Mercurial > hg > nginx-quic
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 |
line wrap: on
line source
/* * 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_ */