Added support for a publisher list (i.e. for mDNS) (#29)

- Added API to initialize a Subscriber session with a list of possible addresses
- Added API to get that list again
- Added API to retrieve the connected publisher and the list of possible publishers

tcp_pubsub/include/tcp_pubsub/callback_data.h

@@ -3,10 +3,8 @@
 
 #pragma once
 
-#include <vector>
-#include <chrono>
 #include <memory>
-#include <cstdint>
+#include <vector>
 
 #include <tcp_pubsub/tcp_pubsub_version.h> // IWYU pragma: keep
 

tcp_pubsub/include/tcp_pubsub/executor.h

@@ -5,9 +5,6 @@
 
 #include <cstddef>
 #include <memory>
-#include <string>
-
-#include <cstdint>
 
 #include "tcp_pubsub_logger.h"
 

tcp_pubsub/include/tcp_pubsub/publisher.h

@@ -5,8 +5,6 @@
 
 #include <cstddef>
 #include <cstdint>
-
-#include <chrono>
 #include <memory>
 #include <string>
 #include <utility>

tcp_pubsub/include/tcp_pubsub/subscriber.h

@@ -4,19 +4,18 @@
 #pragma once
 
 #include <cstdint>
-
-#include <chrono>
 #include <functional>
 #include <memory>
 #include <string>
+#include <utility>
+#include <vector>
 
 #include "executor.h"
 #include "subscriber_session.h"
 #include "callback_data.h"
 
 #include <tcp_pubsub/tcp_pubsub_export.h>
 #include <tcp_pubsub/tcp_pubsub_version.h> // IWYU pragma: keep
-#include <vector>
 
 namespace tcp_pubsub
 {
@@ -111,6 +110,42 @@ namespace tcp_pubsub
      */
     TCP_PUBSUB_EXPORT std::shared_ptr<SubscriberSession>              addSession(const std::string& address, uint16_t port, int max_reconnection_attempts = -1);
 
+    /**
+     * @brief Add a new connection to a publisher
+     * 
+     * Adds a new connection to a publisher. In cases where it is not clear how
+     * the publisher can be reached (e.g. multiple IP addresses), you can
+     * provide a list of pairs of address and port. The Subscriber will try to
+     * connect to all of them. The first one that works will be used. This can
+     * e.g. be used to connect both to "HOSTNAME" and "HOSTNAME.local" (i.e. the
+     * mDNS variant) or to an IPv4 and an IPv6 address. The server list must
+     * have at least one entry.
+     * 
+     * By default, a Session will try to reconnect, when anything failes. How
+     * often this shall happen until the Session will delete itself from the
+     * Subscriber can be controlled by the max_reconnection_attempts parameter.
+     * A negative value will cause the Session to retry indefinitively, so you
+     * will probably have to write your own algorithm code that cancels Sessions
+     * that will not recover any more.
+     * Between reconnection attemps the Session will wait 1 second.
+     * 
+     * Even though it may usually not make sense, you can add multiple
+     * sessions to a single publisher. 
+     * 
+     * This function is thread-safe.
+     * 
+     * @param[in] publisher_list
+     *              A list of [address, port] pairs. The first pair that works
+     *              will be used. The list must have at least one entry.
+     * 
+     * @param[in] max_reconnection_attempts
+     *              How often the Session will try to reconnect in case of an
+     *              issue. A negative value means infinite reconnection attemps.
+     * 
+     * @return A shared pointer to the session. You don't need to store it.
+     */
+    TCP_PUBSUB_EXPORT std::shared_ptr<SubscriberSession>              addSession(const std::vector<std::pair<std::string, uint16_t>>& publisher_list, int max_reconnection_attempts = -1);
+
     /**
      * @brief Get a list of all Sessions.
      * 

tcp_pubsub/include/tcp_pubsub/subscriber_session.h

@@ -3,9 +3,11 @@
 
 #pragma once
 
+#include <cstdint>
 #include <memory>
 #include <string>
-#include <cstdint>
+#include <utility>
+#include <vector>
 
 #include <tcp_pubsub/tcp_pubsub_version.h> // IWYU pragma: keep
 #include <tcp_pubsub/tcp_pubsub_export.h>
@@ -48,18 +50,23 @@ namespace tcp_pubsub
 
   public:
     /**
-     * @brief Get the address used when creating the Session
+     * @brief Get the list of publishers used for creating the session.
+     * 
+     * The session will try to connect to the publishers in the order they are
+     * present in that list. If a connection fails, it will try the next one.
+     * 
+     * For checking which publisher is currently connected, use getConnectedPublisher().
      * 
-     * @return The address / hostname of this Session
+     * @return The list of publishers used for creating the session
      */
-    TCP_PUBSUB_EXPORT std::string getAddress() const;
+    TCP_PUBSUB_EXPORT std::vector<std::pair<std::string, uint16_t>> getPublisherList() const;
 
