这篇文章主要介绍了C++定时器实现和时间轮介绍,定时器可以由很多种数据结构实现,比如最小堆、红黑树、跳表、甚至数组都可以,其本质都是拿到最小时间的任务,然后取出该任务并执行,更多相关内容介绍,需要的小伙伴可以参考一下
定时器
有些时候我们需要延迟执行一些功能,比如每10s进行一次数据采集。或者告知用户技能冷却有多少时间,如果我们将执行这些功能的任务交给主线程,就会造成主线程的阻塞。因此我们可以选择一个创建一个子线程,让其检测定时器中的任务,当有任务的时间到了的时候,就去执行这个任务。
最小堆实现定时器
定时器可以由很多种数据结构实现,比如最小堆、红黑树、跳表、甚至数组都可以,其本质都是拿到最小时间的任务,然后取出该任务并执行。
综合实现难度和效率来看,最小堆是最容易实现定时器的数据结构。
最小堆主要有以下接口:
#pragma once #include#include
具体的实现以及测试为:
#pragma once #include#include
#include#include #include #include "minheap.h" void print_hello(TimerNode *te) { std::cout << "hello world time = " << te->idx << "\t" << te->id << "\t" << current_time() << std::endl; } int main() { MinHeapTimer mht; //一号任务,立刻执行 mht.AddTimer(0, print_hello); //二号任务,一秒后执行 mht.AddTimer(1000, print_hello); mht.AddTimer(7000, print_hello); mht.AddTimer(2000, print_hello); mht.AddTimer(9000, print_hello); mht.AddTimer(10000, print_hello); mht.AddTimer(6000, print_hello); mht.AddTimer(3000, print_hello); while (1) { mht.ExpireTimer(); // usleep(10000); sleep(1); } return 0; }
时间轮
上面的定时器在任务数量很多时,效率会很低,因为我们需要用最小堆来维护这些任务,并且每删除一个任务,都要进行调整。其主要原因是我们不知道其他任务什么时候执行,所以我们只能进行调整,将最近的任务放到堆顶。
如果我们能够向哈希桶那样,将要执行的任务形成链表,挂到要执行的位置,当时间走到那个位置的时候,就执行这些任务,效率岂不是更高?
单层级时间轮
客户端每 5 秒钟发送⼼跳包;服务端若 10 秒内没收到⼼跳数据,则清除连接。
考虑到正常情况下 5 秒钟发送⼀次⼼跳包,10 秒才检测⼀次,如下图到索引为 10 的时候并不能踢掉连接;所以需要每收到⼀次⼼跳包则 used++ ,每检测⼀次 used-- ;当检测到used == 0 则踢掉连接;
#include#include #include #include #include #include #define MAX_CONN ((1 << 16) - 1) //连接的节点,用来记录心跳包发送的次数 typedef struct conn_node { struct conn_node *next; //引用计数的次数,当used==0,相当于自动销毁 uint8_t used; int id; } conn_node_t; //用数组记录所有的连接 static conn_node_t nodes[MAX_CONN] = {0}; static uint32_t iter = 0; //获取一个空的连接节点 conn_node_t *get_node() { iter++; while (nodes[iter & MAX_CONN].used > 0) { iter++; } return &nodes[iter]; } //哈希桶的个数 #define TW_SIZE 16 //检测心跳包的延迟时间,由于哈希桶的个数有限,所以心跳包发送时间不能够超过6 #define EXPIRE 10 //取余操作 #define TW_MASK (TW_SIZE - 1) static uint32_t tick = 0; //哈希桶 typedef struct link_list { conn_node_t head; //一个tail,能够进行快速插入 conn_node_t *tail; } link_list_t; //添加连接 void add_conn(link_list_t *tw, conn_node_t *node, int delay) { //获取对应的哈希桶 link_list_t *list = &tw[(tick + EXPIRE + delay) & TW_MASK]; list->tail->next = node; list->tail = node; node->next = NULL; node->used++; } //清楚这个哈希桶 void link_clear(link_list_t *list) { list->head.next = NULL; list->tail = &(list->head); } //检测哈希桶 void check_conn(link_list_t *tw) { int32_t itick = tick; tick++; //取到对应哈希桶的链表 link_list_t *list = &tw[itick & TW_MASK]; //检测哈希桶对应的链表 conn_node_t *current = list->head.next; while (current) { conn_node_t *temp = current; current = current->next; temp->used--; if (temp->used == 0) { printf("连接:%d 断开\n", temp->id); temp->next = NULL; continue; } printf("这个链接:%d 心跳包还剩:%d个需要检测\n", temp->id, temp->used); } link_clear(list); } //获取时间,单位是s static time_t current_time() { time_t t; struct timespec ti; clock_gettime(CLOCK_MONOTONIC, &ti); t = (time_t)ti.tv_sec; return t; } int main() { memset(nodes, 0, MAX_CONN * sizeof(conn_node_t)); // init link list link_list_t tw[TW_SIZE]; memset(tw, 0, TW_SIZE * sizeof(link_list_t)); for (int i = 0; i id = 10001; add_conn(tw, node, 0); add_conn(tw, node, 5); } //第二个连接发送的心跳包,在第10s时进行检测 { conn_node_t *node = get_node(); node->id = 10002; add_conn(tw, node, 0); } //第二个连接发送的心跳包,在第13s时检测 { conn_node_t *node = get_node(); node->id = 10003; add_conn(tw, node, 3); } time_t start = current_time(); while (1) { time_t now = current_time(); if (now - start > 0) { for (int i = 0; i
