[OSM-dev] Proposal: Database accelerator and dirty tile marker based on simple algorithm.

[Andy Robinson]

Thanks, great response.

Cheers

Andy

Andy Robinson
Andy_J_Robinson at blueyonder.co.uk 

>-----Original Message-----
>From: dev-bounces at openstreetmap.org [mailto:dev-bounces at openstreetmap.org]
>On Behalf Of Nick Hill
>Sent: 21 September 2006 11:08 AM
>To: dev at openstreetmap.org
>Subject: Re: [OSM-dev] Proposal: Database accelerator and dirty tile marker
>based on simple algorithm.
>
>Hello Andy
>
>The server isn't being powered down.
>
>Each tile rendering request is spawning a new process up to a limit set
>in apache.  That process will normally live until until that tile has
>rendered. If the number of processes is not beyond max_servers, the
>process will live to serve another request.
>
>The more tiles we have in the process list, the longer it takes for each
>tile to render. The longer it takes for each tile to render, the more
>tile renderers end up in the process list. This gets to a point where
>the processes leave almost no CPU capacity for other functions, and use
>all available memory.
>
>At these points, munin is not able to register system status; there is
>not enough CPU power or memory to respond to the munin request. At these
>times, it appears the system is turned off.
>
>Ideally, we need a given number of rendering processes operating
>asynchronously from incoming requests. Rendering processes should not be
>queued, instead, rendering requests should be queued. This will optimise
>use of CPU cycles, memory and db.
>
>We need:
>1) A good tile invalidation system. Tiles should be cached until marked
>dirty.
>
>2) Asynchronous tile rendering processes. Asynchronous from incoming
>requests.
>
>3) A system to determine popular tiles. These should be speculatively
>re-rendered after being marked dirty when the system is quiet so they
>will already be rendered when a user asks for them.
>
>
>
>Andy Robinson wrote:
>> Nick,
>>
>> The Munin graphs appear to show the server being powered down or at least
>> not talking to the Munin log quite a lot throughout this week. Most
>> noticeable on the cpu plots. Is there a specific reason for that? The
>> behaviour is not there on previous weeks.
>>
>
>
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