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view src/http/ngx_http_upstream_round_robin.h @ 4621:c90801720a0c
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 |
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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_ */