issue-1774: Function to retrieve info about client connections was added

Author: testisnullus

session.go

@@ -800,6 +800,95 @@ func (s *Session) MapExecuteBatchCAS(batch *Batch, dest map[string]interface{})
 	return applied, iter, iter.err
 }
 
+// connectionType is a custom type that represents the different stages
+// of a client connection in a Cassandra cluster. It is used to filter and categorize
+// connections based on their current state.
+type connectionType string
+
+const (
+	Ready      connectionType = "ready"
+	Connecting connectionType = "connecting"
+	Idle       connectionType = "idle"
+	Closed     connectionType = "closed"
+	Failed     connectionType = "failed"
+)
+
+// ClientConnection represents a client connection to a Cassandra node. It holds detailed
+// information about the connection, including the client address, connection stage, driver details,
+// and various configuration options.
+type ClientConnection struct {
+	Address         string
+	Port            int
+	ConnectionStage string
+	DriverName      string
+	DriverVersion   string
+	Hostname        string
+	KeyspaceName    *string
+	ProtocolVersion int
+	RequestCount    int
+	SSLCipherSuite  *string
+	SSLEnabled      bool
+	SSLProtocol     *string
+	Username        string
+}
+
+// RetrieveClientConnections retrieves a list of client connections from the
+// `system_views.clients` table based on the specified connection type. The function
+// queries the Cassandra database for connections with a given `connection_stage` and
+// scans the results into a slice of `ClientConnection` structs. It handles nullable
+// fields and returns the list of connections or an error if the operation fails.
+func (s *Session) RetrieveClientConnections(connectionType connectionType) ([]*ClientConnection, error) {
+	const stmt = `
+		SELECT address, port, connection_stage, driver_name, driver_version, 
+		       hostname, keyspace_name, protocol_version, request_count, 
+		       ssl_cipher_suite, ssl_enabled, ssl_protocol, username 
+		FROM system_views.clients 
+		WHERE connection_stage = ?`
+
+	iter := s.control.query(stmt, connectionType)
+	if iter.NumRows() == 0 {
+		return nil, ErrConnectionsDoNotExist
+	}
+	defer iter.Close()
+
+	var connections []*ClientConnection
+	for {
+		conn := &ClientConnection{}
+
+		// Variables to hold nullable fields
+		var keyspaceName, sslCipherSuite, sslProtocol *string
+
+		if !iter.Scan(
+			&conn.Address,
+			&conn.Port,
+			&conn.ConnectionStage,
+			&conn.DriverName,
+			&conn.DriverVersion,
+			&conn.Hostname,
+			&keyspaceName,
+			&conn.ProtocolVersion,
+			&conn.RequestCount,
+			&sslCipherSuite,
+			&conn.SSLEnabled,
+			&sslProtocol,
+			&conn.Username,
+		) {
+			if err := iter.Close(); err != nil {
+				return nil, err
+			}
+			break
+		}
+
+		conn.KeyspaceName = keyspaceName
+		conn.SSLCipherSuite = sslCipherSuite
+		conn.SSLProtocol = sslProtocol
+
+		connections = append(connections, conn)
+	}
+
+	return connections, nil
+}
+
 type hostMetrics struct {
 	// Attempts is count of how many times this query has been attempted for this host.
 	// An attempt is either a retry or fetching next page of results.
@@ -2279,16 +2368,17 @@ func (e Error) Error() string {
 }
 
 var (
-	ErrNotFound             = errors.New("not found")
-	ErrUnavailable          = errors.New("unavailable")
-	ErrUnsupported          = errors.New("feature not supported")
-	ErrTooManyStmts         = errors.New("too many statements")
-	ErrUseStmt              = errors.New("use statements aren't supported. Please see https://github.com/apache/cassandra-gocql-driver for explanation.")
-	ErrSessionClosed        = errors.New("session has been closed")
-	ErrNoConnections        = errors.New("gocql: no hosts available in the pool")
-	ErrNoKeyspace           = errors.New("no keyspace provided")
-	ErrKeyspaceDoesNotExist = errors.New("keyspace does not exist")
-	ErrNoMetadata           = errors.New("no metadata available")
+	ErrNotFound              = errors.New("not found")
+	ErrUnavailable           = errors.New("unavailable")
+	ErrUnsupported           = errors.New("feature not supported")
+	ErrTooManyStmts          = errors.New("too many statements")
+	ErrUseStmt               = errors.New("use statements aren't supported. Please see https://github.com/gocql/gocql for explanation.")
+	ErrSessionClosed         = errors.New("session has been closed")
+	ErrNoConnections         = errors.New("gocql: no hosts available in the pool")
+	ErrNoKeyspace            = errors.New("no keyspace provided")
+	ErrKeyspaceDoesNotExist  = errors.New("keyspace does not exist")
+	ErrConnectionsDoNotExist = errors.New("connections do not exist")
+	ErrNoMetadata            = errors.New("no metadata available")
 )
 
 type ErrProtocol struct{ error }

session_test.go

@@ -347,3 +347,77 @@ func TestIsUseStatement(t *testing.T) {
 		}
 	}
 }
+
+func TestRetrieveClientConnections(t *testing.T) {
+	testCases := []struct {
+		name           string
+		connectionType connectionType
+		expectedResult []*ClientConnection
+		expectError    bool
+	}{
+		{
+			name:           "Valid ready connections",
+			connectionType: Ready,
+			expectedResult: []*ClientConnection{
+				{
+					Address:         "127.0.0.1",
+					Port:            9042,
+					ConnectionStage: "ready",
+					DriverName:      "gocql",
+					DriverVersion:   "v1.0.0",
+					Hostname:        "localhost",
+					KeyspaceName:    nil,
+					ProtocolVersion: 4,
+					RequestCount:    10,
+					SSLCipherSuite:  nil,
+					SSLEnabled:      true,
+					SSLProtocol:     nil,
+					Username:        "user1",
+				},
+			},
+			expectError: false,
+		},
+		{
+			name:           "No connections found",
+			connectionType: Closed,
+			expectedResult: nil,
+			expectError:    true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			session := &Session{
+				control: &controlConn{},
+			}
+
+			results, err := session.RetrieveClientConnections(tc.connectionType)
+
+			if tc.expectError {
+				if err == nil {
+					t.Fatalf("expected an error but got none")
+				}
+			} else {
+				if err != nil {
+					t.Fatalf("unexpected error: %v", err)
+				}
+				if !compareClientConnections(results, tc.expectedResult) {
+					t.Fatalf("expected result %+v, got %+v", tc.expectedResult, results)
+				}
+			}
+		})
+	}
+}
+
+// Helper function to compare two slices of ClientConnection pointers
+func compareClientConnections(a, b []*ClientConnection) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if *a[i] != *b[i] {
+			return false
+		}
+	}
+	return true
+}