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/*
*
* Copyright 2015-2016, Google Inc.
* 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 Google Inc. 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 INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#ifndef GRPC_CORE_LIB_STATISTICS_WINDOW_STATS_H
#define GRPC_CORE_LIB_STATISTICS_WINDOW_STATS_H
#include <grpc/support/time.h>
/* Keep rolling sums of a user-defined statistic (containing a number of
measurements) over a a number of time intervals ("windows"). For example,
you can use a window_stats object to answer questions such as
"Approximately how many RPCs/s did I receive over the past minute, and
approximately how many bytes did I send out over that period?".
The type of data to record, and the time intervals to keep are specified
when creating the object via a call to census_window_stats_create().
A window's interval is divided into one or more "buckets"; the interval
must be divisible by the number of buckets. Internally, these buckets
control the granularity of window_stats' measurements. Increasing the
number of buckets lets the object respond more quickly to changes in the
overall rate of data added into the object, at the cost of additional
memory usage.
Here's some code which keeps one minute/hour measurements for two values
(latency in seconds and bytes transferred), with each interval divided into
4 buckets.
typedef struct my_stat {
double latency;
int bytes;
} my_stat;
void add_my_stat(void* base, const void* addme) {
my_stat* b = (my_stat*)base;
const my_stat* a = (const my_stat*)addme;
b->latency += a->latency;
b->bytes += a->bytes;
}
void add_proportion_my_stat(double p, void* base, const void* addme) {
(my_stat*)result->latency += p * (const my_stat*)base->latency;
(my_stat*)result->bytes += p * (const my_stat*)base->bytes;
}
#define kNumIntervals 2
#define kMinInterval 0
#define kHourInterval 1
#define kNumBuckets 4
const struct census_window_stats_stat_info kMyStatInfo
= { sizeof(my_stat), NULL, add_my_stat, add_proportion_my_stat };
gpr_timespec intervals[kNumIntervals] = {{60, 0}, {3600, 0}};
my_stat stat;
my_stat sums[kNumIntervals];
census_window_stats_sums result[kNumIntervals];
struct census_window_stats* stats
= census_window_stats_create(kNumIntervals, intervals, kNumBuckets,
&kMyStatInfo);
// Record a new event, taking 15.3ms, transferring 1784 bytes.
stat.latency = 0.153;
stat.bytes = 1784;
census_window_stats_add(stats, gpr_now(GPR_CLOCK_REALTIME), &stat);
// Get sums and print them out
result[kMinInterval].statistic = &sums[kMinInterval];
result[kHourInterval].statistic = &sums[kHourInterval];
census_window_stats_get_sums(stats, gpr_now(GPR_CLOCK_REALTIME), result);
printf("%d events/min, average time %gs, average bytes %g\n",
result[kMinInterval].count,
(my_stat*)result[kMinInterval].statistic->latency /
result[kMinInterval].count,
(my_stat*)result[kMinInterval].statistic->bytes /
result[kMinInterval].count
);
printf("%d events/hr, average time %gs, average bytes %g\n",
result[kHourInterval].count,
(my_stat*)result[kHourInterval].statistic->latency /
result[kHourInterval].count,
(my_stat*)result[kHourInterval].statistic->bytes /
result[kHourInterval].count
);
*/
/* Opaque structure for representing window_stats object */
struct census_window_stats;
/* Information provided by API user on the information they want to record */
typedef struct census_window_stats_stat_info {
/* Number of bytes in user-defined object. */
size_t stat_size;
/* Function to initialize a user-defined statistics object. If this is set
* to NULL, then the object will be zero-initialized. */
void (*stat_initialize)(void *stat);
/* Function to add one user-defined statistics object ('addme') to 'base' */
void (*stat_add)(void *base, const void *addme);
/* As for previous function, but only add a proportion 'p'. This API will
currently only use 'p' values in the range [0,1], but other values are
possible in the future, and should be supported. */
void (*stat_add_proportion)(double p, void *base, const void *addme);
} census_window_stats_stat_info;
/* Create a new window_stats object. 'nintervals' is the number of
'intervals', and must be >=1. 'granularity' is the number of buckets, with
a larger number using more memory, but providing greater accuracy of
results. 'granularity should be > 2. We also require that each interval be
at least 10 * 'granularity' nanoseconds in size. 'stat_info' contains
information about the statistic to be gathered. Intervals greater than ~192
years will be treated as essentially infinite in size. This function will
GPR_ASSERT() if the object cannot be created or any of the parameters have
invalid values. This function is thread-safe. */
struct census_window_stats *census_window_stats_create(
int nintervals, const gpr_timespec intervals[], int granularity,
const census_window_stats_stat_info *stat_info);
/* Add a new measurement (in 'stat_value'), as of a given time ('when').
This function is thread-compatible. */
void census_window_stats_add(struct census_window_stats *wstats,
const gpr_timespec when, const void *stat_value);
/* Structure used to record a single intervals sum for a given statistic */
typedef struct census_window_stats_sum {
/* Total count of samples. Note that because some internal interpolation
is performed, the count of samples returned for each interval may not be an
integral value. */
double count;
/* Sum for statistic */
void *statistic;
} census_window_stats_sums;
/* Retrieve a set of all values stored in a window_stats object 'wstats'. The
number of 'sums' MUST be the same as the number 'nintervals' used in
census_window_stats_create(). This function is thread-compatible. */
void census_window_stats_get_sums(const struct census_window_stats *wstats,
const gpr_timespec when,
struct census_window_stats_sum sums[]);
/* Destroy a window_stats object. Once this function has been called, the
object will no longer be usable from any of the above functions (and
calling them will most likely result in a NULL-pointer dereference or
assertion failure). This function is thread-compatible. */
void census_window_stats_destroy(struct census_window_stats *wstats);
#endif /* GRPC_CORE_LIB_STATISTICS_WINDOW_STATS_H */
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