nghttpx: Add dns-cache-timeout option

This option controls how long cached DNS entries remain valid.

gennghttpxfun.py

@@ -149,6 +149,7 @@ OPTIONS = [
     "ecdh-curves",
     "tls-sct-dir",
     "backend-connect-timeout",
+    "dns-cache-timeout",
 ]
 
 LOGVARS = [

src/shrpx.cc

@@ -1486,6 +1486,12 @@ void fill_default_config(Config *config) {
 
   auto &apiconf = config->api;
   apiconf.max_request_body = 16_k;
+
+  auto &dnsconf = config->dns;
+  {
+    auto &timeoutconf = dnsconf.timeout;
+    timeoutconf.cache = 10_s;
+  }
 }
 
 } // namespace
@@ -2376,6 +2382,13 @@ API:
               Default: )"
       << util::utos_unit(config->api.max_request_body) << R"(
 
+DNS:
+  --dns-cache-timeout=<DURATION>
+              Set duration that cached DNS results remain valid.  Note
+              that nghttpx caches the unsuccessful results as well.
+              Default: )"
+      << util::duration_str(config->dns.timeout.cache) << R"(
+
 Debug:
   --frontend-http2-dump-request-header=<PATH>
               Dumps request headers received by HTTP/2 frontend to the
@@ -3035,6 +3048,7 @@ int main(int argc, char **argv) {
         {SHRPX_OPT_TLS_SCT_DIR.c_str(), required_argument, &flag, 141},
         {SHRPX_OPT_BACKEND_CONNECT_TIMEOUT.c_str(), required_argument, &flag,
          142},
+        {SHRPX_OPT_DNS_CACHE_TIMEOUT.c_str(), required_argument, &flag, 143},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -3708,6 +3722,10 @@ int main(int argc, char **argv) {
         cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_CONNECT_TIMEOUT,
                              StringRef{optarg});
         break;
+      case 143:
+        // --dns-cache-timeout
+        cmdcfgs.emplace_back(SHRPX_OPT_DNS_CACHE_TIMEOUT, StringRef{optarg});
+        break;
       default:
         break;
       }

src/shrpx_config.cc

@@ -1531,6 +1531,9 @@ int option_lookup_token(const char *name, size_t namelen) {
       }
       break;
     case 't':
+      if (util::strieq_l("dns-cache-timeou", name, 16)) {
+        return SHRPX_OPTID_DNS_CACHE_TIMEOUT;
+      }
       if (util::strieq_l("worker-read-burs", name, 16)) {
         return SHRPX_OPTID_WORKER_READ_BURST;
       }
@@ -3099,6 +3102,8 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     LOG(WARN) << opt << ": This option requires OpenSSL >= 1.0.2";
     return 0;
 #endif // !(!LIBRESSL_IN_USE && OPENSSL_VERSION_NUMBER >= 0x10002000L)
+  case SHRPX_OPTID_DNS_CACHE_TIMEOUT:
+    return parse_duration(&config->dns.timeout.cache, opt, optarg);
   case SHRPX_OPTID_CONF:
     LOG(WARN) << "conf: ignored";
 

src/shrpx_config.h

@@ -312,6 +312,8 @@ constexpr auto SHRPX_OPT_ECDH_CURVES = StringRef::from_lit("ecdh-curves");
 constexpr auto SHRPX_OPT_TLS_SCT_DIR = StringRef::from_lit("tls-sct-dir");
 constexpr auto SHRPX_OPT_BACKEND_CONNECT_TIMEOUT =
     StringRef::from_lit("backend-connect-timeout");
+constexpr auto SHRPX_OPT_DNS_CACHE_TIMEOUT =
+    StringRef::from_lit("dns-cache-timeout");
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
@@ -780,6 +782,12 @@ struct APIConfig {
   bool enabled;
 };
 
+struct DNSConfig {
+  struct {
+    ev_tstamp cache;
+  } timeout;
+};
+
 struct Config {
   Config()
       : balloc(4096, 4096),
@@ -790,6 +798,7 @@ struct Config {
         logging{},
         conn{},
         api{},
+        dns{},
         num_worker{0},
         padding{0},
         rlimit_nofile{0},
@@ -818,6 +827,7 @@ struct Config {
   LoggingConfig logging;
   ConnectionConfig conn;
   APIConfig api;
+  DNSConfig dns;
   StringRef pid_file;
   StringRef conf_path;
   StringRef user;
@@ -894,6 +904,7 @@ enum {
   SHRPX_OPTID_CONF,
   SHRPX_OPTID_DAEMON,
   SHRPX_OPTID_DH_PARAM_FILE,
+  SHRPX_OPTID_DNS_CACHE_TIMEOUT,
   SHRPX_OPTID_ECDH_CURVES,
   SHRPX_OPTID_ERROR_PAGE,
   SHRPX_OPTID_ERRORLOG_FILE,

src/shrpx_dns_tracker.cc

@@ -23,6 +23,7 @@
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 #include "shrpx_dns_tracker.h"
+#include "shrpx_config.h"
 #include "util.h"
 
 namespace shrpx {
@@ -43,18 +44,16 @@ DNSTracker::~DNSTracker() {
   }
 }
 
-namespace {
-constexpr auto DNS_TTL = 30_s;
-} // namespace
-
 ResolverEntry DNSTracker::make_entry(std::unique_ptr<DualDNSResolver> resolv,
                                      ImmutableString host, int status,
                                      const Address *result) {
+  auto &dnsconf = get_config()->dns;
+
   auto ent = ResolverEntry{};
   ent.resolv = std::move(resolv);
   ent.host = std::move(host);
   ent.status = status;
-  ent.expiry = ev_now(loop_) + DNS_TTL;
+  ent.expiry = ev_now(loop_) + dnsconf.timeout.cache;
   if (result) {
     ent.result = *result;
   }
@@ -233,9 +232,11 @@ void DNSTracker::add_to_qlist(ResolverEntry &ent, DNSQuery *dnsq) {
       cb(status, result);
     }
 
+    auto &dnsconf = get_config()->dns;
+
     ent.resolv.reset();
     ent.status = status;
-    ent.expiry = ev_now(loop) + DNS_TTL;
+    ent.expiry = ev_now(loop) + dnsconf.timeout.cache;
     if (ent.status == DNS_STATUS_OK) {
       ent.result = *result;
     }