From 71403d41741cca9d3d7790fce4e517c9cd7ef2d1 Mon Sep 17 00:00:00 2001
From: Athou <jeremiepanzer@gmail.com>
Date: Thu, 1 Aug 2013 21:11:45 +0200
Subject: [PATCH] if under heavy load, don't refresh feeds for users who logged
 in more than a month ago for the last time

---
 .../com/commafeed/backend/dao/FeedDAO.java    | 31 +++++++++++++++----
 .../backend/feeds/FeedRefreshTaskGiver.java   | 14 +++++++--
 .../resources/changelogs/db.changelog-1.2.xml |  6 ++++
 3 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/src/main/java/com/commafeed/backend/dao/FeedDAO.java b/src/main/java/com/commafeed/backend/dao/FeedDAO.java
index 20d576ab..957d8b1f 100644
--- a/src/main/java/com/commafeed/backend/dao/FeedDAO.java
+++ b/src/main/java/com/commafeed/backend/dao/FeedDAO.java
@@ -7,11 +7,13 @@ import javax.ejb.Stateless;
 import javax.persistence.TypedQuery;
 import javax.persistence.criteria.CriteriaQuery;
 import javax.persistence.criteria.Expression;
+import javax.persistence.criteria.Join;
 import javax.persistence.criteria.JoinType;
 import javax.persistence.criteria.Path;
 import javax.persistence.criteria.Predicate;
 import javax.persistence.criteria.Root;
 import javax.persistence.criteria.SetJoin;
+import javax.persistence.criteria.Subquery;
 import javax.persistence.metamodel.SingularAttribute;
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
@@ -25,6 +27,8 @@ import com.commafeed.backend.model.Feed;
 import com.commafeed.backend.model.FeedSubscription;
 import com.commafeed.backend.model.FeedSubscription_;
 import com.commafeed.backend.model.Feed_;
+import com.commafeed.backend.model.User;
+import com.commafeed.backend.model.User_;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 
@@ -38,30 +42,45 @@ public class FeedDAO extends GenericDAO<Feed> {
 		public List<Feed> feeds;
 	}
 
-	private Predicate getUpdatablePredicate(Root<Feed> root) {
+	private List<Predicate> getUpdatablePredicates(CriteriaQuery<?> query, Root<Feed> root, Date lastLoginThreshold) {
 
+		List<Predicate> preds = Lists.newArrayList();
 		Predicate isNull = builder.isNull(root.get(Feed_.disabledUntil));
 		Predicate lessThan = builder.lessThan(root.get(Feed_.disabledUntil), new Date());
+		preds.add(builder.or(isNull, lessThan));
 
-		return builder.or(isNull, lessThan);
+		if (lastLoginThreshold != null) {
+			Subquery<Long> subquery = query.subquery(Long.class);
+			Root<FeedSubscription> subroot = subquery.from(FeedSubscription.class);
+			subquery.select(builder.count(subroot.get(FeedSubscription_.id)));
+
+			Join<FeedSubscription, User> userJoin = subroot.join(FeedSubscription_.user);
+			Predicate p1 = builder.equal(subroot.get(FeedSubscription_.feed), root);
+			Predicate p2 = builder.greaterThanOrEqualTo(userJoin.get(User_.lastLogin), lastLoginThreshold);
+			subquery.where(p1, p2);
+
+			preds.add(builder.exists(subquery));
+		}
+
+		return preds;
 	}
 
-	public Long getUpdatableCount() {
+	public Long getUpdatableCount(Date lastLoginThreshold) {
 		CriteriaQuery<Long> query = builder.createQuery(Long.class);
 		Root<Feed> root = query.from(getType());
 
 		query.select(builder.count(root));
-		query.where(getUpdatablePredicate(root));
+		query.where(getUpdatablePredicates(query, root, lastLoginThreshold).toArray(new Predicate[0]));
 
 		TypedQuery<Long> q = em.createQuery(query);
 		return q.getSingleResult();
 	}
 
-	public List<Feed> findNextUpdatable(int count) {
+	public List<Feed> findNextUpdatable(int count, Date lastLoginThreshold) {
 		CriteriaQuery<Feed> query = builder.createQuery(getType());
 		Root<Feed> root = query.from(getType());
 
-		query.where(getUpdatablePredicate(root));
+		query.where(getUpdatablePredicates(query, root, lastLoginThreshold).toArray(new Predicate[0]));
 		query.orderBy(builder.asc(root.get(Feed_.disabledUntil)));
 
 		TypedQuery<Feed> q = em.createQuery(query);
diff --git a/src/main/java/com/commafeed/backend/feeds/FeedRefreshTaskGiver.java b/src/main/java/com/commafeed/backend/feeds/FeedRefreshTaskGiver.java
index d4bc643a..f7ef1222 100644
--- a/src/main/java/com/commafeed/backend/feeds/FeedRefreshTaskGiver.java
+++ b/src/main/java/com/commafeed/backend/feeds/FeedRefreshTaskGiver.java
@@ -122,7 +122,7 @@ public class FeedRefreshTaskGiver {
 	}
 
 	public Long getUpdatableCount() {
-		return feedDAO.getUpdatableCount();
+		return feedDAO.getUpdatableCount(getLastLoginThreshold());
 	}
 
 	/**
@@ -139,12 +139,12 @@ public class FeedRefreshTaskGiver {
 	 * refills the refresh queue and empties the giveBack queue while at it
 	 */
 	private void refill() {
-		int count = Math.min(300, 3 * backgroundThreads);
+		int count = Math.min(100, 3 * backgroundThreads);
 
 		// first, get feeds that are up to refresh from the database
 		List<FeedRefreshContext> contexts = Lists.newArrayList();
 		if (!applicationSettingsService.get().isCrawlingPaused()) {
-			List<Feed> feeds = feedDAO.findNextUpdatable(count);
+			List<Feed> feeds = feedDAO.findNextUpdatable(count, getLastLoginThreshold());
 			for (Feed feed : feeds) {
 				contexts.add(new FeedRefreshContext(feed, false));
 			}
@@ -195,4 +195,12 @@ public class FeedRefreshTaskGiver {
 		giveBackQueue.add(feed);
 	}
 
+	private Date getLastLoginThreshold() {
+		if (applicationSettingsService.get().isHeavyLoad()) {
+			return DateUtils.addDays(new Date(), -30);
+		} else {
+			return null;
+		}
+	}
+
 }
diff --git a/src/main/resources/changelogs/db.changelog-1.2.xml b/src/main/resources/changelogs/db.changelog-1.2.xml
index 477112e7..34a17eab 100644
--- a/src/main/resources/changelogs/db.changelog-1.2.xml
+++ b/src/main/resources/changelogs/db.changelog-1.2.xml
@@ -128,5 +128,11 @@
 			<column name="refreshIntervalMinutes" valueNumeric="5"></column>
 		</update>
 	</changeSet>
+		
+	<changeSet author="athou" id="add-last-login-index">
+		<createIndex tableName="USERS" indexName="lastlogin_index">
+			<column name="lastLogin" />
+		</createIndex>
+	</changeSet>
 
 </databaseChangeLog>