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).

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_TIMES_H_INCLUDED_
#define _NGX_TIMES_H_INCLUDED_


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


typedef struct {
    time_t      sec;
    ngx_uint_t  msec;
    ngx_int_t   gmtoff;
} ngx_time_t;


void ngx_time_init(void);
void ngx_time_update(void);
void ngx_time_sigsafe_update(void);
u_char *ngx_http_time(u_char *buf, time_t t);
u_char *ngx_http_cookie_time(u_char *buf, time_t t);
void ngx_gmtime(time_t t, ngx_tm_t *tp);

time_t ngx_next_time(time_t when);
#define ngx_next_time_n      "mktime()"


extern volatile ngx_time_t  *ngx_cached_time;

#define ngx_time()           ngx_cached_time->sec
#define ngx_timeofday()      (ngx_time_t *) ngx_cached_time

extern volatile ngx_str_t    ngx_cached_err_log_time;
extern volatile ngx_str_t    ngx_cached_http_time;
extern volatile ngx_str_t    ngx_cached_http_log_time;
extern volatile ngx_str_t    ngx_cached_http_log_iso8601;

/*
 * milliseconds elapsed since epoch and truncated to ngx_msec_t,
 * used in event timers
 */
extern volatile ngx_msec_t  ngx_current_msec;


#endif /* _NGX_TIMES_H_INCLUDED_ */