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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: Rephrasing " worker already used"
Date Mon, 23 Aug 2010 10:39:52 GMT
On 10.08.2010 20:30, Ruediger Pluem wrote:
>
>
> On 08/10/2010 07:55 PM, Jim Jagielski wrote:
>> On Aug 5, 2010, at 7:32 AM, Plüm, Rüdiger, VF-Group wrote:
>>
>>>
>>>> -----Original Message-----
>>>> From: Rainer Jung
>>>> Sent: Donnerstag, 5. August 2010 13:14
>>>> To: dev@httpd.apache.org
>>>> Subject: Rephrasing " worker already used"
>>>>
>>>> The message "worker ... already used by another worker" seems
>>>> to not say
>>>> what's actually happening.
>>>>
>>>> Situation:
>>>>
>>>> ProxyPass /X http://a.b.c.d/A
>>>> ProxyPass /Y http://a.b.c.d/AB
>>>>
>>>> Wouldn't a message
>>>>
>>>> worker "http://a.b.c.d/A" will also be used for URL "/Y"
>>>>
>>>> be more correct?
>>>>
>>>> In addition: we do overwrite the worker config (additional
>>>> attributes)
>>>> when parsing the second ProxyPass. Should we add a message
>>>>
>>>> Merging configuration for worker "http://a.b.c.d/A"
>>> Actually it doesn't merge the configuration. For some parameters like
>>> timeout they get overwritten with the defaults if not configured again in the
>>> ProxyPass directive. So
>>>
>>> ProxyPass /X http://a.b.c.d/A timeout=5
>>> ProxyPass /Y http://a.b.c.d/AB
>>>
>>> Will result in a worker http://a.b.c.d/A with timeout set to the default value
>>> (ProxyTimeout / Timeout).
>>>
>>
>> The question is whether this should be expected... I feel that
>> the docs could be clearer that in many cases, we are looking
>> at prefixes, and not distinct entities.

> IMHO this is not expected. Rainer already indicted that he intends to change this.
> I think if we do not create a new worker in this situation, but using the existing
> one we should at most overwrite the explicitly set parameters, but do not reset
> parameters to default values.

I applied a change to trunk in r987854.

Now all setting of the later worker, which doesn't actually get created 
are ignored. If there are explicit settings for the worker, a warning 
about the specific settings eing ignored is logged.

Furthermore the "worker is used by another worker" sentence has been 
rephrased as "Sharing worker 'URL1' instead of creating new worker 'URL2'".

Finally I added a paragraph about worker sharing to the proxy docs.

IMHO these changes are a candidate for backport.

Still not improved: all ordering issues. At the moment it depends on the 
ordering of the worker definitions in the config, whether worker sharing 
happens or not. Also dependent on the order is e.g. which ProxyPass wins 
in case multiple of those apply. This is documented.

Regards,

Rainer

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