DiscoveryNode.java

/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.cluster.node;

import org.opensearch.LegacyESVersion;
import org.opensearch.Version;
import org.opensearch.common.UUIDs;
import org.opensearch.common.annotation.PublicApi;
import org.opensearch.common.settings.Setting;
import org.opensearch.common.settings.Settings;
import org.opensearch.core.common.io.stream.StreamInput;
import org.opensearch.core.common.io.stream.StreamOutput;
import org.opensearch.core.common.io.stream.Writeable;
import org.opensearch.core.common.transport.TransportAddress;
import org.opensearch.core.xcontent.ToXContentFragment;
import org.opensearch.core.xcontent.XContentBuilder;
import org.opensearch.index.translog.BufferedChecksumStreamOutput;
import org.opensearch.node.Node;

import java.io.IOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static org.opensearch.node.NodeRoleSettings.NODE_ROLES_SETTING;
import static org.opensearch.node.remotestore.RemoteStoreNodeAttribute.REMOTE_STORE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEY;
import static org.opensearch.node.remotestore.RemoteStoreNodeAttribute.REMOTE_STORE_NODE_ATTRIBUTE_KEY_PREFIX;
import static org.opensearch.node.remotestore.RemoteStoreNodeAttribute.REMOTE_STORE_ROUTING_TABLE_REPOSITORY_NAME_ATTRIBUTE_KEY;

/**
 * A discovery node represents a node that is part of the cluster.
 *
 * @opensearch.api
 */
@PublicApi(since = "1.0.0")
public class DiscoveryNode implements Writeable, ToXContentFragment {

    static final String COORDINATING_ONLY = "coordinating_only";

    public static boolean nodeRequiresLocalStorage(Settings settings) {
        boolean localStorageEnable = Node.NODE_LOCAL_STORAGE_SETTING.get(settings);
        if (localStorageEnable == false && (isDataNode(settings) || isClusterManagerNode(settings))) {
            // TODO: make this a proper setting validation logic, requiring multi-settings validation
            throw new IllegalArgumentException("storage can not be disabled for cluster-manager and data nodes");
        }
        return localStorageEnable;
    }

    public static boolean hasRole(final Settings settings, final DiscoveryNodeRole role) {
        /*
         * This method can be called before the o.e.n.NodeRoleSettings.NODE_ROLES_SETTING is initialized. We do not want to trigger
         * initialization prematurely because that will bake the default roles before plugins have had a chance to register them. Therefore,
         * to avoid initializing this setting prematurely, we avoid using the actual node roles setting instance here.
         */
        if (settings.hasValue("node.roles")) {
            return settings.getAsList("node.roles").contains(role.roleName());
        } else if (role.legacySetting() != null && settings.hasValue(role.legacySetting().getKey())) {
            return role.legacySetting().get(settings);
        } else {
            return role.isEnabledByDefault(settings);
        }
    }

    public static boolean isClusterManagerNode(Settings settings) {
        return hasRole(settings, DiscoveryNodeRole.MASTER_ROLE) || hasRole(settings, DiscoveryNodeRole.CLUSTER_MANAGER_ROLE);
    }

    /** @deprecated As of 2.2, because supporting inclusive language, replaced by {@link #isClusterManagerNode(Settings)} */
    @Deprecated
    public static boolean isMasterNode(Settings settings) {
        return isClusterManagerNode(settings);
    }

    /**
     * Due to the way that plugins may not be available when settings are being initialized,
     * not all roles may be available from a static/initializing context such as a {@link Setting}
     * default value function. In that case, be warned that this may not include all plugin roles.
     */
    public static boolean isDataNode(final Settings settings) {
        return getRolesFromSettings(settings).stream().anyMatch(DiscoveryNodeRole::canContainData);
    }

    public static boolean isIngestNode(Settings settings) {
        return hasRole(settings, DiscoveryNodeRole.INGEST_ROLE);
    }

    public static boolean isRemoteClusterClient(final Settings settings) {
        return hasRole(settings, DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE);
    }

    public static boolean isSearchNode(Settings settings) {
        return hasRole(settings, DiscoveryNodeRole.SEARCH_ROLE);
    }

    public static boolean isDedicatedSearchNode(Settings settings) {
        return getRolesFromSettings(settings).stream().allMatch(DiscoveryNodeRole.SEARCH_ROLE::equals);
    }

    private final String nodeName;
    private final String nodeId;
    private final String ephemeralId;
    private final String hostName;
    private final String hostAddress;
    private final TransportAddress address;
    private final Map<String, String> attributes;
    private final Version version;
    private final SortedSet<DiscoveryNodeRole> roles;

