Merge pull request #143 from restx/review-restx-session

Allow to plug other cache mechanisms for RestxSession #141 [breaking]

[breaking] RestxSession.Definition.Entry is now an interface.
Use DefaultSessionDefinitionEntry to get similar behavior if you were instanciating
RestxSession.Definition.Entry before.

[breaking] RestxSession#cleanUpCaches has been removed
It was misleading, was not invalidating the cache and very implementation dependent.
2 invalidate methods have been added to replace it.

Author: xhanin

restx-core/src/main/java/restx/security/DefaultSessionDefinitionEntry.java

@@ -0,0 +1,29 @@
+package restx.security;
+
+import com.google.common.base.Function;
+import com.google.common.base.Optional;
+import restx.security.RestxSession.Definition.Entry;
+
+/**
+ * Date: 20/1/15
+ * Time: 20:56
+ */
+public class DefaultSessionDefinitionEntry<T> implements Entry<T> {
+    private final String sessionDefKey;
+    private final Function<String, Optional<? extends T>> function;
+
+    public DefaultSessionDefinitionEntry(Class<T> clazz, String sessionDefKey, Function<String, Optional<? extends T>> function) {
+        this.sessionDefKey = sessionDefKey;
+        this.function = function;
+    }
+
+    @Override
+    public String getKey() {
+        return sessionDefKey;
+    }
+
+    @Override
+    public Optional<? extends T> getValueForId(String valueId) {
+        return function.apply(valueId);
+    }
+}

restx-core/src/main/java/restx/security/GuavaEntryCacheManager.java

@@ -0,0 +1,87 @@
+package restx.security;
+
+import com.google.common.base.Optional;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+import restx.security.RestxSession.Definition.CachedEntry;
+import restx.security.RestxSession.Definition.Entry;
+import restx.security.RestxSession.Definition.EntryCacheManager;
+
+import java.util.concurrent.ExecutionException;
+
+/**
+ * A restx session entry cache manager based on guava cache.
+ *
+ * You can override the cache settings by overriding the getCacheBuilder() method.
+ *
+ * Note that Guava Cache is not distributed, so be very careful with cache invalidation
+ * when using this cache.
+ *
+ * This is the default EntryCacheManager, see SecurityModule which provides one.
+ */
+public class GuavaEntryCacheManager implements EntryCacheManager {
+    @Override
+    public <T> CachedEntry<T> getCachedEntry(Entry<T> entry) {
+        return new GuavaCacheSessionDefinitionEntry<T>(entry.getKey(), getLoadingCacheFor(entry));
+    }
+
+    protected <T> LoadingCache<String, T> getLoadingCacheFor(final Entry<T> entry) {
+        return getCacheBuilder(entry).build(getCacheLoaderFor(entry));
+    }
+
+    protected <T> CacheLoader<String, T> getCacheLoaderFor(final Entry<T> entry) {
+        return new CacheLoader<String, T>() {
+            @Override
+            public T load(String key) throws Exception {
+                return entry.getValueForId(key).orNull();
+            }
+        };
+    }
+
+    protected <T> CacheBuilder<Object, Object> getCacheBuilder(Entry<T> entry) {
+        return CacheBuilder.newBuilder().maximumSize(1000);
+    }
+
+    /**
+     * A session definition entry implementation using Guava Cache.
+     */
+    public static class GuavaCacheSessionDefinitionEntry<T> implements CachedEntry<T> {
+        private final LoadingCache<String, T> loadingCache;
+        private final String key;
+
+        public GuavaCacheSessionDefinitionEntry(String key, LoadingCache<String, T> loadingCache) {
+            this.key = key;
+            this.loadingCache = loadingCache;
+        }
+
+        @Override
+        public String getKey() {
+            return key;
+        }
+
+        @Override
+        public Optional<T> getValueForId(String valueId) {
+            try {
+                return Optional.fromNullable(loadingCache.get(valueId));
+            } catch (CacheLoader.InvalidCacheLoadException e) {
+                // this exception is raised when cache loader returns null, which may happen if the object behind the key
+                // is deleted. Therefore we just return an absent value
+                return Optional.absent();
+            } catch (ExecutionException e) {
+                throw new RuntimeException(
+                        "impossible to load object from cache using valueid " + valueId + " for " + key + ": " + e.getMessage(), e);
+            }
+        }
+
+        @Override
+        public void invalidateCacheFor(String valueId) {
+            loadingCache.invalidate(valueId);
+        }
+
+        @Override
+        public void invalidateCache() {
+            loadingCache.invalidateAll();
+        }
+    }
+}

