Re: Re: overhead of ZEO connection

On Wed, May 11, 2016 at 8:25 AM, Sanjay Rao <[email protected]> wrote:
> How many connections can be assumed to be safe in that case. ?
> What if my application opens lots of connections(hundreds) ?

This isn't a "safety" issue. Each (ZODB not ZEO) connection has a
cache, which consumes memory.  How much memory your application
consumes depends on how many connections you have and how many objects
are in the caches. Both of
these are tunable.  What's right is a design decision. There isn't a
one-size-fits-all answer.

Note that if your application is compute bound, then it doesn't make
sense to have many threads. For example, traditional (Web1) Zope
applications tended to spend most of their time computing pages.  For
these sorts of applications, I would a) try to make the cache large
enough for most or all of the needed data to fit in RAM and b) use a
single thread, because the GIL wouldn't allow any more throughput with
more threads.

Also, WRT connection pool size, in addition to warning when the number
of connections exceeds the pool size, excess connections will be
discarded when they are closed, discarding their caches. If exceeding
the pool size is rare, then this works well. If you routinely have
more connections, you should consider increasing the pool size, or
more likely reducing the thread count.

Jim

>
> On Tuesday, 10 May 2016 03:40:28 UTC+5:30, Tres Seaver wrote:
>>
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>> On 05/08/2016 08:11 AM, Sanjay Rao wrote:
>>
>> > Thanks for reply. If pool size is 8 then is following true ?
>> >
>> > In application; there are some long running(may run more than a hour)
>> >  threads. there are 8 such threads these 8 long running threads get
>> > all available 8 connections in pool
>> >
>> > There are some short duration threads also, which read/write in
>> > database. These short duration threads won't get connection until at
>> > least one of the long running thread does not release connection.
>>
>> The DB object is willing to create new connections if the pools is empty:
>> it will begin to warn about the overage in the log.
>>
>>
>> Tres.
>> - --
>> ===================================================================
>> Tres Seaver          +1 540-429-0999          [email protected]
>> Palladion Software   "Excellence by Design"    http://palladion.com
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-- 
Jim Fulton
http://jimfulton.info

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