    /**
     * Creates a new {@link DiscoveryNode}
     * <p>
     * <b>Note:</b> if the version of the node is unknown {@link Version#minimumCompatibilityVersion()} should be used for the current
     * version. it corresponds to the minimum version this opensearch version can communicate with. If a higher version is used
     * the node might not be able to communicate with the remote node. After initial handshakes node versions will be discovered
     * and updated.
     * </p>
     *
     * @param id               the nodes unique (persistent) node id. This constructor will auto generate a random ephemeral id.
     * @param address          the nodes transport address
     * @param version          the version of the node
     */
    public DiscoveryNode(final String id, TransportAddress address, Version version) {
        this(id, address, Collections.emptyMap(), DiscoveryNodeRole.BUILT_IN_ROLES, version);
    }

    /**
     * Creates a new {@link DiscoveryNode}
     * <p>
     * <b>Note:</b> if the version of the node is unknown {@link Version#minimumCompatibilityVersion()} should be used for the current
     * version. it corresponds to the minimum version this opensearch version can communicate with. If a higher version is used
     * the node might not be able to communicate with the remote node. After initial handshakes node versions will be discovered
     * and updated.
     * </p>
     *
     * @param id               the nodes unique (persistent) node id. This constructor will auto generate a random ephemeral id.
     * @param address          the nodes transport address
     * @param attributes       node attributes
     * @param roles            node roles
     * @param version          the version of the node
     */
    public DiscoveryNode(
        String id,
        TransportAddress address,
        Map<String, String> attributes,
        Set<DiscoveryNodeRole> roles,
        Version version
    ) {
        this("", id, address, attributes, roles, version);
    }

    /**
     * Creates a new {@link DiscoveryNode}
     * <p>
     * <b>Note:</b> if the version of the node is unknown {@link Version#minimumCompatibilityVersion()} should be used for the current
     * version. it corresponds to the minimum version this opensearch version can communicate with. If a higher version is used
     * the node might not be able to communicate with the remote node. After initial handshakes node versions will be discovered
     * and updated.
     * </p>
     *
     * @param nodeName         the nodes name
     * @param nodeId           the nodes unique persistent id. An ephemeral id will be auto generated.
     * @param address          the nodes transport address
     * @param attributes       node attributes
     * @param roles            node roles
     * @param version          the version of the node
     */
    public DiscoveryNode(
        String nodeName,
        String nodeId,
        TransportAddress address,
        Map<String, String> attributes,
        Set<DiscoveryNodeRole> roles,
        Version version
    ) {
        this(
            nodeName,
            nodeId,
            UUIDs.randomBase64UUID(),
            address.address().getHostString(),
            address.getAddress(),
            address,
            attributes,
            roles,
            version
        );
    }

    /**
     * Creates a new {@link DiscoveryNode}.
     * <p>
     * <b>Note:</b> if the version of the node is unknown {@link Version#minimumCompatibilityVersion()} should be used for the current
     * version. it corresponds to the minimum version this opensearch version can communicate with. If a higher version is used
     * the node might not be able to communicate with the remote node. After initial handshakes node versions will be discovered
     * and updated.
     * </p>
     *
     * @param nodeName         the nodes name
     * @param nodeId           the nodes unique persistent id
     * @param ephemeralId      the nodes unique ephemeral id
     * @param hostAddress      the nodes host address
     * @param address          the nodes transport address
     * @param attributes       node attributes
     * @param roles            node roles
     * @param version          the version of the node
     */
    public DiscoveryNode(
        String nodeName,
        String nodeId,
        String ephemeralId,
        String hostName,
        String hostAddress,
        TransportAddress address,
        Map<String, String> attributes,
        Set<DiscoveryNodeRole> roles,
        Version version
    ) {
        if (nodeName != null) {
            this.nodeName = nodeName.intern();
        } else {
            this.nodeName = "";
        }
        this.nodeId = nodeId.intern();
        this.ephemeralId = ephemeralId.intern();
        this.hostName = hostName.intern();
        this.hostAddress = hostAddress.intern();
        this.address = address;
        if (version == null) {
            this.version = Version.CURRENT;
        } else {
            this.version = version;
        }
        this.attributes = Collections.unmodifiableMap(attributes);
        // verify that no node roles are being provided as attributes
        Predicate<Map<String, String>> predicate = (attrs) -> {
            boolean success = true;
            for (final DiscoveryNodeRole role : DiscoveryNode.roleMap.values()) {
                success &= attrs.containsKey(role.roleName()) == false;
                assert success : role.roleName();
            }
            return success;
        };
        assert predicate.test(attributes) : attributes;
        this.roles = Collections.unmodifiableSortedSet(new TreeSet<>(roles));
    }

