don't see the point of the MirrorBrain stuff
>>
>> at this point tho- will just make things more messy than they
>> already are dealing with SF + ASF mirrors.
>>
>>
>>
>> ----- Original Message -----
>>> From: Rob Weir<robweir@apache.org> To:
>>> ooo-dev@incubator.apache.org Cc: Sent: Saturday, April 7, 2012
>>> 4:03 PM Subject: Re: [DL LOGIC] How to choose a mirror when more
>>> than 1 is available?
>>>
>>> On Sat, Apr 7, 2012 at 3:35 PM, Marcus
>>> (OOo)<marcus.mail@wtnet.de>  wrote:
>>>> Am 04/07/2012 07:38 PM, schrieb Marcus (OOo):
>>>>
>>>>> Am 04/07/2012 05:34 PM, schrieb Rob Weir:
>>>>>>
>>>>>> On Sat, Apr 7, 2012 at 10:13 AM, Marcus
>>> (OOo)<marcus.mail@wtnet.de>
>>>>>> wrote:
>>>>>>>
>>>>>>> For our new release we will have a changed set of
>>>>>>> conditions:
>>>>>>>
>>>>>>> - new central mirror hosts for redirecting download
>>>>>>> requests - therefore also a new set of mirror server that
>>>>>>> host our
>>> builds
>>>>>>> - new set of supported platforms and languages - slighty
>>>>>>> changed file name schema
>>>>>>>
>>>>>>> To get this all under one hat, we have to improve the
>>>>>>> download
>>> logic
>>>>>>> that is currently done by JavaScript.
>>>>>>>
>>>>>>> To fulfill the first condition the download requests have
>>>>>>> to be split-up to more than 1 central mirror redirector.
>>>>>>>
>>>>>>> Here is a suggestion for choosing when (by random number)
>>>>>>> to
>>> redirect to
>>>>>>> which mirror:
>>>>>>>
>>>>>>> http://www.openoffice.org/download/test/index_new_dl.html
>>>>>>>
>>>>>>>
>>>>>>>
Test results:
>>>>>>> - to make debugging easier I've included some screen
>>>>>>> output
>>> and comments
>>>>>>> - I've tested it locally with different combinations of
>>> active/inactive
>>>>>>> hosts and it works well - the fallback method works well,
>>>>>>> too - I've tested different percent values as ratio, but
>>>>>>> not
>>> yet for the
>>>>>>> 2nd case
>>>>>>>
>>>>>>> What do you think?
>>>>>>>
>>>>>>
>>>>>> The logic on the test pages works for me.
>>>>>>
>>>>>> But two additional complexities:
>>>>>>
>>>>>> 1) MirrorBrain let's us link directly to a download file.
>>>>>> We
>>> then
>>>>>> send the user to
>>>>>> http://www.openoffice.org/download/contribute.html while
>>>>>> the file is downloading. But SourceForge and Apache mirror
>>>>>> systems take the user to a different page (not controlled
>>>>>> by us).
>>> So
>>>>>> in those cases the user does not see the contribute.html
>>>>>> page.
>>>>>
>>>>>
>>>>> This should work also for SourceForge. The root path is
>>>>> always the
>>> same.
>>>>> We just need to add a subdir and file name.
>>>>>
>>>>> I don't know how to do it for Apache.
>>>>>
>>>>>> Since the contribute.html page has very useful information
>>>>>> for the user, like links to the install instructions,
>>>>>> information on
>>> support,
>>>>>> contributing to the project, etc., I think it is important
>>>>>> that the user sees this information in all paths.
>>>>>
>>>>>
>>>>> ACK
>>>>>
>>>>>> What could we do? Pop-up (or pop-under) a new HTML page?
>>>>>> But that
>>> is
>>>>>> annoying to some users.
>>>>>
>>>>>
>>>>> Right
>>>>>
>>>>>> The Apache and SF approaches both direct a user off of the
>>>>>> OpenOffice.org website, which is risky.
>>>>>>
>>>>>> 2) What if we have more than three mirror systems? It
>>>>>> sounds like
>>> you
>>>>>> prefer to keep MirrorBrain. That is fine with me. So maybe
>>>>>> we have Apache, SF and MirrorBrain?
>>>>>
>>>>>
>>>>> Yes, would be great. Another available system as possible
>>>>> backup is not bad.
>>>>>
>>>>> For any change of the number of available systems we have to
>>>>> adapt the JS logic.
>>>>>
>>>>>> Imagine an array of mirror networks, each with weights, in
>>>>>> sorted order from smallest to largest. (or sort the array
>>>>>> in code)
>>>>>>
>>>>>> Apache:1 MirrorBrain:2 SourceForge:3
>>>>>>
>>>>>> TotalWeight = MirrorBrain + Apache + SourceForge == 6
>>>>>>
>>>>>> x = rand()
>>>>>>
>>>>>> if (x<  Apache/TotalWeight) doApache() else if (x<
>>>>>> MirrorBrain/TotalWeight) doMirrorBrain() else
>>>>>> doSourceForge()
>>>>>>
>>>>>> Something like that.
>>>>>
>>>>>
>>>>> Redirecting due to weighted values looks good. But also this
>>>>> is working with a fixed set of mirror hosts. A forth had to
>>>>> be build in and therefore the logic has to be adapted.
>>>>>
>>>>> Thanks for your feedback. I'll adapt the script later in the
>>> evening.
>>>>
>>>>
>>>> I've adapted it now. But I'm not sure if it's working correct
>>> with some
>>>> disabled mirrors.
>>>>
>>>
>>> I'm not sure my logic was right in the above code.  For example,
>>> if two mirrors have the same weight it would always pick the
>>> first one in the array.
>>>
>>> But take a look at the approach in this article:
>>>
>>> http://www.javascriptkit.com/javatutors/weighrandom2.shtml
>>>
>>> I think that is much clearer and easier to use.
>>>
>>> Essentially, it says if you want weighted random selection with
>>> weights like:
>>>
>>> Apache:1 MirrorBrain:2 SourceForge:3
>>>
>>> Then create an array with each item repeated according to its
>>> weight, so:
>>>
>>> Apache MirrorBrain MirrorBrain SourceForge SourceForge
>>> SourceForge
>>>
>>> Then just pick a random number 0...length-1 and return the value
>>> at that index.
>>>
>>> As for unavailable mirrors, or even unavailable servers within a
>>> mirror network, is there really anything we can do?  Other than
>>> tell the user to refresh and try again?
>>>
>>> -Rob
>>>
>>>> Marcus
>>>
>

-- 
------------------------------------------------------------------------
MzK

"Women and cats will do as they please,
  and men and dogs should relax and get used to the idea."
                                     -- Robert Heinlein

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