Fix synchronization

pom.xml

@@ -49,6 +49,12 @@
             <artifactId>lmdbjava</artifactId>
             <version>0.8.2</version>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>5.9.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
 </project>

src/main/java/it/cavallium/filequeue/LMDBEnvManager.java

@@ -50,9 +50,9 @@ public class LMDBEnvManager {
 	private static Env<byte[]> open(File path) {
 		return Env.create(ByteArrayProxy.PROXY_BA)
 				// 128GiB
-				.setMapSize(128L * 1024 * 1024 * 1024)
+				.setMapSize(Integer.parseInt(System.getProperty("fq.writemap.size.gb", "32")) * 1024L * 1024 * 1024)
 				.setMaxReaders(1024)
 				.setMaxDbs(1024)
-				.open(path, EnvFlags.MDB_NOSYNC);
+				.open(path, EnvFlags.MDB_NOSYNC, EnvFlags.MDB_WRITEMAP, EnvFlags.MDB_NOMETASYNC);
 	}
 }

src/main/java/it/cavallium/filequeue/QueueToConsumer.java

@@ -8,6 +8,8 @@ class QueueToConsumer<T> implements IQueueToConsumer<T> {
 
 	private final long BACKOFF_NS = Duration.ofMillis(2).toNanos();
 	private final long MAX_BACKOFF_NS = Duration.ofMillis(500).toNanos();
+
+	private final long HALF_SECOND_NS = Duration.ofMillis(500).toNanos();
 	private final AtomicLong preAddQueued;
 	private final AtomicLong afterAddQueued;
 	private final SimpleQueue<T> queue;
@@ -50,7 +52,10 @@ class QueueToConsumer<T> implements IQueueToConsumer<T> {
 		}
 		if (shouldAdd && !closed) {
 			queue.add(value);
-			afterAddQueued.incrementAndGet();
+			var queueSize = afterAddQueued.incrementAndGet();
+			if (queueSize == 1) {
+				LockSupport.unpark(manager);
+			}
 		}
 	}
 
@@ -66,22 +71,21 @@ class QueueToConsumer<T> implements IQueueToConsumer<T> {
 			try {
 				while (!closed) {
 					T element;
-					boolean shouldRemove = preAddQueued.getAndUpdate(n -> n > 0 ? n - 1 : 0) > 0;
-					while (!closed) {
-						if (afterAddQueued.get() > 0) {
-							if (!closed && shouldRemove) {
-								element = queue.remove();
-								long nextDelay = BACKOFF_NS;
-								while (!closed && !consumer.tryConsume(element)) {
-									LockSupport.parkNanos(nextDelay);
-									if (nextDelay + BACKOFF_NS <= MAX_BACKOFF_NS) {
-										nextDelay += BACKOFF_NS;
-									} else if (nextDelay < MAX_BACKOFF_NS) {
-										nextDelay = MAX_BACKOFF_NS;
-									}
-								}
+					boolean shouldRemove = afterAddQueued.getAndUpdate(n -> n > 0 ? n - 1 : 0) > 0;
+					if (shouldRemove) {
+						element = queue.remove();
+						long nextDelay = BACKOFF_NS;
+						while (!closed && !consumer.tryConsume(element)) {
+							LockSupport.parkNanos(nextDelay);
+							if (nextDelay + BACKOFF_NS <= MAX_BACKOFF_NS) {
+								nextDelay += BACKOFF_NS;
+							} else if (nextDelay < MAX_BACKOFF_NS) {
+								nextDelay = MAX_BACKOFF_NS;
 							}
 						}
+						preAddQueued.updateAndGet(n -> n > 0 ? n - 1 : 0);
+					} else {
+						LockSupport.parkNanos(HALF_SECOND_NS);
 					}
 				}
 			} finally {

src/test/java/it/cavallium/filequeue/TestQueueToConsumer.java

@@ -0,0 +1,37 @@
+package it.cavallium.filequeue;
+
+import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.atomic.AtomicBoolean;
+import org.junit.jupiter.api.Test;
+
+public class TestQueueToConsumer {
+
+	@Test
+	public void test() {
+		var q = new SimpleQueueJava<String>(new ConcurrentLinkedDeque<>());
+		AtomicBoolean ab = new AtomicBoolean();
+		try (var qtc = new QueueToConsumer<String>(q, new QueueConsumer<String>() {
+			@Override
+			public boolean tryConsume(String value) {
+				System.out.println("value:" + value + " thread: " + Thread.currentThread());
+				if (ab.get()) {
+					ab.set(false);
+					return false;
+				} else {
+					ab.set(true);
+					return true;
+				}
+			}
+		})) {
+			qtc.startQueue();
+			qtc.add("ciao");
+			qtc.add("mondo");
+			for (int i = 0; i < 1000; i++) {
+				qtc.add(i + "n");
+			}
+			Thread.sleep(100);
+		} catch (InterruptedException e) {
+			throw new RuntimeException(e);
+		}
+	}
+}