nghttpx: Add --max-worker-processes option

gennghttpxfun.py

@@ -195,6 +195,7 @@ OPTIONS = [
     "frontend-quic-server-id",
     "frontend-quic-secret-file",
     "rlimit-memlock",
+    "max-worker-processes",
 ]
 
 LOGVARS = [

src/shrpx.cc

@@ -300,6 +300,17 @@ void worker_process_remove(const WorkerProcess *wp) {
 }
 } // namespace
 
+namespace {
+void worker_process_adjust_limit() {
+  auto config = get_config();
+
+  if (config->max_worker_processes &&
+      worker_processes.size() > config->max_worker_processes) {
+    worker_processes.pop_front();
+  }
+}
+} // namespace
+
 namespace {
 void worker_process_remove_all() {
   std::deque<std::unique_ptr<WorkerProcess>>().swap(worker_processes);
@@ -3201,6 +3212,19 @@ Process:
               process.   nghttpx still  spawns  additional process  if
               neverbleed  is used.   In the  single process  mode, the
               signal handling feature is disabled.
+  --max-worker-processes=<N>
+              The maximum number of  worker processes.  nghttpx spawns
+              new worker  process when  it reloads  its configuration.
+              The previous worker  process enters graceful termination
+              period and will terminate  when it finishes handling the
+              existing    connections.     However,    if    reloading
+              configurations  happen   very  frequently,   the  worker
+              processes might be piled up if they take a bit long time
+              to finish  the existing connections.  With  this option,
+              if  the number  of  worker processes  exceeds the  given
+              value,   the  oldest   worker   process  is   terminated
+              immediately.  Specifying 0 means no  limit and it is the
+              default behaviour.
 
 Scripting:
   --mruby-file=<PATH>
@@ -3773,6 +3797,8 @@ void reload_config(WorkerProcess *wp) {
   ipc_send(last_wp.get(), SHRPX_IPC_UNLOAD_BPF_OBJECT);
 #endif // ENABLE_HTTP3
 
+  worker_process_adjust_limit();
+
   if (!get_config()->pid_file.empty()) {
     save_pid();
   }
@@ -4101,6 +4127,7 @@ int main(int argc, char **argv) {
         {SHRPX_OPT_FRONTEND_QUIC_SECRET_FILE.c_str(), required_argument, &flag,
          186},
         {SHRPX_OPT_RLIMIT_MEMLOCK.c_str(), required_argument, &flag, 187},
+        {SHRPX_OPT_MAX_WORKER_PROCESSES.c_str(), required_argument, &flag, 188},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -4992,6 +5019,10 @@ int main(int argc, char **argv) {
         // --rlimit-memlock
         cmdcfgs.emplace_back(SHRPX_OPT_RLIMIT_MEMLOCK, StringRef{optarg});
         break;
+      case 188:
+        // --max-worker-processes
+        cmdcfgs.emplace_back(SHRPX_OPT_MAX_WORKER_PROCESSES, StringRef{optarg});
+        break;
       default:
         break;
       }

src/shrpx_config.cc

@@ -2248,6 +2248,9 @@ int option_lookup_token(const char *name, size_t namelen) {
       }
       break;
     case 's':
+      if (util::strieq_l("max-worker-processe", name, 19)) {
+        return SHRPX_OPTID_MAX_WORKER_PROCESSES;
+      }
       if (util::strieq_l("tls13-client-cipher", name, 19)) {
         return SHRPX_OPTID_TLS13_CLIENT_CIPHERS;
       }
@@ -4139,6 +4142,8 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   }
+  case SHRPX_OPTID_MAX_WORKER_PROCESSES:
+    return parse_uint(&config->max_worker_processes, opt, optarg);
   case SHRPX_OPTID_CONF:
     LOG(WARN) << "conf: ignored";
 

src/shrpx_config.h

@@ -396,6 +396,8 @@ constexpr auto SHRPX_OPT_FRONTEND_QUIC_SERVER_ID =
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_SECRET_FILE =
     StringRef::from_lit("frontend-quic-secret-file");
 constexpr auto SHRPX_OPT_RLIMIT_MEMLOCK = StringRef::from_lit("rlimit-memlock");
+constexpr auto SHRPX_OPT_MAX_WORKER_PROCESSES =
+    StringRef::from_lit("max-worker-processes");
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
@@ -1075,7 +1077,8 @@ struct Config {
         single_process{false},
         single_thread{false},
         ignore_per_pattern_mruby_error{false},
-        ev_loop_flags{0} {
+        ev_loop_flags{0},
+        max_worker_processes{0} {
   }
   ~Config();
 
@@ -1129,6 +1132,7 @@ struct Config {
   bool ignore_per_pattern_mruby_error;
   // flags passed to ev_default_loop() and ev_loop_new()
   int ev_loop_flags;
+  size_t max_worker_processes;
 };
 
 const Config *get_config();
@@ -1255,6 +1259,7 @@ enum {
   SHRPX_OPTID_MAX_HEADER_FIELDS,
   SHRPX_OPTID_MAX_REQUEST_HEADER_FIELDS,
   SHRPX_OPTID_MAX_RESPONSE_HEADER_FIELDS,
+  SHRPX_OPTID_MAX_WORKER_PROCESSES,
   SHRPX_OPTID_MRUBY_FILE,
   SHRPX_OPTID_NO_ADD_X_FORWARDED_PROTO,
   SHRPX_OPTID_NO_HOST_REWRITE,