[05/11] logging-log4j2 git commit: LOG4J2-1080 DiscardingAsyncEventRouter drops events below a certain log level when the queue is getting too full

[rp...@apache.org]

LOG4J2-1080 DiscardingAsyncEventRouter drops events below a certain log level when the queue is getting too full


Project: http://git-wip-us.apache.org/repos/asf/logging-log4j2/repo
Commit: http://git-wip-us.apache.org/repos/asf/logging-log4j2/commit/d48b2b7e
Tree: http://git-wip-us.apache.org/repos/asf/logging-log4j2/tree/d48b2b7e
Diff: http://git-wip-us.apache.org/repos/asf/logging-log4j2/diff/d48b2b7e

Branch: refs/heads/master
Commit: d48b2b7ed2200a38019dd46507c25395410b3791
Parents: 992ed1e
Author: rpopma <rp...@apache.org>
Authored: Wed Dec 23 22:10:21 2015 +0900
Committer: rpopma <rp...@apache.org>
Committed: Wed Dec 23 22:10:21 2015 +0900

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 .../core/async/DiscardingAsyncEventRouter.java  | 93 ++++++++++++++++++++
 1 file changed, 93 insertions(+)
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http://git-wip-us.apache.org/repos/asf/logging-log4j2/blob/d48b2b7e/log4j-core/src/main/java/org/apache/logging/log4j/core/async/DiscardingAsyncEventRouter.java
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diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/async/DiscardingAsyncEventRouter.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/async/DiscardingAsyncEventRouter.java
new file mode 100644
index 0000000..2f5805a
--- /dev/null
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/async/DiscardingAsyncEventRouter.java
@@ -0,0 +1,93 @@
+/*
+ * 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.logging.log4j.core.async;
+
+import org.apache.logging.log4j.Level;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.status.StatusLogger;
+
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * Discarding router extends the DefaultAsyncEventRouter by first verifying if the queue is fuller than the specified
+ * threshold ratio; if this is the case, log events {@linkplain Level#isMoreSpecificThan(Level) more specific} than
+ * the specified threshold level are dropped. If this is not the case, the {@linkplain DefaultAsyncEventRouter
+ * default routing rules hold.
+ */
+public class DiscardingAsyncEventRouter extends DefaultAsyncEventRouter {
+    private static final Logger LOGGER = StatusLogger.getLogger();
+
+    private final int thresholdQueueRemainingCapacity;
+    private final Level thresholdLevel;
+    private final AtomicLong discardCount = new AtomicLong();
+
+    /**
+     * Constructs a router that will discard events {@linkplain Level#isLessSpecificThan(Level) equal or less specific}
+     * than the specified threshold level when the queue is fuller than the specified threshold ratio.
+     *
+     * @param queueSize size of the queue
+     * @param thresholdQueueFilledRatio threshold ratio: if queue is fuller than this, start discarding events
+     * @param thresholdLevel level of events to discard
+     */
+    public DiscardingAsyncEventRouter(final int queueSize, final float thresholdQueueFilledRatio,
+            final Level thresholdLevel) {
+        thresholdQueueRemainingCapacity = calcThresholdQueueRemainingCapacity(queueSize, thresholdQueueFilledRatio);
+        this.thresholdLevel = Objects.requireNonNull(thresholdLevel, "thresholdLevel");
+    }
+
+    private static int calcThresholdQueueRemainingCapacity(final int queueSize,
+            final float thresholdQueueFilledRatio) {
+        if (thresholdQueueFilledRatio >= 1F) {
+            return 0;
+        }
+        if (thresholdQueueFilledRatio <= 0F) {
+            return queueSize;
+        }
+        return (int) ((1 - thresholdQueueFilledRatio) * queueSize);
+    }
+
+    @Override
+    public EventRoute getRoute(final long backgroundThreadId, final Level level, final int queueSize,
+            final int queueRemainingCapacity) {
+        if (queueRemainingCapacity <= thresholdQueueRemainingCapacity && level.isLessSpecificThan(thresholdLevel)) {
+            if (discardCount.getAndIncrement() == 0) {
+                LOGGER.warn("Async remaining queue capacity is {}, discarding event with level {}. " +
+                        "This message will only appear once; future events from {} " +
+                        "are silently discarded until queue capacity becomes available.",
+                        queueRemainingCapacity, level, thresholdLevel);
+            }
+            return EventRoute.DISCARD;
+        }
+        return super.getRoute(backgroundThreadId, level, queueSize, queueRemainingCapacity);
+    }
+
+    public static long getDiscardCount(final AsyncEventRouter router) {
+        if (router instanceof DiscardingAsyncEventRouter) {
+            return ((DiscardingAsyncEventRouter) router).discardCount.get();
+        }
+        return 0;
+    }
+
+    public int getThresholdQueueRemainingCapacity() {
+        return thresholdQueueRemainingCapacity;
+    }
+
+    public Level getThresholdLevel() {
+        return thresholdLevel;
+    }
+}