Mercurial > hg > nginx-quic
view src/core/ngx_queue.c @ 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 |
line wrap: on
line source
/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> /* * find the middle queue element if the queue has odd number of elements * or the first element of the queue's second part otherwise */ ngx_queue_t * ngx_queue_middle(ngx_queue_t *queue) { ngx_queue_t *middle, *next; middle = ngx_queue_head(queue); if (middle == ngx_queue_last(queue)) { return middle; } next = ngx_queue_head(queue); for ( ;; ) { middle = ngx_queue_next(middle); next = ngx_queue_next(next); if (next == ngx_queue_last(queue)) { return middle; } next = ngx_queue_next(next); if (next == ngx_queue_last(queue)) { return middle; } } } /* the stable insertion sort */ void ngx_queue_sort(ngx_queue_t *queue, ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *)) { ngx_queue_t *q, *prev, *next; q = ngx_queue_head(queue); if (q == ngx_queue_last(queue)) { return; } for (q = ngx_queue_next(q); q != ngx_queue_sentinel(queue); q = next) { prev = ngx_queue_prev(q); next = ngx_queue_next(q); ngx_queue_remove(q); do { if (cmp(prev, q) <= 0) { break; } prev = ngx_queue_prev(prev); } while (prev != ngx_queue_sentinel(queue)); ngx_queue_insert_after(prev, q); } }