    /** Creates a DiscoveryNode representing the local node. */
    public static DiscoveryNode createLocal(Settings settings, TransportAddress publishAddress, String nodeId) {
        Map<String, String> attributes = Node.NODE_ATTRIBUTES.getAsMap(settings);
        Set<DiscoveryNodeRole> roles = getRolesFromSettings(settings);
        return new DiscoveryNode(Node.NODE_NAME_SETTING.get(settings), nodeId, publishAddress, attributes, roles, Version.CURRENT);
    }

    /** extract node roles from the given settings */
    public static Set<DiscoveryNodeRole> getRolesFromSettings(final Settings settings) {
        if (NODE_ROLES_SETTING.exists(settings)) {
            validateLegacySettings(settings, roleMap);
            return Collections.unmodifiableSet(new HashSet<>(NODE_ROLES_SETTING.get(settings)));
        } else {
            return roleMap.values().stream().filter(s -> s.isEnabledByDefault(settings)).collect(Collectors.toSet());
        }
    }

    private static void validateLegacySettings(final Settings settings, final Map<String, DiscoveryNodeRole> roleMap) {
        for (final DiscoveryNodeRole role : roleMap.values()) {
            if (role.legacySetting() != null && role.legacySetting().exists(settings)) {
                final String message = String.format(
                    Locale.ROOT,
                    "can not explicitly configure node roles and use legacy role setting [%s]=[%s]",
                    role.legacySetting().getKey(),
                    role.legacySetting().get(settings)
                );
                throw new IllegalArgumentException(message);
            }
        }
    }

    /**
     * Creates a new {@link DiscoveryNode} by reading from the stream provided as argument
     * @param in the stream
     * @throws IOException if there is an error while reading from the stream
     */
    public DiscoveryNode(StreamInput in) throws IOException {
        this.nodeName = in.readString().intern();
        this.nodeId = in.readString().intern();
        this.ephemeralId = in.readString().intern();
        this.hostName = in.readString().intern();
        this.hostAddress = in.readString().intern();
        this.address = new TransportAddress(in);
        int size = in.readVInt();
        this.attributes = new HashMap<>(size);
        for (int i = 0; i < size; i++) {
            this.attributes.put(in.readString(), in.readString());
        }
        int rolesSize = in.readVInt();
        final Set<DiscoveryNodeRole> roles = new HashSet<>(rolesSize);
        if (in.getVersion().onOrAfter(LegacyESVersion.V_7_3_0)) {
            for (int i = 0; i < rolesSize; i++) {
                final String roleName = in.readString();
                final String roleNameAbbreviation = in.readString();
                final boolean canContainData;
                if (in.getVersion().onOrAfter(LegacyESVersion.V_7_10_0)) {
                    canContainData = in.readBoolean();
                } else {
                    canContainData = roleName.equals(DiscoveryNodeRole.DATA_ROLE.roleName());
                }
                final DiscoveryNodeRole role = roleMap.get(roleName);
                if (role == null) {
                    if (in.getVersion().onOrAfter(Version.V_2_1_0)) {
                        roles.add(new DiscoveryNodeRole.DynamicRole(roleName, roleNameAbbreviation, canContainData));
                    } else {
                        roles.add(new DiscoveryNodeRole.UnknownRole(roleName, roleNameAbbreviation, canContainData));
                    }
                } else {
                    assert roleName.equals(role.roleName()) : "role name [" + roleName + "] does not match role [" + role.roleName() + "]";
                    assert roleNameAbbreviation.equals(role.roleNameAbbreviation()) : "role name abbreviation ["
                        + roleName
                        + "] does not match role ["
                        + role.roleNameAbbreviation()
                        + "]";
                    roles.add(role);
                }
            }
        } else {
            // an old node will only send us legacy roles since pluggable roles is a new concept
            for (int i = 0; i < rolesSize; i++) {
                final LegacyRole legacyRole = in.readEnum(LegacyRole.class);
                switch (legacyRole) {
                    case MASTER:
                        roles.add(DiscoveryNodeRole.CLUSTER_MANAGER_ROLE);
                        break;
                    case DATA:
                        roles.add(DiscoveryNodeRole.DATA_ROLE);
                        break;
                    case INGEST:
                        roles.add(DiscoveryNodeRole.INGEST_ROLE);
                        break;
                    default:
                        throw new AssertionError(legacyRole.roleName());
                }
            }
        }
        this.roles = Collections.unmodifiableSortedSet(new TreeSet<>(roles));
        this.version = in.readVersion();
    }

