⚡ Optimize GraalVM polyglot context allocation with virtual threads. …

…Added a queue to reuse contexts, improving performance.

polyglot/src/main/java/org/restheart/polyglot/ContextQueue.java

@@ -0,0 +1,103 @@
+/*-
+ * ========================LICENSE_START=================================
+ * restheart-polyglot
+ * %%
+ * Copyright (C) 2020 - 2024 SoftInstigate
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * =========================LICENSE_END==================================
+ */
+package org.restheart.polyglot;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.ArrayBlockingQueue;
+
+import org.graalvm.polyglot.Context;
+import org.graalvm.polyglot.Engine;
+import org.graalvm.polyglot.HostAccess;
+import org.graalvm.polyglot.io.IOAccess;
+import org.restheart.configuration.Configuration;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.mongodb.client.MongoClient;
+
+public class ContextQueue {
+    private static final Logger LOGGER = LoggerFactory.getLogger(ContextQueue.class);
+    private final int QUEUE_SIZE = 4 * Runtime.getRuntime().availableProcessors();
+    private final ArrayBlockingQueue<Context> QUEUE = new ArrayBlockingQueue<>(QUEUE_SIZE);
+
+    public ContextQueue(Engine engine, String name, Configuration conf, Logger logger, Optional<MongoClient> mclient, String modulesReplacements, Map<String, String> OPTS) {
+        for (var c = 0; c < QUEUE_SIZE; c++) {
+            QUEUE.add(newContext(engine, name, conf, logger, mclient, modulesReplacements, OPTS));
+        }
+    }
+
+    public Context take() throws InterruptedException {
+        return QUEUE.take();
+    }
+
+    public void release(Context ctx) {
+        try {
+            QUEUE.add(ctx);
+        } catch(IllegalStateException ise) {
+            try (ctx) {
+                // queue is full
+                LOGGER.warn("Error releasing Context in {}", Thread.currentThread().getName());
+            }
+        }
+    }
+
+    public static Context newContext(Engine engine, String name, Configuration conf, Logger LOGGER, Optional<MongoClient> mclient, String modulesReplacements, Map<String, String> OPTS) {
+        if (modulesReplacements!= null) {
+            LOGGER.debug("modules-replacements: {} ", modulesReplacements);
+            OPTS.put("js.commonjs-core-modules-replacements", modulesReplacements);
+        } else {
+            OPTS.remove("js.commonjs-core-modules-replacements");
+        }
+
+        var ctx = Context.newBuilder().engine(engine)
+            .allowAllAccess(true)
+            .allowHostAccess(HostAccess.ALL)
+            .allowHostClassLookup(className -> true)
+            .allowIO(IOAccess.ALL)
+            .allowExperimentalOptions(true)
+            .options(OPTS)
+            .build();
+
+        addBindings(ctx, name, conf, LOGGER, mclient);
+
+        return ctx;
+    }
+
+    private static void addBindings(Context ctx,
+        String pluginName,
+        Configuration conf,
+        Logger logger,
+        Optional<MongoClient> mclient) {
+        ctx.getBindings("js").putMember("LOGGER", logger);
+
+        if (mclient.isPresent()) {
+            ctx.getBindings("js").putMember("mclient", mclient.get());
+        }
+
+        var args = conf != null
+            ? conf.getOrDefault(pluginName, new HashMap<>())
+            : new HashMap<String, Object>();
+
+        ctx.getBindings("js").putMember("pluginArgs", args);
+    }
+}