上面的时间轮受哈希桶大小和延迟10s收到心跳包的影响,只能在[0,6]秒内发送数据心跳包,如果想要延迟长时间,则需要扩大哈希桶的大小。
如果我们不发送心跳包,而是改成在若干秒后执行一个任务,比如50s后执行任务,但哈希桶大小只有16,我们可以在任务节点中增加一个参数round,用来记录需要走多少遍哈希桶,比如50s,对应到大小为16的哈希桶则round=3,idx=2。
不过这样做,在check_conn取任务时就不能够把整个链表都取出来,而是需要取出round==0的任务。
typedef struct node { struct conn_node *next; //需要走多少轮哈希桶,当round==0时,则说明需要执行这个任务 int round; int id; } node_t;
这样做能解决时间轮刻度范围过大造成的空间浪费,但是却带来了另一个问题:时间轮每次都需要遍历任务列表,耗时增加,当时间轮刻度粒度很小(秒级甚至毫秒级),任务列表又特别长时,这种遍历的办法是不可接受的。
多层级时间轮
参照时钟表盘的运转规律,可以将定时任务根据触发的紧急程度,分布到不同层级的时间轮中;
假设时间精度为 10ms ;在第 1 层级每 10ms 移动⼀格;每移动⼀格执⾏该格⼦当中所有的定时任务;
当第 1 层指针从 255 格开始移动,此时层级 2 移动⼀格;层级 2 移动⼀格的⾏为定义为,将该格当中的定时任务重新映射到层级 1 当中;同理,层级 2 当中从 63 格开始移动,层级 3 格⼦中的定时任务重新映射到层级 2 ; 以此类推层级 4 往层级 3 映射,层级 5 往层级 4 映射。
只有任务在第一层时才会被执行,其他层都是将任务重新映射到上一层。
timewheel.h:
#pragma once #include#define TIME_NEAR_SHIFT 8 #define TIME_NEAR (1 << TIME_NEAR_SHIFT) #define TIME_LEVEL_SHIFT 6 #define TIME_LEVEL (1 << TIME_LEVEL_SHIFT) #define TIME_NEAR_MASK (TIME_NEAR - 1) #define TIME_LEVEL_MASK (TIME_LEVEL - 1) typedef struct timer_node timer_node_t; typedef void (*handler_pt)(struct timer_node *node); struct timer_node { struct timer_node *next; uint32_t expire; //时间 handler_pt callback; //回调函数 uint8_t cancel; //是否删除 int id; // 此时携带参数 }; timer_node_t *add_timer(int time, handler_pt func, int threadid); void expire_timer(void); void del_timer(timer_node_t *node); void init_timer(void); void clear_timer();
spinlock.h:
#pragma once struct spinlock { int lock; }; void spinlock_init(struct spinlock *lock) { lock->lock = 0; } void spinlock_lock(struct spinlock *lock) { while (__sync_lock_test_and_set(&lock->lock, 1)) { } } int spinlock_trylock(struct spinlock *lock) { return __sync_lock_test_and_set(&lock->lock, 1) == 0; } void spinlock_unlock(struct spinlock *lock) { __sync_lock_release(&lock->lock); } void spinlock_destroy(struct spinlock *lock) { (void)lock; }
timewheel.cpp:
#include "spinlock.h" #include "timewheel.h" #include#include #include #include typedef struct link_list { timer_node_t head; timer_node_t *tail; } link_list_t; //多级时间轮 typedef struct timer { //第一级 link_list_t near[TIME_NEAR]; // 2-4级 link_list_t t[4][TIME_LEVEL]; struct spinlock lock; uint32_t time; uint64_t current; uint64_t current_point; } s_timer_t; static s_timer_t *TI = NULL; timer_node_t *link_clear(link_list_t *list) { timer_node_t *ret = list->head.next; list->head.next = 0; list->tail = &(list->head); return ret; } //链接一个节点 void link(link_list_t *list, timer_node_t *node) { list->tail->next = node; list->tail = node; node->next = 0; } void add_node(s_timer_t *T, timer_node_t *node) { uint32_t time = node->expire; uint32_t current_time = T->time; uint32_t msec = time - current_time; //根据时间 if (msec near[time & TIME_NEAR_MASK], node); } else if (msec <(1 << (TIME_NEAR_SHIFT + TIME_LEVEL_SHIFT))) { //[0x100, 0x4000) link(&T->t[0][((time >> TIME_NEAR_SHIFT) & TIME_LEVEL_MASK)], node); } else if (msec <(1 << (TIME_NEAR_SHIFT + 2 * TIME_LEVEL_SHIFT))) { //[0x4000, 0x100000) link(&T->t[1][((time >> (TIME_NEAR_SHIFT + TIME_LEVEL_SHIFT)) & TIME_LEVEL_MASK)], node); } else if (msec <(1 << (TIME_NEAR_SHIFT + 3 * TIME_LEVEL_SHIFT))) { //[0x100000, 0x4000000) link(&T->t[2][((time >> (TIME_NEAR_SHIFT + 2 * TIME_LEVEL_SHIFT)) & TIME_LEVEL_MASK)], node); } else { //[0x4000000, 0xffffffff] link(&T->t[3][((time >> (TIME_NEAR_SHIFT + 3 * TIME_LEVEL_SHIFT)) & TIME_LEVEL_MASK)], node); } } //增加事件 timer_node_t *add_timer(int time, handler_pt func, int threadid) { timer_node_t *node = (timer_node_t *)malloc(sizeof(*node)); spinlock_lock(&TI->lock); node->expire = time + TI->time; // 每10ms加1 0 node->callback = func; node->id = threadid; if (time <= 0) { node->callback(node); free(node); spinlock_unlock(&TI->lock); return NULL; } add_node(TI, node); spinlock_unlock(&TI->lock); return node; } void move_list(s_timer_t *T, int level, int idx) { timer_node_t *current = link_clear(&T->t[level][idx]); while (current) { timer_node_t *temp = current->next; add_node(T, current); current = temp; } } void timer_shift(s_timer_t *T) { int mask = TIME_NEAR; uint32_t ct = ++T->time; if (ct == 0) { move_list(T, 3, 0); } else { // ct / 256 uint32_t time = ct >> TIME_NEAR_SHIFT; int i = 0; // ct % 256 == 0 while ((ct & (mask - 1)) == 0) { int idx = time & TIME_LEVEL_MASK; if (idx != 0) { move_list(T, i, idx); break; } mask <<= TIME_LEVEL_SHIFT; time >>= TIME_LEVEL_SHIFT; ++i; } } } void dispatch_list(timer_node_t *current) { do { timer_node_t *temp = current; current = current->next; if (temp->cancel == 0) temp->callback(temp); free(temp); } while (current); } void timer_execute(s_timer_t *T) { int idx = T->time & TIME_NEAR_MASK; while (T->near[idx].head.next) { timer_node_t *current = link_clear(&T->near[idx]); spinlock_unlock(&T->lock); dispatch_list(current); spinlock_lock(&T->lock); } } void timer_update(s_timer_t *T) { spinlock_lock(&T->lock); timer_execute(T); timer_shift(T); timer_execute(T); spinlock_unlock(&T->lock); } void del_timer(timer_node_t *node) { node->cancel = 1; } s_timer_t *timer_create_timer() { s_timer_t *r = (s_timer_t *)malloc(sizeof(s_timer_t)); memset(r, 0, sizeof(*r)); int i, j; for (i = 0; i near[i]); } for (i = 0; i <4; i++) { for (j = 0; j t[i][j]); } } spinlock_init(&r->lock); r->current = 0; return r; } uint64_t gettime() { uint64_t t; struct timespec ti; clock_gettime(CLOCK_MONOTONIC, &ti); t = (uint64_t)ti.tv_sec * 100; t += ti.tv_nsec / 10000000; return t; } void expire_timer(void) { uint64_t cp = gettime(); if (cp != TI->current_point) { uint32_t diff = (uint32_t)(cp - TI->current_point); TI->current_point = cp; int i; for (i = 0; i current_point = gettime(); } void clear_timer() { int i, j; for (i = 0; i near[i]; timer_node_t *current = list->head.next; while (current) { timer_node_t *temp = current; current = current->next; free(temp); } link_clear(&TI->near[i]); } for (i = 0; i <4; i++) { for (j = 0; j t[i][j]; timer_node_t *current = list->head.next; while (current) { timer_node_t *temp = current; current = current->next; free(temp); } link_clear(&TI->t[i][j]); } } }
tw-timer.cpp:
#include#include #include #include #include #include "timewheel.h" struct context { int quit; int thread; }; struct thread_param { struct context *ctx; int id; }; static struct context ctx = {0}; void do_timer(timer_node_t *node) { printf("timer expired:%d - thread-id:%d\n", node->expire, node->id); } void *thread_worker(void *p) { struct thread_param *tp = (struct thread_param *)p; int id = tp->id; struct context *ctx = tp->ctx; while (!ctx->quit) { int expire = rand() % 200; add_timer(expire, do_timer, id); usleep(expire * (10 - 1) * 1000); } printf("thread_worker:%d exit!\n", id); return NULL; } void do_quit(timer_node_t *node) { ctx.quit = 1; } int main() { srand(time(NULL)); ctx.thread = 8; pthread_t pid[ctx.thread]; init_timer(); add_timer(6000, do_quit, 100); struct thread_param task_thread_p[ctx.thread]; int i; for (i = 0; i
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