Mercurial > hg > nginx-quic
annotate 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 |
rev | line source |
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2026 | 1 |
2 /* | |
3 * Copyright (C) Igor Sysoev | |
4412 | 4 * Copyright (C) Nginx, Inc. |
2026 | 5 */ |
6 | |
7 | |
8 #include <ngx_config.h> | |
9 #include <ngx_core.h> | |
10 | |
11 | |
12 /* | |
13 * find the middle queue element if the queue has odd number of elements | |
14 * or the first element of the queue's second part otherwise | |
15 */ | |
16 | |
17 ngx_queue_t * | |
18 ngx_queue_middle(ngx_queue_t *queue) | |
19 { | |
20 ngx_queue_t *middle, *next; | |
21 | |
22 middle = ngx_queue_head(queue); | |
23 | |
24 if (middle == ngx_queue_last(queue)) { | |
25 return middle; | |
26 } | |
27 | |
28 next = ngx_queue_head(queue); | |
29 | |
30 for ( ;; ) { | |
31 middle = ngx_queue_next(middle); | |
32 | |
33 next = ngx_queue_next(next); | |
34 | |
35 if (next == ngx_queue_last(queue)) { | |
36 return middle; | |
37 } | |
38 | |
39 next = ngx_queue_next(next); | |
40 | |
41 if (next == ngx_queue_last(queue)) { | |
42 return middle; | |
43 } | |
44 } | |
45 } | |
46 | |
47 | |
48 /* the stable insertion sort */ | |
49 | |
50 void | |
51 ngx_queue_sort(ngx_queue_t *queue, | |
52 ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *)) | |
53 { | |
54 ngx_queue_t *q, *prev, *next; | |
55 | |
56 q = ngx_queue_head(queue); | |
57 | |
58 if (q == ngx_queue_last(queue)) { | |
59 return; | |
60 } | |
61 | |
62 for (q = ngx_queue_next(q); q != ngx_queue_sentinel(queue); q = next) { | |
63 | |
64 prev = ngx_queue_prev(q); | |
65 next = ngx_queue_next(q); | |
66 | |
67 ngx_queue_remove(q); | |
68 | |
69 do { | |
70 if (cmp(prev, q) <= 0) { | |
71 break; | |
72 } | |
73 | |
74 prev = ngx_queue_prev(prev); | |
75 | |
76 } while (prev != ngx_queue_sentinel(queue)); | |
77 | |
78 ngx_queue_insert_after(prev, q); | |
79 } | |
80 } |