restx-core/src/main/java/restx/security/RestxSession.java

@@ -1,36 +1,31 @@
 package restx.security;
 
 import com.google.common.base.Optional;
-import com.google.common.cache.CacheBuilder;
-import com.google.common.cache.CacheLoader;
-import com.google.common.cache.LoadingCache;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Maps;
 import org.joda.time.Duration;
 import restx.factory.Component;
 
 import java.util.Map;
-import java.util.concurrent.ExecutionException;
+import java.util.Map.Entry;
 
 /**
  * RestxSession is used to store information which can be used across several HTTP requests from the same client.
  *
  * It is organized as a Map, information is stored by keys.
  *
- * It doesn't use the JEE Session mechanism, but a more lightweight system relying on a signed session cookie
- * (therefore it cannot be tampered by the client).
+ * It doesn't use the JEE Session mechanism, but a more lightweight system relying on signed session data stored
+ * on the client (being signed, it cannot be tampered by the client).
  *
- * The session cookie doesn't store the whole values (which could put a high load on the network and even cause
- * problems related to cookie size limit), but rather stores a a value id for each session key.
+ * The session data doesn't store the whole values (which could put a high load on the network and even cause
+ * problems related to data storage limit on the client), but rather stores a a value id for each session key.
  *
  * A value id MUST identify uniquely a value when used for a given session key, and the session MUST be configured
  * with a CacheLoader per key, able to load the value corresponding to the value id for a particular key.
  *
  * Therefore on the server the session enables to access arbitrary large objects, it will only put pressure on a
- * server cache, and on cache loaders if requests are heavily distributed. Indeed the cache is not distributed,
- * so a in a large clustered environment cache miss will be very likely and cache loaders will often be called.
- * Hence in such environment you should be careful to use very efficient cache loaders if you rely heavily on
- * session.
+ * server cache, and on cache loaders if requests are heavily distributed and depending on cache implementation.
  *
  * An example (using an arbitrary json like notation):
  * <pre>
@@ -39,42 +34,126 @@
  *              "USER": (valueId) -&gt; { return db.findOne("{_id: #}", valueId).as(User.class); }
  *          }
  *          "valueIdsByKeys": {
- *              "USER": "johndoe@acme.com" // valued from session cookie
+ *              "USER": "johndoe@acme.com" // valued from client session data
  *          }
  *     }
  * </pre>
  * With such a restx session, when you call a #get(User.class, "USER"), the session will first check its
  * valueIdsByKeys map to find the corresponding valueId ("johndoe@acme.com"). Then it will check the cache for
  * this valueId, and in case of cache miss will use the provided cache loader which will load the user from db.
+ *
+ * If you want to define your own session keys, you should define a Definition.Entry component for it allowing
+ * to load values based on their ids. You don't have to take care of caching in the Entry, caching is performed
+ * by EntryCacheManager.
  */
 public class RestxSession {
     @Component
     public static class Definition {
-        public static class Entry<T> {
-            private final Class<T> clazz;
-            private final String key;
-            private final CacheLoader<String, T> loader;
-
-            public Entry(Class<T> clazz, String key, CacheLoader<String, T> loader) {
-                this.clazz = clazz;
-                this.key = key;
-                this.loader = loader;
-            }
+        /**
+         * A session definition entry is responsible for loading session values by session value id, for a
+         * particular definition key.
+         *
+         * They don't implement caching themselves, see CachedEntry for entries supporting caching.
+         *
+         * @param <T> the type of values this Entry handles.
+         */
+        public static interface Entry<T> {
+            /**
+             * Returns the definition key that this entry handles.
+             * @return the definition key that this entry handles.
+             */
+            String getKey();
+
+            /**
+             * Gives the value corresponding to the given valueId.
+             *
+             * @param valueId the id of the value to get.
+             *
+             * @return the value, or absent if not found.
+             */
+            Optional<? extends T> getValueForId(String valueId);
         }
-        private final ImmutableMap<String, LoadingCache<String, ?>> caches;
+
+        /**
+         * A cached version of session definition entry.
+         *
+         * This does not derive from Entry, because its its getting method does not have the same semantic as the
+         * original one: here it returns a value which may not be the freshest one, while an Entry should always
+         * return current one.
+         *
+         * CachedEntry instances are usually created from a Entry instance using a EntryCacheManager.
+         *
+         * @param <T> the type of values this CachedEntry handles.
+         */
+        public static interface CachedEntry<T> {
+            /**
+             * Returns the definition key that this entry handles.
+             * @return the definition key that this entry handles.
+             */
+            String getKey();
+
+            /**
+             * Gives the value corresponding to the given valueId.
+             * This value may come from a cache, so its freshness depends on configuration and implementation.
+             *
+             * @param valueId the id of the value to get.
+             *
+             * @return the value, or absent if not found.
+             */
+            Optional<? extends T> getValueForId(String valueId);
+
+            /**
+             * Invalidates the cache for a single value id.
+             *
+             * @param valueId the value id for which cache should be invalidated.
+             */
+            void invalidateCacheFor(String valueId);
+
+            /**
+             * Invalidates the full cache of this entry.
+             *
+             * This may impact more than this single entry if this entry cache is backed by a broader cache.
+             */
+            void invalidateCache();
+        }
+
+        /**
+         * A cache manager for session definition entry.
+         *
+         * It transforms Entry into CachedEntry
+         */
+        public static interface EntryCacheManager {
+            <T> CachedEntry<T> getCachedEntry(Entry<T> entry);
+        }
+
+        private final ImmutableMap<String, CachedEntry<?>> entries;
 
