Status tracking infrastructure. (#317)

* Added node's current status information tracker.
* Used the status tracker for responding to status messages.
* Used change-event notifications to broadcast UNL change event.

src/status.cpp

@@ -0,0 +1,87 @@
+#include "status.hpp"
+#include "util/sequence_hash.hpp"
+#include "ledger/ledger_common.hpp"
+#include "conf.hpp"
+
+namespace status
+{
+    moodycamel::ConcurrentQueue<change_event> event_queue;
+
+    std::shared_mutex ledger_mutex;
+    util::sequence_hash lcl_id;        // Last ledger id/hash pair.
+    ledger::ledger_record last_ledger; // Last ledger record that the node created.
+    bool is_in_sync = false;           // Indicates whether this node is in sync with other nodes or not.
+
+    std::shared_mutex unl_mutex;
+    std::set<std::string> unl; // List of last reported unl binary pubkeys.
+
+    std::shared_mutex peers_mutex;
+    std::set<conf::peer_ip_port> peers; // Known ip:port pairs for connection verified peers.
+
+    //----- Ledger status
+
+    void init_ledger(const util::sequence_hash &ledger_id, const ledger::ledger_record &ledger)
+    {
+        // Not acquiring the mutex lock since this is called during startup only.
+        lcl_id = ledger_id;
+        last_ledger = ledger;
+        is_in_sync = true;
+    }
+
+    void ledger_created(const util::sequence_hash &ledger_id, const ledger::ledger_record &ledger)
+    {
+        std::unique_lock lock(ledger_mutex);
+        lcl_id = ledger_id;
+        last_ledger = ledger;
+        is_in_sync = true; // Creating a ledger automatically means we are in sync.
+    }
+
+    void sync_status_changed(const bool in_sync)
+    {
+        std::unique_lock lock(ledger_mutex);
+        is_in_sync = in_sync;
+    }
+
+    const util::sequence_hash get_lcl_id()
+    {
+        std::shared_lock lock(ledger_mutex);
+        return lcl_id;
+    }
+
+    //----- UNL status
+
+    void init_unl(const std::set<std::string> &init_unl)
+    {
+        // Not acquiring the mutex lock since this is called during startup only.
+        unl = init_unl;
+    }
+
+    void unl_changed(const std::set<std::string> &new_unl)
+    {
+        std::unique_lock lock(unl_mutex);
+        unl = new_unl;
+
+        event_queue.try_enqueue(unl_change_event{unl});
+    }
+
+    const std::set<std::string> get_unl()
+    {
+        std::shared_lock lock(unl_mutex);
+        return unl;
+    }
+
+    //----- Peers status
+
+    void set_peers(const std::set<conf::peer_ip_port> &updated_peers)
+    {
+        std::unique_lock lock(peers_mutex);
+        peers = std::move(updated_peers);
+    }
+
+    const std::set<conf::peer_ip_port> get_peers()
+    {
+        std::unique_lock lock(peers_mutex);
+        return peers;
+    }
+
+} // namespace status