added scheduler

src/main/java/com/commafeed/backend/task/SchedulingService.java

@@ -0,0 +1,56 @@
+package com.commafeed.backend.task;
+
+import io.dropwizard.lifecycle.Managed;
+
+import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import lombok.extern.slf4j.Slf4j;
+
+import com.google.common.collect.Lists;
+
+@Slf4j
+public class SchedulingService implements Managed {
+
+	public static interface ScheduledTask {
+		void run();
+
+		long getInitialDelay();
+
+		long getPeriod();
+
+		TimeUnit getTimeUnit();
+	}
+
+	private List<ScheduledTask> tasks = Lists.newArrayList();
+	private ScheduledExecutorService executor;
+
+	@Override
+	public void start() throws Exception {
+		executor = Executors.newScheduledThreadPool(tasks.size());
+		for (final ScheduledTask task : tasks) {
+			Runnable runnable = new Runnable() {
+				@Override
+				public void run() {
+					try {
+						task.run();
+					} catch (Exception e) {
+						log.error(e.getMessage(), e);
+					}
+				}
+			};
+			executor.scheduleWithFixedDelay(runnable, task.getInitialDelay(), task.getPeriod(), task.getTimeUnit());
+		}
+	}
+
+	@Override
+	public void stop() throws Exception {
+		executor.shutdown();
+	}
+
+	public void register(ScheduledTask task) {
+		tasks.add(task);
+	}
+}