# How does nginx know about FastCGI's stderr? **URL:** \ **Category:** NGINX\ **Created:** [March 15, 2010, 4:16am UTC](https://www.ruby-forum.com/t/how-does-nginx-know-about-fastcgis-stderr/185144 "2010-03-15T04:16:06Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 15, 2010, 4:16am UTC](https://www.ruby-forum.com/t/how-does-nginx-know-about-fastcgis-stderr/185144/1 "2010-03-15T04:16:06Z")
nginx’s error.log says: 2010/03/15 11:13:15 [error] 10978#0: \*10642 FastCGI sent in stderr: "PHP Deprecated: Function ereg() is deprecated in /usr/local/cacti/lib/rrd.php on line 734 PHP Deprecated: Function ereg() is deprecated in /usr/local/cacti/lib/rrd.php on line 1020 etc. But I don’t know how nginx knows about FastCGI’s stderr? – Ren Xiaolei ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 15, 2010, 10:50am UTC](https://www.ruby-forum.com/t/how-does-nginx-know-about-fastcgis-stderr/185144/2 "2010-03-15T10:50:31Z")
Hello! On Mon, Mar 15, 2010 at 11:15:36AM +0800, 任晓磊 wrote: > nginx’s error.log says: > 2010/03/15 11:13:15 [error] 10978#0: \*10642 FastCGI sent in stderr: > "PHP Deprecated: Function ereg() is deprecated in > /usr/local/cacti/lib/rrd.php on line 734 > PHP Deprecated: Function ereg() is deprecated in > /usr/local/cacti/lib/rrd.php on line 1020 > > etc. But I don’t know how nginx knows about FastCGI’s stderr? [http://www.fastcgi.com/devkit/doc/fcgi-spec.html](http://www.fastcgi.com/devkit/doc/fcgi-spec.html) Maxim D. ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 15, 2010, 1:56pm UTC](https://www.ruby-forum.com/t/how-does-nginx-know-about-fastcgis-stderr/185144/3 "2010-03-15T13:56:40Z")
On Mon, Mar 15, 2010 at 5:49 PM, Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > [http://www.fastcgi.com/devkit/doc/fcgi-spec.html](http://www.fastcgi.com/devkit/doc/fcgi-spec.html) > Thank you, Maxim. The document above tells me the detail. I thought > the protocol is a couple of stdio pipes before read this. So, could you tell me why I see 502 when something in FastCGI’s stderr? Does texts from FastCGI’s stderr lead to 502 ? But the specs says they’re just application-level errors. – Ren Xiaolei ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 15, 2010, 2:15pm UTC](https://www.ruby-forum.com/t/how-does-nginx-know-about-fastcgis-stderr/185144/4 "2010-03-15T14:15:59Z")
Hello! On Mon, Mar 15, 2010 at 08:56:11PM +0800, 任晓磊 wrote: > On Mon, Mar 15, 2010 at 5:49 PM, Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > [http://www.fastcgi.com/devkit/doc/fcgi-spec.html](http://www.fastcgi.com/devkit/doc/fcgi-spec.html) > > Thank you, Maxim. The document above tells me the detail. I thought > > the protocol is a couple of stdio pipes before read this. > > So, could you tell me why I see 502 when something in FastCGI’s > stderr? Does texts from FastCGI’s stderr lead to 502 ? But the specs > says they’re just application-level errors. Writing to stderr shouldn’t lead to 502 from nginx. This may happen in two cases: 1. Application actually dies (or aborts request) after writing to stderr. 2. Bug in nginx. There is one known bug with fastcgi\_cache and large stderr from fastcgi apps which may lead to 502 returned unexpectedly. It’s mostly fixed in 0.8.34, though fix may lead to segfaults in nginx worker when fastcgi\_cache isn’t used, patch is here: > **[nginx 0.8.34 segmentation fault](http://mailman.nginx.org/pipermail/nginx-ru/2010-March/032836.html)** Maxim D. ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 15, 2010, 2:31pm UTC](https://www.ruby-forum.com/t/how-does-nginx-know-about-fastcgis-stderr/185144/5 "2010-03-15T14:31:12Z")
On Mon, Mar 15, 2010 at 9:15 PM, Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > 1. Bug in nginx. Â There is one known bug with fastcgi\_cache and > large stderr from fastcgi apps which may lead to 502 returned > unexpectedly. Â It’s mostly fixed in 0.8.34, though fix may lead to > segfaults in nginx worker when fastcgi\_cache isn’t used, patch is > here: > > [nginx 0.8.34 segmentation fault](http://nginx.org/pipermail/nginx-ru/2010-March/032836.html) ## Mostly like to be this. OK, I’ll wait for next version in 0.7 series, and try. Sorry to not helping because of my poor programming skill. Ren Xiaolei