ecache: Erlang ETS Based TTL Cache
ecache stores your cache items in ets. Each cache item gets its own monitoring process to auto-delete the cache item when the TTL expires.
ecache has the API of pcache but stores data in ets instead of storing data in individual processes.
The cache server is designed to memoize a specific Module:Fun. The key in a cache is the Argument passed to Module:Fun/1.
Start a cache:
CacheName = my_cache, M = database, F = get_result, Size = 16, % 16 MB cache Time = 300000, % 300,000 ms = 300s = 5 minute TTL Server = ecache_server:start_link(CacheName, M, F, Size, Time).
The TTL is an idle timer. When an entry is accessed, the TTL for the entry is reset. A cache with a five minute TTL expires entries when nothing touches an entry for five minutes.
You can update a cached value by marking an entry dirty. You can mark an entry dirty with no arguments so it immediately gets deleted (the next request will request the data from your backing function again) or you can dirty an entry with a new value in-place.
Example of Cache Usage
Result = ecache:get(my_cache, <<"bob">>). ecache:dirty(my_cache, <<"bob">>, <<"newvalue">>). % replace entry for <<"bob">> ecache:dirty(my_cache, <<"bob">>). % remove entry from cache ecache:empty(my_cache). % remove all entries from cache RandomValues = ecache:rand(my_cache, 12). RandomKeys = ecache:rand_keys(my_cache, 12).
Example of Caching Arbitrary M:F/1 Calls
Bonus feature: Instead of creating one cache per backing function, you can also memoize any arbitrary M:F/1 call.
Result = ecache:memoize(my_cache, OtherMod, OtherFun, Arg). ecache:dirty_memoize(my_cache, OtherMod, OtherFun, Arg). % remove entry from cache
ecache:memoize/4 helps us get around annoying issues of one-cache-per-mod-fun.
Your root cache Mod:Fun could point to a function you never use if you only want to use
Nobody likes writing supervisor entries by hand, so we provide a supervisor entry helper. This is quite useful because many production applications will have 5 to 100 individual cache pools.
SupervisorWorkerTuple = ecache:cache_sup(Name, M, F, Size).
For more examples, see https://github.com/mattsta/ecache/blob/master/test/ecache_tests.erl
ecache is pcache but converted to use ets instead of processes. ecache is more efficient, allows compression (because cache entries are stored in ets and ets supports compression), and is easier to understand.
Version 1.0 (actually version 0.3.1)
Initial conversion from pcache. Supports Erlang versions before 18.0 (uses
erlang:now() for TTL math).
Modern release. Provides proper stack traces if your underlying cache functions fail. Uses
os:timestamp() instead of
now() for TTL math.
rebar eunit suite=ecache
Add tests for
- Other TTL variation
- Cache pools? Cross-server awareness?
- Expose per-entry TTL to external setting/updating
- Expose ETS configuration to make compression and read/write optimizations settable per-cache.