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Upstream: smooth weighted round-robin balancing.

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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).
This commit is contained in:
Maxim Dounin 2012-05-14 09:57:20 +00:00
parent e302ed6fc3
commit 52327e0627
2 changed files with 76 additions and 173 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

248
src/http/ngx_http_upstream_round_robin.c
View File

@ -12,8 +12,8 @@
static ngx_int_t ngx_http_upstream_cmp_servers(const void *one, static ngx_int_t ngx_http_upstream_cmp_servers(const void *one,
const void *two); const void *two);
static ngx_uint_t static ngx_http_upstream_rr_peer_t *ngx_http_upstream_get_peer(
ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers); ngx_http_upstream_rr_peer_data_t *rrp);
#if (NGX_HTTP_SSL) #if (NGX_HTTP_SSL)
@ -81,7 +81,8 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
peers->peer[n].fail_timeout = server[i].fail_timeout; peers->peer[n].fail_timeout = server[i].fail_timeout;
peers->peer[n].down = server[i].down; peers->peer[n].down = server[i].down;
peers->peer[n].weight = server[i].down ? 0 : server[i].weight; peers->peer[n].weight = server[i].down ? 0 : server[i].weight;
peers->peer[n].current_weight = peers->peer[n].weight; peers->peer[n].effective_weight = peers->peer[n].weight;
peers->peer[n].current_weight = 0;
n++; n++;
} }
} }
@ -131,7 +132,8 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
backup->peer[n].socklen = server[i].addrs[j].socklen; backup->peer[n].socklen = server[i].addrs[j].socklen;
backup->peer[n].name = server[i].addrs[j].name; backup->peer[n].name = server[i].addrs[j].name;
backup->peer[n].weight = server[i].weight; backup->peer[n].weight = server[i].weight;
backup->peer[n].current_weight = server[i].weight; backup->peer[n].effective_weight = server[i].weight;
backup->peer[n].current_weight = 0;
backup->peer[n].max_fails = server[i].max_fails; backup->peer[n].max_fails = server[i].max_fails;
backup->peer[n].fail_timeout = server[i].fail_timeout; backup->peer[n].fail_timeout = server[i].fail_timeout;
backup->peer[n].down = server[i].down; backup->peer[n].down = server[i].down;
@ -190,7 +192,8 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
peers->peer[i].socklen = u.addrs[i].socklen; peers->peer[i].socklen = u.addrs[i].socklen;
peers->peer[i].name = u.addrs[i].name; peers->peer[i].name = u.addrs[i].name;
peers->peer[i].weight = 1; peers->peer[i].weight = 1;
peers->peer[i].current_weight = 1; peers->peer[i].effective_weight = 1;
peers->peer[i].current_weight = 0;
peers->peer[i].max_fails = 1; peers->peer[i].max_fails = 1;
peers->peer[i].fail_timeout = 10; peers->peer[i].fail_timeout = 10;
} }
@ -306,7 +309,8 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
peers->peer[0].socklen = ur->socklen; peers->peer[0].socklen = ur->socklen;
peers->peer[0].name = ur->host; peers->peer[0].name = ur->host;
peers->peer[0].weight = 1; peers->peer[0].weight = 1;
peers->peer[0].current_weight = 1; peers->peer[0].effective_weight = 1;
peers->peer[0].current_weight = 0;
peers->peer[0].max_fails = 1; peers->peer[0].max_fails = 1;
peers->peer[0].fail_timeout = 10; peers->peer[0].fail_timeout = 10;
@ -338,7 +342,8 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
peers->peer[i].name.len = len; peers->peer[i].name.len = len;
peers->peer[i].name.data = p; peers->peer[i].name.data = p;
peers->peer[i].weight = 1; peers->peer[i].weight = 1;
peers->peer[i].current_weight = 1; peers->peer[i].effective_weight = 1;
peers->peer[i].current_weight = 0;
peers->peer[i].max_fails = 1; peers->peer[i].max_fails = 1;
peers->peer[i].fail_timeout = 10; peers->peer[i].fail_timeout = 10;
} }
@ -378,8 +383,6 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
{ {
ngx_http_upstream_rr_peer_data_t *rrp = data; ngx_http_upstream_rr_peer_data_t *rrp = data;
time_t now;
uintptr_t m;
ngx_int_t rc; ngx_int_t rc;
ngx_uint_t i, n; ngx_uint_t i, n;
ngx_connection_t *c; ngx_connection_t *c;
@ -389,8 +392,6 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0, ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
"get rr peer, try: %ui", pc->tries); "get rr peer, try: %ui", pc->tries);
now = ngx_time();
/* ngx_lock_mutex(rrp->peers->mutex); */ /* ngx_lock_mutex(rrp->peers->mutex); */
if (rrp->peers->last_cached) { if (rrp->peers->last_cached) {
@ -423,118 +424,15 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
/* there are several peers */ /* there are several peers */
if (pc->tries == rrp->peers->number) { peer = ngx_http_upstream_get_peer(rrp);
/* it's a first try - get a current peer */ if (peer == NULL) {
goto failed;
i = pc->tries;
for ( ;; ) {
rrp->current = ngx_http_upstream_get_peer(rrp->peers);
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
"get rr peer, current: %ui %i",
rrp->current,
rrp->peers->peer[rrp->current].current_weight);
