common/src/main/java/org/apache/cassandra/sidecar/common/CQLSessionProvider.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.cassandra.sidecar.common;

import com.datastax.driver.core.Session;
import org.jetbrains.annotations.Nullable;

/**
 * A provider of a CQL Session. The session should be connected to:
 * <ul>
 *     <li>All locally-managed instances.</li>
 *     <li>At least one non-local instance. Preferably, at least two non-replica instances.</li>
 * </ul>
 */
public interface CQLSessionProvider
{
    /**
     * Provides a Session connected to the cluster. If null it means the connection was
     * could not be established. The session still might throw a NoHostAvailableException if the
     * cluster is otherwise unreachable.
     *
     * @return Session
     */
    @Nullable Session get();

    /**
     * Closes the CQLSessionProvider
     */
    void close();

    /**
     * Gets the current Session object if it already exists.
     * Otherwise, returns null.
     * @return the connected {@link Session} object if available. Null otherwise.
     */
    @Nullable Session getIfConnected();
}