# Slow performance when sending a large file upload request via proxy\_pass **URL:** \ **Category:** NGINX\ **Created:** [July 17, 2016, 4:19pm UTC](https://www.ruby-forum.com/t/slow-performance-when-sending-a-large-file-upload-request-via-proxy-pass/244958 "2016-07-17T16:19:23Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\ **Post date:** [July 17, 2016, 4:19pm UTC](https://www.ruby-forum.com/t/slow-performance-when-sending-a-large-file-upload-request-via-proxy-pass/244958/1 "2016-07-17T16:19:23Z")
I’m trying to diagnose some strange behavior in my web app, and at the moment it seems like nginx may be at fault, though I’d be happy to learn otherwise. On the client side, I’m using flow.js ([GitHub - flowjs/flow.js: A JavaScript library providing multiple simultaneous, stable, fault-tolerant and resumable/restartable file uploads via the HTML5 File API.](https://github.com/flowjs/flow.js)) to upload a file to the server. This library should allow me to upload very large files by splitting them up into (by default) 1MB chunks, and sending each chunk as a standard file form upload request. On the server, I am connecting to a Python WSGI server (gunicorn) via try\_files / proxy\_pass. The configuration is very standard: ``` location / { root /var/www; index index.html index.htm; try_files $uri $uri/ @proxy_to_app; } location @proxy_to_app { proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect off; proxy_pass http://app_server; } ``` The Python code is pretty simple, mainly just opening the file and writing the data. According to the gunicorn access log, each request takes around 135ms: ``` 127.0.0.1 - - [17/Jul/2016:05:07:07 +0000] "POST /files HTTP/1.0" ``` 200 - … 0.135206 127.0.0.1 - - [17/Jul/2016:05:07:07 +0000] “POST /files HTTP/1.0” 200 - … 0.136749 127.0.0.1 - - [17/Jul/2016:05:07:07 +0000] “POST /files HTTP/1.0” 200 - … 0.137314 But in the nginx access log, the $request\_time varies wildly and is usually very large: ``` 10.0.0.0 - - [17/Jul/2016:05:07:06 +0000] "POST /files HTTP/1.1" 200 ``` … 0.956 10.0.0.0 - - [17/Jul/2016:05:07:07 +0000] “POST /files HTTP/1.1” 200 … 0.553 10.0.0.0 - - [17/Jul/2016:05:07:07 +0000] “POST /files HTTP/1.1” 200 … 0.888 At first I thought it might be the network itself taking a long time to send the data, but looking at the network logs in the browser doesn’t seem to bear this out. Once the socket connection is established, Chrome says that the request time is often as low as 8ms, with the extra ~.5s-1s spent waiting for a response. So the question is, what is nginx doing during all that extra time? On normal (small) requests, the times in the two logs are identical, but even dialing down the chunk size to flow.js to 128kb or 64kb results in a delay in nginx, and it’s making it take way too long to upload these files (I can’t just set the chunk size to something super small like 4kb, because the overhead of making so many requests makes the uploads slower). I’ve tried messing with various configuration options including proxy\_buffer\_size and proxy\_request\_buffering, to no effect. Any ideas on next steps for how I could begin to diagnose this? Extra info: ``` CentOS 7, running on AWS nginx version: nginx/1.10.1 built by gcc 4.8.5 20150623 (Red Hat 4.8.5-4) (GCC) built with OpenSSL 1.0.1e-fips 11 Feb 2013 TLS SNI support enabled configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx ``` –modules-path=/usr/lib64/nginx/modules –conf-path=/etc/nginx/nginx.conf –error-log-path=/var/log/nginx/error.log –http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid –lock-path=/var/run/nginx.lock –http-client-body-temp-path=/var/cache/nginx/client\_temp –http-proxy-temp-path=/var/cache/nginx/proxy\_temp –http-fastcgi-temp-path=/var/cache/nginx/fastcgi\_temp –http-uwsgi-temp-path=/var/cache/nginx/uwsgi\_temp –http-scgi-temp-path=/var/cache/nginx/scgi\_temp --user=nginx –group=nginx –with-http\_ssl\_module --with-http\_realip\_module –with-http\_addition\_module –with-http\_sub\_module --with-http\_dav\_module --with-http\_flv\_module –with-http\_mp4\_module --with-http\_gunzip\_module –with-http\_gzip\_static\_module --with-http\_random\_index\_module –with-http\_secure\_link\_module --with-http\_stub\_status\_module –with-http\_auth\_request\_module --with-http\_xslt\_module=dynamic –with-http\_image\_filter\_module=dynamic --with-http\_geoip\_module=dynamic –with-http\_perl\_module=dynamic –add-dynamic-module=njs-1c50334fbea6/nginx –with-threads --with-stream --with-stream\_ssl\_module –with-http\_slice\_module --with-mail --with-mail\_ssl\_module –with-file-aio –with-ipv6 --with-http\_v2\_module --with-cc-opt=‘-O2 -g -pipe -Wall -Wp,-D\_FORTIFY\_SOURCE=2 -fexceptions -fstack-protector-strong –param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic’ Posted at Nginx Forum: > **[Slow performance when sending a large file upload request via proxy\_pass](https://forum.nginx.org/read.php?2,268317,268317#msg-268317)** > > I'm trying to diagnose some strange behavior in my web app, and at the moment it seems like nginx may be at fault, though I'd be happy to learn otherwise. On the client side, I'm using flow.js (https://github.com/flowjs/flow.js) to upload a file to...