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README.md

onion-cache

Build Status

Multilevel cache system for Java 8

Goal - Build a multilayer cache system:

  • That makes simple add/remove different layers of cache.
  • With a system that fallback through one or multiple cache layers before getting the needed object from the main datasource.

How I design it:

  • I try to generealize the concept of cache layer in order to write less logic as possible.
  • I came up with 3 main entity that describes a Cache Layer.
    • A service, which represent a client wrapper for cache/datastore service in real world. It must implement 4 basic methods: GET, SET, SETEX, DELETE. In this way you can implement your own RedisService that can use HSET instead of SET.
    • A marshaller, which marshall/unmarshall the data you want to cache. It must implement 2 methods: marshall() and unMarshall().
    • A DataModel that will be the father of your data models (!!!)
  • OnionCache addLayer() method will insert a cache layer. The last layer will be the main datasource.
    • A typical use case will be (in order!): addLayer(LRU); addLayer(Redis); addLayer(MySQL);
    • Then, you can get/set/delete your data into multiple level of cache with one call to OnionCache.
  • You can extend it building new services, keys, marshallers.
  • At the moment OnionCache comes with some services: LRUCache, Redis, DynamoDb, FileSystem (this is useful if you use as main datastore a network file system like Amazon NFS)

Requirements:

  • Every model you use with OnionCache must implements the ICacheLayerDataModel interface.

  • ICacheLayerDataModel interface comes with 2 methods:

    • ICacheLayerDataModelKey dataModelUniqueKey()
      • This return an object that extends the interface ICacheLayerDataModelKey, with represent a unique key for your data object.
    • String dataModelTableName();
      • This return the model datasource table name.
  • Under /models you can find an example with dynamodb as datasource.

Installation:

Look at https://jitpack.io/#enryold/onion-cache/

Let's start:

Imagine a system that saves data on DynamoDb, but some datas are very popular in certain period of time with an increase of throughput-rate. In this case is useful to put Redis or Memcached between your webapp and DynamoDb and an LRU cache inside your application to avoid any network call.

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First of all we have to create all the layers we need in our system design, with their services, keys, and marshallers

// THIS EXAMPLE CAN BE FOUND UNDER /test FOLDER IN METHOD NAMED test_LRU_REDIS_DYNAMODB_FALLBACK()


// SERVICES FIRST

// IN MEMORY LRU SERVICE, 100 is the size of the LRU map. 
InMemoryLRUService inMemoryLRUService = new InMemoryLRUService(100);

// REDIS SERVICE
RedisService redisService = new RedisService("localhost", 6379);

// DYNAMODB SERVICE
DynamoDBService onionDynamoDBService = new DynamoDBService(dynamodb);

// NOW BUILD CACHE LAYERS FOR THE MODEL Person, WITH REPRESENT A PERSON WITH NAME AND SURNAME PROPERTIES.
CacheLayer LRULayer = new CacheLayer<InMemoryLRUService, CacheLayerJsonMarshaller<Person>, Person>()
    .withMainService(inMemoryLRUService)
    .withMainServiceMarshaller(new CacheLayerJsonMarshaller<>(Person.class, String.class));

CacheLayer DynamoDBLayer = new CacheLayer<DynamoDBService, CacheLayerDynamoDBMarshaller<Person>, Person>()
    .withMainService(onionDynamoDBService)
    .withMainServiceMarshaller(new CacheLayerDynamoDBMarshaller<>(Person.class, Person.class));

// IN REDIS WE CAN SET DEFAULT EXPIRATION FOR KEYS IN SECONDS
CacheLayer redisLayer = new CacheLayer<RedisService, CacheLayerJsonMarshaller<Person>, Person>()
    .withMainService(redisService)
    .withMainServiceMarshaller(new CacheLayerJsonMarshaller<>(Person.class, String.class))
    .withDefaultExpiration(3600);

// NOW WE ARE READY TO BUILD OUR ONIONCACHE OBJECT, THE ORDER OF addLayer IS IMPORTANT!!
OnionCache<Person> onionCache = new OnionCache<Person>()
    .addLayer(LRULayer)
    .addLayer(redisLayer)
    .addLayer(DynamoDBLayer);
    
// THEN, WE CAN USER ONIONCACHE TO RETRIEVE OUR OBJECTS FROM THE LAYERS. 
Optional<Person> object = onionCache.get(new Person("Jason", "Bourne"));

// HOWEVER, WE CAN ALSO SET A NEW OBJECT, WITH CUSTOM DEFAULT EXPIRATION (This works only in Redis/Memcached)
Person goJason = new Person("Jason", "Bourne");
boolean success = onionCache.set(goJason.getName(), goJason.getSurname(), goJason, 30 );

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