     /**
-     * @brief Get the port used when creating the Session.
+     * @brief Get the currently connected publisher address
      * 
-     * @return The port this Session is connecting to
+     * @return The address and port of the currently connected publisher
      */
-    TCP_PUBSUB_EXPORT uint16_t    getPort()    const;
+    TCP_PUBSUB_EXPORT std::pair<std::string, uint16_t>              getConnectedPublisher() const;
 
     /**
      * @brief Cancels the Session

tcp_pubsub/include/tcp_pubsub/tcp_pubsub_logger.h

@@ -3,11 +3,9 @@
 
 #pragma once
 
-#include <string>
 #include <functional>
 #include <iostream>
-
-#include <cstdint>
+#include <string>
 
 #include <tcp_pubsub/tcp_pubsub_version.h> // IWYU pragma: keep
 

tcp_pubsub/src/executor.cpp

@@ -1,9 +1,10 @@
 // Copyright (c) Continental. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for details.
 
+#include <tcp_pubsub/executor.h>
+
 #include <cstddef>
 #include <memory>
-#include <tcp_pubsub/executor.h>
 
 #include "executor_impl.h"
 #include "tcp_pubsub/tcp_pubsub_logger.h"

tcp_pubsub/src/executor_impl.cpp

@@ -2,14 +2,18 @@
 // Licensed under the MIT license. See LICENSE file in the project root for details.
 
 #include "executor_impl.h"
-#include "tcp_pubsub/tcp_pubsub_logger.h"
-#include "tcp_pubsub_logger_abstraction.h"
+
 #include <cstddef>
 #include <memory>
 #include <sstream>
 #include <string>
 #include <thread>
 
+#include <asio.hpp>
+
+#include "tcp_pubsub/tcp_pubsub_logger.h"
+#include "tcp_pubsub_logger_abstraction.h"
+
 namespace tcp_pubsub
 {
   Executor_Impl::Executor_Impl(const logger::logger_t& log_function)

tcp_pubsub/src/publisher.cpp

@@ -1,17 +1,17 @@
 // Copyright (c) Continental. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for details.
 
+#include <tcp_pubsub/publisher.h>
+
 #include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
-#include <tcp_pubsub/publisher.h>
 #include <tcp_pubsub/executor.h>
 
-#include "executor_impl.h"
 #include "publisher_impl.h"
 
 namespace tcp_pubsub

tcp_pubsub/src/publisher_impl.cpp

@@ -3,19 +3,13 @@
 
 #include "publisher_impl.h"
 
-#include "tcp_header.h"
-#include "publisher_session.h"
-#include "portable_endian.h"
-
-#include "executor_impl.h"
-#include "tcp_pubsub/tcp_pubsub_logger.h"
-#include "tcp_pubsub_logger_abstraction.h"
+#include <algorithm>
+#include <asio.hpp>
+#include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <functional>
 #include <ios>
-#include <tcp_pubsub/executor.h>
-
-#include <cstddef>
 #include <memory>
 #include <mutex>
 #include <sstream>
@@ -24,6 +18,15 @@
 #include <utility>
 #include <vector>
 
+#include "executor_impl.h" // IWYU pragma: keep
+#include "portable_endian.h"
+#include "publisher_session.h"
+#include "tcp_header.h"
+#include "tcp_pubsub/tcp_pubsub_logger.h"
+#include "tcp_pubsub_logger_abstraction.h"
+#include <tcp_pubsub/executor.h>
+
+
 namespace tcp_pubsub
 {
 

tcp_pubsub/src/publisher_session.cpp

@@ -16,10 +16,11 @@
 #include <thread>
 #include <vector>
 
-#include "tcp_header.h"
-#include "portable_endian.h"
+#include <asio.hpp>
 
+#include "portable_endian.h"
 #include "protocol_handshake_message.h"
+#include "tcp_header.h"
 #include "tcp_pubsub/tcp_pubsub_logger.h"
 #include "tcp_pubsub_logger_abstraction.h"
 

tcp_pubsub/src/publisher_session.h

@@ -3,11 +3,10 @@
 
 #pragma once
 
+#include <asio.hpp>
 #include <atomic>
 #include <cstdint>
 #include <functional>
-
-#include <asio.hpp>
 #include <memory>
 #include <mutex>
 #include <string>

tcp_pubsub/src/subscriber.cpp

@@ -1,18 +1,19 @@
 // Copyright (c) Continental. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for details.
 
