proxy_buffering off causes truncated responses when backend emits response in small chunks
W. Andrew Loe III
andrew at andrewloe.com
Wed Feb 8 01:13:42 UTC 2012
Mystery solved. I will just proxy_max_temp_file_size 0, as the intention
was to just avoid the disk.
On Tue, Feb 7, 2012 at 4:23 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:
> On Tue, Feb 07, 2012 at 03:54:08PM -0800, W. Andrew Loe III wrote:
> > We use nginx as both a load-balancer and webserver. This issue is with
> > nginx functioning as a load-balancer.
> > We reverse proxy to 6 nginx webservers running a number of Unicorn
> > application servers, these webserver nginx instances also run Evan
> > mod_zip to assemble archives on the fly. We have discovered under certain
> > circumstances the load-balancing nginx will "hang-up" on the webserver if
> > the load-balancer is configured with proxy_buffering off, however
> > proxy_buffering on seems to succeed. We would prefer to run without
> > proxy_buffering to prevent the load-balancer's local storage from being
> > overrun.
> If you want to disable disk buffering you don't need to disable
> buffering at all. Use
> proxy_max_temp_file_size 0;
> The only valid reason to disable buffering completely with
> "proxy_buffering off" is when you need even single byte from
> backend to be immediately passed to client, i.e. as in some
> streaming / long polling cases.
> > Our default setup uses nginx 0.7.65 for both the load-balancer and the
> > webserver, however switching to using 1.0.12 as the load-balancer has the
> > same problem. We have experimented with different software doing the
> > load-balancing and it does not exhibit this issue.
> > I've have linked the nginx configuration file we're using on the load
> > balancer, and debug logs for both 0.7.65 and 1.0.12.
> > https://x.onehub.com/transfers/sg32zsar
> > The buffering on log is very long, but it does show success of a 4.8GB
> > response, the other responses always fail at the same point (826 MB).
> > The client sees the following (in access.log):
> > $ curl -b cookie.txt -o US.zip
> > % Total % Received % Xferd Average Speed Time Time Time
> > Current
> > Dload Upload Total Spent Left
> > Speed
> > 16 4922M 16 826M 0 0 1906k 0 0:44:03 0:07:23 0:36:40
> > 1075k
> > curl: (18) transfer closed with 4294967296 bytes remaining to read
> The response is over 4G, and this won't work with "proxy_buffering
> off" in 1.0.x on 32bit systems. The non-buffered mode was
> originally designed for small memcached responses and used to use
> size_t for length storage.
> You have to upgrade to 1.1.x where it now uses off_t and will be
> able to handle large responses even on 32bit platforms.
> Alternatively, just forget about "proxy_buffering off" as you
> don't need it anyway, see above.
> Maxim Dounin
> nginx mailing list
> nginx at nginx.org
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