From 41bfa9283e52dc66cea00a0f2ef612906cb3b0f9 Mon Sep 17 00:00:00 2001
From: Vsevolod Stakhov <vsevolod@highsecure.ru>
Date: Thu, 25 Mar 2021 20:24:31 +0000
Subject: [PATCH] [Rework] Try to resolve failed upstreams more agressively

---
 src/libutil/upstream.c | 76 ++++++++++++++++++++++++++++++------------
 1 file changed, 54 insertions(+), 22 deletions(-)

diff --git a/src/libutil/upstream.c b/src/libutil/upstream.c
index 612354043..889b524ac 100644
--- a/src/libutil/upstream.c
+++ b/src/libutil/upstream.c
@@ -59,6 +59,7 @@ struct upstream {
 	gchar *name;
 	ev_timer ev;
 	gdouble last_fail;
+	gdouble last_resolve;
 	gpointer ud;
 	enum rspamd_upstream_flag flags;
 	struct upstream_list *ls;
@@ -127,6 +128,10 @@ struct upstream_ctx {
         rspamd_upstream_log_id, "upstream", upstream->uid, \
         G_STRFUNC, \
         __VA_ARGS__)
+#define msg_info_upstream(...)   rspamd_default_log_function (G_LOG_LEVEL_INFO, \
+        "upstream", upstream->uid, \
+        G_STRFUNC, \
+        __VA_ARGS__)
 
 INIT_LOG_MODULE(upstream)
 
@@ -623,42 +628,64 @@ rspamd_upstream_revive_cb (struct ev_loop *loop, ev_timer *w, int revents)
 
 static void
 rspamd_upstream_resolve_addrs (const struct upstream_list *ls,
-		struct upstream *up)
+		struct upstream *upstream)
 {
-	if (up->ctx->res != NULL &&
-			up->ctx->configured &&
-			up->dns_requests == 0 &&
-			!(up->flags & RSPAMD_UPSTREAM_FLAG_NORESOLVE)) {
+	/* XXX: maybe make it configurable */
+	static const gdouble min_resolve_interval = 60.0;
+
+	if (upstream->ctx->res != NULL &&
+		upstream->ctx->configured &&
+		upstream->dns_requests == 0 &&
+		!(upstream->flags & RSPAMD_UPSTREAM_FLAG_NORESOLVE)) {
+
+		gdouble now = ev_now (upstream->ctx->event_loop);
+
+		if (now - upstream->last_resolve < min_resolve_interval) {
+			msg_info_upstream ("do not resolve upstream %s as it was checked %.0f "
+					  "seconds ago (%.0f is minimum)",
+					upstream->name, now - upstream->last_resolve,
+					min_resolve_interval);
+
+			return;
+		}
+
 		/* Resolve name of the upstream one more time */
-		if (up->name[0] != '/') {
-			if (up->flags & RSPAMD_UPSTREAM_FLAG_SRV_RESOLVE) {
-				if (rdns_make_request_full (up->ctx->res,
-						rspamd_upstream_dns_srv_cb, up,
+		if (upstream->name[0] != '/') {
+			upstream->last_resolve = now;
+
+			if (upstream->flags & RSPAMD_UPSTREAM_FLAG_SRV_RESOLVE) {
+				if (rdns_make_request_full (upstream->ctx->res,
+						rspamd_upstream_dns_srv_cb, upstream,
 						ls->limits->dns_timeout, ls->limits->dns_retransmits,
-						1, up->name, RDNS_REQUEST_SRV) != NULL) {
-					up->dns_requests++;
-					REF_RETAIN (up);
+						1, upstream->name, RDNS_REQUEST_SRV) != NULL) {
+					upstream->dns_requests++;
+					REF_RETAIN (upstream);
 				}
 			}
 			else {
-				if (rdns_make_request_full (up->ctx->res,
-						rspamd_upstream_dns_cb, up,
+				if (rdns_make_request_full (upstream->ctx->res,
+						rspamd_upstream_dns_cb, upstream,
 						ls->limits->dns_timeout, ls->limits->dns_retransmits,
-						1, up->name, RDNS_REQUEST_A) != NULL) {
-					up->dns_requests++;
-					REF_RETAIN (up);
+						1, upstream->name, RDNS_REQUEST_A) != NULL) {
+					upstream->dns_requests++;
+					REF_RETAIN (upstream);
 				}
 
-				if (rdns_make_request_full (up->ctx->res,
-						rspamd_upstream_dns_cb, up,
+				if (rdns_make_request_full (upstream->ctx->res,
+						rspamd_upstream_dns_cb, upstream,
 						ls->limits->dns_timeout, ls->limits->dns_retransmits,
-						1, up->name, RDNS_REQUEST_AAAA) != NULL) {
-					up->dns_requests++;
-					REF_RETAIN (up);
+						1, upstream->name, RDNS_REQUEST_AAAA) != NULL) {
+					upstream->dns_requests++;
+					REF_RETAIN (upstream);
 				}
 			}
 		}
 	}
+	else if (upstream->dns_requests != 0) {
+		msg_info_upstream ("do not resolve upstream %s as another request for "
+					 "resolving has been already issued",
+					 upstream->name);
+	}
 }
 
 static void
@@ -757,6 +784,11 @@ rspamd_upstream_fail (struct upstream *upstream,
 			upstream->last_fail = sec_cur;
 			upstream->errors = 1;
 
+			if (upstream->ls && upstream->dns_requests == 0) {
+				/* Try to re-resolve address immediately */
+				rspamd_upstream_resolve_addrs (upstream->ls, upstream);
+			}
+
 			DL_FOREACH (upstream->ls->watchers, w) {
 				if (w->events_mask & RSPAMD_UPSTREAM_WATCH_FAILURE) {
 					w->func (upstream, RSPAMD_UPSTREAM_WATCH_FAILURE, 1, w->ud);
-- 
2.39.5