    @Override
    public void writeTo(StreamOutput out) throws IOException {
        if (out.getVersion().onOrAfter(Version.V_2_17_0)) {
            writeToUtil(out, false);
        } else {
            writeToUtil(out, true);
        }
    }

    public void writeToWithAttribute(StreamOutput out) throws IOException {
        writeToUtil(out, true);
    }

    public void writeToUtil(StreamOutput out, boolean includeAllAttributes) throws IOException {
        writeNodeDetails(out);
        if (includeAllAttributes) {
            out.writeVInt(attributes.size());
            for (Map.Entry<String, String> entry : attributes.entrySet()) {
                out.writeString(entry.getKey());
                out.writeString(entry.getValue());
            }
        } else {
            out.writeVInt(0);
        }
        writeRolesAndVersion(out);
    }

    public void writeVerifiableTo(BufferedChecksumStreamOutput out) throws IOException {
        writeNodeDetails(out);
        out.writeMap(attributes, StreamOutput::writeString, StreamOutput::writeString);
        writeRolesAndVersion(out);
    }

    private void writeNodeDetails(StreamOutput out) throws IOException {
        out.writeString(nodeName);
        out.writeString(nodeId);
        out.writeString(ephemeralId);
        out.writeString(hostName);
        out.writeString(hostAddress);
        address.writeTo(out);
    }

    private void writeRolesAndVersion(StreamOutput out) throws IOException {
        if (out.getVersion().onOrAfter(LegacyESVersion.V_7_3_0)) {
            out.writeVInt(roles.size());
            for (final DiscoveryNodeRole role : roles) {
                final DiscoveryNodeRole compatibleRole = role.getCompatibilityRole(out.getVersion());
                out.writeString(compatibleRole.roleName());
                out.writeString(compatibleRole.roleNameAbbreviation());
                if (out.getVersion().onOrAfter(LegacyESVersion.V_7_10_0)) {
                    out.writeBoolean(compatibleRole.canContainData());
                }
            }
        } else {
            // an old node will only understand legacy roles since pluggable roles is a new concept
            final List<DiscoveryNodeRole> rolesToWrite = roles.stream()
                .filter(DiscoveryNodeRole.LEGACY_ROLES::contains)
                .collect(Collectors.toList());
            out.writeVInt(rolesToWrite.size());
            for (final DiscoveryNodeRole role : rolesToWrite) {
                if (role.isClusterManager()) {
                    out.writeEnum(LegacyRole.MASTER);
                } else if (role.equals(DiscoveryNodeRole.DATA_ROLE)) {
                    out.writeEnum(LegacyRole.DATA);
                } else if (role.equals(DiscoveryNodeRole.INGEST_ROLE)) {
                    out.writeEnum(LegacyRole.INGEST);
                }
            }
        }
        if (out.getVersion().before(Version.V_1_0_0) && version.onOrAfter(Version.V_1_0_0)) {
            out.writeVersion(LegacyESVersion.V_7_10_2);
        } else {
            out.writeVersion(version);
        }
    }

