MXS-2068: Move RWBackend into mysqlcommon

This cleanly allows multiple modules to use it.

server/core/response_stat.cc

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+#include <maxscale/response_stat.hh>
+
+#include <algorithm>
+
+namespace maxscale
+{
+ResponseStat::ResponseStat(int num_filter_samples,
+                           int num_synch_medians,
+                           maxbase::Duration sync_duration)
+    : m_num_filter_samples {num_filter_samples}
+    , m_num_synch_medians{num_synch_medians}
+    , m_sync_duration{sync_duration}
+    , m_sample_count{0}
+    , m_samples(num_filter_samples)
+    , m_last_start{maxbase::TimePoint()}
+    , m_next_sync{maxbase::Clock::now() + sync_duration}
+{
+}
+
+
+void ResponseStat::query_started()
+{
+    m_last_start = maxbase::Clock::now();
+}
+
+void ResponseStat::query_ended()
+{
+    if (m_last_start == maxbase::TimePoint())
+    {
+        // m_last_start is defaulted. Ignore, avoids extra logic in call sites.
+        return;
+    }
+    m_samples[m_sample_count] = maxbase::Clock::now() - m_last_start;
+
+    if (++m_sample_count == m_num_filter_samples)
+    {
+        std::sort(m_samples.begin(), m_samples.end());
+        maxbase::Duration new_sample = m_samples[m_num_filter_samples / 2];
+        m_average.add(std::chrono::duration<double>(new_sample).count());
+        m_sample_count = 0;
+    }
+    m_last_start = maxbase::TimePoint();
+}
+
+bool ResponseStat::make_valid()
+{
+    if (!m_average.num_samples() && m_sample_count)
+    {
+        maxbase::Duration new_sample = m_samples[m_sample_count / 2];
+        m_average.add(std::chrono::duration<double>(new_sample).count());
+        m_sample_count = 0;
+    }
+
+    return is_valid();
+}
+
+bool ResponseStat::is_valid() const
+{
+    return m_average.num_samples();
+}
+
+int ResponseStat::num_samples() const
+{
+    return m_average.num_samples();
+}
+
+maxbase::Duration ResponseStat::average() const
+{
+    return maxbase::Duration(m_average.average());
+}
+
+bool ResponseStat::sync_time_reached()
+{
+    auto now = maxbase::Clock::now();
+    bool reached = m_next_sync < now
+        || m_average.num_samples() >= m_num_synch_medians;
+
+    if (reached)
+    {
+        m_next_sync = now + m_sync_duration;
+    }
+    return reached;
+}
+
+void ResponseStat::reset()
+{
+    m_sample_count = 0;
+    m_average.reset();
+    m_next_sync = maxbase::Clock::now() + m_sync_duration;
+}
+}