feat: add LRU cache for DID Documents

core/common/util/src/main/java/org/eclipse/edc/util/collection/ConcurrentLruCache.java

@@ -0,0 +1,99 @@
+/*
+ *  Copyright (c) 2023 Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
+ *
+ *  This program and the accompanying materials are made available under the
+ *  terms of the Apache License, Version 2.0 which is available at
+ *  https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Contributors:
+ *       Bayerische Motoren Werke Aktiengesellschaft (BMW AG) - initial API and implementation
+ *
+ */
+
+package org.eclipse.edc.util.collection;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+/**
+ * A thread-safe LRU cache with a specified capacity.
+ * <p>
+ * This class extends {@link LinkedHashMap} and adds concurrency using a ReentrantReadWriteLock.
+ * The cache uses a LinkedHashMap to store the entries and automatically evicts the least recently used entry
+ * when the capacity is reached.
+ *
+ * @param <K> the type of keys maintained by this cache
+ * @param <V> the type of mapped values
+ */
+public class ConcurrentLruCache<K, V> extends LinkedHashMap<K, V> {
+    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+    private final int capacity;
+
+    public ConcurrentLruCache(int capacity) {
+        super(capacity + 1, 1, true);
+        this.capacity = capacity;
+    }
+
+    @Override
+    public V put(K key, V value) {
+        lock.writeLock().lock();
+        try {
+            return super.put(key, value);
+        } finally {
+            lock.writeLock().unlock();
+        }
+    }
+
+    @Override
+    public V remove(Object key) {
+        lock.writeLock().lock();
+        try {
+            return super.remove(key);
+        } finally {
+            lock.writeLock().unlock();
+        }
+    }
+
+    @Override
+    public boolean remove(Object key, Object value) {
+        lock.writeLock().lock();
+        try {
+            return super.remove(key, value);
+        } finally {
+            lock.writeLock().unlock();
+        }
+    }
+
+    @Override
+    public Object clone() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public V get(Object key) {
+        lock.readLock().lock();
+        try {
+            return super.get(key);
+        } finally {
+            lock.readLock().unlock();
+        }
+    }
+
+    @Override
+    public void clear() {
+        lock.writeLock().lock();
+        try {
+            super.clear();
+        } finally {
+            lock.writeLock().unlock();
+        }
+    }
+
+    @Override
+    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
+        return size() > capacity;
+    }
+}

core/common/util/src/test/java/org/eclipse/edc/util/collection/LruCacheTest.java → core/common/util/src/test/java/org/eclipse/edc/util/collection/ConcurrentLruCacheTest.java

@@ -14,29 +14,25 @@
 
 package org.eclipse.edc.util.collection;
 
-import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-class LruCacheTest {
-    private LruCache<String, String> cache;
+class ConcurrentLruCacheTest {
+    private final ConcurrentLruCache<String, String> cache = new ConcurrentLruCache<>(2);
 
     @Test
     void verifyEviction() {
         cache.put("foo", "foo");
         cache.put("bar", "bar");
-        assertThat(cache.containsKey("foo")).isTrue();
-        assertThat(cache.containsKey("bar")).isTrue();
+        assertThat(cache)
+                .containsKey("foo")
+                .containsKey("bar");
 
         cache.put("baz", "baz");
-        assertThat(cache.containsKey("baz")).isTrue();
-        assertThat(cache.containsKey("bar")).isTrue();
-        assertThat(cache.containsKey("foo")).isFalse();
-    }
-
-    @BeforeEach
-    void setUp() {
-        cache = new LruCache<>(2);
+        assertThat(cache)
+                .containsKey("baz")
+                .containsKey("bar")
+                .doesNotContainKey("foo");
     }
 }

extensions/common/iam/decentralized-identity/identity-did-core/build.gradle.kts

@@ -5,6 +5,7 @@ plugins {
 
 dependencies {
     api(project(":spi:common:identity-did-spi"))
+    implementation(project(":core:common:util"))
     implementation(project(":extensions:common:iam:decentralized-identity:identity-did-crypto"))
 
     implementation(libs.jakarta.rsApi)

extensions/common/iam/decentralized-identity/identity-did-core/src/main/java/org/eclipse/edc/iam/did/resolution/DidResolverRegistryImpl.java

@@ -18,21 +18,36 @@
 import org.eclipse.edc.iam.did.spi.resolution.DidResolver;
 import org.eclipse.edc.iam.did.spi.resolution.DidResolverRegistry;
 import org.eclipse.edc.spi.result.Result;
+import org.eclipse.edc.util.collection.ConcurrentLruCache;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 
 /**
- * Default implementation.
+ * Default implementation, that delegates to several {@link DidResolver} objects, caching the results in a {@link ConcurrentLruCache}
  */
 public class DidResolverRegistryImpl implements DidResolverRegistry {
     private static final String DID = "did";
     private static final int DID_PREFIX = 0;
     private static final int DID_METHOD_NAME = 1;
-
+    private final ConcurrentLruCache<String, DidDocument> didCache;
     private final Map<String, DidResolver> resolvers = new HashMap<>();
 
+    public DidResolverRegistryImpl() {
+        didCache = new ConcurrentLruCache<>(50);
+    }
+
+    /**
+     * Constructs a DidResolverRegistryImpl object with the specified cache size.
+     *
+     * @param cacheSize the maximum number of entries that the cache can hold. Pass 0 to effectively deactivate the cache.
+     */
+    public DidResolverRegistryImpl(int cacheSize) {
+        didCache = new ConcurrentLruCache<>(cacheSize);
+    }
+
     @Override
     public void register(DidResolver resolver) {
         resolvers.put(resolver.getMethod(), resolver);
@@ -41,6 +56,7 @@ public void register(DidResolver resolver) {
     @Override
     public Result<DidDocument> resolve(String didKey) {
         Objects.requireNonNull(didKey);
+
         // for the definition of DID syntax, .cf https://www.w3.org/TR/did-core/#did-syntax
         var tokens = didKey.split(":");
         if (tokens.length < 3) {
@@ -50,10 +66,26 @@ public Result<DidDocument> resolve(String didKey) {
             return Result.failure("Invalid DID prefix");
         }
         var methodName = tokens[DID_METHOD_NAME];
-        var resolver = resolvers.get(methodName);
-        if (resolver == null) {
-            return Result.failure("No resolver registered for DID Method: " + methodName);
+
+        return resolveCachedDocument(didKey, methodName);
+    }
+
+    @NotNull
+    private Result<DidDocument> resolveCachedDocument(String didKey, String methodName) {
+        var didDocument = didCache.get(didKey);
+        if (didDocument == null) {
+            var resolver = resolvers.get(methodName);
+            if (resolver == null) {
+                return Result.failure("No resolver registered for DID Method: " + methodName);
+            }
+            var resolveResult = resolver.resolve(didKey);
+            if (resolveResult.failed()) {
+                return resolveResult;
+            }
+            didDocument = resolveResult.getContent();
+            didCache.put(didKey, didDocument);
         }
-        return resolver.resolve(didKey);
+
+        return Result.success(didDocument);
     }
 }