driver/cluster_topology_info.h

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#ifndef __CLUSTERTOPOLOGYINFO_H__
#define __CLUSTERTOPOLOGYINFO_H__

#include "host_info.h"

#include <ctime>
#include <set>
#include <vector>

// This class holds topology information for one cluster.
// Cluster topology consists of an instance endpoint, a set of nodes in the cluster,
// the type of each node in the cluster, and the status of each node in the cluster.
class CLUSTER_TOPOLOGY_INFO {
public:
    CLUSTER_TOPOLOGY_INFO();
    CLUSTER_TOPOLOGY_INFO(const CLUSTER_TOPOLOGY_INFO& src_info); //copy constructor
    virtual ~CLUSTER_TOPOLOGY_INFO();

    void add_host(std::shared_ptr<HOST_INFO> host_info);
    void remove_host(std::shared_ptr<HOST_INFO> host_info);
    size_t total_hosts();
    size_t num_readers(); // return number of readers in the cluster
    std::time_t time_last_updated();

    std::shared_ptr<HOST_INFO> get_writer();
    std::shared_ptr<HOST_INFO> get_next_reader();
    // TODO - Ponder if the get_reader below is needed. In general user of this should not need to deal with indexes.
    // One case that comes to mind, if we were to try to do a random shuffle of readers or hosts in general like JDBC driver
    // we could do random shuffle of host indices and call the get_reader for specific index in order we wanted.
    std::shared_ptr<HOST_INFO> get_reader(int i);
    std::vector<std::shared_ptr<HOST_INFO>> get_writers();
    std::vector<std::shared_ptr<HOST_INFO>> get_readers();
    std::vector<std::shared_ptr<HOST_INFO>> get_instances();

private:
    int current_reader = -1;
    std::time_t last_updated;
    std::set<std::string> down_hosts; // maybe not needed, HOST_INFO has is_host_down() method
    //std::vector<HOST_INFO*> hosts;
    std::shared_ptr<HOST_INFO> last_used_reader;  // TODO perhaps this overlaps with current_reader and is not needed

    // TODO - can we do without pointers -
    // perhaps ok for now, we are using copies CLUSTER_TOPOLOGY_INFO returned by get_topology and get_cached_topology from TOPOLOGY_SERVICE.
    // However, perhaps smart shared pointers could be used.
    std::vector<std::shared_ptr<HOST_INFO>> writers;
    std::vector<std::shared_ptr<HOST_INFO>> readers;

    std::shared_ptr<HOST_INFO> get_last_used_reader();
    void set_last_used_reader(std::shared_ptr<HOST_INFO> reader);
    void mark_host_down(std::shared_ptr<HOST_INFO> host);
    void mark_host_up(std::shared_ptr<HOST_INFO> host);
    std::set<std::string> get_down_hosts();
    void update_time();

    friend class TOPOLOGY_SERVICE;
};

#endif /* __CLUSTERTOPOLOGYINFO_H__ */