Rails app running on puma and nginx keeps dying every few hours with Bad Gateway - ruby-on-rails

Question

I have a rails app that I just deployed to Digital Ocean and it's running on Puma and Nginx.
Eventually all it returns is a bad gateway and this is what is in the error.log
2014/09/09 22:23:06 [error] 5729#0: *3059 connect() to unix:///var/www/mysite/mysite_app.sock failed (111: Connection refused) while connecting to upstream, client: 67.5.19.192, server: mysite.com, request: "GET / HTTP/1.1", upstream: "http://unix:///var/www/mysite/mysite_app.sock:/", host: "mysite.com"
To fix it, I just restart puma and it seems to work.
How can I debug this to figure out why it keeps dying?
Here's my nginx config:
upstream mysite {
server unix:///var/www/mysite/mysite_app.sock;
}
server {
listen 80;
server_name mysite.com;
root /var/www/mysite/current/public;
client_max_body_size 20M;
location / {
proxy_pass http://mysite; # match the name of upstream directive which is defined above
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
location ~* ^/assets/ {
# Per RFC2616 - 1 year maximum expiry
expires 1y;
add_header Cache-Control public;
# Some browsers still send conditional-GET requests if there's a
# Last-Modified header or an ETag header even if they haven't
# reached the expiry date sent in the Expires header.
add_header Last-Modified "";
add_header ETag "";
break;
}
}
EDIT
Could this be caused from running out of memory?
Here's my current state of memory, but as I keep running this command every so often, the amount of free memory goes down and once i restart puma it jumps back up to like 150.
$ free -m
total used free shared buffers cached
Mem: 490 440 50 0 17 84
-/+ buffers/cache: 338 151
Swap: 0 0 0

Answer 1

It seems this is actually an issue with ruby 2.1 (specifically i'm using 2.1.2) and its garbage collection.
A google search like this seems to have lots of various threads on it http://bit.ly/1s2vBC0
Here's a ruby bug ticket on the issue: https://bugs.ruby-lang.org/issues/9607

Answer 2

Lack of memory can be issue, but you better look into puma and rails logs, not nginx only. In the application folder:
tail -f log/puma*
tail -f log/production.log

Answer 3

I've had similar issues but I note that 2.1.3 has now been released and specifically discusses memory issues:
https://www.ruby-lang.org/en/news/2014/09/19/ruby-2-1-3-is-released/
I'm going to try it now!