code: function healthcheck(node) {
      var ended = false;
      var node_id = node.host + ':' + node.port;
      var client = net.connect(
        {port: node.adminport, host: node.host},
        function onConnect() {
          if (!ended) {
            client.write('health\r\n');
          }
        }
      );
  
      client.setTimeout(healthCheckInterval, function() {
        client.end();
        markNodeAsUnhealthy(node_id);
        client.removeAllListeners('data');
        ended = true;
      });
  
      client.on('data', function(data) {
        if (ended) {
          return;
        }
  
        var health_status = data.toString();
        client.end();
        ended = true;
  
        if (health_status.indexOf('up') < 0) {
          markNodeAsUnhealthy(node_id);
        } else {
          markNodeAsHealthy(node_id);
        }
      });
  
      client.on('error', function(e) {
        if (ended) {
          return;
        }
  
        if (e.code !== 'ECONNREFUSED' && e.code !== 'EHOSTUNREACH' && e.code !== 'ECONNRESET') {
          log('Error during healthcheck on node ' + node_id + ' with ' + e.code, 'ERROR');
        }
  
        markNodeAsUnhealthy(node_id);
      });
    }
docs: Perform health check on node