Re: Large File Download

sendfile sounds like its exactly what I'm looking for. I see it in the API
documentation for Apache2::RequestIO but how do I get a reference to it
from the reference to Apache2::RequestRec which is passed to my handler?

On Sat, Mar 28, 2015 at 9:54 AM, Perrin Harkins <[email protected]> wrote:

> Yeah, sendfile() is how I've done this in the past, although I was using
> mod_perl 1.x for it.
>
> On Sat, Mar 28, 2015 at 5:55 AM, André Warnier <[email protected]> wrote:
>
>> Randolf Richardson wrote:
>>
>>> I know that it's possible(and arguably best practice) to use Apache to
>>>> download large files efficiently and quickly, without passing them
>>>> through
>>>> mod_perl. However, the data I need to download from my application is
>>>> both
>>>> dynamically generated and sensitive so I cannot expose it to the
>>>> internet
>>>> for anonymous download via Apache. So, I'm wondering if mod_perl has a
>>>> capability similar to the output stream of a java servlet.
>>>> Specifically, I
>>>> want to return bits and pieces of the file at a time over the wire so
>>>> that
>>>> I can avoid loading the entire file into memory prior to sending it to
>>>> the
>>>> browser. Currently, I'm loading the entire file into memory before
>>>> sending
>>>> it and
>>>>
>>>> Is this possible with mod_perl and, if so, how should I go about
>>>> implementing it?
>>>>
>>>
>>>         Yes, it is possible -- instead of loading the entire contents of
>>> a file into RAM, just read blocks in a loop and keep sending them until you
>>> reach EoF (End of File).
>>>
>>>         You can also use $r->flush along the way if you like, but as I
>>> understand it this isn't necessary because Apache HTTPd will send the data
>>> as soon as its internal buffers contain enough data.  Of course, if you can
>>> tune your block size in your loop to match Apache's output buffer size,
>>> then that will probably help.  (I don't know much about the details of
>>> Apache's output buffers because I've not read up too much on them, so I
>>> hope my assumptions about this are correct.)
>>>
>>>         One of the added benefits you get from using a loop is that you
>>> can also implement rate limiting if that becomes useful.  You can certainly
>>> also implement access controls as well by cross-checking the file being
>>> sent with whatever internal database queries you'd normally use to ensure
>>> it's okay to send the file first.
>>>
>>>
>> You can also :
>> 1) write the data to a file
>> 2) $r->sendfile(...);
>> 3) add a cleanup handler, to delete the file when the request has been
>> served.
>> See here for details : http://perl.apache.org/docs/2.
>> 0/api/Apache2/RequestIO.html#C_sendfile_
>>
>> For this to work, there is an Apache configuration directive which must
>> be set to "on". I believe it is called "UseSendFile".
>> Essentially what senfile() does, is to delegate the actual reading and
>> sending of the file to Apache httpd and the underlying OS, using code which
>> is specifically optimised for this purpose.  It is much kore efficient than
>> doing this in a read/write loop by yourself, at the cost of having less
>> fine control over the operation.
>>
>
>


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