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本节研究Nginx中线程池模块的相关实现；
（1）线程池模块属于核心模块，因此其配置内存ngx_thread_pool_conf_t将会预先申请好；ngx_thread_pool_conf_t中主要管理各个线程池结构；
（2）在ngx_thread_pool_init_worker和 ngx_thread_pool_exit_worker分别会创建每一个线程池和销毁每一个线程池；
ngx_module_t ngx_thread_pool_module = {
NGX_MODULE_V1,
&ngx_thread_pool_module_ctx, /* module context */
ngx_thread_pool_commands, /* module directives */
NGX_CORE_MODULE, /* module type */ //核心模块
NULL, /* init master */
NULL, /* init module */
ngx_thread_pool_init_worker, /* init process */
NULL, /* init thread */
NULL, /* exit thread */
ngx_thread_pool_exit_worker, /* exit process */
NULL, /* exit master */
NGX_MODULE_V1_PADDING
};
//核心模块上下文
static ngx_core_module_t ngx_thread_pool_module_ctx = {
ngx_string("thread_pool"),
ngx_thread_pool_create_conf,
ngx_thread_pool_init_conf
};
//线程模块配置结构
typedef struct {
ngx_array_t pools; //管理多个线程池
} ngx_thread_pool_conf_t;//线程模块配置申请内存
static void *
ngx_thread_pool_create_conf(ngx_cycle_t *cycle)
{
ngx_thread_pool_conf_t *tcf;
tcf = ngx_pcalloc(cycle->pool, sizeof(ngx_thread_pool_conf_t));
if (tcf == NULL) {
return NULL;
}
//总的线程池的个数
if (ngx_array_init(&tcf->pools, cycle->pool, 4,
sizeof(ngx_thread_pool_t *))
!= NGX_OK)
{
return NULL;
}
return tcf;
}//线程模块配置初始化
static char *
ngx_thread_pool_init_conf(ngx_cycle_t *cycle, void *conf)
{
ngx_thread_pool_conf_t *tcf = conf;
ngx_uint_t i;
ngx_thread_pool_t **tpp;
tpp = tcf->pools.elts;
for (i = 0; i < tcf->pools.nelts; i++) {
if (tpp[i]->threads) { //线程数目不为0时，直接跳过
continue;
}
if (tpp[i]->name.len == ngx_thread_pool_default.len
&& ngx_strncmp(tpp[i]->name.data, ngx_thread_pool_default.data,
ngx_thread_pool_default.len)
== 0)
{
tpp[i]->threads = 32; //默认的线程数
tpp[i]->max_queue = 65536; //默认的任务数
continue;
}
ngx_log_error(NGX_LOG_EMERG, cycle->log, 0,
"unknown thread pool \"%V\" in %s:%ui",
&tpp[i]->name, tpp[i]->file, tpp[i]->line);
return NGX_CONF_ERROR;
}
return NGX_CONF_OK;
}
static ngx_command_t ngx_thread_pool_commands[] = {
{ ngx_string("thread_pool"),
NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE23, //main配置项目
ngx_thread_pool, //解析函数
0,
0,
NULL },
ngx_null_command
};
//"ngx_thread_pool"配置解析
static char *
ngx_thread_pool(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
ngx_str_t *value;
ngx_uint_t i;
ngx_thread_pool_t *tp;
value = cf->args->elts;
tp = ngx_thread_pool_add(cf, &value[1]); //添加线程池
if (tp == NULL) {
return NGX_CONF_ERROR;
}
if (tp->threads) {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
"duplicate thread pool \"%V\"", &tp->name);
return NGX_CONF_ERROR;
}
tp->max_queue = 65536;
for (i = 2; i < cf->args->nelts; i++) {
if (ngx_strncmp(value[i].data, "threads=", 8) == 0) {
tp->threads = ngx_atoi(value[i].data + 8, value[i].len - 8); //线程数目设置
if (tp->threads == (ngx_uint_t) NGX_ERROR || tp->threads == 0) {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
"invalid threads value \"%V\"", &value[i]);
return NGX_CONF_ERROR;
}
continue;
}
if (ngx_strncmp(value[i].data, "max_queue=", 10) == 0) {
tp->max_queue = ngx_atoi(value[i].data + 10, value[i].len - 10); //任务数设置
if (tp->max_queue == NGX_ERROR) {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
"invalid max_queue value \"%V\"", &value[i]);
return NGX_CONF_ERROR;
}
continue;
}
}
if (tp->threads == 0) { //若线程池为空时
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
"\"%V\" must have \"threads\" parameter",
&cmd->name);
return NGX_CONF_ERROR;
}
return NGX_CONF_OK;
}
//在worker进程进入循环前调用
static ngx_int_t
