-unsigned int counter = 0; // Just an example
+/**
+ * collectd - src/daemon/distribution.c
+ * Copyright (C) 2019-2020 Google LLC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ * Svetlana Shmidt <sshmidt at google.com>
+ **/
-int my_function() { return ++counter; }
+#include "distribution.h"
+
+#include <pthread.h>
+
+typedef struct bucket_s {
+ uint64_t bucket_counter;
+ double maximum;
+} bucket_t;
+
+struct distribution_s {
+ bucket_t *tree;
+ size_t num_buckets;
+ double total_sum;
+ pthread_mutex_t mutex;
+};
+
+/**
+ * This code uses an Euler path to avoid gaps in the tree-to-array mapping.
+ * This way the tree contained N buckets contains 2 * N - 1 nodes
+ * Thus, left subtree has 2 * (mid - left + 1) - 1 nodes,
+ * therefore the right subtree starts at node_index + 2 * (mid - left + 1).
+ * For a detailed explanation, see https://docs.google.com/document/d/1ccsg5ffUfqt9-mBDGTymRn8X-9Wk1CuGYeMlRxmxiok/edit?usp=sharing".
+ */
+
+static size_t left_child_index(size_t node_index,
+ __attribute__((unused)) size_t left,
+ __attribute__((unused)) size_t right) {
+ return node_index + 1;
+}
+
+static size_t right_child_index(size_t node_index, size_t left, size_t right) {
+ size_t mid = (left + right) / 2;
+ return node_index + 2 * (mid - left + 1);
+}
+
+static size_t tree_size(size_t num_buckets) {
+ return 2 * num_buckets - 1;
+}
+
+static bucket_t merge_buckets(bucket_t left_child, bucket_t right_child) {
+ return (bucket_t) {
+ .bucket_counter = left_child.bucket_counter + right_child.bucket_counter,
+ .maximum = right_child.maximum,
+ };
+}
+
+static void build_tree(distribution_t *d, bucket_t *buckets, size_t node_index, size_t left, size_t right) {
+ if (left > right)
+ return;
+ if (left == right) {
+ d->tree[node_index] = buckets[left];
+ return;
+ }
+ size_t mid = (left + right) / 2;
+ size_t left_child = left_child_index(node_index, left, right);
+ size_t right_child = right_child_index(node_index, left, right);
+ build_tree(d, buckets, left_child, left, mid);
+ build_tree(d, buckets, right_child, mid + 1, right);
+ d->tree[node_index] = merge_buckets(d->tree[left_child], d->tree[right_child]);
+}
+
+static distribution_t* build_distribution_from_bucket_array(size_t num_buckets, bucket_t *bucket_array) {
+ distribution_t *new_distribution = calloc(1, sizeof(*new_distribution));
+ bucket_t *nodes = calloc(tree_size(num_buckets), sizeof(*nodes));
+ if (new_distribution == NULL || nodes == NULL) {
+ free(new_distribution);
+ free(nodes);
+ return NULL;
+ }
+ new_distribution->tree = nodes;
+
+ new_distribution->num_buckets = num_buckets;
+ build_tree(new_distribution, bucket_array, 0, 0, num_buckets - 1);
+ pthread_mutex_init(&new_distribution->mutex, NULL);
+ return new_distribution;
+}
+
+distribution_t* distribution_new_linear(size_t num_buckets, double size) {
+ if (num_buckets == 0 || size <= 0) {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ bucket_t bucket_array[num_buckets];
+ for (size_t i = 0; i < num_buckets; i++) {
+ bucket_array[i] = (bucket_t) {
+ .bucket_counter = 0,
+ .maximum = (i == num_buckets - 1) ? INFINITY : (i + 1) * size,
+ };
+ }
+ return build_distribution_from_bucket_array(num_buckets, bucket_array);
+}
+
+distribution_t* distribution_new_exponential(size_t num_buckets, double base, double factor) {
+ if (num_buckets == 0 || base <= 1 || factor <= 0) {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ bucket_t bucket_array[num_buckets];
+ for (size_t i = 0; i < num_buckets; i++) {
+ bucket_array[i] = (bucket_t) {
+ .bucket_counter = 0,
+ .maximum = (i == num_buckets - 1) ? INFINITY : factor * pow(base, i), //check if it's slow
+ };
+ }
+ return build_distribution_from_bucket_array(num_buckets, bucket_array);
+}
+
+distribution_t* distribution_new_custom(size_t array_size, double *custom_buckets_boundaries) {
+ for (size_t i = 0; i < array_size; i++) {
+ double previous_boundary = 0;
+ if (i > 0) {
+ previous_boundary = custom_buckets_boundaries[i - 1];
+ }
+ if (custom_buckets_boundaries[i] <= previous_boundary) {
+ errno = EINVAL;
+ return NULL;
+ }
+ }
+ if (array_size > 0 && custom_buckets_boundaries[array_size - 1] == INFINITY) {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ size_t num_buckets = array_size + 1;
+ bucket_t bucket_array[num_buckets];
+ for (size_t i = 0; i < num_buckets; i++) {
+ bucket_array[i] = (bucket_t) {
+ .bucket_counter = 0,
+ .maximum = (i == num_buckets - 1) ? INFINITY : custom_buckets_boundaries[i],
+ };
+ }
