A simple lru/static cache that uses a redis instance
PLEASE NOTE - dont use this in production, this is more an experiment than anything else at the moment, I am deferring packaging and putting it on npm until I have worked on it a bit more.
I was inspired by the following article: http://oldblog.antirez.com/post/redis-as-LRU-cache.html
Instructions:
Install redis, must be >= v2.6.14 Run your redis server, with a memory limit set and the volatile_ttl memory policy:
root$ redis-server --maxmemory 5mb --maxmemory-policy volatile-ttl
download this project to a folder
run 'npm install' in your project folder root to get all the required modules (redis, async)
and then run 'node node_redis_cache_test 100000' this will run the rather incomplete and ugly test script I created for the cache it tests adding and fetching a small collection, and then pushes 100000 test objects into the volatile cache, and then randomly attempts fetching the items - finally lists cache hits/misses etc. The misses go up as you add more items to the test, this is because I assume our redis db is only allowed 5mb of memory space, so items are pushed out based on their ttl. Volatile gets reset the objects ttl in the cache - ensuring items that are fetched more often will not be kicked out first.
The node_redis_cache.js module is what is doing the work, with the help of node_redis and async https://github.com/mranney/node_redis https://github.com/caolan/async
The module is instantiated like so: var cache = require('./redis_lru_cache');
And has the following methods:
cache.initialize({dbKey:'redis_lru_test'}, function(e){ //this is the initialization code, look in the function to see what other optional params you can use //the dbKey parameter is essential as it uniquely identifies your application in redis //the idea is you may have multiple apps caching to the same redis instance })
putAllStatic:function(objectKeyPropertyName, items, done) //puts a bunch of objects in the cache - that will always live in the cache (no ttl) //objectKeyPropertyName - the name of the property in your list object objects that should be used to key each item //items - the list of items //done - the callback (e, resp)
putAllVolatile:functionobjectKeyPropertyName, items, ttl, done) //puts a bunch of objects in the cache - that all have an expiry set in milliseconds //objectKeyPropertyName - the name of the property in your list object objects that should be used to key each item //items - the list of items //ttl - amount of time in milliseconds the items can live in the cache until they are expired //done - the callback (e, resp)
putCollectionStatic:function(collectionKey, objectKeyPropertyName, collectionItems, done) //puts a bunch of objects in the cache, under an umbrella set (static so no ttl) collectionKey - the key of the collection you wish to add the items to //objectKeyPropertyName - the name of the property in your list object objects that should be used to key each item //items - the list of items //done - the callback (e, resp)
putCollectionVolatile:function(collectionKey, objectKeyPropertyName, collectionItems, ttl, done) //puts a bunch of objects in the cache, under an umbrella set with a ttl collectionKey - the key of the collection you wish to add the items to //objectKeyPropertyName - the name of the property in your list object objects that should be used to key each item //items - the list of items //ttl - amount of time in milliseconds the items can live in the cache until they are expired //done - the callback (e, resp)
putVolatile:function(collectionKey, key, item, ttl, done) //puts a single item into the cache, if the collectionKey is null - it is not grouped
putStatic:function(collectionKey, key, item, done) //puts a single item into the cache with no expiry
getVolatile:function(key, ttl, done) //gets a single object - updates its ttl on fetching it, by yr ttl amount //done - the callback (e, item)
getStatic:function(key, done) //gets a single static object with the specified key //done - the callback (e, item)
getCollectionVolatile:function(collectionKey, ttl, done) //gets all objects that exist under the collectionKey //done - yr callback (e, items)
getCollectionStatic:function(collectionKey, done) //gets all static objects taht exist under teh collection key //done - yr callback (e, items)