Flask app : error while reading response header from upstream - nginx

Question

The site runs with nginx and an uwsgi (flask app) and shellinabox terminal.
After every 20 or 30 minutes, the shellinabox terminal is not getting loaded and the nginx log shows this -
2012/05/26 14:20:27 [error] 4547#0: *117 readv() failed (104: Connection reset by peer) while reading upstream, client: 192.168.122.128, server: _, request: "POST /login/ HTTP/1.1", upstream: "uwsgi://127.0.0.1:1973", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/login/"
2012/05/26 14:20:31 [crit] 4547#0: *105 mkdir() "/var/lib/nginx/tmp/proxy/3/00" failed (13: Permission denied) while reading upstream, client: 192.168.122.128, server: _, request: "GET /terminal/proxy/ShellInABox.js HTTP/1.1", upstream: "http://127.0.0.1:4200/ShellInABox.js", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/proxy/index/"
2012/05/26 14:21:06 [error] 4547#0: *103 upstream timed out (110: Connection timed out) while reading response header from upstream
, client: 192.168.122.128, server: _, request: "POST /terminal/proxy/? HTTP/1.1", upstream: "http://127.0.0.1:4200/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/proxy/index/"
2012/05/26 14:21:06 [error] 4547#0: *103 open() "/var/www/MYwebapp/templates/50x.html" failed (13: Permission denied), client: 192.168.122.128, server: _, request: "POST /terminal/proxy/? HTTP/1.1", upstream: "http://127.0.0.1:4200/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/proxy/index/"
2012/05/26 14:22:31 [error] 4547#0: *136 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 192.168.122.128, server: _, request: "GET /terminal/proxy/index/ HTTP/1.1", upstream: "http://127.0.0.1:4200/index/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/"
2012/05/26 14:22:31 [error] 4547#0: *136 open() "/var/www/MYwebapp/templates/50x.html" failed (13: Permission denied), client: 192.168.122.128, server: _, request: "GET /terminal/proxy/index/ HTTP/1.1", upstream: "http://127.0.0.1:4200/index/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/"
I tried to put sometime-out values ... nothing helped so far.
As I'm pretty much new to nginx/uwsgi/shellinabox, I'm currently stuck with this.
Here is my nginx.conf file -
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/MYwebapp_access.log main;
sendfile on;
#tcp_nopush on;
#keepalive_timeout 0;
keepalive_timeout 65;
#gzip on;
#
# The default server
#
server {
listen 80;
server_name _;
#charset koi8-r;
#access_log logs/host.access.log main;
location /terminal/proxy {
rewrite ^/terminal/proxy/(.*)$ /$1 break;
proxy_pass http://localhost:4200/index;
proxy_set_header X-Real-IP $remote_addr;
#proxy_read_timeout 3000;
uwsgi_connect_timeout 6000;
uwsgi_read_timeout 6000;
uwsgi_send_timeout 6000;
}
location / { try_files $uri #MYwebapp; }
location #MYwebapp {
include uwsgi_params;
uwsgi_pass localhost:1973;
uwsgi_connect_timeout 6000;
uwsgi_read_timeout 6000;
uwsgi_send_timeout 6000;
}
error_page 404 /404.html;
location = /404.html {
root /var/www/MYwebapp/templates;
}
# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /var/www/MYwebapp/templates;
}
}
# Load config files from the /etc/nginx/conf.d directory
include /etc/nginx/conf.d/*.conf;
2012/05/26 14:21:06 [error] 4547#0: *103 upstream timed out (110: Connection timed out) while reading response header from upstream
, client: 192.168.122.128, server: _, request: "POST /terminal/proxy/? HTTP/1.1", upstream: "http://127.0.0.1:4200/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/proxy/index/"
2012/05/26 14:21:06 [error] 4547#0: *103 open() "/var/www/MYwebapp/templates/50x.html" failed (13: Permission denied), client: 192.168.122.128, server: _, request: "POST /terminal/proxy/? HTTP/1.1", upstream: "http://127.0.0.1:4200/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/proxy/index/"
2012/05/26 14:22:31 [error] 4547#0: *136 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 192.168.122.128, server: _, request: "GET /terminal/proxy/index/ HTTP/1.1", upstream: "http://127.0.0.1:4200/index/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/"
2012/05/26 14:22:31 [error] 4547#0: *136 open() "/var/www/MYwebapp/templates/50x.html" failed (13: Permission denied), client: 192.168.122.128, server: _, request: "GET /terminal/proxy/index/ HTTP/1.1", upstream: "http://127.0.0.1:4200/index/", host: "www.MYwebapp.org", referrer: "http://www.MYwebapp.org/terminal/"