WebCaching framework

Note

This is a port of the old caching subsystem to the new uWSGI caching API documented here The uWSGI caching framework.Using the options here will create a new-style cache named “default”.

To enable web caching, allocate slots for your items using the cache option. The following command line would create a cache that can contain at most 1000 items.

  1. ./uwsgi --socket 127.0.0.1:3031 --module mysimpleapp --master --processes 4 --cache 1000

To use the cache in your application,

  1. uwsgi.cache_set("foo_key", "foo_value") # set a key
  2. value = uwsgi.cache_get("foo_key") # get a key.

Persistent storage

You can store cache data in a backing store file to implement persistence. Simply add the cache-store <filename> option.Every kernel will commit data to the disk at a different rate. You can set if/when to force this with cache-store-sync <n>, where n is the number of master cycles to wait before each disk sync.

Cache sweeper

Since uWSGI 1.2, cache item expiration is managed by a thread in the master process, to reduce the risk of deadlock. This thread can be disabled (making item expiry a no-op) with the cache-no-expire option.

The frequency of the cache sweeper thread can be set with cache-expire-freq <seconds>. You can make the sweeper log the number of freed items with cache-report-freed-items.

Directly accessing the cache from your web server

  1. location / {
  2.  uwsgi_pass 127.0.0.1:3031;
  3.  uwsgi_modifier1 111;
  4.  uwsgi_modifier2 3;
  5.  uwsgi_param key $request_uri;
  6. }

That’s it! Nginx would now get HTTP responses from a remote uwsgi protocol compliant server. Although honestly this is not very useful, as if you get a cache miss, you will see a blank page.

A better system, that will fallback to a real uwsgi request would be

  1. location / {
  2.   uwsgi_pass 192.168.173.3:3032;
  3.   uwsgi_modifier1 111;
  4.   uwsgi_modifier2 3;
  5.   uwsgi_param key $request_uri;
  6.   uwsgi_pass_request_headers off;
  7.   error_page 502 504 = @real;
  8. }
  9.  
  10. location @real {
  11.   uwsgi_pass 192.168.173.3:3032;
  12.   uwsgi_modifier1 0;
  13.   uwsgi_modifier2 0;
  14.   include uwsgi_params;
  15. }

Django cache backend

If you are running Django, there’s a ready-to-use application called django-uwsgi-cache. It is maintained by Ionel Cristian Mărieș at https://github.com/ionelmc/django-uwsgi-cache and available on pypi.