Concept of slave, connected to the master server and spawning game servers

- Master server is now composed of two separate servers, one accepting game
  clients, and one accepting slave servers
- Introduce some way to communicate over IPC (used between the slaves their
  child game servers)
- Child game servers are spawned and managed by the slave

src/main/batajelo_master_server.cpp

@@ -10,14 +10,12 @@ int main()
   if (!Config::read_conf("./batajelo.conf"))
     return 1;
   log_debug("Starting master server");
-  log_debug(Config::get("db_login", "non"));
+  log_debug(Config::get("db_login", ""));
 
   srand(getpid());
-  MasterServer s(7878);
-  s.start();
+  MasterServer s(7878, 7877);
 
-  while (s.is_started())
-    s.poll(0);
+  s.run();
 
   log_debug("Exiting...");
   return 0;

src/main/batajelo_slave.cpp

+#include <slave/slave.hpp>
+#include <logging/logging.hpp>
+
+int main()
+{
+  Slave slave;
+  slave.run();
+  log_debug("Slave exiting...");
+}

src/master_server/master_server.cpp

 #include <master_server/master_server.hpp>
 
-MasterServer::MasterServer(const short port):
-  Server<RemoteClient>(port)
+MasterServer::MasterServer(const short client_port,
+                           const short slave_port):
+  to_client_server(this, client_port),
+  to_slave_server(this, slave_port)
 {
 }
 
-const RemoteClient* MasterServer::find_client_by_login(const std::string& login) const
-{
-  for (const RemoteClient* client: this->clients)
-    {
-      const auto user = client->get_user();
-      if (user && user->login == login)
-        return client;
-    }
-  return nullptr;
-}
-
 Database* MasterServer::get_database()
 {
   return &this->database;
 }
 
-void MasterServer::on_new_client(RemoteClient* client)
-{
-  client->set_server(this);
-}
-
-void MasterServer::on_client_left(RemoteClient* client)
+void MasterServer::run()
 {
-  log_debug("Client left");
+  this->to_client_server.start();
+  this->to_slave_server.start();
+  while (true)
+    IoService::get().poll();
 }

src/master_server/master_server.hpp

 #ifndef MASTER_SERVER_HPP_INCLUDED
 #define MASTER_SERVER_HPP_INCLUDED
 
-#include <network/server.hpp>
-#include <master_server/remote_client.hpp>
+#include <master_server/master_to_client_server.hpp>
+#include <master_server/master_to_slave_server.hpp>
+
 #include <database/database.hpp>
 
-class MasterServer: public Server<RemoteClient>
+class MasterServer
 {
 public:
-  MasterServer(const short port);
+  MasterServer(const short client_port, const short slave_port);
   ~MasterServer() = default;
-  /**
-   * Search for a connected client with this login
-   * @return RemoteClient* can be nullptr if nothing is found
-   */
-  const RemoteClient* find_client_by_login(const std::string& login) const;
-  void on_new_client(RemoteClient* client) override final;
-  void on_client_left(RemoteClient* client) override final;
   Database* get_database();
+  void run();
 
 private:
+  MasterToClientServer to_client_server;
+  MasterToSlaveServer to_slave_server;
+
   Database database;
+
   MasterServer(const MasterServer&) = delete;
   MasterServer(MasterServer&&) = delete;
   MasterServer& operator=(const MasterServer&) = delete;

src/master_server/master_to_client_server.cpp

+#include <master_server/master_to_client_server.hpp>
+#include <master_server/master_server.hpp>
+
+MasterToClientServer::MasterToClientServer(MasterServer* master,
+                                           const short port):
+  Server<RemoteClient>(port),
+  master(master)
+{
+}
+
+const RemoteClient* MasterToClientServer::find_client_by_login(const std::string& login) const
+{
+  for (const RemoteClient* client: this->clients)
+    {
+      const auto user = client->get_user();
+      if (user && user->login == login)
+        return client;
+    }
+  return nullptr;
+}
+
+void MasterToClientServer::on_new_client(RemoteClient* client)
+{
+  log_debug("starting RemoteClient");
+  client->set_server(this);
+}
+
+void MasterToClientServer::on_client_left(RemoteClient* client)
+{
+  log_debug("RemoteClient left");
+}
+
+Database* MasterToClientServer::get_database()
+{
+  return this->master->get_database();
+}

