Proof-of-concept squid proxy settings for proxying http://rubygems.org/ Tested on one project on my local machine both cold, and warm with internet turned off.

rewrite.rb

#!/usr/bin/env ruby
# url rewriter for rubygems squid proxy

STDOUT.sync = true
   
while line = gets
  url = line.split(' ')[0]

  # Cargo-culted this conditional, not sure if it is necessary
  response = if url
    # Need to find a better way to cache this redirect, rather than hard-coding
    # it.
    if url.include?("http://rubygems.org/gems/")
      "302:" + url.gsub(
        "http://rubygems.org/",
        "http://production.cf.rubygems.org/"
      )
    else
      ""
    end
  else
    ""
  end

  puts response
end

squid.conf

##########################################################################
#
# Proof-of-concept squid proxy settings for proxying http://rubygems.org/
# Caches everything so is resilient to network outage or upstream outage.
# Works with bundler, gives a significant speed up when cache is warm (100%+)
#
##########################################################################

# Disable default patterns that prevent caching of query params
# refresh_pattern -i (/cgi-bin/|\?) 0  0%	0
# refresh_pattern .		0	20%	4320

# Cache calls to resolve dependency list for at least 15 minutes, at max a day
# TODO: What is the actual behaviour of this? Desired is refresh after 15, but
# continue to work for a day if upstream is unavailable.
refresh_pattern -i /api/v1/dependencies 900 100% 86400

# "Cache" redirects so that the proxy is completely isolated from the internet
# when it is warm.
url_rewrite_program rewrite.rb

# 1 Gb disk cache. Probably larger is better.
cache_dir ufs /usr/local/var/cache/squid 1024 16 256

# BELOW THIS LINE IS DEFAULT SQUID CONFIG

# Recommended minimum configuration:
#

# Example rule allowing access from your local networks.
# Adapt to list your (internal) IP networks from where browsing
# should be allowed
acl localnet src 10.0.0.0/8	# RFC1918 possible internal network
acl localnet src 172.16.0.0/12	# RFC1918 possible internal network
acl localnet src 192.168.0.0/16	# RFC1918 possible internal network
acl localnet src fc00::/7       # RFC 4193 local private network range
acl localnet src fe80::/10      # RFC 4291 link-local (directly plugged) machines

acl SSL_ports port 443
acl Safe_ports port 80		# http
acl Safe_ports port 21		# ftp
acl Safe_ports port 443		# https
acl Safe_ports port 70		# gopher
acl Safe_ports port 210		# wais
acl Safe_ports port 1025-65535	# unregistered ports
acl Safe_ports port 280		# http-mgmt
acl Safe_ports port 488		# gss-http
acl Safe_ports port 591		# filemaker
acl Safe_ports port 777		# multiling http
acl CONNECT method CONNECT

#
# Recommended minimum Access Permission configuration:
#
# Only allow cachemgr access from localhost
http_access allow localhost manager
http_access deny manager

# Deny requests to certain unsafe ports
http_access deny !Safe_ports

# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports

# We strongly recommend the following be uncommented to protect innocent
# web applications running on the proxy server who think the only
# one who can access services on "localhost" is a local user
#http_access deny to_localhost

#
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS
#

# Example rule allowing access from your local networks.
# Adapt localnet in the ACL section to list your (internal) IP networks
# from where browsing should be allowed
http_access allow localnet
http_access allow localhost

# And finally deny all other access to this proxy
http_access deny all

# Squid normally listens to port 3128
http_port 3128

# Leave coredumps in the first cache dir
coredump_dir /usr/local/var/cache/squid

@xaviershay, what about the call that bundler makes for dependency resolution? I wonder if bundle install --full-index would use a cached gems index in that case? That might work.

I would be interested to see how successful this is, have you run a report on using the logs produced ?

http://cord.de/tools/squid/calamaris/ is what i use to gather information about HITS/MISSES and how much is "saved".

I want a rubygems caching proxy to work. It seems like with the heavy use of RVM and various ruby interpreters, installing gems faster would be a significant gain.

I know I'm a year late but playing with Docker has got me really hoping for a way to cache gem downloads. Anyone ever come up with a good solution?