fa7ec95069
Changes that allow slow or new servers to quickly apply samples towards the server average. The most important changes are to not ignore the first N samples, and apply an average to the server as soon as there is one available. The new ResponseStat::make_valid() will use filter samples to add an average, if no averages have yet been added, even if the number of filter samples is less than the filter limit.
63 lines
2.4 KiB
C++
63 lines
2.4 KiB
C++
/*
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* Copyright (c) 2016 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
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*
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* Change Date: 2022-01-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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#pragma once
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#include <maxscale/ccdefs.hh>
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#include <maxbase/stopwatch.hh>
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#include <maxbase/average.hh>
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/** This could arguably be a utility, but is written specifically for rwsplit
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* so it stays here at least for now.
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*/
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namespace maxscale
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{
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/**
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* Query response statistics. Uses median of N samples to filter noise, then
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* uses those medians to calculate the average response time.
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* The class makes an average of the durations between calls to query_started()
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* and query_ended(). Once the stats are good, sync_time_reached(int max) returns true,
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* based on the average containing at least max samples (or medians), or the time
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* sync_duration (constructor arg) has passed since the last reset().
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*/
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class ResponseStat
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{
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public:
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/*
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* @param num_filter_samples - collect num samples, use median
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* @param num_synch_medians - this many medians before the average should be synced, or
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* @param sync_duration - this much time between syncs.
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*/
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ResponseStat(int num_filter_samples = 5,
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int num_synch_medians = 500,
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maxbase::Duration sync_duration = std::chrono::seconds(5));
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void query_started();
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void query_ended();// ok to call without a query_started
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bool make_valid(); // make valid even if there are too few filter_samples
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bool is_valid() const;
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int num_samples() const;
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maxbase::Duration average() const;
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bool sync_time_reached(); // is it time to apply the average?
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void reset();
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private:
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const int m_num_filter_samples;
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const int m_num_synch_medians;
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const maxbase::Duration m_sync_duration;
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int m_sample_count;
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std::vector<maxbase::Duration> m_samples; // N sampels from which median is used
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maxbase::CumulativeAverage m_average;
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maxbase::TimePoint m_last_start;
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maxbase::TimePoint m_next_sync;
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};
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}
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