src/master_server/master_to_client_server.hpp

+#ifndef MASTERTOCLIENT_SERVER_HPP_INCLUDED
+#define MASTERTOCLIENT_SERVER_HPP_INCLUDED
+
+#include <network/server.hpp>
+#include <master_server/remote_client.hpp>
+
+class MasterServer;
+class Database;
+
+class MasterToClientServer: public Server<RemoteClient>
+{
+public:
+  MasterToClientServer(MasterServer* master,
+                       const short port);
+  ~MasterToClientServer() = default;
+  /**
+   * Search for a connected client with this login
+   * @return RemoteClient* can be nullptr if nothing is found
+   */
+  const RemoteClient* find_client_by_login(const std::string& login) const;
+  void on_new_client(RemoteClient* client) override final;
+  void on_client_left(RemoteClient* client) override final;
+  Database* get_database();
+
+private:
+  MasterServer* master;
+
+  MasterToClientServer(const MasterToClientServer&) = delete;
+  MasterToClientServer(MasterToClientServer&&) = delete;
+  MasterToClientServer& operator=(const MasterToClientServer&) = delete;
+  MasterToClientServer& operator=(MasterToClientServer&&) = delete;
+};
+
+#endif /* MASTERTOCLIENT_SERVER_HPP_INCLUDED */

src/master_server/master_to_slave_server.cpp

+#include <master_server/master_to_slave_server.hpp>
+
+#include <logging/logging.hpp>
+
+MasterToSlaveServer::MasterToSlaveServer(MasterServer* master,
+                                         const short port):
+  Server<RemoteSlaveClient>(port),
+  master(master)
+{
+}
+
+void MasterToSlaveServer::on_new_client(RemoteSlaveClient* client)
+{
+  log_debug("Starting RemoteSlaveClient");
+  client->set_server(this);
+}
+
+void MasterToSlaveServer::on_client_left(RemoteSlaveClient* client)
+{
+  log_debug("Ending RemoteSlaveClient");
+}

src/master_server/master_to_slave_server.hpp

+#ifndef MASTERTOSLAVE_SERVER_HPP_INCLUDED
+#define MASTERTOSLAVE_SERVER_HPP_INCLUDED
+
+#include <network/server.hpp>
+#include <master_server/remote_slave_client.hpp>
+
+class MasterServer;
+
+class MasterToSlaveServer: public Server<RemoteSlaveClient>
+{
+public:
+  MasterToSlaveServer(MasterServer* master,
+                      const short port);
+  ~MasterToSlaveServer() = default;
+
+  void on_new_client(RemoteSlaveClient* client) override final;
+  void on_client_left(RemoteSlaveClient* client) override final;
+
+private:
+  MasterServer* master;
+
+  MasterToSlaveServer(const MasterToSlaveServer&) = delete;
+  MasterToSlaveServer(MasterToSlaveServer&&) = delete;
+  MasterToSlaveServer& operator=(const MasterToSlaveServer&) = delete;
+  MasterToSlaveServer& operator=(MasterToSlaveServer&&) = delete;
+};
+
+#endif /* MASTERTOSLAVE_SERVER_HPP_INCLUDED */

src/master_server/remote_client.cpp

 #include <master_server/remote_client.hpp>
-#include <master_server/master_server.hpp>
+#include <master_server/master_to_client_server.hpp>
+
+#include <database/database.hpp>
 #include "master.pb.h"
 
 RemoteClient::RemoteClient():
@@ -14,7 +16,7 @@ RemoteClient::~RemoteClient()
   log_info("Deleting remote client " << this->id);
 }
 
-void RemoteClient::set_server(MasterServer* server)
+void RemoteClient::set_server(MasterToClientServer* server)
 {
   this->server = server;
 }

src/master_server/remote_client.hpp

@@ -17,7 +17,7 @@
 
 #include <network/remote_client_base.hpp>
 
-class MasterServer;
+class MasterToClientServer;
 class Message;
 class TransferSender;
 
@@ -27,7 +27,7 @@ public:
   RemoteClient();
   ~RemoteClient();
   void on_connection_closed() override final;
-  void set_server(MasterServer* server);
+  void set_server(MasterToClientServer* server);
 
   /**
    * Sends a file to the remote client.
@@ -75,7 +75,7 @@ private:
   /**
    * A pointer to the server owning use
    */
-  MasterServer* server;
+  MasterToClientServer* server;
   /**
    * A list of all the current file transfers with the client.
    */

src/master_server/remote_slave_client.cpp

+#include <master_server/remote_slave_client.hpp>
+#include <master_server/master_to_slave_server.hpp>
+
+void RemoteSlaveClient::set_server(MasterToSlaveServer* server)
+{
+  this->server = server;
+}
+
+void RemoteSlaveClient::on_connection_closed()
+{
+  this->server->remove_client(this);
+}
+
+void RemoteSlaveClient::install_callbacks()
+{
+  this->send_message("START", "");
+}