         @SuppressWarnings("unchecked") // can't use Iterable<Entry<?> as parameter in injectable constructor ATM
-        public Definition(Iterable<Entry> entries) {
-            ImmutableMap.Builder<String, LoadingCache<String, ?>> builder = ImmutableMap.builder();
+        public Definition(EntryCacheManager cacheManager, Iterable<Entry> entries) {
+            ImmutableMap.Builder<String, CachedEntry<?>> builder = ImmutableMap.builder();
             for (Entry<?> entry : entries) {
-                builder.put(entry.key, CacheBuilder.newBuilder().maximumSize(1000).build(entry.loader));
+                builder.put(entry.getKey(), cacheManager.getCachedEntry(entry));
             }
-            caches = builder.build();
+            this.entries = builder.build();
+        }
+
+        public ImmutableSet<String> entriesKeySet() {
+            return entries.keySet();
+        }
+
+        public boolean hasEntryForKey(String key) {
+            return entries.containsKey(key);
         }
 
         @SuppressWarnings("unchecked")
-        public <T> LoadingCache<String, T> getCache(Class<T> clazz, String key) {
-            return (LoadingCache<String, T>) caches.get(key);
+        public <T> Optional<CachedEntry<T>> getEntry(String key) {
+            return Optional.fromNullable((CachedEntry<T>) entries.get(key));
+        }
+
+        public void invalidateAllCaches() {
+            for (CachedEntry<?> entry : entries.values()) {
+                entry.invalidateCache();
+            }
         }
     }
 