ngx_thread_pool_init_worker(ngx_cycle_t *cycle)
{
ngx_uint_t i;
ngx_thread_pool_t **tpp;
ngx_thread_pool_conf_t *tcf;
if (ngx_process != NGX_PROCESS_WORKER
&& ngx_process != NGX_PROCESS_SINGLE)
{
return NGX_OK;
}
tcf = (ngx_thread_pool_conf_t *) ngx_get_conf(cycle->conf_ctx,
ngx_thread_pool_module);
if (tcf == NULL) {
return NGX_OK;
}
//初始化已完成任务队列头
ngx_thread_pool_queue_init(&ngx_thread_pool_done);
tpp = tcf->pools.elts;
for (i = 0; i < tcf->pools.nelts; i++) {
if (ngx_thread_pool_init(tpp[i], cycle->log, cycle->pool) != NGX_OK) { //初始化每一个线程池
return NGX_ERROR;
}
}
return NGX_OK;
}
//在worker进程退出前调用
static void
ngx_thread_pool_exit_worker(ngx_cycle_t *cycle)
{
ngx_uint_t i;
ngx_thread_pool_t **tpp;
ngx_thread_pool_conf_t *tcf;
if (ngx_process != NGX_PROCESS_WORKER
&& ngx_process != NGX_PROCESS_SINGLE)
{
return;
}
tcf = (ngx_thread_pool_conf_t *) ngx_get_conf(cycle->conf_ctx,
ngx_thread_pool_module);
if (tcf == NULL) {
return;
}
tpp = tcf->pools.elts;
for (i = 0; i < tcf->pools.nelts; i++) {
ngx_thread_pool_destroy(tpp[i]); //销毁每一个线程池
}
}
//线程池描述
struct ngx_thread_pool_s {
ngx_thread_mutex_t mtx; //互斥量
ngx_thread_pool_queue_t queue; //任务队列
ngx_int_t waiting; //等待的任务数
ngx_thread_cond_t cond; //条件
ngx_log_t *log;
ngx_str_t name; //线程池名称
ngx_uint_t threads; //线程池数目
ngx_int_t max_queue; //任务数的最大个数
u_char *file;
ngx_uint_t line;
};
//初始化一个线程池
static ngx_int_t
ngx_thread_pool_init(ngx_thread_pool_t *tp, ngx_log_t *log, ngx_pool_t *pool)
{
int err;
pthread_t tid;
ngx_uint_t n;
pthread_attr_t attr;
if (ngx_notify == NULL) { //没有通知处理
ngx_log_error(NGX_LOG_ALERT, log, 0,
"the configured event method cannot be used with thread pools");
return NGX_ERROR;
}
ngx_thread_pool_queue_init(&tp->queue); //初始化该线程池中任务队列
if (ngx_thread_mutex_create(&tp->mtx, log) != NGX_OK) { //创建该线程池的互斥量
return NGX_ERROR;
}
if (ngx_thread_cond_create(&tp->cond, log) != NGX_OK) { //创建线程池的条件变量
(void) ngx_thread_mutex_destroy(&tp->mtx, log);
return NGX_ERROR;
}
tp->log = log;
err = pthread_attr_init(&attr); //设置线程属性
if (err) {
ngx_log_error(NGX_LOG_ALERT, log, err,
"pthread_attr_init() failed");
return NGX_ERROR;
}
#if 0
err = pthread_attr_setstacksize(&attr, PTHREAD_STACK_MIN); //设置栈大小
if (err) {
ngx_log_error(NGX_LOG_ALERT, log, err,
"pthread_attr_setstacksize() failed");
return NGX_ERROR;
}
#endif
for (n = 0; n < tp->threads; n++) {
err = pthread_create(&tid, &attr, ngx_thread_pool_cycle, tp);
//创建线程池, ngx_thread_pool_cycle为线程执行的函数
if (err) {
ngx_log_error(NGX_LOG_ALERT, log, err,
"pthread_create() failed");
return NGX_ERROR;
}
}
(void) pthread_attr_destroy(&attr); //摧毁线程属性
return NGX_OK;
}//销毁线程池
static void
ngx_thread_pool_destroy(ngx_thread_pool_t *tp)
{
ngx_uint_t n;
ngx_thread_task_t task;
volatile ngx_uint_t lock;
ngx_memzero(&task, sizeof(ngx_thread_task_t));
task.handler = ngx_thread_pool_exit_handler; //任务退出执行函数
task.ctx = (void *) &lock; //指向传入的参数
for (n = 0; n < tp->threads; n++) { //tp中所有的线程池添加该任务
lock = 1;
if (ngx_thread_task_post(tp, &task) != NGX_OK) {
return;
}
while (lock) { //主进程判断如果lock没有改变，就让CPU给其他线程执行，以此等待，相当于pthread_join
ngx_sched_yield();
}
task.event.active = 0;
}
//此时到这边，所有的线程都已经退出
(void) ngx_thread_cond_destroy(&tp->cond, tp->log); //条件变量销毁
(void) ngx_thread_mutex_destroy(&tp->mtx, tp->log); //互斥量销毁
}
//各个线程的退出任务
static void
ngx_thread_pool_exit_handler(void *data, ngx_log_t *log)
{
ngx_uint_t *lock = data; //获取参数
*lock = 0; //变为0
pthread_exit(0);
}
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原文地址：http://blog.csdn.net/skyuppour/article/details/45938251
