| /* |
| * |
| * Copyright 2015 gRPC authors. |
| * |
| * Licensed 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. |
| * |
| */ |
| |
| #ifndef GRPC_CORE_EXT_CENSUS_WINDOW_STATS_H |
| #define GRPC_CORE_EXT_CENSUS_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_EXT_CENSUS_WINDOW_STATS_H */ |