# HG changeset patch
# User Mini Hawthorne <m...@f5.com>
# Date 1689189645 25200
# Wed Jul 12 12:20:45 2023 -0700
# Node ID 8c8d8118c7ac0a0426f48dbfed94e279dddff992
# Parent 621ba257aeac3017ea83b24fafa201e07c1c7756
Upstream: copy upstream zone DNS valid time during config reload.
Previously, all upstream DNS entries would be immediately re-resolved
on config reload. With a large number of upstreams, this creates
a spike of DNS resolution requests. These spikes can overwhelm the
DNS server or cause drops on the network.
This patch retains the TTL of previous resolutions across reloads
by copying each upstream's name's expiry time across configuration
cycles. As a result, no additional resolutions are needed.
diff --git a/src/http/modules/ngx_http_upstream_zone_module.c
b/src/http/modules/ngx_http_upstream_zone_module.c
--- a/src/http/modules/ngx_http_upstream_zone_module.c
+++ b/src/http/modules/ngx_http_upstream_zone_module.c
@@ -443,6 +443,8 @@ ngx_http_upstream_zone_copy_peer(ngx_htt
ngx_memcpy(dst->host->service.data, src->host->service.data,
src->host->service.len);
}
+
+ dst->host->valid = src->host->valid;
}
}
@@ -547,6 +549,8 @@ ngx_http_upstream_zone_preresolve(ngx_ht
peer->host = template->host;
+ template->host->valid = host->valid;
+
server = template->host->service.len ? &opeer->server
: &template->server;
@@ -694,6 +698,8 @@ ngx_http_upstream_zone_init_worker(ngx_c
static void
ngx_http_upstream_zone_resolve_timer(ngx_event_t *event)
{
+ time_t now, valid;
+ ngx_msec_t timer;
ngx_resolver_ctx_t *ctx;
ngx_http_upstream_host_t *host;
ngx_http_upstream_rr_peer_t *template;
@@ -705,6 +711,9 @@ ngx_http_upstream_zone_resolve_timer(ngx
peers = host->peers;
template = host->peer;
+ now = ngx_time();
+ valid = host->valid;
+
if (template->zombie) {
(void) ngx_http_upstream_rr_peer_unref(peers, template);
@@ -721,6 +730,10 @@ ngx_http_upstream_zone_resolve_timer(ngx
return;
}
+ if (valid > now) {
+ goto retry;
+ }
+
ctx = ngx_resolve_start(uscf->resolver, NULL);
if (ctx == NULL) {
goto retry;
@@ -745,7 +758,11 @@ ngx_http_upstream_zone_resolve_timer(ngx
retry:
- ngx_add_timer(event, ngx_max(uscf->resolver_timeout, 1000));
+ /* don't delay zombie cleanup longer than resolver_timeout */
+ timer = (ngx_msec_t) 1000 * (valid > now ? valid - now + 1 : 1);
+ timer = ngx_min(timer, uscf->resolver_timeout);
+
+ ngx_add_timer(event, ngx_max(timer, 1000));
}
@@ -1026,6 +1043,8 @@ again:
done:
+ host->valid = ctx->valid;
+
ngx_http_upstream_rr_peers_unlock(peers);
while (++i < ctx->naddrs) {
diff --git a/src/http/ngx_http_upstream_round_robin.h
b/src/http/ngx_http_upstream_round_robin.h
--- a/src/http/ngx_http_upstream_round_robin.h
+++ b/src/http/ngx_http_upstream_round_robin.h
@@ -25,6 +25,7 @@ typedef struct {
ngx_uint_t worker;
ngx_str_t name;
ngx_str_t service;
+ time_t valid;
ngx_http_upstream_rr_peers_t *peers;
ngx_http_upstream_rr_peer_t *peer;
} ngx_http_upstream_host_t;
diff --git a/src/stream/ngx_stream_upstream_round_robin.h
b/src/stream/ngx_stream_upstream_round_robin.h
--- a/src/stream/ngx_stream_upstream_round_robin.h
+++ b/src/stream/ngx_stream_upstream_round_robin.h
@@ -25,6 +25,7 @@ typedef struct {
ngx_uint_t worker;
ngx_str_t name;
ngx_str_t service;
+ time_t valid;
ngx_stream_upstream_rr_peers_t *peers;
ngx_stream_upstream_rr_peer_t *peer;
} ngx_stream_upstream_host_t;
diff --git a/src/stream/ngx_stream_upstream_zone_module.c
b/src/stream/ngx_stream_upstream_zone_module.c
--- a/src/stream/ngx_stream_upstream_zone_module.c
+++ b/src/stream/ngx_stream_upstream_zone_module.c
@@ -544,6 +544,8 @@ ngx_stream_upstream_zone_preresolve(ngx_
peer->host = template->host;
+ template->host->valid = host->valid;
+
server = template->host->service.len ? &opeer->server
: &template->server;
@@ -692,6 +694,8 @@ ngx_stream_upstream_zone_init_worker(ngx
static void
ngx_stream_upstream_zone_resolve_timer(ngx_event_t *event)
{
+ time_t now, valid;
+ ngx_msec_t timer;
ngx_resolver_ctx_t *ctx;
ngx_stream_upstream_host_t *host;
ngx_stream_upstream_rr_peer_t *template;
@@ -703,6 +707,9 @@ ngx_stream_upstream_zone_resolve_timer(n
peers = host->peers;
template = host->peer;
+ now = ngx_time();
+ valid = host->valid;
+
if (template->zombie) {
(void) ngx_stream_upstream_rr_peer_unref(peers, template);
@@ -719,6 +726,10 @@ ngx_stream_upstream_zone_resolve_timer(n
return;
}
+ if (valid > now) {
+ goto retry;
+ }
+
ctx = ngx_resolve_start(uscf->resolver, NULL);
if (ctx == NULL) {
goto retry;
@@ -743,7 +754,11 @@ ngx_stream_upstream_zone_resolve_timer(n
retry:
- ngx_add_timer(event, ngx_max(uscf->resolver_timeout, 1000));
+ /* don't delay zombie cleanup longer than resolver_timeout */
+ timer = (ngx_msec_t) 1000 * (valid > now ? valid - now + 1 : 1);
+ timer = ngx_min(timer, uscf->resolver_timeout);
+
+ ngx_add_timer(event, ngx_max(timer, 1000));
}
@@ -1024,6 +1039,8 @@ again:
done:
+ host->valid = ctx->valid;
+
ngx_stream_upstream_rr_peers_unlock(peers);
while (++i < ctx->naddrs) {
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