fix(rpc): improve error reporting for socket path issues.

include/mgmt/rpc/server/CommBase.h

@@ -36,7 +36,7 @@ struct BaseCommInterface {
   virtual std::string const &name() const                        = 0;
 };
 
-enum class InternalError { MAX_TRANSIENT_ERRORS_HANDLED = 1, POLLIN_ERROR, PARTIAL_READ, FULL_BUFFER };
+enum class InternalError { MAX_TRANSIENT_ERRORS_HANDLED = 1, POLLIN_ERROR, PARTIAL_READ, FULL_BUFFER, INVALID_SOCKET_PATH };
 std::error_code make_error_code(rpc::comm::InternalError e);
 
 } // namespace rpc::comm

src/mgmt/rpc/server/CommBase.cc

@@ -44,6 +44,9 @@ CommInternalErrorCategory::message(int ev) const
     return {"No more data to be read, but the buffer contains some invalid? data."};
   case rpc::comm::InternalError::FULL_BUFFER:
     return {"Buffer's full."};
+  case rpc::comm::InternalError::INVALID_SOCKET_PATH:
+    return {"Invalid RPC socket path: the path is either empty or exceeds the maximum length supported by the operating system. "
+            "Check the value of rpc.unix.sock_path_name in the configuration file."};
   default:
     return "Internal Communication Error" + std::to_string(ev);
   }

src/mgmt/rpc/server/IPCSocketServer.cc

@@ -139,15 +139,15 @@ IPCSocketServer::configure(YAML::Node const &params)
 std::error_code
 IPCSocketServer::init()
 {
+  std::error_code ec; // Flag possible errors.
   // Need to run some validations on the pathname to avoid issue. Normally this would not be an issue, but some tests may fail on
   // this.
   if (_conf.sockPathName.empty() || _conf.sockPathName.size() > sizeof _serverAddr.sun_path) {
-    Dbg(dbg_ctl, "Invalid unix path name, check the size.");
-    return std::make_error_code(static_cast<std::errc>(ENAMETOOLONG));
+    Dbg(dbg_ctl, "Invalid unix path name, check the size. Empty or too long.");
+    ec = InternalError::INVALID_SOCKET_PATH;
+    return ec;
   }
 
-  std::error_code ec; // Flag possible errors.
-
   if (this->create_socket(ec); ec) {
     return ec;
   }

src/traffic_server/traffic_server.cc

@@ -755,7 +755,7 @@ initialize_jsonrpc_server()
     // jsonrpcServer object.
     ink_assert(jsonrpcServer == nullptr);
     std::string msg;
-    return {false, swoc::bwprint(msg, "Server failed: '{}'", ex.what())};
+    return {false, swoc::bwprint(msg, "Error: '{}'", ex.what())};
   }
   // Register admin handlers.
   rpc::admin::register_admin_jsonrpc_handlers();
@@ -1995,7 +1995,10 @@ main(int /* argc ATS_UNUSED */, const char **argv)
   if (!command_flag) { // No need if we are going into command mode.
     // JSONRPC server and handlers
     if (auto &&[ok, msg] = initialize_jsonrpc_server(); !ok) {
-      Warning("JSONRPC server could not be started.\n  Why?: '%s' ... Continuing without it.", msg.c_str());
+      fprintf(stderr,
+              "[ERROR] JSONRPC server could not be started because: '%s', ATS will start without it, but traffic_ctl will not be "
+              "available.\n",
+              msg.c_str());
     }
   }