Mercurial > hg > nginx-quic
view src/os/unix/ngx_os.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 | b63e829621ab |
line wrap: on
line source
/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #ifndef _NGX_OS_H_INCLUDED_ #define _NGX_OS_H_INCLUDED_ #include <ngx_config.h> #include <ngx_core.h> #define NGX_IO_SENDFILE 1 typedef ssize_t (*ngx_recv_pt)(ngx_connection_t *c, u_char *buf, size_t size); typedef ssize_t (*ngx_recv_chain_pt)(ngx_connection_t *c, ngx_chain_t *in); typedef ssize_t (*ngx_send_pt)(ngx_connection_t *c, u_char *buf, size_t size); typedef ngx_chain_t *(*ngx_send_chain_pt)(ngx_connection_t *c, ngx_chain_t *in, off_t limit); typedef struct { ngx_recv_pt recv; ngx_recv_chain_pt recv_chain; ngx_recv_pt udp_recv; ngx_send_pt send; ngx_send_chain_pt send_chain; ngx_uint_t flags; } ngx_os_io_t; ngx_int_t ngx_os_init(ngx_log_t *log); void ngx_os_status(ngx_log_t *log); ngx_int_t ngx_os_specific_init(ngx_log_t *log); void ngx_os_specific_status(ngx_log_t *log); ngx_int_t ngx_daemon(ngx_log_t *log); ngx_int_t ngx_os_signal_process(ngx_cycle_t *cycle, char *sig, ngx_int_t pid); ssize_t ngx_unix_recv(ngx_connection_t *c, u_char *buf, size_t size); ssize_t ngx_readv_chain(ngx_connection_t *c, ngx_chain_t *entry); ssize_t ngx_udp_unix_recv(ngx_connection_t *c, u_char *buf, size_t size); ssize_t ngx_unix_send(ngx_connection_t *c, u_char *buf, size_t size); ngx_chain_t *ngx_writev_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit); #if (NGX_HAVE_AIO) ssize_t ngx_aio_read(ngx_connection_t *c, u_char *buf, size_t size); ssize_t ngx_aio_read_chain(ngx_connection_t *c, ngx_chain_t *cl); ssize_t ngx_aio_write(ngx_connection_t *c, u_char *buf, size_t size); ngx_chain_t *ngx_aio_write_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit); #endif extern ngx_os_io_t ngx_os_io; extern ngx_int_t ngx_ncpu; extern ngx_int_t ngx_max_sockets; extern ngx_uint_t ngx_inherited_nonblocking; extern ngx_uint_t ngx_tcp_nodelay_and_tcp_nopush; #if (NGX_FREEBSD) #include <ngx_freebsd.h> #elif (NGX_LINUX) #include <ngx_linux.h> #elif (NGX_SOLARIS) #include <ngx_solaris.h> #elif (NGX_DARWIN) #include <ngx_darwin.h> #endif #endif /* _NGX_OS_H_INCLUDED_ */