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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).
author Maxim Dounin <mdounin@mdounin.ru>
date Mon, 14 May 2012 09:57:20 +0000
parents d620f497c50f
children 382c523d253a
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_HTTP_UPSTREAM_ROUND_ROBIN_H_INCLUDED_
#define _NGX_HTTP_UPSTREAM_ROUND_ROBIN_H_INCLUDED_


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


typedef struct {
    struct sockaddr                *sockaddr;
    socklen_t                       socklen;
    ngx_str_t                       name;

    ngx_int_t                       current_weight;
    ngx_int_t                       effective_weight;
    ngx_int_t                       weight;

    ngx_uint_t                      fails;
    time_t                          accessed;
    time_t                          checked;

    ngx_uint_t                      max_fails;
    time_t                          fail_timeout;

    ngx_uint_t                      down;          /* unsigned  down:1; */

#if (NGX_HTTP_SSL)
    ngx_ssl_session_t              *ssl_session;   /* local to a process */
#endif
} ngx_http_upstream_rr_peer_t;


typedef struct ngx_http_upstream_rr_peers_s  ngx_http_upstream_rr_peers_t;

struct ngx_http_upstream_rr_peers_s {
    ngx_uint_t                      single;        /* unsigned  single:1; */
    ngx_uint_t                      number;
    ngx_uint_t                      last_cached;

 /* ngx_mutex_t                    *mutex; */
    ngx_connection_t              **cached;

    ngx_str_t                      *name;

    ngx_http_upstream_rr_peers_t   *next;

    ngx_http_upstream_rr_peer_t     peer[1];
};


typedef struct {
    ngx_http_upstream_rr_peers_t   *peers;
    ngx_uint_t                      current;
    uintptr_t                      *tried;
    uintptr_t                       data;
} ngx_http_upstream_rr_peer_data_t;


ngx_int_t ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
    ngx_http_upstream_srv_conf_t *us);
ngx_int_t ngx_http_upstream_init_round_robin_peer(ngx_http_request_t *r,
    ngx_http_upstream_srv_conf_t *us);
ngx_int_t ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
    ngx_http_upstream_resolved_t *ur);
ngx_int_t ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc,
    void *data);
void ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc,
    void *data, ngx_uint_t state);

#if (NGX_HTTP_SSL)
ngx_int_t
    ngx_http_upstream_set_round_robin_peer_session(ngx_peer_connection_t *pc,
    void *data);
void ngx_http_upstream_save_round_robin_peer_session(ngx_peer_connection_t *pc,
    void *data);
#endif


#endif /* _NGX_HTTP_UPSTREAM_ROUND_ROBIN_H_INCLUDED_ */