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/*
 * Copyright (c) 2013, 2024, Oracle and/or its affiliates.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2.0, as published by
 * the Free Software Foundation.
 *
 * This program is designed to work with certain software that is licensed under separate terms, as designated in a particular file or component or in
 * included license documentation. The authors of MySQL hereby grant you an additional permission to link the program and your derivative works with the
 * separately licensed software that they have either included with the program or referenced in the documentation.
 *
 * Without limiting anything contained in the foregoing, this file, which is part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
 * version 1.0, a copy of which can be found at http://oss.oracle.com/licenses/universal-foss-exception.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0, for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

package com.mysql.cj.jdbc.ha;

import java.sql.SQLException;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;

/**
 * Group of connection objects that can be configured as a group. This is used for promotion/demotion of replicas and sources in a replication configuration,
 * and for exposing metrics around replication-aware connections.
 */
public class ReplicationConnectionGroup {

    private String groupName;
    private long connections = 0;
    private long replicasAdded = 0;
    private long replicasRemoved = 0;
    private long replicasPromoted = 0;
    private long activeConnections = 0;
    private HashMap replicationConnections = new HashMap<>();
    private Set replicaHostList = new CopyOnWriteArraySet<>();
    private boolean isInitialized = false;
    private Set sourceHostList = new CopyOnWriteArraySet<>();

    ReplicationConnectionGroup(String groupName) {
        this.groupName = groupName;
    }

    public long getConnectionCount() {
        return this.connections;
    }

    public long registerReplicationConnection(ReplicationConnection conn, List localSourceList, List localReplicaList) {
        long currentConnectionId;

        synchronized (this) {
            if (!this.isInitialized) {
                if (localSourceList != null) {
                    this.sourceHostList.addAll(localSourceList);
                }
                if (localReplicaList != null) {
                    this.replicaHostList.addAll(localReplicaList);
                }
                this.isInitialized = true;
            }
            currentConnectionId = ++this.connections;
            this.replicationConnections.put(Long.valueOf(currentConnectionId), conn);
        }
        this.activeConnections++;

        return currentConnectionId;
    }

    public String getGroupName() {
        return this.groupName;
    }

    public Collection getSourceHosts() {
        return this.sourceHostList;
    }

    public Collection getReplicaHosts() {
        return this.replicaHostList;
    }

    /**
     * Adds a host to the replicas hosts list.
     *
     * We can safely assume that if this host was added to the replicas list, then it must be added to each one of the replication connections from this group
     * as well.
     * Unnecessary calls to {@link ReplicationConnection#addReplicaHost(String)} could result in undesirable locking issues, assuming that this method is
     * synchronized by nature.
     *
     * This is a no-op if the group already has this host in a replica role.
     *
     * @param hostPortPair
     *            "host:port"
     * @throws SQLException
     *             if an error occurs
     */
    public void addReplicaHost(String hostPortPair) throws SQLException {
        // only add if it's not already a replica host
        if (this.replicaHostList.add(hostPortPair)) {
            this.replicasAdded++;

            // add the replica to all connections:
            for (ReplicationConnection c : this.replicationConnections.values()) {
                c.addReplicaHost(hostPortPair);
            }
        }
    }

    public void handleCloseConnection(ReplicationConnection conn) {
        this.replicationConnections.remove(conn.getConnectionGroupId());
        this.activeConnections--;
    }

    /**
     * Removes a host from the replicas hosts list.
     *
     * We can safely assume that if this host was removed from the replicas list, then it must be removed from each one of the replication connections from this
     * group as well.
     * Unnecessary calls to {@link ReplicationConnection#removeReplica(String, boolean)} could result in undesirable locking issues, assuming that this method
     * is synchronized by nature.
     *
     * This is a no-op if the group doesn't have this host in a replica role.
     *
     * @param hostPortPair
     *            "host:port"
     * @param closeGently
     *            remove host when it's not in use
     * @throws SQLException
     *             if an error occurs
     */
    public void removeReplicaHost(String hostPortPair, boolean closeGently) throws SQLException {
        if (this.replicaHostList.remove(hostPortPair)) {
            this.replicasRemoved++;

            // remove the replica from all connections:
            for (ReplicationConnection c : this.replicationConnections.values()) {
                c.removeReplica(hostPortPair, closeGently);
            }
        }
    }

    /**
     * Promotes a replica host to source.
     *
     * We can safely assume that if this host was removed from the replicas list or added to the sources list, then the same host promotion must happen in each
     * one of the replication connections from this group as well.
     *
     * Unnecessary calls to {@link ReplicationConnection#promoteReplicaToSource(String)} could result in undesirable locking issues, assuming that this method
     * is synchronized by nature.
     *
     * This is a no-op if the group already has this host in a source role and not in replica role.
     *
     * @param hostPortPair
     *            "host:port"
     * @throws SQLException
     *             if an error occurs
     */
    public void promoteReplicaToSource(String hostPortPair) throws SQLException {
        // remove host from replicas AND add host to sources, note that both operands need to be evaluated.
        if (this.replicaHostList.remove(hostPortPair) | this.sourceHostList.add(hostPortPair)) {
            this.replicasPromoted++;

            for (ReplicationConnection c : this.replicationConnections.values()) {
                c.promoteReplicaToSource(hostPortPair);
            }
        }
    }

    /**
     * Removes a host from the sources hosts list.
     *
     * @param hostPortPair
     *            host:port
     * @throws SQLException
     *             if an error occurs
     */
    public void removeSourceHost(String hostPortPair) throws SQLException {
        this.removeSourceHost(hostPortPair, true);
    }

    /**
     * Removes a host from the sources hosts list.
     *
     * We can safely assume that if this host was removed from the sources list, then it must be removed from each one of the replication connections from this
     * group as well.
     * Unnecessary calls to {@link ReplicationConnection#removeSourceHost(String, boolean)} could result in undesirable locking issues, assuming that this
     * method is synchronized by nature.
     *
     * This is a no-op if the group doesn't have this host in a source role.
     *
     * @param hostPortPair
     *            "host:port"
     * @param closeGently
     *            remove host when it's not in use
     * @throws SQLException
     *             if an error occurs
     */
    public void removeSourceHost(String hostPortPair, boolean closeGently) throws SQLException {
        if (this.sourceHostList.remove(hostPortPair)) {
            // remove the source from all connections:
            for (ReplicationConnection c : this.replicationConnections.values()) {
                c.removeSourceHost(hostPortPair, closeGently);
            }
        }
    }

    public int getConnectionCountWithHostAsReplica(String hostPortPair) {
        int matched = 0;

        for (ReplicationConnection c : this.replicationConnections.values()) {
            if (c.isHostReplica(hostPortPair)) {
                matched++;
            }
        }
        return matched;
    }

    public int getConnectionCountWithHostAsSource(String hostPortPair) {
        int matched = 0;

        for (ReplicationConnection c : this.replicationConnections.values()) {
            if (c.isHostSource(hostPortPair)) {
                matched++;
            }
        }
        return matched;
    }

    public long getNumberOfReplicasAdded() {
        return this.replicasAdded;
    }

    public long getNumberOfReplicasRemoved() {
        return this.replicasRemoved;
    }

    public long getNumberOfReplicaPromotions() {
        return this.replicasPromoted;
    }

    public long getTotalConnectionCount() {
        return this.connections;
    }

    public long getActiveConnectionCount() {
        return this.activeConnections;
    }

    @Override
    public String toString() {
        return "ReplicationConnectionGroup[groupName=" + this.groupName + ",sourceHostList=" + this.sourceHostList + ",replicaHostList=" + this.replicaHostList
                + "]";
    }

}