[mapguide-internals] Re: Please review RFC 66

[Kenneth Skovhede, GEOGRAF A/S]

1)
On my setup "GETFEATUREPROVIDERS" returns 13Kb worth of xml.
It may not consume CPU resources, but it does consume bandwidth,
especially since it is not required, and it happens a fixed intervals,
even if the user is inactive.

If its too much work to put in a real function, I think Zac's proposal 
is way better,
but I'm not sure it will work if admin functions are disabled in the 
WebTier.

2)
There is a clear 1-1 relation between the server timeout setting and the 
client ping setting.
If you can read the timeout value on viewer startup, that is fine, but I 
don't think you can.

If you require the admin-user to change the time in two places, you can 
be certain
that there will be a pile of support requests.
Also, for a non-specialist, it is not immediately obvious that the two 
should not be the
same, eg. setting both to 15 minutes will make the sessions expire at 
random, due to races
and clock drift.

3) I have seen scenarios where a single reqest fails.
If you know the duration of the session, it is easy to ignore 
"connection broken" responses,
and only stop pinging when there has been no positive response within a 
session duration.

I think you need to adress issue 1 and 2.
Issue 3 is easy and will improve failure resilience, but not required.

Regards, Kenneth Skovhede, GEOGRAF A/S



Zac Spitzer skrev:
> how about GETSITEVERSION ? that's what I have used for keepalives in
> my own stuff
> and it returns a much smaller response?
>
> z
>
> On Mon, Jun 22, 2009 at 4:05 PM, Christine
> Bao<Christine.Bao at autodesk.com> wrote:
>   
>> Hi Kenneth,
>>
>>     Thank you for your suggestion. Here are my comments:
>>
>>
>> 1.       A real function to support "keep alive" pings
>>
>> We plan to call "GETFEATUREPROVIDERS" through MapAgent to keep alive. This function is light-weighted and won't cause much overhead. Using this method is the easiest way to approach it. Your suggestion makes sense, but we'll need to add another API which is only for this purpose, so we decide not to do this.
>>
>>
>>
>> 2.       The client read out timeout value to adjust ping interval
>>
>> I'm afraid it's too much complicated. The plan is to ping server at a fixed time interval (of course you can set it in configuration), and the interval won't change during runtime. It works as Fusion does.
>>
>>
>>
>> 3.       Connection broken
>>
>> Once the connection broken or timeout because server down, the client will stop ping server. But it will not recovery from a broken/timeout session.
>>
>> Thanks & regards,
>> Christine
>>
>>
>> ------------------------------
>>
>>
>>
>> Message: 3
>>
>> Date: Fri, 19 Jun 2009 12:41:14 +0200
>>
>> From: "Kenneth Skovhede, GEOGRAF A/S" <ks at geograf.dk>
>>
>> Subject: Re: [mapguide-internals] RE: Please review RFC 66
>>
>> To: MapGuide Internals Mail List <mapguide-internals at lists.osgeo.org>
>>
>> Message-ID: <4A3B6B4A.7050206 at geograf.dk>
>>
>> Content-Type: text/plain; charset=ISO-8859-3; format=flowed
>>
>>
>>
>> I commented on the issue as well.
>>
>>
>>
>> You are free to ignore it, but in case you somehow missed it, here it is:
>>
>> http://n2.nabble.com/Please-review-RFC-66-tc3090381.html#a3092233
>>
>>
>>
>> Regards, Kenneth Skovhede, GEOGRAF A/S
>>
>>
>>
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>>     
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