# How to disable buffering when using FastCGI? **URL:** \ **Category:** NGINX\ **Created:** [October 13, 2009, 1:30pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212 "2009-10-13T13:30:34Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 1:30pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/1 "2009-10-13T13:30:34Z")
Is there a way to disable buffering when using FastCGI? (for a Comet style application) Is there an option “fastcgi\_buffering off”, working like the option “proxy\_buffering off” in the HTTP proxy module? Thanks, Nicolas Grilly ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 1:32pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/2 "2009-10-13T13:32:54Z")
Nicolas Grilly wrote: > Is there a way to disable buffering when using FastCGI? (for a Comet > style application) > > Is there an option “fastcgi\_buffering off”, working like the option > “proxy\_buffering off” in the HTTP proxy module? Have you tried: fastcgi\_buffers 0 0; ? – _Phillip B Oldham_ ActivityHQ [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) * * * _Policies_ This e-mail and its attachments are intended for the above named recipient(s) only and may be confidential. If they have come to you in error, please reply to this e-mail and highlight the error. No action should be taken regarding content, nor must you copy or show them to anyone. This e-mail has been created in the knowledge that Internet e-mail is not a 100% secure communications medium, and we have taken steps to ensure that this e-mail and attachments are free from any virus. We must advise that in keeping with good computing practice the recipient should ensure they are completely virus free, and that you understand and observe the lack of security when e-mailing us. ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 2:21pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/3 "2009-10-13T14:21:30Z")
Hello! On Tue, Oct 13, 2009 at 12:17:05PM +0200, Nicolas Grilly wrote: > Is there a way to disable buffering when using FastCGI? (for a Comet > style application) > > Is there an option “fastcgi\_buffering off”, working like the option > “proxy\_buffering off” in the HTTP proxy module? No, there is no such option. Buffering can’t be disabled for fastcgi. Maxim D. ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 4:21pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/4 "2009-10-13T16:21:30Z")
2009/10/13 Phillip O. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > Nicolas Grilly wrote: > Is there a way to disable buffering when using FastCGI? (for a Comet > style application) > > Is there an option “fastcgi\_buffering off”, working like the option > “proxy\_buffering off” in the HTTP proxy module? > > Have you tried: > > fastcgi\_buffers 0 0; Yes, I have tried this option, but it disables buffering only for the FastCGI module, not for the output filters (especially gzip and SSL modules). So, this option is not enough to completely disable buffering. ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 4:54pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/5 "2009-10-13T16:54:18Z")
Hello Nicolas, Tuesday, October 13, 2009, 9:20:00 PM, you wrote: > > fastcgi. > > Hello Maxim, > Is there no such option just because nobody implemented it? Or is it > because of some kind of technical constraint? Yes. It’s because of FastCGI protocol internals. It splits “stream” into blocks max 32KB each. Each block has header info (how many bytes it contains, etc). So nginx can’t send content to the client until it get the whole block from upstream. > Do you recommend to people developing Comet style application to use > HTTP proxying instead of FastCGI? Yes. Nginx can establish pipe between backend and client just after headers are sent in case when proxy\_buffering = off and gzip = off. > Is it difficult to implement the option “fastcgi\_buffering off”, using > the same technique as in the source code of module HTTP proxy? It is not possible. See comment above. > Thanks for your advice, ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 4:26pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/6 "2009-10-13T16:26:12Z")
On Tue, Oct 13, 2009 at 13:19, Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On Tue, Oct 13, 2009 at 12:17:05PM +0200, Nicolas Grilly wrote: > > > Is there a way to disable buffering when using FastCGI? (for a Comet > > style application) > > > > Is there an option “fastcgi\_buffering off”, working like the option > > “proxy\_buffering off” in the HTTP proxy module? > > No, there is no such option. šBuffering can’t be disabled for > fastcgi. Hello Maxim, Is there no such option just because nobody implemented it? Or is it because of some kind of technical constraint? Do you recommend to people developing Comet style application to use HTTP proxying instead of FastCGI? Is it difficult to implement the option “fastcgi\_buffering off”, using the same technique as in the source code of module HTTP proxy? Thanks for your advice, Nicolas Grilly ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 7:35pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/7 "2009-10-13T19:35:16Z")