+ return build_distribution_from_bucket_array(num_buckets, bucket_array);
+}
+
+void distribution_destroy(distribution_t *d) {
+ if (d == NULL)
+ return;
+ pthread_mutex_destroy(&d->mutex);
+ free(d->tree);
+ free(d);
+}
+
+distribution_t* distribution_clone(distribution_t *dist) {
+ if (dist == NULL)
+ return NULL;
+ distribution_t *new_distribution = calloc(1, sizeof(*new_distribution));
+ bucket_t *nodes = calloc(tree_size(dist->num_buckets), sizeof(*nodes));
+ if (new_distribution == NULL || nodes == NULL) {
+ free(new_distribution);
+ free(nodes);
+ return NULL;
+ }
+ pthread_mutex_lock(&dist->mutex);
+ memcpy(nodes, dist->tree, tree_size(dist->num_buckets) * sizeof(bucket_t));
+ new_distribution->num_buckets = dist->num_buckets;
+ new_distribution->total_sum = dist->total_sum;
+ pthread_mutex_unlock(&dist->mutex);
+ new_distribution->tree = nodes;
+ pthread_mutex_init(&new_distribution->mutex, NULL);
+ return new_distribution;
+}
+
+static void update_tree(distribution_t *dist, size_t node_index, size_t left, size_t right, double gauge) {
+ if (left > right)
+ return;
+ dist->tree[node_index].bucket_counter++;
+ if (left == right) {
+ return;
+ }
+ size_t mid = (left + right) / 2;
+ size_t left_child = left_child_index(node_index, left, right);
+ size_t right_child = right_child_index(node_index, left, right);
+ if (dist->tree[left_child].maximum > gauge)
+ update_tree(dist, left_child, left, mid, gauge);
+ else
+ update_tree(dist, right_child, mid + 1, right, gauge);
+}
+
+void distribution_update(distribution_t *dist, double gauge) {
+ if (dist == NULL)
+ return;
+ if (gauge < 0) {
+ errno = EINVAL;
+ return;
+ }
+ pthread_mutex_lock(&dist->mutex);
+ update_tree(dist, 0, 0, dist->num_buckets - 1, gauge);
+ dist->total_sum += gauge;
+ pthread_mutex_unlock(&dist->mutex);
+}
+
+static double tree_get_counter(distribution_t *d, size_t node_index, size_t left,
+ size_t right, uint64_t counter) {
+ if (left > right)
+ return NAN;
+ if (left == right) {
+ return d->tree[node_index].maximum;
+ }
+ size_t mid = (left + right) / 2;
+ size_t left_child = left_child_index(node_index, left, right);
+ size_t right_child = right_child_index(node_index, left, right);
+ if (d->tree[left_child].bucket_counter >= counter)
+ return tree_get_counter(d, left_child, left, mid, counter);
+ else
+ return tree_get_counter(d, right_child, mid + 1, right, counter - d->tree[left_child].bucket_counter);
+}
+
+double distribution_percentile(distribution_t *dist, double percent) {
+ if (percent <= 0 || percent > 100) {
+ errno = EINVAL;
+ return NAN;
+ }
+ pthread_mutex_lock(&dist->mutex);
+ if (dist->tree[0].bucket_counter == 0)
+ return NAN;
+ uint64_t counter = ceil(dist->tree[0].bucket_counter * percent / 100.0);
+ double percentile = tree_get_counter(dist, 0, 0, dist->num_buckets - 1, counter);
+ pthread_mutex_unlock(&dist->mutex);
+ return percentile;
+}
+
+double distribution_average(distribution_t *dist) {
+ pthread_mutex_lock(&dist->mutex);
+ if (dist == NULL || dist->tree[0].bucket_counter == 0) {
+ return NAN;
+ }
+ double average = dist->total_sum / dist->tree[0].bucket_counter;
+ pthread_mutex_unlock(&dist->mutex);
+ return average;
+}
+
+size_t distribution_num_buckets(distribution_t *dist) {
+ if (dist == NULL)
+ return 0;
+ return dist->num_buckets;
+}
+
+static void tree_write_leave_buckets(distribution_t *dist, bucket_t *write_ptr, size_t node_index, size_t left, size_t right) {
+ if (left > right)
+ return;
+ if (left == right) {
+ write_ptr[left] = dist->tree[node_index];
+ return;
+ }
+ size_t mid = (left + right) / 2;
+ size_t left_child = left_child_index(node_index, left, right);
+ size_t right_child = right_child_index(node_index, left, right);
+ tree_write_leave_buckets(dist, write_ptr, left_child, left, mid);
+ tree_write_leave_buckets(dist, write_ptr, right_child, mid + 1, right);
+}
+
+buckets_array_t get_buckets(distribution_t *dist) {
+ buckets_array_t bucket_array = {
+ .num_buckets = dist == NULL ? 0 : dist->num_buckets,
+ .buckets = dist == NULL ? NULL : calloc(dist->num_buckets, sizeof(*bucket_array.buckets)),
+ };
+ if (dist == NULL)
+ return bucket_array;
+ bucket_t *write_ptr = bucket_array.buckets;
+ pthread_mutex_lock(&dist->mutex);
+ tree_write_leave_buckets(dist, write_ptr, 0, 0, dist->num_buckets - 1);
+ pthread_mutex_unlock(&dist->mutex);
+ return bucket_array;
+}
+
+void destroy_buckets_array(buckets_array_t buckets_array) {
+ free(buckets_array.buckets);
+}
projects / thirdparty / collectd.git / commitdiff
