Aggregate Timer warnings.

The Timer code logs a warning if a timer callback is started late or
overruns the start time for the next callback. In cases where there
are a lot of these warnings, the time taken to do the logging itself
severly worsens the situation.

This commit aggregates timer warnings and give a statistical report
every 5 seconds at most.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@1036169 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 81 insertions, 0 deletions

diff --git a/cpp/src/qpid/sys/TimerWarnings.h b/cpp/src/qpid/sys/TimerWarnings.h
new file mode 100644
index 0000000000..337a434ab5
--- /dev/null
+++ b/cpp/src/qpid/sys/TimerWarnings.h
@@ -0,0 +1,81 @@
+#ifndef QPID_SYS_TIMERWARNINGS_H
+#define QPID_SYS_TIMERWARNINGS_H
+
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "qpid/sys/Time.h"
+#include <map>
+#include <string>
+
+namespace qpid {
+namespace sys {
+
+/**
+ * The Timer class logs warnings when timer tasks are late and/or overrun.
+ *
+ * It is too expensive to log a warning for every late/overrun
+ * incident, doing so aggravates the problem of tasks over-running and
+ * being late.
+ *
+ * This class collects statistical data about each incident and prints
+ * an aggregated report at regular intervals.
+ */
+class TimerWarnings
+{
+  public:
+    TimerWarnings(Duration reportInterval);
+
+    void late(const std::string& task, Duration delay);
+
+    void overran(const std::string& task, Duration overrun, Duration time);
+
+    void lateAndOverran(const std::string& task,
+                        Duration delay, Duration overrun, Duration time);
+
+  private:
+    struct Statistic {
+        Statistic() : total(0), count(0) {}
+        void add(int64_t value) { total += value; ++count; }
+        int64_t average() const { return count ? total/count : 0; }
+        int64_t total;
+        int64_t count;
+    };
+
+    // Keep statistics for 3 classes of incident:  late, overrun and both.
+    struct TaskStats {
+        Statistic lateDelay;    // Just late
+        Statistic overranOverrun, overranTime; // Just overrun
+        // Both
+        Statistic lateAndOverranDelay, lateAndOverranOverrun, lateAndOverranTime;
+    };
+
+    typedef std::map<std::string, TaskStats> TaskStatsMap;
+
+    void log();
+
+    Duration interval;
+    AbsTime nextReport;
+    TaskStatsMap taskStats;
+};
+}} // namespace qpid::sys
+
+#endif  /*!QPID_SYS_TIMERWARNINGS_H*/