# HG changeset patch
# User Mini Hawthorne <m...@f5.com>
# Date 1689189645 25200
# Wed Jul 12 12:20:45 2023 -0700
# Node ID b396d0c2c62c796c76921dcf20960f8ba2515aba
# Parent 20cc5e474a0bff2bc1fadcc73aae61384f8eefbd
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
@@ -545,6 +545,8 @@ 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;
@@ -626,6 +628,8 @@ ngx_http_upstream_zone_remove_peer_locke
static ngx_int_t
ngx_http_upstream_zone_init_worker(ngx_cycle_t *cycle)
{
+ time_t now;
+ ngx_msec_t timer;
ngx_uint_t i;
ngx_event_t *event;
ngx_http_upstream_rr_peer_t *peer;
@@ -639,6 +643,7 @@ ngx_http_upstream_zone_init_worker(ngx_c
return NGX_OK;
}
+ now = ngx_time();
umcf = ngx_http_cycle_get_module_main_conf(cycle,
ngx_http_upstream_module);
if (umcf == NULL) {
@@ -670,7 +675,10 @@ ngx_http_upstream_zone_init_worker(ngx_c
event->log = cycle->log;
event->cancelable = 1;
- ngx_add_timer(event, 1);
+ timer = (peer->host->valid > now
+ ? (ngx_msec_t) 1000 * (peer->host->valid - now) : 1);
+
+ ngx_add_timer(event, timer);
}
ngx_http_upstream_rr_peers_unlock(peers);
@@ -979,6 +987,8 @@ 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
@@ -542,6 +542,8 @@ ngx_stream_upstream_zone_preresolve(ngx_
peer->host = template->host;
+ template->host->valid = host->valid;
+
server = template->host->service.len ? &opeer->server
: &template->server;
@@ -623,6 +625,8 @@ ngx_stream_upstream_zone_remove_peer_loc
static ngx_int_t
ngx_stream_upstream_zone_init_worker(ngx_cycle_t *cycle)
{
+ time_t now;
+ ngx_msec_t timer;
ngx_uint_t i;
ngx_event_t *event;
ngx_stream_upstream_rr_peer_t *peer;
@@ -636,6 +640,7 @@ ngx_stream_upstream_zone_init_worker(ngx
return NGX_OK;
}
+ now = ngx_time();
umcf = ngx_stream_cycle_get_module_main_conf(cycle,
ngx_stream_upstream_module);
@@ -668,7 +673,10 @@ ngx_stream_upstream_zone_init_worker(ngx
event->log = cycle->log;
event->cancelable = 1;
- ngx_add_timer(event, 1);
+ timer = (peer->host->valid > now
+ ? (ngx_msec_t) 1000 * (peer->host->valid - now) : 1);
+
+ ngx_add_timer(event, timer);
}
ngx_stream_upstream_rr_peers_unlock(peers);
@@ -977,6 +985,8 @@ again:
done:
+ host->valid = ctx->valid;
+
ngx_stream_upstream_rr_peers_unlock(peers);
while (++i < ctx->naddrs) {
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