The docs say

• lastHeartbeat - time of the transmission time of last heartbeat received from this member
• lastHeartbeatRecv - time that the last heartbeat was received from this member

whereas the code comment says

    // This is the last time we got a response from a heartbeat request to a given member.
    Date_t _lastHeartbeat;
    // This is the last time we got a heartbeat request from a given member.
    Date_t _lastHeartbeatRecv;

The description in the docs for lastHeartbeat is inconsistent with the code comment.

Also the code comments mention "requests" and "responses", and I think the docs would be clearer if they did the same.