Hello! On Tue, Oct 13, 2009 at 04:20:00PM +0200, Nicolas Grilly wrote: > > fastcgi. > > Hello Maxim, > > Is there no such option just because nobody implemented it? Or is it > because of some kind of technical constraint? Something like this. FastCGI requires buffer processing which isn’t compatible with current code for unbuffered connections. > Do you recommend to people developing Comet style application to use > HTTP proxying instead of FastCGI? For now you should either close & reopen connections, or use HTTP proxy instead. > Is it difficult to implement the option “fastcgi\_buffering off”, using > the same technique as in the source code of module HTTP proxy? Current “proxy\_buffering off” implementation is something wierd and should be nuked, IMHO. The same implementation for FastCGI just won’t work. I believe buffering control in upstream module (which includes fastcgi, proxy and memcached) should be changed to something more flexible. In particular, fastcgi should be aware of FastCGI record boundaries, and shouldn’t try to buffer too much as long as it got full record. I’ve posted some preliminary patches for this as a part of backend keepalive support work, but they are a bit stale now. Maxim D. ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 8:36pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/8 "2009-10-13T20:36:44Z")
Hello again Maxim, 2009/10/13 Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > On Tue, Oct 13, 2009 at 04:20:00PM +0200, Nicolas Grilly wrote: > > > Is there no such option just because nobody implemented it? Or is it > > because of some kind of technical constraint? > > Something like this. šFastCGI requires buffer processing which > isn’t compatible with current code for unbuffered connections. Understood. > > Do you recommend to people developing Comet style application to use > > HTTP proxying instead of FastCGI? > > For now you should either close & reopen connections, or use HTTP > proxy instead. So, for now, I guess my best bet is to use HTTP proxying 🙂 > record boundaries, and shouldn’t try to buffer too much as long as > it got full record. > > I’ve posted some preliminary patches for this as a part of backend > keepalive support work, but they are a bit stale now. It would be a perfect solution! If the fastcgi module is aware of FastCGI record boundaries and stops buffering after having received a full record, then the problem is solved. This gives to the FastCGI backend complete control over the amount of buffering, sending short records in order to limit buffering, or sending long records (around 8KB) for normal buffering. Is it your plan for the future of the upstream module? Cheers, Nicolas ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 8:20pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/9 "2009-10-13T20:20:57Z")
Hello Denis! Thanks for your explanations. 2009/10/13 Denis F. Latypoff [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > Tuesday, October 13, 2009, 9:20:00 PM, you wrote: > > > Is there no such option just because nobody implemented it? Or is it > > because of some kind of technical constraint? > > Yes. It’s because of FastCGI protocol internals. It splits “stream” > into blocks max 32KB each. Each block has header info (how many bytes > it contains, etc). So nginx can’t send content to the client until it > get the whole block from upstream. I agree that when a FastCGI backend sends a record to the web server, the web server must wait for the complete record before forwarding it to the client. This implies a lot of buffering if the records sent by the FastCGI backend are very long. Alternatively, the FastCGI backend can choose to send very short records (for example 50 bytes) and then the web server must be able to forward each record immediately after reception, without any buffering. Source: the FastCGI specification ([http://www.fastcgi.com/drupal/node/6?q=node/22](http://www.fastcgi.com/drupal/node/6?q=node/22)) and its Python implementation ([http://trac.saddi.com/flup/browser/flup/server/fcgi\_base.py](http://trac.saddi.com/flup/browser/flup/server/fcgi_base.py)) But even when the records sent by the FastCGI backend are very short (around 50 bytes), Nginx doesn’t send them immediately. Nginx seems to buffer over FastCGI record boundaries. Am I correct? > > Is it difficult to implement the option “fastcgi\_buffering off”, using > > the same technique as in the source code of module HTTP proxy? > > It is not possible. See comment above. May be we can force Nginx to send data back to the client just after having received each FastCGI record? Is it possible? Thanks a lot for your advice, Cheers, Nicolas Grilly ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 14, 2009, 2:31pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/10 "2009-10-14T14:31:39Z")
Hello Maxim, 2009/10/13 Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > to optimize brain-damaged backends. šBut as long as fastcgi > finished record and not started another one - it’s probably a good > idea to pass data we got so far downstream. šAnd current aproach > won’t work with keepalive connections anyway. > > But please keep in mind that I’m not Igor. Thank you for your explanations! I will keep an eye on the evolution of the FastCGI buffering, but I understand this is a complex topic. In the meantime, I will use HTTP proxying. Nicolas Grilly ---
**Author:** ![Nicolas\_Grilly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/77aa72/32.png) [@Nicolas\_Grilly](https://www.ruby-forum.com/u/Nicolas_Grilly)\ **Post date:** [October 13, 2009, 9:52pm UTC](https://www.ruby-forum.com/t/how-to-disable-buffering-when-using-fastcgi/177212/11 "2009-10-13T21:52:16Z")
Hello! On Tue, Oct 13, 2009 at 08:24:53PM +0200, Nicolas Grilly wrote: […] > > record boundaries, and shouldn’t try to buffer too much as long as > > 8KB) for normal buffering. Is it your plan for the future of the > > upstream module? Complete control isn’t really good thing, as it limits the ability to optimize brain-damaged backends. But as long as fastcgi finished record and not started another one - it’s probably a good idea to pass data we got so far downstream. And current aproach won’t work with keepalive connections anyway. But please keep in mind that I’m not Igor. Maxim D.