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comparison src/core/ngx_resolver.c @ 6366:2e5c027f2a98

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Resolver: per-request DNS server balancer. Previously, a global server balancer was used to assign the next DNS server to send a query to. That could lead to a non-uniform distribution of servers per request. A request could be assigned to the same dead server several times in a row and wait longer for a valid server or even time out without being processed. Now each query is sent to all servers sequentially in a circle until a response is received or timeout expires. Initial server for each request is still globally balanced.
author Roman Arutyunyan <arut@nginx.com>
date Thu, 28 Jan 2016 15:28:20 +0300
parents d35b4d590b2d
children 5a16d40c63de
comparison
equal deleted inserted replaced
6365:d35b4d590b2d 6366:2e5c027f2a98
683 } while (ctx); 683 } while (ctx);
684 684
685 return NGX_OK; 685 return NGX_OK;
686 } 686 }
687 687
688 rn->last_connection = r->last_connection++;
689 if (r->last_connection == r->connections.nelts) {
690 r->last_connection = 0;
691 }
692
688 rn->naddrs = (u_short) -1; 693 rn->naddrs = (u_short) -1;
689 #if (NGX_HAVE_INET6) 694 #if (NGX_HAVE_INET6)
690 rn->naddrs6 = r->ipv6 ? (u_short) -1 : 0; 695 rn->naddrs6 = r->ipv6 ? (u_short) -1 : 0;
691 #endif 696 #endif
692 697
895 900
896 if (ngx_resolver_create_addr_query(r, rn, &ctx->addr) != NGX_OK) { 901 if (ngx_resolver_create_addr_query(r, rn, &ctx->addr) != NGX_OK) {
897 goto failed; 902 goto failed;
898 } 903 }
899 904
905 rn->last_connection = r->last_connection++;
906 if (r->last_connection == r->connections.nelts) {
907 r->last_connection = 0;
908 }
909
900 rn->naddrs = (u_short) -1; 910 rn->naddrs = (u_short) -1;
901 #if (NGX_HAVE_INET6) 911 #if (NGX_HAVE_INET6)
902 rn->naddrs6 = (u_short) -1; 912 rn->naddrs6 = (u_short) -1;
903 #endif 913 #endif
904 914
1096 { 1106 {
1097 ssize_t n; 1107 ssize_t n;
1098 ngx_resolver_connection_t *rec; 1108 ngx_resolver_connection_t *rec;
1099 1109
1100 rec = r->connections.elts; 1110 rec = r->connections.elts;
1101 1111 rec = &rec[rn->last_connection];
1102 rec = &rec[r->last_connection++];
1103 if (r->last_connection == r->connections.nelts) {
1104 r->last_connection = 0;
1105 }
1106 1112
1107 if (rec->udp == NULL) { 1113 if (rec->udp == NULL) {
1108 1114
1109 rec->log = *r->log; 1115 rec->log = *r->log;
1110 rec->log.handler = ngx_resolver_log_error; 1116 rec->log.handler = ngx_resolver_log_error;
1241 (size_t) rn->nlen, rn->name, rn->waiting); 1247 (size_t) rn->nlen, rn->name, rn->waiting);
1242 1248
1243 ngx_queue_remove(q); 1249 ngx_queue_remove(q);
1244 1250
1245 if (rn->waiting) { 1251 if (rn->waiting) {
1252
1253 if (++rn->last_connection == r->connections.nelts) {
1254 rn->last_connection = 0;
1255 }
1246 1256
1247 (void) ngx_resolver_send_query(r, rn); 1257 (void) ngx_resolver_send_query(r, rn);
1248 1258
1249 rn->expire = now + r->resend_timeout; 1259 rn->expire = now + r->resend_timeout;
1250 1260