Mercurial > hg > nginx-quic
view src/os/unix/ngx_process.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 | f31162fefe01 |
children | 8b84d60ef13d |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #ifndef _NGX_PROCESS_H_INCLUDED_ #define _NGX_PROCESS_H_INCLUDED_ #include <ngx_setaffinity.h> #include <ngx_setproctitle.h> typedef pid_t ngx_pid_t; #define NGX_INVALID_PID -1 typedef void (*ngx_spawn_proc_pt) (ngx_cycle_t *cycle, void *data); typedef struct { ngx_pid_t pid; int status; ngx_socket_t channel[2]; ngx_spawn_proc_pt proc; void *data; char *name; unsigned respawn:1; unsigned just_spawn:1; unsigned detached:1; unsigned exiting:1; unsigned exited:1; } ngx_process_t; typedef struct { char *path; char *name; char *const *argv; char *const *envp; } ngx_exec_ctx_t; #define NGX_MAX_PROCESSES 1024 #define NGX_PROCESS_NORESPAWN -1 #define NGX_PROCESS_JUST_SPAWN -2 #define NGX_PROCESS_RESPAWN -3 #define NGX_PROCESS_JUST_RESPAWN -4 #define NGX_PROCESS_DETACHED -5 #define ngx_getpid getpid #ifndef ngx_log_pid #define ngx_log_pid ngx_pid #endif ngx_pid_t ngx_spawn_process(ngx_cycle_t *cycle, ngx_spawn_proc_pt proc, void *data, char *name, ngx_int_t respawn); ngx_pid_t ngx_execute(ngx_cycle_t *cycle, ngx_exec_ctx_t *ctx); ngx_int_t ngx_init_signals(ngx_log_t *log); void ngx_debug_point(void); #if (NGX_HAVE_SCHED_YIELD) #define ngx_sched_yield() sched_yield() #else #define ngx_sched_yield() usleep(1) #endif extern int ngx_argc; extern char **ngx_argv; extern char **ngx_os_argv; extern ngx_pid_t ngx_pid; extern ngx_socket_t ngx_channel; extern ngx_int_t ngx_process_slot; extern ngx_int_t ngx_last_process; extern ngx_process_t ngx_processes[NGX_MAX_PROCESSES]; #endif /* _NGX_PROCESS_H_INCLUDED_ */