Performance metrics and diagnostic information can be obtained from the C/C++ driver using cass_session_get_metrics(). The resulting CassMetrics object contains several useful metrics for accessing request performance and/or debugging issues.

CassMetrics metrics;

/* Get a snapshot of the driver's metrics */
cass_session_get_metrics(session, &metrics);

Request metrics

The requests field contains information about request latency and throughput. All latency times are in microseconds and throughput numbers are in requests per seconds.


The stats field contains information about connections and backpressure markers. If the number of available_connections is less than the number of total_connections this could mean the number of I/O threads or number of connections may need to be increased. The same is true for exceeded_pending_requests_water_mark and exceeded_write_bytes_water_mark metrics. It could also mean the Cassandra cluster is unable to handle the current request load.


The errors field contains information about the occurrence of requests and connection timeouts. Request timeouts occur when a request fails to get a timely response (default: 12 seconds). Pending request timeouts occur whens a request waits too long to be serviced by an assigned host. This can occur when too many requests are in-flight for a single host. Connection timeouts occur when the process of establishing new connections is unresponsive (default: 5 seconds).