n = rrp->current / (8 * sizeof(uintptr_t));
m = (uintptr_t) 1 << rrp->current % (8 * sizeof(uintptr_t));
if (!(rrp->tried[n] & m)) {
peer = &rrp->peers->peer[rrp->current];
if (!peer->down) {
if (peer->max_fails == 0
|| peer->fails < peer->max_fails)
{
break;
}
if (now - peer->checked > peer->fail_timeout) {
peer->checked = now;
break;
}
peer->current_weight = 0;
} else {
rrp->tried[n] |= m;
}
pc->tries--;
}
if (pc->tries == 0) {
goto failed;
}
if (--i == 0) {
ngx_log_error(NGX_LOG_ALERT, pc->log, 0,
"round robin upstream stuck on %ui tries",
pc->tries);
goto failed;
}
}
peer->current_weight--;
} else {
i = pc->tries;
for ( ;; ) {
n = rrp->current / (8 * sizeof(uintptr_t));
m = (uintptr_t) 1 << rrp->current % (8 * sizeof(uintptr_t));
if (!(rrp->tried[n] & m)) {
peer = &rrp->peers->peer[rrp->current];
if (!peer->down) {
if (peer->max_fails == 0
|| peer->fails < peer->max_fails)
{
break;
}
if (now - peer->checked > peer->fail_timeout) {
peer->checked = now;
break;
}
peer->current_weight = 0;
} else {
rrp->tried[n] |= m;
}
pc->tries--;
}
rrp->current++;
if (rrp->current >= rrp->peers->number) {
rrp->current = 0;
}
if (pc->tries == 0) {
goto failed;
}
if (--i == 0) {
ngx_log_error(NGX_LOG_ALERT, pc->log, 0,
"round robin upstream stuck on %ui tries",
pc->tries);
goto failed;
}
}
peer->current_weight--;
} }
rrp->tried[n] |= m; ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
"get rr peer, current: %ui %i",
rrp->current, peer->current_weight);
} }
pc->sockaddr = peer->sockaddr; pc->sockaddr = peer->sockaddr;
@ -545,11 +443,6 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
if (pc->tries == 1 && rrp->peers->next) { if (pc->tries == 1 && rrp->peers->next) {
pc->tries += rrp->peers->next->number; pc->tries += rrp->peers->next->number;
n = rrp->peers->next->number / (8 * sizeof(uintptr_t)) + 1;
for (i = 0; i < n; i++) {
rrp->tried[i] = 0;
}
} }
return NGX_OK; return NGX_OK;
@ -595,56 +488,71 @@ failed:
} }
static ngx_uint_t static ngx_http_upstream_rr_peer_t *
ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers) ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
{ {
ngx_uint_t i, n, reset = 0; time_t now;
ngx_http_upstream_rr_peer_t *peer; uintptr_t m;
ngx_int_t total;
ngx_uint_t i, n;
ngx_http_upstream_rr_peer_t *peer, *best;
peer = &peers->peer[0]; now = ngx_time();
for ( ;; ) { best = NULL;
total = 0;
for (i = 0; i < peers->number; i++) { for (i = 0; i < rrp->peers->number; i++) {
if (peer[i].current_weight <= 0) { n = i / (8 * sizeof(uintptr_t));
continue; m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
}
n = i; if (rrp->tried[n] & m) {
continue;
while (i < peers->number - 1) {
i++;
if (peer[i].current_weight <= 0) {
continue;
}
if (peer[n].current_weight * 1000 / peer[i].current_weight
> peer[n].weight * 1000 / peer[i].weight)
{
return n;
}
n = i;
}
if (peer[i].current_weight > 0) {
n = i;
}
return n;
} }
if (reset++) { peer = &rrp->peers->peer[i];
return 0;
if (peer->down) {
continue;
} }
for (i = 0; i < peers->number; i++) { if (peer->max_fails
peer[i].current_weight = peer[i].weight; && peer->fails >= peer->max_fails
&& now - peer->checked <= peer->fail_timeout)
{
continue;
}
peer->current_weight += peer->effective_weight;
total += peer->effective_weight;
if (peer->effective_weight < peer->weight) {
peer->effective_weight++;
}
if (best == NULL || peer->current_weight > best->current_weight) {
best = peer;
} }
} }
if (best == NULL) {
return NULL;
}
i = best - &rrp->peers->peer[0];
rrp->current = i;
n = i / (8 * sizeof(uintptr_t));
m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
rrp->tried[n] |= m;
best->current_weight -= total;
best->checked = now;
return best;
} }
@ -683,15 +591,15 @@ ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
peer->checked = now; peer->checked = now;
if (peer->max_fails) { if (peer->max_fails) {
peer->current_weight -= peer->weight / peer->max_fails; peer->effective_weight -= peer->weight / peer->max_fails;
} }
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0, ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
"free rr peer failed: %ui %i", "free rr peer failed: %ui %i",
rrp->current, peer->current_weight); rrp->current, peer->effective_weight);
if (peer->current_weight < 0) { if (peer->effective_weight < 0) {
peer->current_weight = 0; peer->effective_weight = 0;
} }
/* ngx_unlock_mutex(rrp->peers->mutex); */ /* ngx_unlock_mutex(rrp->peers->mutex); */
@ -705,12 +613,6 @@ ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
} }
} }
rrp->current++;
if (rrp->current >= rrp->peers->number) {
rrp->current = 0;
}
if (pc->tries) { if (pc->tries) {
pc->tries--; pc->tries--;
} }

1
src/http/ngx_http_upstream_round_robin.h
View File

@ -20,6 +20,7 @@ typedef struct {
ngx_str_t name; ngx_str_t name;
ngx_int_t current_weight; ngx_int_t current_weight;
ngx_int_t effective_weight;
ngx_int_t weight; ngx_int_t weight;
ngx_uint_t fails; ngx_uint_t fails;