Raft allocator adds its own allocation entry to the log

libuavcan/include/uavcan/error.hpp

@@ -34,6 +34,7 @@ const int16_t ErrRecursiveCall           = 9;
 const int16_t ErrLogic                   = 10;
 const int16_t ErrPassiveMode             = 11;  ///< Operation not permitted in passive mode
 const int16_t ErrTransferTooLong         = 12;  ///< Transfer of this length cannot be sent with given transfer type
+const int16_t ErrInvalidConfiguration    = 13;
 /**
  * @}
  */

libuavcan/include/uavcan/protocol/dynamic_node_id_server/distributed/raft_core.hpp

@@ -36,6 +36,13 @@ public:
      */
     virtual void handleLogCommitOnLeader(const Entry& committed_entry) = 0;
 
+    /**
+     * Invoked by the Raft core when the local node becomes a leader or ceases to be one.
+     * By default the local node is not leader.
+     * It is possible to commit to the log right from this method.
+     */
+    virtual void handleLocalLeadershipChange(bool local_node_is_leader) = 0;
+
     virtual ~IRaftLeaderMonitor() { }
 };
 
@@ -270,24 +277,46 @@ class RaftCore : private TimerBase
 
     void switchState(ServerState new_state)
     {
-        if (server_state_ != new_state)
+        if (server_state_ == new_state)
         {
-            UAVCAN_TRACE("dynamic_node_id_server::distributed::RaftCore", "State switch: %d --> %d",
-                         int(server_state_), int(new_state));
-            trace(TraceRaftStateSwitch, new_state);
+            return;
+        }
 
-            server_state_ = new_state;
+        /*
+         * Logging
+         */
+        UAVCAN_TRACE("dynamic_node_id_server::distributed::RaftCore", "State switch: %d --> %d",
+                     int(server_state_), int(new_state));
+        trace(TraceRaftStateSwitch, new_state);
 
-            cluster_.resetAllServerIndices();
+        /*
+         * Updating the current state
+         */
+        const ServerState old_state = server_state_;
+        server_state_ = new_state;
 
-            next_server_index_ = 0;
-            num_votes_received_in_this_campaign_ = 0;
+        /*
+         * Resetting specific states
+         */
+        cluster_.resetAllServerIndices();
 
-            for (uint8_t i = 0; i < NumRequestVoteClients; i++)
-            {
-                request_vote_clients_[i]->cancel();
-            }
-            append_entries_client_.cancel();
+        next_server_index_ = 0;
+        num_votes_received_in_this_campaign_ = 0;
+
+        for (uint8_t i = 0; i < NumRequestVoteClients; i++)
+        {
+            request_vote_clients_[i]->cancel();
+        }
+        append_entries_client_.cancel();
+
+        /*
+         * Calling the switch handler
+         * Note that the handler may commit to the log directly
+         */
+        if ((old_state == ServerStateLeader) ||
+            (new_state == ServerStateLeader))
+        {
+            leader_monitor_.handleLocalLeadershipChange(new_state == ServerStateLeader);
         }
     }
 

libuavcan/include/uavcan/protocol/dynamic_node_id_server/distributed/server.hpp

@@ -56,6 +56,11 @@ class Server : IAllocationRequestHandler
         }
     };
 
+    /*
+     * Constants
+     */
+    UniqueID own_unique_id_;
+
     /*
      * States
      */
@@ -183,6 +188,26 @@ class Server : IAllocationRequestHandler
         tryPublishAllocationResult(entry);
     }
 
+    virtual void handleLocalLeadershipChange(bool local_node_is_leader)
+    {
+        if (!local_node_is_leader)
+        {
+            return;
+        }
+
+        const LazyConstructor<RaftCore::LogEntryInfo> result =
+            raft_core_.traverseLogFromEndUntil(NodeIDLogPredicate(node_.getNodeID()));
+
+        if (!result.isConstructed())
+        {
+            const int res = raft_core_.appendLog(own_unique_id_, node_.getNodeID());
+            if (res < 0)
+            {
+                node_.registerInternalFailure("Raft log append with self ID");
+            }
+        }
+    }
+
     /*
      * Private methods
      */
@@ -231,14 +256,36 @@ public:
         , node_discoverer_(node, tracer, *this)
     { }
 
-    int init(uint8_t cluster_size = ClusterManager::ClusterSizeUnknown)
+    int init(const UniqueID& own_unique_id, const uint8_t cluster_size = ClusterManager::ClusterSizeUnknown)
     {
+        /*
+         * Initializing Raft core first, because the next step requires Log to be loaded
+         */
         int res = raft_core_.init(cluster_size);
         if (res < 0)
         {
             return res;
         }
 
+        /*
+         * Making sure that the server is started with the same node ID
+         */
+        own_unique_id_ = own_unique_id;
+
+        const LazyConstructor<RaftCore::LogEntryInfo> own_log_entry =
+            raft_core_.traverseLogFromEndUntil(NodeIDLogPredicate(node_.getNodeID()));
+
+        if (own_log_entry.isConstructed())
+        {
+            if (own_log_entry->entry.unique_id != own_unique_id_)
+            {
+                return -ErrInvalidConfiguration;
+            }
+        }
+
+        /*
+         * Misc
+         */
         res = allocation_request_manager_.init();
         if (res < 0)
         {

libuavcan/test/protocol/dynamic_node_id_server/distributed/server.cpp

@@ -136,12 +136,18 @@ TEST(DynamicNodeIDServer, Main)
     // Node A is Allocator, Node B is Allocatee
     InterlinkedTestNodesWithSysClock nodes(uavcan::NodeID(10), uavcan::NodeID::Broadcast);
 
+    UniqueID own_unique_id;
+    own_unique_id[0] = 0xAA;
+    own_unique_id[3] = 0xCC;
+    own_unique_id[7] = 0xEE;
+    own_unique_id[9] = 0xBB;
+
     /*
      * Server
      */
     DistributedServer server(nodes.a, storage, tracer);
 
-    ASSERT_LE(0, server.init(1));
+    ASSERT_LE(0, server.init(own_unique_id, 1));
 
     /*
      * Client