[OSM-dev] Data corruption :) II

Tom Hughes tom at compton.nu
Mon Nov 24 13:07:18 GMT 2008


Stefan de Konink wrote:
> Tom Hughes wrote:
>
>>>> + loss of control unless all proxy targets are maintained by
>>>>   the OSM admin team
>>>
>>> The OSM admin team maintains the proxy. And targets get checked if 
>>> they have the latest minutely's every hour -> if not, remove from pool.
>>
>> Absolutely not. That way leads to chaos. We know this from the t at h 
>> proxy experience where there was always at least one server that 
>> didn't seem to be working.
> 
> If not working; not in the pool? That is pretty trivial. Just an 
> automatic script.

...and how often should that script run? You say hourly and I say that 
is nowhere near good enough.

Just taking out machines is not a solution though as we need to make 
sure we have enough machines available to handle the load, and we can't 
do that if other people can reduce our resource arbitrarily, either by 
accident or deliberately. That is why all the resource used to provide 
the API needs to be managed by one group of people that are able to 
ensure that things are properly managed.

It really is quite simple - any solution which involves resources not 
under the control of the admin team is one which I will not be involved 
in managing.

>>>>> What is the down time you expect for 0.6 migration?
>>>>
>>>> We are still attempting to quantify that.
>>>
>>> New server an option?
>>
>> Moving to a new database server is part of the migration plan.
> 
> Then why would there be any serious downtime then? (Longer than 5 
> minutes to synchronise with the latest diff)

Synchronise what with the latest diffs? Diffs have nothing to do with 
this - we will be dumping the old database on the current server, then
mangling it to 0.6 format and reloading it on the new server. At least 
that is the current plan.

Because we will be moving servers we will in fact probably be able to 
keep the site running in read only mode on the old server during the 
move, although it may be that we decide it is not a good idea to do so 
as it might lead to people having offline edits in 0.5 format which 
would be hard to upload after the change.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://www.compton.nu/




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