src/master_server/remote_slave_client.hpp

+#ifndef REMOTE_SLAVE_CLIENT_HPP_INCLUDED
+#define REMOTE_SLAVE_CLIENT_HPP_INCLUDED
+
+#include <network/remote_client_base.hpp>
+
+class MasterToSlaveServer;
+
+class RemoteSlaveClient: public RemoteClientBase
+{
+public:
+  RemoteSlaveClient() = default;
+  ~RemoteSlaveClient() = default;
+  void on_connection_closed() override final;
+  void set_server(MasterToSlaveServer* server);
+
+private:
+  MasterToSlaveServer* server;
+  void install_callbacks() override final;
+
+  RemoteSlaveClient(const RemoteSlaveClient&) = delete;
+  RemoteSlaveClient(RemoteSlaveClient&&) = delete;
+  RemoteSlaveClient& operator=(const RemoteSlaveClient&) = delete;
+  RemoteSlaveClient& operator=(RemoteSlaveClient&&) = delete;
+};
+
+#endif /* REMOTE_SLAVE_CLIENT_HPP_INCLUDED */

src/network/ipc_endpoint.cpp

+#include <network/ipc_endpoint.hpp>
+#include <network/ioservice.hpp>
+#include <boost/filesystem.hpp>
+#include <boost/asio.hpp>
+#include <stdexcept>
+
+#include <errno.h>
+
+#include <logging/logging.hpp>
+
+using namespace std::string_literals;
+
+IPCEndpoint::IPCEndpoint():
+  must_destroy(true),
+  mqd(-1),
+  mq_name{},
+  stream_descriptor(IoService::get())
+{
+retry:
+  {
+    auto path = boost::filesystem::unique_path();
+    this->mq_name = "/"s + path.string();
+  }
+  log_debug("Trying to create an ipc endpoint : " << this->mq_name);
+  mqd_t mqd = ::mq_open(this->mq_name.data(),
+                        O_CREAT|O_RDWR|O_EXCL,
+                        S_IRUSR|S_IWUSR,
+                        nullptr);
+  if (mqd == static_cast<mqd_t>(-1))
+    {
+      if (errno == EEXIST)
+        {
+          // We're out of luck, we randomly generated a name that we are
+          // already using. Try generating a new one
+          goto retry;
+        }
+      else
+        throw std::runtime_error("mq_open failed: "s + strerror(errno));
+    }
+  this->mqd = mqd;
+  this->resize_recv_buffer();
+}
+
+IPCEndpoint::IPCEndpoint(const std::string& path):
+  must_destroy(false),
+  mqd(-1),
+  mq_name{path},
+  stream_descriptor(IoService::get())
+{
+  log_debug("Trying to open an existing ipc endpoint : " << this->mq_name);
+  this->mqd = ::mq_open(this->mq_name.data(),
+                        O_RDWR);
+  if (this->mqd == static_cast<mqd_t>(-1))
+    throw std::runtime_error("mq_open failed: "s + strerror(errno));
+  this->resize_recv_buffer();
+}
+
+IPCEndpoint::~IPCEndpoint()
+{
+  log_debug("~IPCEndpoint");
+  if (::mq_close(this->mqd) == -1)
+    log_error("Failed to close message queue: " << strerror(errno));
+  if (this->must_destroy)
+    {
+      log_debug("Destroying message queue: " << this->mq_name);
+      if (::mq_unlink(this->mq_name.data()) == -1)
+        log_error("Failed to unlink message queue " << this->mq_name << ": " << strerror(errno));
+    }
+}
+
+std::string IPCEndpoint::get_path() const
+{
+  return this->mq_name;
+}
+
+void IPCEndpoint::resize_recv_buffer()
+{
+  mq_attr attr;
+  auto res = ::mq_getattr(this->mqd, &attr);
+  if (res == -1)
+    throw std::runtime_error("mq_getattr failed: "s + strerror(errno));
+  this->recv_buffer.resize(attr.mq_msgsize);
+}
+
+std::size_t IPCEndpoint::get_max_msgsize() const
+{
+  return this->recv_buffer.size();
+}
+
+std::string IPCEndpoint::recv()
+{
+  auto size = ::mq_receive(this->mqd, this->recv_buffer.data(),
+                           this->recv_buffer.size(), nullptr);
+  if (size == -1)
+    throw std::runtime_error("mq_receive failed: "s + strerror(errno));
+  return {this->recv_buffer.data(),
+      static_cast<std::string::size_type>(size)};
+}
+
+void IPCEndpoint::send(const std::string& msg)
+{
+  auto res = ::mq_send(this->mqd, msg.data(), msg.size(), 0);
+  if (res == -1)
+    throw std::runtime_error("mq_send failed: "s + strerror(errno));
+}
+
+void IPCEndpoint::watch_read(std::function<void(const std::string&)>&& cb)
+{
+  this->stream_descriptor.assign(this->mqd);
+  this->read_cb = std::move(cb);
+  this->watch_read();
+}
+
+void IPCEndpoint::watch_read()
+{
+  // Do not actually read anything using boost because we are using
+  // null_buffers.  Boost will just call our callback when someone is ready
+  // to be read, and we do it manually ourself in the callback.
+  auto cb = [this](const boost::system::error_code& error,
+                   std::size_t)
+    {
+      if (error)
+        log_debug("Error polling on the IPC file descriptor");
+      else
+        {
+          log_debug("Ready to read");
+          auto res = this->recv();
+          this->read_cb(res);
+        }
+      this->watch_read();
+    };
+  this->stream_descriptor.async_read_some(boost::asio::null_buffers(),
+                                          cb);
+}

