Apple iOS Apps and caching at the edge proxy

apple-iosPROXY

Our network contains a growing number of iOS devices, all of which with very similar configurations. All Internet access is via a transparent proxy.

We've found that iOS updates and some free apps cache fine on the proxy, but any paid apps fail to cache properly (as they seem to be encrypted to the Apple ID (?)).

I'm just wondering if there's any way forward with this where we could cache the paid apps so that they are purchased n times, but downloaded from the proxy cache instead of from the Internet each time. Bandwidth caps aside, the download direct from the Internet slows everything down for everyone, regardless of fairness queueing and related 'fixes'.

I know this is quite unlikely, but I figured there's nothing to lose and everything to gain before I look into other solutions (eg, QoS).

Best Answer

The data you want to cache isn't meant to be cached. It's specific to the user(s) who are downloading them. (Caching paid apps as they're downloaded would also make a great way to steal them, as well.)

This is why the origin server is sending headers like Cache-Control: private or no-cache along with it, to specifically instruct downstream caches like your proxy server not to cache the data.

Some caches such as squid provide ways of overriding these directives; since you didn't say what you were using, please see your documentation for details if you're really absolutely determined to do this. (But please don't. It'll break practically every other site that relies on this behavior being correct.)

Related Solutions

Nginx – How to Set Up as a Caching Reverse Proxy

I don't think that there is a way to explicitly invalidate cached items, but here is an example of how to do the rest. Update: As mentioned by Piotr in another answer, there is a cache purge module that you can use. You can also force a refresh of a cached item using nginx's proxy_cache_bypass - see Cherian's answer for more information.

In this configuration, items that aren't cached will be retrieved from example.net and stored. The cached versions will be served up to future clients until they are no longer valid (60 minutes).

Your Cache-Control and Expires HTTP headers will be honored, so if you want to explicitly set an expiration date, you can do that by setting the correct headers in whatever you are proxying to.

There are lots of parameters that you can tune - see the nginx Proxy module documentation for more information about all of this including details on the meaning of the different settings/parameters: http://nginx.org/r/proxy_cache_path

http {
  proxy_cache_path  /var/www/cache levels=1:2 keys_zone=my-cache:8m max_size=1000m inactive=600m;
  proxy_temp_path /var/www/cache/tmp; 


  server {
    location / {
      proxy_pass http://example.net;
      proxy_cache my-cache;
      proxy_cache_valid  200 302  60m;
      proxy_cache_valid  404      1m;
    }
  }
}

Caching proxy for yum and debian repositories

The closest thing will probably be mrepo. It's run out of band from Yum itself, though. You'd set up local mirrors of your favorite yum repos with mrepo and point your yum clients to that instead. It handles apt repos also, if that's of any benefit.

Best Answer

Related Solutions

Nginx – How to Set Up as a Caching Reverse Proxy

Caching proxy for yum and debian repositories

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