Mercurial > hg > nginx-quic
view src/os/unix/ngx_freebsd_rfork_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 | 15a7deeaa19a |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #ifndef _NGX_FREEBSD_RFORK_THREAD_H_INCLUDED_ #define _NGX_FREEBSD_RFORK_THREAD_H_INCLUDED_ #include <sys/ipc.h> #include <sys/sem.h> #include <sched.h> typedef pid_t ngx_tid_t; #define ngx_log_pid ngx_thread_self() #define ngx_log_tid 0 #define NGX_TID_T_FMT "%P" #define NGX_MUTEX_LIGHT 1 #define NGX_MUTEX_LOCK_BUSY 0x80000000 typedef volatile struct { ngx_atomic_t lock; ngx_log_t *log; int semid; } ngx_mutex_t; #define NGX_CV_SIGNAL 64 typedef struct { int signo; int kq; ngx_tid_t tid; ngx_log_t *log; } ngx_cond_t; #define ngx_thread_sigmask(how, set, oset) \ (sigprocmask(how, set, oset) == -1) ? ngx_errno : 0 #define ngx_thread_sigmask_n "sigprocmask()" #define ngx_thread_join(t, p) #define ngx_setthrtitle(n) setproctitle(n) extern char *ngx_freebsd_kern_usrstack; extern size_t ngx_thread_stack_size; static ngx_inline ngx_int_t ngx_gettid() { char *sp; if (ngx_thread_stack_size == 0) { return 0; } #if ( __i386__ ) __asm__ volatile ("mov %%esp, %0" : "=q" (sp)); #elif ( __amd64__ ) __asm__ volatile ("mov %%rsp, %0" : "=q" (sp)); #else #error "rfork()ed threads are not supported on this platform" #endif return (ngx_freebsd_kern_usrstack - sp) / ngx_thread_stack_size; } ngx_tid_t ngx_thread_self(); typedef ngx_uint_t ngx_tls_key_t; #define NGX_THREAD_KEYS_MAX 16 extern void **ngx_tls; ngx_err_t ngx_thread_key_create(ngx_tls_key_t *key); #define ngx_thread_key_create_n "the tls key creation" ngx_err_t ngx_thread_set_tls(ngx_tls_key_t key, void *value); #define ngx_thread_set_tls_n "the tls key setting" static void * ngx_thread_get_tls(ngx_tls_key_t key) { if (key >= NGX_THREAD_KEYS_MAX) { return NULL; } return ngx_tls[key * NGX_THREAD_KEYS_MAX + ngx_gettid()]; } #define ngx_mutex_trylock(m) ngx_mutex_dolock(m, 1) #define ngx_mutex_lock(m) (void) ngx_mutex_dolock(m, 0) ngx_int_t ngx_mutex_dolock(ngx_mutex_t *m, ngx_int_t try); void ngx_mutex_unlock(ngx_mutex_t *m); typedef int (*ngx_rfork_thread_func_pt)(void *arg); #endif /* _NGX_FREEBSD_RFORK_THREAD_H_INCLUDED_ */