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markt-asf pushed a commit to branch 11.0.x
in repository https://gitbox.apache.org/repos/asf/tomcat.git
commit 5f24c07d7570b8a874771e1c5ec0bf00d0ad1934
Author: Mark Thomas <[email protected]>
AuthorDate: Mon Aug 17 12:43:05 2026 +0100
Fix potential concurrency issues when ordering sessions
Assisted by: Claude:Sonnet 5
---
.../catalina/manager/HTMLManagerServlet.java | 9 ++--
.../catalina/session/PersistentManagerBase.java | 6 +--
.../apache/catalina/util/SessionComparators.java | 52 ++++++++++++++++++++++
webapps/docs/changelog.xml | 8 ++++
4 files changed, 67 insertions(+), 8 deletions(-)
diff --git a/java/org/apache/catalina/manager/HTMLManagerServlet.java b/java/org/apache/catalina/manager/HTMLManagerServlet.java
index 9b097e5ab0..f7e16a621a 100644
--- a/java/org/apache/catalina/manager/HTMLManagerServlet.java
+++ b/java/org/apache/catalina/manager/HTMLManagerServlet.java
@@ -48,6 +48,7 @@ import org.apache.catalina.Session;
import org.apache.catalina.manager.util.SessionUtils;
import org.apache.catalina.util.ContextName;
import org.apache.catalina.util.ServerInfo;
+import org.apache.catalina.util.SessionComparators;
import org.apache.catalina.util.URLEncoder;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.security.Escape;
@@ -1102,7 +1103,7 @@ public class HTMLManagerServlet extends ManagerServlet {
} else if ("id".equalsIgnoreCase(sortBy)) {
return comparingNullable(Session::getId);
} else if ("LastAccessedTime".equalsIgnoreCase(sortBy)) {
- return Comparator.comparingLong(Session::getLastAccessedTime);
+ return SessionComparators.comparingLongSnapshot(Session::getLastAccessedTime);
} else if ("MaxInactiveInterval".equalsIgnoreCase(sortBy)) {
return Comparator.comparingInt(Session::getMaxInactiveInterval);
} else if ("new".equalsIgnoreCase(sortBy)) {
@@ -1112,11 +1113,11 @@ public class HTMLManagerServlet extends ManagerServlet {
} else if ("user".equalsIgnoreCase(sortBy)) {
return comparingNullable(JspHelper::guessDisplayUserFromSession);
} else if ("UsedTime".equalsIgnoreCase(sortBy)) {
- return Comparator.comparingLong(SessionUtils::getUsedTimeForSession);
+ return SessionComparators.comparingLongSnapshot(SessionUtils::getUsedTimeForSession);
} else if ("InactiveTime".equalsIgnoreCase(sortBy)) {
- return Comparator.comparingLong(SessionUtils::getInactiveTimeForSession);
+ return SessionComparators.comparingLongSnapshot(SessionUtils::getInactiveTimeForSession);
} else if ("TTL".equalsIgnoreCase(sortBy)) {
- return Comparator.comparingLong(SessionUtils::getTTLForSession);
+ return SessionComparators.comparingLongSnapshot(SessionUtils::getTTLForSession);
} else {
return null;
}
diff --git a/java/org/apache/catalina/session/PersistentManagerBase.java b/java/org/apache/catalina/session/PersistentManagerBase.java
index 13d6a1fa7d..ed9181dc20 100644
--- a/java/org/apache/catalina/session/PersistentManagerBase.java
+++ b/java/org/apache/catalina/session/PersistentManagerBase.java
@@ -18,7 +18,6 @@ package org.apache.catalina.session;
import java.io.IOException;
import java.util.Arrays;
-import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
@@ -30,6 +29,7 @@ import org.apache.catalina.LifecycleState;
import org.apache.catalina.Session;
import org.apache.catalina.Store;
import org.apache.catalina.StoreManager;
+import org.apache.catalina.util.SessionComparators;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
@@ -809,7 +809,7 @@ public abstract class PersistentManagerBase extends ManagerBase implements Store
}
int toswap = sessions.length - limit;
- Arrays.sort(sessions, Comparator.comparingLong(Session::getLastAccessedTimeInternal));
+ Arrays.sort(sessions, SessionComparators.comparingLongSnapshot(Session::getLastAccessedTimeInternal));
for (int i = 0; i < sessions.length && toswap > 0; i++) {
StandardSession session = (StandardSession) sessions[i];
@@ -833,7 +833,6 @@ public abstract class PersistentManagerBase extends ManagerBase implements Store
}
}
}
-
}
@@ -877,6 +876,5 @@ public abstract class PersistentManagerBase extends ManagerBase implements Store
}
}
}
-
}
diff --git a/java/org/apache/catalina/util/SessionComparators.java b/java/org/apache/catalina/util/SessionComparators.java
new file mode 100644
index 0000000000..7ca1815dc4
--- /dev/null
+++ b/java/org/apache/catalina/util/SessionComparators.java
@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.catalina.util;
+
+import java.util.Comparator;
+import java.util.IdentityHashMap;
+import java.util.Map;
+import java.util.function.ToLongFunction;
+
+import org.apache.catalina.Session;
+
+/**
+ * Utility class for building {@link Comparator}s over {@link Session}s.
+ */
+public class SessionComparators {
+
+ private SessionComparators() {
+ // Utility class. Hide the default constructor.
+ }
+
+
+ /**
+ * Builds a {@link Comparator} equivalent to {@link Comparator#comparingLong(ToLongFunction)}, except that each
+ * session's extracted value is only read once and then cached for the remainder of the sort. Some values used to
+ * sort sessions (e.g. last accessed time, or values derived from the current time) can change while a sort is in
+ * progress, either because the session is concurrently accessed or simply because time passes. Without caching,
+ * that can make the comparator return inconsistent results for the same pair of sessions across different
+ * comparisons in the same sort, which trips {@code java.util.TimSort}'s consistency check.
+ *
+ * @param keyExtractor Function that extracts the sort key from a session
+ *
+ * @return a comparator that sorts sessions by the (cached) extracted key
+ */
+ public static Comparator<Session> comparingLongSnapshot(ToLongFunction<Session> keyExtractor) {
+ Map<Session,Long> cache = new IdentityHashMap<>();
+ return Comparator.comparingLong(s -> cache.computeIfAbsent(s, keyExtractor::applyAsLong).longValue());
+ }
+}
diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
index 0bc65c5c8e..270f7a4e23 100644
--- a/webapps/docs/changelog.xml
+++ b/webapps/docs/changelog.xml
@@ -145,6 +145,14 @@
</fix>
</changelog>
</subsection>
+ <subsection name="Web applications">
+ <changelog>
+ <fix>
+ Manager: Fix a potential concurrency issue when ordering sessions prior
+ to displaying a list of session. (markt)
+ </fix>
+ </changelog>
+ </subsection>
</section>
<section name="Tomcat 11.0.25 (markt)" rtext="release in progress">
<subsection name="Catalina">
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