+#include <tcp_pubsub/subscriber.h>
+
 #include <cstdint>
 #include <functional>
 #include <memory>
 #include <string>
-#include <tcp_pubsub/subscriber.h>
-
-#include <tcp_pubsub/executor.h>
+#include <utility>
 #include <vector>
 
 #include "subscriber_impl.h"
 #include "tcp_pubsub/callback_data.h"
 #include "tcp_pubsub/subscriber_session.h"
+#include <tcp_pubsub/executor.h>
 
 namespace tcp_pubsub
 {
@@ -26,7 +27,11 @@ namespace tcp_pubsub
   }
 
   std::shared_ptr<SubscriberSession> Subscriber::addSession(const std::string& address, uint16_t port, int max_reconnection_attempts)
-    { return subscriber_impl_->addSession(address, port, max_reconnection_attempts); }
+  { return subscriber_impl_->addSession(std::vector<std::pair<std::string, uint16_t>>{{address, port}}, max_reconnection_attempts); }
+
+  std::shared_ptr<SubscriberSession> Subscriber::addSession(const std::vector<std::pair<std::string, uint16_t>>& publisher_list, int max_reconnection_attempts)
+    { return subscriber_impl_->addSession(publisher_list, max_reconnection_attempts); }
+
 
   std::vector<std::shared_ptr<SubscriberSession>> Subscriber::getSessions() const
     { return subscriber_impl_->getSessions(); }

tcp_pubsub/src/subscriber_impl.cpp

@@ -3,15 +3,6 @@
 
 #include "subscriber_impl.h"
 
-#include "executor_impl.h"
-#include "portable_endian.h"
-#include "subscriber_session_impl.h"
-#include "tcp_header.h"
-#include "tcp_pubsub/callback_data.h"
-#include "tcp_pubsub/executor.h"
-#include "tcp_pubsub/subscriber_session.h"
-#include "tcp_pubsub/tcp_pubsub_logger.h"
-#include "tcp_pubsub_logger_abstraction.h"
 #include <algorithm>
 #include <cstdint>
 #include <functional>
@@ -24,6 +15,15 @@
 #include <utility>
 #include <vector>
 
+#include "executor_impl.h" // IWYU pragma: keep
+#include "subscriber_session_impl.h"
+#include "tcp_header.h"
+#include "tcp_pubsub/callback_data.h"
+#include "tcp_pubsub/executor.h"
+#include "tcp_pubsub/subscriber_session.h"
+#include "tcp_pubsub/tcp_pubsub_logger.h"
+#include "tcp_pubsub_logger_abstraction.h"
+
 namespace tcp_pubsub
 {
   ////////////////////////////////////////////////
@@ -55,10 +55,19 @@ namespace tcp_pubsub
   ////////////////////////////////////////////////
   // Session Management
   ////////////////////////////////////////////////
-  std::shared_ptr<SubscriberSession> Subscriber_Impl::addSession(const std::string& address, uint16_t port, int max_reconnection_attempts)
+  std::shared_ptr<SubscriberSession> Subscriber_Impl::addSession(const std::vector<std::pair<std::string, uint16_t>>& publisher_list, int max_reconnection_attempts)
   {
 #if (TCP_PUBSUB_LOG_DEBUG_VERBOSE_ENABLED)
-    log_(logger::LogLevel::DebugVerbose, "Subscriber " + subscriberIdString() + ": Adding session for endpoint " + address + ":" + std::to_string(port) + ".");
+    // Create a list of all publishers as string
+    std::string publisher_list_string;
+    for (const auto& publisher : publisher_list)
+    {
+      publisher_list_string += publisher.first + ":" + std::to_string(publisher.second);
+      if (&publisher != &publisher_list.back())
+        publisher_list_string += ", ";
+    }
+
+    log_(logger::LogLevel::DebugVerbose, "Subscriber " + subscriberIdString() + ": Adding session for endpoints {" + publisher_list_string + "}.");
 #endif
 
     // Function for getting a free buffer
@@ -101,8 +110,7 @@ namespace tcp_pubsub
     // cannot access it. Thus, we crate the object manually with new.
     std::shared_ptr<SubscriberSession> subscriber_session(
        new SubscriberSession(std::make_shared<SubscriberSession_Impl>(executor_->executor_impl_->ioService()
-                                                                    , address
-                                                                    , port
+                                                                    , publisher_list
                                                                     , max_reconnection_attempts
                                                                     , get_free_buffer_handler
                                                                     , subscriber_session_closed_handler