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Tracing

Tracing can be used to troubleshoot query performance problems and can be enabled per request. When enabled, it provides detailed request information related to internal, server-side operations. Those operations are stored in tables under the system_traces keyspace.

Enabling

Tracing can be enabled per request for both statements (CassStatement) and batches (CassBatch).

Enable Tracing on a Statement (CassStatement)

const char* query = "SELECT * FROM keyspace1.table1";
CassStatement* statement = cass_statement_new(query, 0);

/* Enable tracing on the statement */
cass_statement_set_tracing(statement, cass_true)

/* ... */

Enable Tracing on a Batch (CassBatch)

CassBatch* batch = cass_batch_new(CASS_BATCH_TYPE_UNLOGGED);

/* Enable tracing on the batch */
cass_batch_set_tracing(batch, cass_true)

/* ... */

Tracing Identifier

When tracing is enabled, a request’s future (CassFuture) will provide a unique tracing identifier. This tracing identifier can be used by an application to query tables in the system_traces keyspace.

CassUuid tracing_id;
if (cass_future_tracing_id(future, &tracing_id) == CASS_OK) {
  /* Use `tracing_id` to query tables in the `system_trace` keyspace */
} else {
  /* Handle error. If this happens then either a request error occurred or the
   * request type for the future does not support tracing.
   */
}

Note: The driver does not return the actual tracing data for the request. The application itself must use the returned tracing identifier to query the tables.

Configuration

By default, when tracing is enabled, the driver will wait for the query’s tracing data to become available in the server-side tables before setting the request’s future. The amount of time it will wait, retry, and the consistency level of the tracing data can be controls by setting CassCluster configuration options.

CassCluster* cluster = cass_cluster_new();

/* Wait a maximum of 15 milliseconds for tracing data to become available */
cass_cluster_set_tracing_max_wait_time(cluster, 15);

/* Wait 3 milliseconds before rechecking for the tracing data */
cass_cluster_set_tracing_retry_wait_time(cluster, 3);

/* Check the tracing data tables using consistency level ONE */
cass_cluster_set_tracing_consistency(cluster, CASS_CONSISTENCY_ONE);

/* ... */