[MRESOLVER-587] Memory usage improvements (#536)

Do not use `Object` as descriptor key, use dedicated type. And intern the `List<Dependency>` on artifact descriptors. Also introduce "intern"-ing of ArtifactDescriptor dependencies and managedDependencies that is configurable (speed vs memory).

---

https://issues.apache.org/jira/browse/MRESOLVER-587

maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/collect/DataPool.java

@@ -58,12 +58,23 @@ public final class DataPool {
 
  private static final String CONFIG_PROP_COLLECTOR_POOL_DESCRIPTOR = "aether.dependencyCollector.pool.descriptor";
 
+ private static final String CONFIG_PROP_COLLECTOR_POOL_DEPENDENCY_LISTS =
+ "aether.dependencyCollector.pool.dependencyLists";
+
+ private static final String CONFIG_PROP_COLLECTOR_POOL_INTERN_ARTIFACT_DESCRIPTOR_DEPENDENCIES =
+ "aether.dependencyCollector.pool.internArtifactDescriptorDependencies";
+
+ private static final String CONFIG_PROP_COLLECTOR_POOL_INTERN_ARTIFACT_DESCRIPTOR_MANAGED_DEPENDENCIES =
+ "aether.dependencyCollector.pool.internArtifactDescriptorManagedDependencies";
+
  private static final String ARTIFACT_POOL = DataPool.class.getName() + "$Artifact";
 
  private static final String DEPENDENCY_POOL = DataPool.class.getName() + "$Dependency";
 
  private static final String DESCRIPTORS = DataPool.class.getName() + "$Descriptors";
 
+ private static final String DEPENDENCY_LISTS_POOL = DataPool.class.getName() + "$DependencyLists";
+
  public static final ArtifactDescriptorResult NO_DESCRIPTOR =
  new ArtifactDescriptorResult(new ArtifactDescriptorRequest());
 
@@ -80,7 +91,12 @@ public final class DataPool {
  /**
  * Descriptor interning pool, lives across session (if session carries non-null {@link RepositoryCache}).
  */
- private final InternPool<Object, Descriptor> descriptors;
+ private final InternPool<DescriptorKey, Descriptor> descriptors;
+
+ /**
+ * {@link Dependency} list interning pool, lives across session (if session carries non-null {@link RepositoryCache}).
+ */
+ private final InternPool<List<Dependency>, List<Dependency>> dependencyLists;
 
  /**
  * Constraint cache, lives during single collection invocation (same as this DataPool instance).
@@ -92,17 +108,29 @@ public final class DataPool {
  */
  private final ConcurrentHashMap<Object, List<DependencyNode>> nodes;
 
+ private final boolean internArtifactDescriptorDependencies;
+
+ private final boolean internArtifactDescriptorManagedDependencies;
+
  @SuppressWarnings("unchecked")
  public DataPool(RepositorySystemSession session) {
  final RepositoryCache cache = session.getCache();
 
+ internArtifactDescriptorDependencies = ConfigUtils.getBoolean(
+ session, false, CONFIG_PROP_COLLECTOR_POOL_INTERN_ARTIFACT_DESCRIPTOR_DEPENDENCIES);
+ internArtifactDescriptorManagedDependencies = ConfigUtils.getBoolean(
+ session, true, CONFIG_PROP_COLLECTOR_POOL_INTERN_ARTIFACT_DESCRIPTOR_MANAGED_DEPENDENCIES);
+
  InternPool<Artifact, Artifact> artifactsPool = null;
  InternPool<Dependency, Dependency> dependenciesPool = null;
- InternPool<Object, Descriptor> descriptorsPool = null;
+ InternPool<DescriptorKey, Descriptor> descriptorsPool = null;
+ InternPool<List<Dependency>, List<Dependency>> dependencyListsPool = null;
  if (cache != null) {
  artifactsPool = (InternPool<Artifact, Artifact>) cache.get(session, ARTIFACT_POOL);
  dependenciesPool = (InternPool<Dependency, Dependency>) cache.get(session, DEPENDENCY_POOL);
- descriptorsPool = (InternPool<Object, Descriptor>) cache.get(session, DESCRIPTORS);
+ descriptorsPool = (InternPool<DescriptorKey, Descriptor>) cache.get(session, DESCRIPTORS);
+ dependencyListsPool =
+ (InternPool<List<Dependency>, List<Dependency>>) cache.get(session, DEPENDENCY_LISTS_POOL);
  }
 
  if (artifactsPool == null) {
@@ -132,9 +160,20 @@ public DataPool(RepositorySystemSession session) {
  }
  }
 
