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http://issues.apache.org/jira/browse/MODPYTHON-107?page=comments#action_12362040
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Graham Dumpleton commented on MODPYTHON-107:
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For PSP, the generated code actually explicitly says not to flush the output
and so is okay in that respect. Unfortunately, the CONTENT_LENGTH output filter
does not in work with PSP.
The reason is that although each individual req.write() doesn't flush, the PSP
code itself does an explicit flush after running the generated page code.
exec code in global_scope
req.flush()
For it to work, the req.flush() call would have to be removed.
Removing this shouldn't cause any issues when mod_python.psp is used as the
handler, but it may or may not be noticeable where people use PSP.run() method
from a distinct handler. This is because output would no longer be flushed by
PSP.run(). Frankly though, I don't think anyone would notice as it will get
flushed on any subsequent write or when handler returns.
> mod_python.publisher shouldn't flush result when written.
> ---------------------------------------------------------
>
> Key: MODPYTHON-107
> URL: http://issues.apache.org/jira/browse/MODPYTHON-107
> Project: mod_python
> Type: Improvement
> Components: publisher
> Versions: 3.2
> Reporter: Graham Dumpleton
>
> In mod_python.publisher, the result returned from a published function is
> returned as the content of the response after it has been converted to a
> string, using:
> req.write(result)
> In doing this, the second argument of req.write() is defaulting to '1', which
> indicates that the output should be flushed immediately.
> This fact prevents an output filter like CONTENT_LENGTH being used in
> conjunction with mod_python.publisher.
> This output filter will add a content length header to the response, but only
> if it is able to read the full content the first time the output filter is
> called. Because the output is flushed at this point, the output filter isn't
> able to do that, as it gets called twice. The first time it gets called will
> be with the actual content, the second time happens when the handler returns
> apache.OK and is effectively a null output call to force the output filter to
> be closed off.
> If instead the output is written as:
> req.write(result,0)
> the output will not be flushed immediately and instead will be output in one
> call when apache.OK is returned. There is no loss of efficiency in doing this
> and instead it will actually eliminate a redundant call into the output
> filter.
> For further details of this issue see discussion in:
> http://www.mail-archive.com/python-dev@httpd.apache.org/msg00951.html
> This makes one wander if there should be a configurable option for
> mod_python.psp to tell it not to flush output as well so that CONTENT_LENGTH
> could be used in that case as well. ???
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