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#ifndef QPID_SYS_LATENCYTRACKER_H
#define QPID_SYS_LATENCYTRACKER_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 <string>
#include <limits>
#include <map>
namespace qpid {
namespace sys {
/**@file Tools for measuring latency. NOT SUITABLE FOR PROUDCTION BUILDS.
* Uses should be compiled only if QPID_LATENCY_TRACKER is defined.
* See the convenience macros at the end of this file.
*/
/** Used by LatencyCounter and LatencyTracker below */
class LatencyStatistic {
public:
LatencyStatistic(std::string name_) : name(name_), count(0), total(0), min(std::numeric_limits<int64_t>::max()), max(0) {}
~LatencyStatistic() { print(); }
void record(Duration d) {
total += d;
++count;
if (d > max) max=d;
if (d < min) min=d;
}
void print() {
if (count) {
double meanMsec = (double(total)/count)/TIME_MSEC;
printf("\n==== Latency metric %s: samples=%lu mean=%fms (%f-%f)\n", name.c_str(), count, meanMsec, double(min)/TIME_MSEC, double(max)/TIME_MSEC);
}
else
printf("\n==== Latency metric %s: no samples.\n", name.c_str());
}
private:
std::string name;
unsigned long count;
int64_t total, min, max;
};
/** Measure delay between seeing the same value at start and finish. */
template <class T> class LatencyTracker {
public:
LatencyTracker(std::string name) : measuring(false), stat(name) {}
void start(T value) {
sys::Mutex::ScopedLock l(lock);
if (!measuring) {
measureAt = value;
measuring = true;
startTime = AbsTime::now();
}
}
void finish(T value) {
sys::Mutex::ScopedLock l(lock);
if(measuring && measureAt == value) {
stat.record(Duration(startTime, AbsTime::now()));
measuring = false;
}
}
private:
sys::Mutex lock;
bool measuring;
T measureAt;
AbsTime startTime;
LatencyStatistic stat;
};
/** Measures delay between the nth call to start and the nth call to finish.
* E.g. to measure latency between sending & receiving an ordered stream of messages.
*/
class LatencyCounter {
public:
LatencyCounter(std::string name) : measuring(false), startCount(0), finishCount(0), stat(name) {}
void start() {
sys::Mutex::ScopedLock l(lock);
if (!measuring) {
measureAt = startCount;
measuring = true;
startTime = AbsTime::now();
}
++startCount;
}
void finish() {
sys::Mutex::ScopedLock l(lock);
if (measuring && measureAt == finishCount) {
stat.record(Duration(startTime, AbsTime::now()));
measuring = false;
}
++finishCount;
}
private:
sys::Mutex lock;
bool measuring;
uint64_t startCount, finishCount, measureAt;
AbsTime startTime;
LatencyStatistic stat;
};
/** Measures time spent in a scope. */
class LatencyScope {
public:
LatencyScope(LatencyStatistic& s) : stat(s), startTime(AbsTime::now()) {}
~LatencyScope() {
sys::Mutex::ScopedLock l(lock);
stat.record(Duration(startTime, AbsTime::now()));
}
private:
sys::Mutex lock;
LatencyStatistic& stat;
AbsTime startTime;
};
/** Macros to wrap latency tracking so disabled unless QPID_LATENCY_TRACKER is defined */
#if defined(QPID_LATENCY_TRACKER)
#define LATENCY_TRACK(X) X
#else
#define LATENCY_TRACK(X)
#endif
}} // namespace qpid::sys
#endif /*!QPID_SYS_LATENCYTRACKER_H*/
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