src/network/ipc_endpoint.hpp

+#ifndef IPC_ENDPOINT_HPP_INCLUDED
+#define IPC_ENDPOINT_HPP_INCLUDED
+
+/**
+ * Uses message queues (man mq_open)
+ */
+
+#include <functional>
+#include <vector>
+#include <string>
+
+#include <boost/asio/posix/stream_descriptor.hpp>
+
+#include <mqueue.h>
+
+class IPCEndpoint
+{
+public:
+  /**
+   * Use the given path to open an existing IPC message queue.
+   */
+  IPCEndpoint(const std::string& path);
+  /**
+   * Generate the path and use to create a new IPC message queue.
+   */
+  IPCEndpoint();
+  ~IPCEndpoint();
+
+  std::string get_path() const;
+  std::size_t get_max_msgsize() const;
+  std::string recv();
+  void send(const std::string& msg);
+  void watch_read(std::function<void(const std::string&)>&& cb);
+
+private:
+  /**
+   * Whether or not this object is responsible for the destruction of the
+   * message queue.  It's true when we are the one who created it, false
+   * otherwise.
+   */
+  bool must_destroy;
+  mqd_t mqd;
+  std::string mq_name;
+  boost::asio::posix::stream_descriptor stream_descriptor;
+  std::vector<char> recv_buffer;
+  std::function<void(const std::string&)> read_cb;
+
+  void resize_recv_buffer();
+  void watch_read();
+
+  IPCEndpoint(const IPCEndpoint&) = delete;
+  IPCEndpoint(IPCEndpoint&&) = delete;
+  IPCEndpoint& operator=(const IPCEndpoint&) = delete;
+  IPCEndpoint& operator=(IPCEndpoint&&) = delete;
+};
+
+#endif /* IPC_ENDPOINT_HPP_INCLUDED */

src/network/remote_client_base.hpp

@@ -30,8 +30,8 @@
 class RemoteClientBase: public MessageHandler, public TimedEventHandler, public PingHandler
 {
 public:
-  explicit RemoteClientBase(boost::asio::io_service&);
-  ~RemoteClientBase();
+  RemoteClientBase();
+  virtual ~RemoteClientBase();
   /**
    * starts the client (install the read handler, etc)
    */
@@ -56,6 +56,11 @@ public:
 
   virtual void on_connection_closed() = 0;
 
+  boost::asio::ip::tcp::endpoint& get_endpoint()
+  {
+    return this->endpoint;
+  }
+
 protected:
   /**
    * The client number (aka id).
@@ -70,10 +75,11 @@ protected:
   void install_read_handler(void);
 private:
   /**
-   * We keep a reference on the io_service that was passed to us by the
-   * Server, for convenience.
+   * A endpoint containing the information of the remote peer.  It is set by
+   * asio, when async_accept succeeds, just before the accept handler is
+   * called.
    */
-  boost::asio::io_service& io_service;
+  boost::asio::ip::tcp::endpoint endpoint;
 };
 
 #endif // REMOTE_CLIENT_BASE

src/slave/slave.cpp

+#include <slave/slave.hpp>
+#include <network/ioservice.hpp>
+#include <logging/logging.hpp>
+
+short Slave::min_port = 7790;
+std::size_t Slave::max_children = 2;
+
+Slave::Slave():
+  running(false),
+  signal_set(IoService::get(), SIGINT, SIGTERM),
+  client(this),
+  children_handler(this)
+{
+  this->signal_set.async_wait([this](const boost::system::error_code& error,
+                                     int)
+                              {
+                                log_debug("Received SIGINT.");
+                                this->running = false;
+                              });
+}
+
+void Slave::run()
+{
+  this->running = true;
+  this->client.start();
+  while (this->running)
+    this->client.poll();
+}
+
+void Slave::start_game()
+{
+  this->children_handler.start_subprocess();
+}
+
+void Slave::fill_info(ser::slave::SlaveInfo& info)
+{
+  info.set_free_slots(Slave::max_children - this->children_handler.size());
+}

src/slave/slave.hpp

+#ifndef SLAVE_HPP_INCLUDED
+#define SLAVE_HPP_INCLUDED
+
+#include <slave/slave_client.hpp>
+#include <slave/children_handler.hpp>
+
+#include <boost/asio/signal_set.hpp>
+
+#include "slave.pb.h"
+
+class Slave
+{