nghttpx: Add --num-accept and --accept-delay options

src/shrpx.cc

@@ -757,6 +757,8 @@ void fill_default_config() {
   mod_config()->tls_ctx_per_worker = false;
   mod_config()->downstream_request_buffer_size = 16 * 1024;
   mod_config()->downstream_response_buffer_size = 16 * 1024;
+  mod_config()->num_accept = 16;
+  mod_config()->accept_delay = 0.5;
 }
 } // namespace
 
@@ -897,6 +899,15 @@ Performance:
               Default: )"
       << util::utos_with_unit(get_config()->downstream_response_buffer_size)
       << R"(
+  --num-accept=<N>
+              The number of connections acceptor can accept at once.
+              Default: )" << get_config()->num_accept << R"(
+  --accept-delay=<MSEC>
+              Acceptors  get idle  in <MSEC>  milliseconds after  they
+              accepted at  most N connections,  where N is  defined in
+              --num-accept option.
+              Default: )" << static_cast<int>(get_config()->accept_delay * 1000)
+      << R"(
 
 Timeout:
   --frontend-http2-read-timeout=<SEC>
@@ -1301,6 +1312,8 @@ int main(int argc, char **argv) {
         {"tls-ctx-per-worker", no_argument, &flag, 70},
         {"backend-response-buffer", required_argument, &flag, 71},
         {"backend-request-buffer", required_argument, &flag, 72},
+        {"num-accept", required_argument, &flag, 73},
+        {"accept-delay", required_argument, &flag, 74},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -1630,6 +1643,14 @@ int main(int argc, char **argv) {
         // --backend-request-buffer
         cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_REQUEST_BUFFER, optarg);
         break;
+      case 73:
+        // --num-accept
+        cmdcfgs.emplace_back(SHRPX_OPT_NUM_ACCEPT, optarg);
+        break;
+      case 74:
+        // --accept-delay
+        cmdcfgs.emplace_back(SHRPX_OPT_ACCEPT_DELAY, optarg);
+        break;
       default:
         break;
       }

src/shrpx_accept_handler.cc

@@ -56,6 +56,7 @@ AcceptHandler::~AcceptHandler() {
 }
 
 void AcceptHandler::accept_connection() {
+  size_t n = 0;
   for (;;) {
     sockaddr_union sockaddr;
     socklen_t addrlen = sizeof(sockaddr);
@@ -83,7 +84,7 @@ void AcceptHandler::accept_connection() {
         continue;
       }
 
-      return;
+      break;
     }
 
 #ifndef HAVE_ACCEPT4
@@ -94,7 +95,12 @@ void AcceptHandler::accept_connection() {
     util::make_socket_nodelay(cfd);
 
     conn_hnr_->handle_connection(cfd, &sockaddr.sa, addrlen);
+    ++n;
+    if (n == get_config()->num_accept) {
+      break;
     }
+  }
+  conn_hnr_->disable_acceptor_temporary(get_config()->accept_delay);
 }
 
 void AcceptHandler::enable() { ev_io_start(conn_hnr_->get_loop(), &wev_); }

src/shrpx_config.cc

@@ -143,6 +143,8 @@ const char SHRPX_OPT_RLIMIT_NOFILE[] = "rlimit-nofile";
 const char SHRPX_OPT_TLS_CTX_PER_WORKER[] = "tls-ctx-per-worker";
 const char SHRPX_OPT_BACKEND_REQUEST_BUFFER[] = "backend-request-buffer";
 const char SHRPX_OPT_BACKEND_RESPONSE_BUFFER[] = "backend-response-buffer";
+const char SHRPX_OPT_NUM_ACCEPT[] = "num-accept";
+const char SHRPX_OPT_ACCEPT_DELAY[] = "accept-delay";
 
 namespace {
 Config *config = nullptr;
@@ -1156,6 +1158,28 @@ int parse_config(const char *opt, const char *optarg) {
     return 0;
   }
 
+  if (util::strieq(opt, SHRPX_OPT_NUM_ACCEPT)) {
+    size_t n;
+    if (parse_uint(&n, opt, optarg) != 0) {
+      return -1;
+    }
+
+    mod_config()->num_accept = n;
+
+    return 0;
+  }
+
+  if (util::strieq(opt, SHRPX_OPT_ACCEPT_DELAY)) {
+    size_t n;
+    if (parse_uint(&n, opt, optarg) != 0) {
+      return -1;
+    }
+
+    mod_config()->accept_delay = n / 1000.;
+
+    return 0;
+  }
+
   if (util::strieq(opt, "conf")) {
     LOG(WARN) << "conf: ignored";
 

src/shrpx_config.h

@@ -131,6 +131,8 @@ extern const char SHRPX_OPT_RLIMIT_NOFILE[];
 extern const char SHRPX_OPT_TLS_CTX_PER_WORKER[];
 extern const char SHRPX_OPT_BACKEND_REQUEST_BUFFER[];
 extern const char SHRPX_OPT_BACKEND_RESPONSE_BUFFER[];
+extern const char SHRPX_OPT_NUM_ACCEPT[];
+extern const char SHRPX_OPT_ACCEPT_DELAY[];
 
 union sockaddr_union {
   sockaddr_storage storage;
@@ -197,6 +199,7 @@ struct Config {
   ev_tstamp stream_write_timeout;
   ev_tstamp downstream_idle_read_timeout;
   ev_tstamp listener_disable_timeout;
+  ev_tstamp accept_delay;
   std::unique_ptr<char[]> host;
   std::unique_ptr<char[]> private_key_file;
   std::unique_ptr<char[]> private_key_passwd;
@@ -260,6 +263,7 @@ struct Config {
   size_t rlimit_nofile;
   size_t downstream_request_buffer_size;
   size_t downstream_response_buffer_size;
+  size_t num_accept;
   // Bit mask to disable SSL/TLS protocol versions.  This will be
   // passed to SSL_CTX_set_options().
   long int tls_proto_mask;