IT: introduce test that checks connection count if configured per-shard

This tests `cass_cluster_set_core_connections_per_shard` as well as
`cass_session_get_metrics`.

Author: muzarski

Makefile

@@ -27,6 +27,7 @@ SCYLLA_TEST_FILTER := $(subst ${SPACE},${EMPTY},ClusterTests.*\
 :UseKeyspaceCaseSensitiveTests.*\
 :MetricsTests.Integration_Cassandra_ErrorsRequestTimeouts\
 :MetricsTests.Integration_Cassandra_Requests\
+:MetricsTests.Integration_Cassandra_StatsShardConnections\
 :-PreparedTests.Integration_Cassandra_PreparedIDUnchangedDuringReprepare\
 :HeartbeatTests.Integration_Cassandra_HeartbeatFailed\
 :ControlConnectionTests.Integration_Cassandra_TopologyChange\
@@ -68,6 +69,7 @@ CASSANDRA_TEST_FILTER := $(subst ${SPACE},${EMPTY},ClusterTests.*\
 :UseKeyspaceCaseSensitiveTests.*\
 :MetricsTests.Integration_Cassandra_ErrorsRequestTimeouts\
 :MetricsTests.Integration_Cassandra_Requests\
+:MetricsTests.Integration_Cassandra_StatsShardConnections\
 :-PreparedTests.Integration_Cassandra_PreparedIDUnchangedDuringReprepare\
 :PreparedTests.Integration_Cassandra_FailFastWhenPreparedIDChangesDuringReprepare\
 :HeartbeatTests.Integration_Cassandra_HeartbeatFailed\

tests/src/integration/objects/cluster.hpp

@@ -170,6 +170,19 @@ class Cluster : public Object<CassCluster, cass_cluster_free> {
     return *this;
   }
 
+    /**
+   * Assign the number of connections made to each shard
+   *
+   * NOTE: One extra connection is established (the control connection)
+   *
+   * @param connections Number of connection per shard (default: 1)
+   * @return Cluster object
+   */
+  Cluster& with_core_connections_per_shard(unsigned int connections = 1u) {
+    EXPECT_EQ(CASS_OK, cass_cluster_set_core_connections_per_shard(get(), connections));
+    return *this;
+  }
+
   /**
    * Sets credentials for plain text authentication
    *

tests/src/integration/tests/test_metrics.cpp

@@ -76,6 +76,31 @@ CASSANDRA_INTEGRATION_TEST_F(MetricsTests, ErrorsConnectionTimeouts) {
   EXPECT_GE(2u, metrics.errors.connection_timeouts);
 }
 
+/**
+ * This test ensures that the driver is reporting the number of connections
+ * when connection pool size is configured per shard.
+ */
+CASSANDRA_INTEGRATION_TEST_F(MetricsTests, StatsShardConnections) {
+  CHECK_FAILURE;
+
+  const unsigned int CONNS_PER_SHARD = 2;
+
+  Session session =
+      default_cluster().with_core_connections_per_shard(CONNS_PER_SHARD).connect();
+
+  size_t nr_hosts = explode(contact_points_, ',').size();
+  size_t nr_shards = Options::is_scylla() ? Options::smp() : 1;
+  size_t expected_connection_count = nr_hosts * nr_shards * CONNS_PER_SHARD;
+
+  CassMetrics metrics = session.metrics();
+  for (int i = 0; i < 100 && metrics.stats.total_connections < expected_connection_count; ++i) {
+    metrics = session.metrics();
+    msleep(100);
+  }
+
+  EXPECT_GE(metrics.stats.total_connections, expected_connection_count);
+}
+
 /**
  * This test ensures that the driver is reporting the proper timeouts for requests
  *