@@ -105,33 +184,24 @@ public static RestxSession current() {
         this.expires = expires;
     }
 
-    public RestxSession cleanUpCaches() {
-        for (LoadingCache<String, ?> cache : definition.caches.values()) {
-            cache.cleanUp();
+    public RestxSession invalidateCaches() {
+        for (Entry<String, String> entry : valueidsByKey.entrySet()) {
+            definition.getEntry(entry.getKey()).get().invalidateCacheFor(entry.getValue());
         }
         return this;
     }
 
-
     public <T> Optional<T> get(Class<T> clazz, String key) {
         return getValue(definition, clazz, key, valueidsByKey.get(key));
     }
 
+    @SuppressWarnings("unchecked")
     static <T> Optional<T> getValue(Definition definition, Class<T> clazz, String key, String valueid) {
         if (valueid == null) {
             return Optional.absent();
         }
 
-        try {
-            return Optional.fromNullable(definition.getCache(clazz, key).get(valueid));
-        } catch (CacheLoader.InvalidCacheLoadException e) {
-            // this exception is raised when cache loader returns null, which may happen if the object behind the key
-            // is deleted. Therefore we just return an absent value
-            return Optional.absent();
-        } catch (ExecutionException e) {
-            throw new RuntimeException(
-                    "impossible to load object from cache using valueid " + valueid + " for " + key + ": " + e.getMessage(), e);
-        }
+        return (Optional<T>) definition.getEntry(key).get().getValueForId(valueid);
     }
 
     public RestxSession expires(Duration duration) {
@@ -143,9 +213,9 @@ public Duration getExpires() {
     }
 
     public <T> RestxSession define(Class<T> clazz, String key, String valueid) {
-        if (!definition.caches.containsKey(key)) {
+        if (!definition.hasEntryForKey(key)) {
             throw new IllegalArgumentException("undefined context key: " + key + "." +
-                    " Keys defined are: " + definition.caches.keySet());
+                    " Keys defined are: " + definition.entriesKeySet());
         }
         // create new map by using a mutable map, not a builder, in case the the given entry overrides a previous one
         Map<String,String> newValueidsByKey = Maps.newHashMap();

restx-core/src/main/java/restx/security/RestxSessionCookieFilter.java

@@ -20,7 +20,6 @@
 
 import restx.AbstractRouteLifecycleListener;
 import restx.RestxContext;
-import restx.RestxFilter;
 import restx.RestxHandler;
 import restx.RestxHandlerMatch;
 import restx.RestxRequest;
@@ -37,9 +36,7 @@
 import restx.jackson.FrontObjectMapperFactory;
 
 /**
- * User: xavierhanin
- * Date: 2/8/13
- * Time: 8:59 PM
+ * This filter is used to store and get a RestxSession in Cookies (one for data, one for signature).
  */
 @Component(priority = -200)
 public class RestxSessionCookieFilter implements RestxRouteFilter, RestxHandler {
@@ -79,11 +76,11 @@ public Optional<RestxHandlerMatch> match(RestxRoute route) {
     public void handle(RestxRequestMatch match, RestxRequest req, final RestxResponse resp, RestxContext ctx) throws IOException {
         final RestxSession session = buildContextFromRequest(req);
         if (RestxContext.Modes.RECORDING.equals(ctx.getMode())) {
-            // we clean up caches in recording mode so that each request records the cache loading
+            // we invalidate caches in recording mode so that each request records the cache loading
             // Note: having this piece of code here is not a very nice isolation of responsibilities
             // we could put it in a separate filter, but then it's not easy to be sure it's called right after this
             // filter. Until such a feature is introduced, the easy solution to put it here is used.
-            session.cleanUpCaches();
+            sessionDefinition.invalidateAllCaches();
         }
         RestxSession.setCurrent(session);
         try {