Add thrift-listen-sock-fd standalone option

Summary: Let the standalone mcrouter thrift server adopt a caller-provided, pre-bound listening socket instead of binding a port itself, mirroring the existing pre-bound-socket path used by AsyncMcServer. Existing port-based behavior is unchanged by default.

Differential Revision: D112156692

fbshipit-source-id: 10d51ca95819f7c1009c1abae5d1963dea7efccc

Author: Joshua Pollack

mcrouter/Server-inl.h

@@ -394,11 +394,15 @@ bool runServerDual(
         std::make_shared<ThriftAcceptorFactory>(
             *thriftServer, std::move(aclCheckerThrift), qos));
 
-    // Set listening port for cleartext and SSL connections
-    if (standaloneOpts.thrift_port > 0) {
+    // Set listening socket for cleartext and SSL connections
+    if (standaloneOpts.thrift_listen_sock_fd >= 0) {
+      thriftServer->useExistingSocket(standaloneOpts.thrift_listen_sock_fd);
+      // A single adopted socket can only be bound by one acceptor.
+      thriftServer->setNumAcceptThreads(1);
+    } else if (standaloneOpts.thrift_port > 0) {
       thriftServer->setPort(standaloneOpts.thrift_port);
     } else {
-      LOG(ERROR) << "Must specify thrift port";
+      LOG(ERROR) << "Must specify thrift port or thrift listen socket fd";
       router->shutdown();
       freeAllRouters();
       return false;

mcrouter/StandaloneUtils.cpp

@@ -139,6 +139,12 @@ bool areOptionsValid(
     LOG(ERROR) << "invalid ports";
     return false;
   }
+  if (standaloneOpts.use_thrift && standaloneOpts.listen_sock_fd >= 0 &&
+      standaloneOpts.thrift_listen_sock_fd >= 0 &&
+      standaloneOpts.listen_sock_fd == standaloneOpts.thrift_listen_sock_fd) {
+    LOG(ERROR) << "listen-sock-fd and thrift-listen-sock-fd must be different";
+    return false;
+  }
 
   if (opts.keepalive_idle_s <= 0 || opts.keepalive_interval_s <= 0 ||
       opts.keepalive_cnt < 0) {

mcrouter/standalone_options_list.h

@@ -285,6 +285,14 @@ MCROUTER_OPTION_INTEGER(
     no_short,
     "Thrift Port to listen on")
 
+MCROUTER_OPTION_INTEGER(
+    int,
+    thrift_listen_sock_fd,
+    -1,
+    "thrift-listen-sock-fd",
+    no_short,
+    "Thrift listen socket to take over")
+
 MCROUTER_OPTION_DOUBLE(
     double,
     core_multiplier,