make sure we have something to do before entering synchronized block

src/main/java/com/commafeed/backend/feeds/FeedRefreshUpdater.java

@@ -14,12 +14,14 @@ import javax.annotation.PreDestroy;
 import javax.inject.Inject;
 import javax.inject.Singleton;
 
+import org.apache.commons.collections.CollectionUtils;
 import org.apache.commons.lang.StringUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import com.commafeed.backend.MetricsBean;
 import com.commafeed.backend.dao.FeedDAO;
+import com.commafeed.backend.dao.FeedEntryDAO;
 import com.commafeed.backend.dao.FeedSubscriptionDAO;
 import com.commafeed.backend.model.ApplicationSettings;
 import com.commafeed.backend.model.Feed;
@@ -29,6 +31,7 @@ import com.commafeed.backend.model.FeedSubscription;
 import com.commafeed.backend.pubsubhubbub.SubscriptionHandler;
 import com.commafeed.backend.services.ApplicationSettingsService;
 import com.commafeed.backend.services.FeedUpdateService;
+import com.google.common.collect.Lists;
 import com.google.common.util.concurrent.Striped;
 
 @Singleton
@@ -58,6 +61,9 @@ public class FeedRefreshUpdater {
 	@Inject
 	FeedSubscriptionDAO feedSubscriptionDAO;
 
+	@Inject
+	FeedEntryDAO feedEntryDAO;
+
 	private ThreadPoolExecutor pool;
 	private BlockingQueue<Runnable> queue;
 	private Striped<Lock> locks;
@@ -113,7 +119,7 @@ public class FeedRefreshUpdater {
 		@Override
 		public void run() {
 			boolean ok = true;
-			if (entries != null) {
+			if (CollectionUtils.isNotEmpty(entries) && hasWork()) {
 				List<FeedSubscription> subscriptions = feedSubscriptionDAO
 						.findByFeed(feed);
 				for (FeedEntry entry : entries) {
@@ -131,6 +137,26 @@ public class FeedRefreshUpdater {
 			taskGiver.giveBack(feed);
 		}
 
+		private boolean hasWork() {
+			boolean hasWork = false;
+
+			List<String> guids = Lists.newArrayList();
+			for (FeedEntry entry : entries) {
+				guids.add(entry.getGuid());
+			}
+
+			List<FeedEntry> existingEntries = feedEntryDAO.findByGuids(guids);
+			for (FeedEntry entry : entries) {
+				FeedEntry foundEntry = FeedUtils.findEntry(existingEntries,
+						entry);
+				if (foundEntry == null
+						|| FeedUtils.findFeed(foundEntry.getFeeds(), feed) == null) {
+					hasWork = true;
+					break;
+				}
+			}
+			return hasWork;
+		}
 	}
 
 	private boolean updateEntry(final Feed feed, final FeedEntry entry,

src/main/java/com/commafeed/backend/feeds/FeedUtils.java

@@ -3,11 +3,13 @@ package com.commafeed.backend.feeds;
 import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;
 import java.util.Calendar;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
 
 import org.apache.commons.collections.CollectionUtils;
+import org.apache.commons.lang.ObjectUtils;
 import org.apache.commons.lang.StringUtils;
 import org.apache.commons.lang3.time.DateUtils;
 import org.apache.commons.math.stat.descriptive.SummaryStatistics;
@@ -19,6 +21,7 @@ import org.mozilla.universalchardet.UniversalDetector;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.commafeed.backend.model.Feed;
 import com.commafeed.backend.model.FeedEntry;
 import com.google.api.client.util.Lists;
 
@@ -93,6 +96,30 @@ public class FeedUtils {
 		return content;
 	}
 
+	public static FeedEntry findEntry(Collection<FeedEntry> list,
+			FeedEntry entry) {
+		FeedEntry found = null;
+		for (FeedEntry e : list) {
+			if (StringUtils.equals(entry.getGuid(), e.getGuid())
+					&& StringUtils.equals(entry.getUrl(), e.getUrl())) {
+				found = e;
+				break;
+			}
+		}
+		return found;
+	}
+
+	public static Feed findFeed(Collection<Feed> list, Feed feed) {
+		Feed found = null;
+		for (Feed f : list) {
+			if (ObjectUtils.equals(feed.getId(), f.getId())) {
+				found = f;
+				break;
+			}
+		}
+		return found;
+	}
+
 	public static String trimInvalidXmlCharacters(String xml) {
 		if (StringUtils.isBlank(xml)) {
 			return null;