view src/os/unix/ngx_thread.h @ 4667:d05ab8793a69 stable-1.2

Merge of r4622, r4623: balancing changes. *) Upstream: smooth weighted round-robin balancing. For edge case weights like { 5, 1, 1 } we now produce { a, a, b, a, c, a, a } sequence instead of { c, b, a, a, a, a, a } produced previously. Algorithm is as follows: on each peer selection we increase current_weight of each eligible peer by its weight, select peer with greatest current_weight and reduce its current_weight by total number of weight points distributed among peers. In case of { 5, 1, 1 } weights this gives the following sequence of current_weight's: a b c 0 0 0 (initial state) 5 1 1 (a selected) -2 1 1 3 2 2 (a selected) -4 2 2 1 3 3 (b selected) 1 -4 3 6 -3 4 (a selected) -1 -3 4 4 -2 5 (c selected) 4 -2 -2 9 -1 -1 (a selected) 2 -1 -1 7 0 0 (a selected) 0 0 0 To preserve weight reduction in case of failures the effective_weight variable was introduced, which usually matches peer's weight, but is reduced temporarily on peer failures. This change also fixes loop with backup servers and proxy_next_upstream http_404 (ticket #47), and skipping alive upstreams in some cases if there are multiple dead ones (ticket #64). *) Upstream: fixed ip_hash rebalancing with the "down" flag. Due to weight being set to 0 for down peers, order of peers after sorting wasn't the same as without the "down" flag (with down peers at the end), resulting in client rebalancing for clients on other servers. The only rebalancing which should happen after adding "down" to a server is one for clients on the server. The problem was introduced in r1377 (which fixed endless loop by setting weight to 0 for down servers). The loop is no longer possible with new smooth algorithm, so preserving original weight is safe.
author Maxim Dounin <mdounin@mdounin.ru>
date Mon, 04 Jun 2012 11:21:58 +0000
parents d620f497c50f
children 457ec43dd8d5
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_THREAD_H_INCLUDED_
#define _NGX_THREAD_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>

#if (NGX_THREADS)

#define NGX_MAX_THREADS      128

#if (NGX_USE_RFORK)
#include <ngx_freebsd_rfork_thread.h>


#else /* use pthreads */

#include <pthread.h>

typedef pthread_t                    ngx_tid_t;

#define ngx_thread_self()            pthread_self()
#define ngx_log_tid                  (int) ngx_thread_self()

#if (NGX_FREEBSD) && !(NGX_LINUXTHREADS)
#define NGX_TID_T_FMT                "%p"
#else
#define NGX_TID_T_FMT                "%d"
#endif


typedef pthread_key_t                ngx_tls_key_t;

#define ngx_thread_key_create(key)   pthread_key_create(key, NULL)
#define ngx_thread_key_create_n      "pthread_key_create()"
#define ngx_thread_set_tls           pthread_setspecific
#define ngx_thread_set_tls_n         "pthread_setspecific()"
#define ngx_thread_get_tls           pthread_getspecific


#define NGX_MUTEX_LIGHT     0

typedef struct {
    pthread_mutex_t   mutex;
    ngx_log_t        *log;
} ngx_mutex_t;

typedef struct {
    pthread_cond_t    cond;
    ngx_log_t        *log;
} ngx_cond_t;

#define ngx_thread_sigmask     pthread_sigmask
#define ngx_thread_sigmask_n  "pthread_sigmask()"

#define ngx_thread_join(t, p)  pthread_join(t, p)

#define ngx_setthrtitle(n)



ngx_int_t ngx_mutex_trylock(ngx_mutex_t *m);
void ngx_mutex_lock(ngx_mutex_t *m);
void ngx_mutex_unlock(ngx_mutex_t *m);

#endif


#define ngx_thread_volatile   volatile


typedef struct {
    ngx_tid_t    tid;
    ngx_cond_t  *cv;
    ngx_uint_t   state;
} ngx_thread_t;

#define NGX_THREAD_FREE   1
#define NGX_THREAD_BUSY   2
#define NGX_THREAD_EXIT   3
#define NGX_THREAD_DONE   4

extern ngx_int_t              ngx_threads_n;
extern volatile ngx_thread_t  ngx_threads[NGX_MAX_THREADS];


typedef void *  ngx_thread_value_t;

ngx_int_t ngx_init_threads(int n, size_t size, ngx_cycle_t *cycle);
ngx_err_t ngx_create_thread(ngx_tid_t *tid,
    ngx_thread_value_t (*func)(void *arg), void *arg, ngx_log_t *log);

ngx_mutex_t *ngx_mutex_init(ngx_log_t *log, ngx_uint_t flags);
void ngx_mutex_destroy(ngx_mutex_t *m);


ngx_cond_t *ngx_cond_init(ngx_log_t *log);
void ngx_cond_destroy(ngx_cond_t *cv);
ngx_int_t ngx_cond_wait(ngx_cond_t *cv, ngx_mutex_t *m);
ngx_int_t ngx_cond_signal(ngx_cond_t *cv);


#else /* !NGX_THREADS */

#define ngx_thread_volatile

#define ngx_log_tid           0
#define NGX_TID_T_FMT         "%d"

#define ngx_mutex_trylock(m)  NGX_OK
#define ngx_mutex_lock(m)
#define ngx_mutex_unlock(m)

#define ngx_cond_signal(cv)

#define ngx_thread_main()     1

#endif


#endif /* _NGX_THREAD_H_INCLUDED_ */