Use global timer

common/src/main/java/io/bitsquare/common/FrameRateTimer.java

@@ -0,0 +1,65 @@
+package io.bitsquare.common;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.time.Duration;
+
+/**
+ * We simulate a global frame rate timer similar to FXTimer to avoid creation of threads for each timer call.
+ * Used only in headless apps like the seed node.
+ */
+public class FrameRateTimer implements Timer, Runnable {
+    private final Logger log = LoggerFactory.getLogger(FrameRateTimer.class);
+
+    private long interval;
+    private Runnable runnable;
+    private long startTs;
+    private boolean isPeriodically;
+
+    public FrameRateTimer() {
+    }
+
+    @Override
+    public void run() {
+        try {
+            long currentTimeMillis = System.currentTimeMillis();
+            if ((currentTimeMillis - startTs) >= interval) {
+                runnable.run();
+                if (isPeriodically)
+                    startTs = currentTimeMillis;
+                else
+                    stop();
+            }
+        } catch (Throwable t) {
+            log.error(t.getMessage());
+            t.printStackTrace();
+            stop();
+            throw t;
+        }
+    }
+
+    @Override
+    public Timer runLater(Duration delay, Runnable runnable) {
+        this.interval = delay.toMillis();
+        this.runnable = runnable;
+        startTs = System.currentTimeMillis();
+        MasterTimer.addListener(this);
+        return this;
+    }
+
+    @Override
+    public Timer runPeriodically(Duration interval, Runnable runnable) {
+        this.interval = interval.toMillis();
+        isPeriodically = true;
+        this.runnable = runnable;
+        startTs = System.currentTimeMillis();
+        MasterTimer.addListener(this);
+        return this;
+    }
+
+    @Override
+    public void stop() {
+        MasterTimer.removeListener(this);
+    }
+}

common/src/main/java/io/bitsquare/common/MasterTimer.java

@@ -0,0 +1,35 @@
+package io.bitsquare.common;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Set;
+import java.util.TimerTask;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+public class MasterTimer {
+    private final static Logger log = LoggerFactory.getLogger(MasterTimer.class);
+    private static final java.util.Timer timer = new java.util.Timer();
+    public static long FRAME_INTERVAL_MS = 16;
+
+    static {
+        timer.scheduleAtFixedRate(new TimerTask() {
+            @Override
+            public void run() {
+                listeners.stream().forEach(UserThread::execute);
+            }
+        }, FRAME_INTERVAL_MS, FRAME_INTERVAL_MS); // frame rate of 60 fps is about 16 ms
+    }
+
+    private static Set<Runnable> listeners = new CopyOnWriteArraySet<>();
+
+    public static void addListener(Runnable runnable) {
+        listeners.add(runnable);
+    }
+
+    public static void removeListener(Runnable runnable) {
+        listeners.remove(runnable);
+    }
+
+
+}