/* latency.h -- latency monitor API header file

* See latency.c for more information.

*

* ----------------------------------------------------------------------------

*

* Copyright (c) 2014, Salvatore Sanfilippo <antirez at gmail dot com>

* All rights reserved.

*

* Redistribution and use in source and binary forms, with or without

* modification, are permitted provided that the following conditions are met:

*

* * Redistributions of source code must retain the above copyright notice,

* this list of conditions and the following disclaimer.

* * Redistributions in binary form must reproduce the above copyright

* notice, this list of conditions and the following disclaimer in the

* documentation and/or other materials provided with the distribution.

* * Neither the name of Redis nor the names of its contributors may be used

* to endorse or promote products derived from this software without

* specific prior written permission.

*

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

* POSSIBILITY OF SUCH DAMAGE.

*/

#ifndef __LATENCY_H

#define __LATENCY_H

#define LATENCY_TS_LEN 160 /* History length for every monitored event. */

/* Representation of a latency sample: the sampling time and the latency

* observed in milliseconds. */

/* 延时样品例子 */

struct latencySample {

//延时Sample创建的时间

int32_t time; /* We don't use time_t to force 4 bytes usage everywhere. */

//延时的具体时间， 单位为毫秒

uint32_t latency; /* Latency in milliseconds. */

};

/* The latency time series for a given event. */

/* 针对某个事件采集的一系列延时sample */

struct latencyTimeSeries {

//下一个延时Sample的下标

int idx; /* Index of the next sample to store. */

//最大的延时

uint32_t max; /* Max latency observed for this event. */

//最近的延时记录

struct latencySample samples[LATENCY_TS_LEN]; /* Latest history. */

};

/* Latency statistics structure. */

/* 延时sample的数据统计结果结构体 */

struct latencyStats {

//绝对最高的延时时间

uint32_t all_time_high; /* Absolute max observed since latest reset. */

//平均Sample延时时间

uint32_t avg; /* Average of current samples. */

//Sample的最小延时时间

uint32_t min; /* Min of current samples. */

//Sample的最大延时时间

uint32_t max; /* Max of current samples. */

//平均相对误差，与平均延时相比

uint32_t mad; /* Mean absolute deviation. */

//samples的总数

uint32_t samples; /* Number of non-zero samples. */

//最早的延时记录点的创建时间

time_t period; /* Number of seconds since first event and now. */

};

void latencyMonitorInit(void); /* 延时监听初始化操作，创建Event字典对象 */

void latencyAddSample(char *event, mstime_t latency); /* 添加Sample到指定的Event对象的Sample列表中 */

/* Latency monitoring macros. */

/* Start monitoring an event. We just set the current time. */

/* 对某个事件设置监听，就是设置一下当前的时间 */

#define latencyStartMonitor(var) if (server.latency_monitor_threshold) { \

var = mstime(); \

} else { \

var = 0; \

}

/* End monitoring an event, compute the difference with the current time

* to check the amount of time elapsed. */

/* 结束监听，算出过了多少时间 */

#define latencyEndMonitor(var) if (server.latency_monitor_threshold) { \

var = mstime() - var; \

}

/* Add the sample only if the elapsed time is >= to the configured threshold. */

/* 如果延时时间超出server.latency_monitor_threshold，则将Sample加入延时列表中 */

#define latencyAddSampleIfNeeded(event,var) \

if (server.latency_monitor_threshold && \

(var) >= server.latency_monitor_threshold) \

latencyAddSample((event),(var));

#endif /* __LATENCY_H */