Disable the IPC sync context factory by default (can be enabled using the new environment option)

common/src/main/java/org/mvndaemon/mvnd/common/Environment.java

@@ -247,7 +247,11 @@ public enum Environment {
     /**
      * Regexp pattern that will force eviction of the plugin realms if one of its dependencies matches.
      */
-    MVND_PLUGIN_REALM_EVICT_PATTERN("mvnd.pluginRealmEvictPattern", null, "", OptionType.STRING, Flags.OPTIONAL);
+    MVND_PLUGIN_REALM_EVICT_PATTERN("mvnd.pluginRealmEvictPattern", null, "", OptionType.STRING, Flags.OPTIONAL),
+    /**
+     * The SyncContextFactory to use (can be either 'noop' or 'ipc' for a server-wide factory).
+     */
+    MVND_SYNC_CONTEXT_FACTORY("mvnd.syncContextFactory", null, "noop", OptionType.BOOLEAN, Flags.OPTIONAL);
 
     static Properties properties;
 

daemon/src/main/java/org/mvndaemon/mvnd/sync/MvndSyncContextFactory.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.mvndaemon.mvnd.sync;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import javax.inject.Named;
+import javax.inject.Singleton;
+import org.eclipse.aether.RepositorySystemSession;
+import org.eclipse.aether.SyncContext;
+import org.eclipse.aether.artifact.Artifact;
+import org.eclipse.aether.impl.SyncContextFactory;
+import org.eclipse.aether.metadata.Metadata;
+import org.eclipse.sisu.Priority;
+import org.mvndaemon.mvnd.common.Environment;
+
+@Singleton
+@Named
+@Priority(20)
+public class MvndSyncContextFactory implements SyncContextFactory {
+
+    public static final String FACTORY_NOOP = "noop";
+    public static final String FACTORY_IPC = "ipc";
+
+    public static final String IPC_SYNC_CONTEXT_FACTORY = "org.mvndaemon.mvnd.sync.IpcSyncContextFactory";
+
+    private final Map<String, SyncContextFactory> factories;
+
+    @SuppressWarnings("unchecked")
+    public MvndSyncContextFactory() {
+        try {
+            Map<String, SyncContextFactory> map = new HashMap<>();
+            map.put(FACTORY_NOOP, new NoopSyncContextFactory());
+            Class<? extends SyncContextFactory> factoryClass = (Class<? extends SyncContextFactory>) getClass().getClassLoader()
+                    .loadClass(IPC_SYNC_CONTEXT_FACTORY);
+            map.put(FACTORY_IPC, factoryClass.getDeclaredConstructor().newInstance());
+            factories = Collections.unmodifiableMap(map);
+        } catch (Exception e) {
+            throw new RuntimeException("Unable to create IpcSyncContextFactory instance", e);
+        }
+    }
+
+    @Override
+    public SyncContext newInstance(RepositorySystemSession repositorySystemSession, boolean shared) {
+        String name = Environment.MVND_SYNC_CONTEXT_FACTORY.asOptional()
+                .orElseGet(Environment.MVND_SYNC_CONTEXT_FACTORY::getDefault);
+        SyncContextFactory factory = factories.get(name);
+        if (factory == null) {
+            throw new RuntimeException("Unable to find SyncContextFactory named '" + name + "'");
+        }
+        return factory.newInstance(repositorySystemSession, shared);
+    }
+
+    private static class NoopSyncContextFactory implements SyncContextFactory {
+        @Override
+        public SyncContext newInstance(RepositorySystemSession repositorySystemSession, boolean shared) {
+            return new SyncContext() {
+                @Override
+                public void acquire(Collection<? extends Artifact> artifacts, Collection<? extends Metadata> metadatas) {
+                }
+
+                @Override
+                public void close() {
+                }
+            };
+        }
+    }
+}