+ if (dependencyListsPool == null) {
+ String dependencyListsPoolType =
+ ConfigUtils.getString(session, HARD, CONFIG_PROP_COLLECTOR_POOL_DEPENDENCY_LISTS);
+
+ dependencyListsPool = createPool(dependencyListsPoolType);
+ if (cache != null) {
+ cache.put(session, DEPENDENCY_LISTS_POOL, dependencyListsPool);
+ }
+ }
+
  this.artifacts = artifactsPool;
  this.dependencies = dependenciesPool;
  this.descriptors = descriptorsPool;
+ this.dependencyLists = dependencyListsPool;
 
  this.constraints = new ConcurrentHashMap<>(256);
  this.nodes = new ConcurrentHashMap<>(256);
@@ -148,26 +187,36 @@ public Dependency intern(Dependency dependency) {
  return dependencies.intern(dependency, dependency);
  }
 
- public Object toKey(ArtifactDescriptorRequest request) {
- return request.getArtifact();
+ public DescriptorKey toKey(ArtifactDescriptorRequest request) {
+ return new DescriptorKey(request.getArtifact());
  }
 
- public ArtifactDescriptorResult getDescriptor(Object key, ArtifactDescriptorRequest request) {
+ public ArtifactDescriptorResult getDescriptor(DescriptorKey key, ArtifactDescriptorRequest request) {
  Descriptor descriptor = descriptors.get(key);
  if (descriptor != null) {
  return descriptor.toResult(request);
  }
  return null;
  }
 
- public void putDescriptor(Object key, ArtifactDescriptorResult result) {
+ public void putDescriptor(DescriptorKey key, ArtifactDescriptorResult result) {
+ if (internArtifactDescriptorDependencies) {
+ result.setDependencies(intern(result.getDependencies()));
+ }
+ if (internArtifactDescriptorManagedDependencies) {
+ result.setManagedDependencies(intern(result.getManagedDependencies()));
+ }
  descriptors.intern(key, new GoodDescriptor(result));
  }
 
- public void putDescriptor(Object key, ArtifactDescriptorException e) {
+ public void putDescriptor(DescriptorKey key, ArtifactDescriptorException e) {
  descriptors.intern(key, BadDescriptor.INSTANCE);
  }
 
+ private List<Dependency> intern(List<Dependency> dependencies) {
+ return dependencyLists.intern(dependencies, dependencies);
+ }
+
  public Object toKey(VersionRangeRequest request) {
  return new ConstraintKey(request);
  }
@@ -202,8 +251,39 @@ public void putChildren(Object key, List<DependencyNode> children) {
  nodes.put(key, children);
  }
 
- abstract static class Descriptor {
+ public static final class DescriptorKey {
+ private final Artifact artifact;
+ private final int hashCode;
+
+ private DescriptorKey(Artifact artifact) {
+ this.artifact = artifact;
+ this.hashCode = Objects.hashCode(artifact);
+ }
+
+ @Override
+ public boolean equals(Object o) {
+ if (this == o) {
+ return true;
+ }
+ if (o == null || getClass() != o.getClass()) {
+ return false;
+ }
+ DescriptorKey that = (DescriptorKey) o;
+ return Objects.equals(artifact, that.artifact);
+ }
 
+ @Override
+ public int hashCode() {
+ return hashCode;
+ }
+
+ @Override
+ public String toString() {
+ return getClass().getSimpleName() + "{" + "artifact='" + artifact + '\'' + '}';
+ }
+ }
+
+ abstract static class Descriptor {
  public abstract ArtifactDescriptorResult toResult(ArtifactDescriptorRequest request);
  }
 

maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/collect/bf/BfDependencyCollector.java

@@ -448,7 +448,7 @@ private ArtifactDescriptorResult resolveCachedArtifactDescriptor(
  RepositorySystemSession session,
  DependencyProcessingContext context,
  Results results) {
- Object key = pool.toKey(descriptorRequest);
+ DataPool.DescriptorKey key = pool.toKey(descriptorRequest);
  ArtifactDescriptorResult descriptorResult = pool.getDescriptor(key, descriptorRequest);
  if (descriptorResult == null) {
  try {

maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/collect/df/DfDependencyCollector.java

@@ -375,7 +375,7 @@ private ArtifactDescriptorResult resolveCachedArtifactDescriptor(
  Dependency d,
  Results results,
  Args args) {
- Object key = pool.toKey(descriptorRequest);
+ DataPool.DescriptorKey key = pool.toKey(descriptorRequest);
  ArtifactDescriptorResult descriptorResult = pool.getDescriptor(key, descriptorRequest);
  if (descriptorResult == null) {
  try {

maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/collect/DataPoolTest.java

@@ -51,7 +51,7 @@ public void testArtifactDescriptorCaching() {
  result.addAlias(new DefaultArtifact("gid:alias:4"));
 
  DataPool pool = newDataPool();
- Object key = pool.toKey(request);
+ DataPool.DescriptorKey key = pool.toKey(request);
  pool.putDescriptor(key, result);
  ArtifactDescriptorResult cached = pool.getDescriptor(key, request);
  assertNotNull(cached);