details: http://hg.nginx.org/nginx/rev/54683f650cbd branches: changeset: 7312:54683f650cbd user: Maxim Dounin <mdou...@mdounin.ru> date: Thu Jul 05 22:21:14 2018 +0300 description: Resolver: retry sending queries on errors (ticket #1511).
Errors when sending UDP datagrams can happen, e.g., when local IP address changes (see fa0e093b64d7), or an unavailable DNS server on the LAN can cause send() to fail with EHOSTDOWN on BSD systems. If this happens during initial query, retry sending immediately, to a different DNS server when possible. If this is not enough, allow normal resend to happen by ignoring the return code of the second ngx_resolver_send_query() call, much like we do in ngx_resolver_resend(). diffstat: src/core/ngx_resolver.c | 20 ++++++++++++++++++-- 1 files changed, 18 insertions(+), 2 deletions(-) diffs (37 lines): diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c --- a/src/core/ngx_resolver.c +++ b/src/core/ngx_resolver.c @@ -847,7 +847,15 @@ ngx_resolve_name_locked(ngx_resolver_t * rn->nsrvs = 0; if (ngx_resolver_send_query(r, rn) != NGX_OK) { - goto failed; + + /* immediately retry once on failure */ + + rn->last_connection++; + if (rn->last_connection == r->connections.nelts) { + rn->last_connection = 0; + } + + (void) ngx_resolver_send_query(r, rn); } if (ngx_resolver_set_timeout(r, ctx) != NGX_OK) { @@ -1051,7 +1059,15 @@ ngx_resolve_addr(ngx_resolver_ctx_t *ctx rn->nsrvs = 0; if (ngx_resolver_send_query(r, rn) != NGX_OK) { - goto failed; + + /* immediately retry once on failure */ + + rn->last_connection++; + if (rn->last_connection == r->connections.nelts) { + rn->last_connection = 0; + } + + (void) ngx_resolver_send_query(r, rn); } if (ngx_resolver_set_timeout(r, ctx) != NGX_OK) { _______________________________________________ nginx-devel mailing list nginx-devel@nginx.org http://mailman.nginx.org/mailman/listinfo/nginx-devel