    /**
     * The address that the node can be communicated with.
     */
    public TransportAddress getAddress() {
        return address;
    }

    /**
     * The unique id of the node.
     */
    public String getId() {
        return nodeId;
    }

    /**
     * The unique ephemeral id of the node. Ephemeral ids are meant to be attached the life span
     * of a node process. When ever a node is restarted, it's ephemeral id is required to change (while it's {@link #getId()}
     * will be read from the data folder and will remain the same across restarts). Since all node attributes and addresses
     * are maintained during the life span of a node process, we can (and are) using the ephemeralId in
     * {@link DiscoveryNode#equals(Object)}.
     */
    public String getEphemeralId() {
        return ephemeralId;
    }

    /**
     * The name of the node.
     */
    public String getName() {
        return this.nodeName;
    }

    /**
     * The node attributes.
     */
    public Map<String, String> getAttributes() {
        return this.attributes;
    }

    /**
     * Should this node hold data (shards) or not.
     */
    public boolean isDataNode() {
        return roles.stream().anyMatch(DiscoveryNodeRole::canContainData);
    }

    /**
     * Can this node become cluster-manager or not.
     */
    public boolean isClusterManagerNode() {
        return roles.contains(DiscoveryNodeRole.MASTER_ROLE) || roles.contains(DiscoveryNodeRole.CLUSTER_MANAGER_ROLE);
    }

    /**
     * Can this node become cluster-manager or not.
     *
     * @deprecated As of 2.2, because supporting inclusive language, replaced by {@link #isClusterManagerNode()}
     */
    @Deprecated
    public boolean isMasterNode() {
        return isClusterManagerNode();
    }

    /**
     * Returns a boolean that tells whether this an ingest node or not
     */
    public boolean isIngestNode() {
        return roles.contains(DiscoveryNodeRole.INGEST_ROLE);
    }

    /**
     * Returns whether or not the node can be a remote cluster client.
     *
     * @return true if the node can be a remote cluster client, false otherwise
     */
    public boolean isRemoteClusterClient() {
        return roles.contains(DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE);
    }

    /**
     * Returns whether the node is dedicated to provide search capability.
     *
     * @return true if the node contains search role, false otherwise
     */
    public boolean isSearchNode() {
        return roles.contains(DiscoveryNodeRole.SEARCH_ROLE);
    }

    /**
     * Returns whether the node is a remote store node.
     *
     * @return true if the node contains remote store node attributes, false otherwise
     */
    public boolean isRemoteStoreNode() {
        return this.getAttributes().keySet().stream().anyMatch(key -> key.startsWith(REMOTE_STORE_NODE_ATTRIBUTE_KEY_PREFIX));
    }

    /**
     * Returns whether remote cluster state publication is enabled on this node
     * @return true if the node contains remote cluster state node attribute and remote routing table node attribute
     */
    public boolean isRemoteStatePublicationEnabled() {
        return this.getAttributes()
            .keySet()
            .stream()
            .anyMatch(key -> (key.equals(REMOTE_STORE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEY)))
            && this.getAttributes().keySet().stream().anyMatch(key -> key.equals(REMOTE_STORE_ROUTING_TABLE_REPOSITORY_NAME_ATTRIBUTE_KEY));
    }

    /**
     * Returns a set of all the roles that the node has. The roles are returned in sorted order by the role name.
     * <p>
     * If a node does not have any specific role, the returned set is empty, which means that the node is a coordinating-only node.
     *
     * @return the sorted set of roles
     */
    public Set<DiscoveryNodeRole> getRoles() {
        return roles;
    }

    public Version getVersion() {
        return this.version;
    }

    public String getHostName() {
        return this.hostName;
    }

    public String getHostAddress() {
        return this.hostAddress;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        DiscoveryNode that = (DiscoveryNode) o;

        return ephemeralId.equals(that.ephemeralId);
    }

    @Override
    public int hashCode() {
        // we only need to hash the id because it's highly unlikely that two nodes
        // in our system will have the same id but be different
        // This is done so that this class can be used efficiently as a key in a map
        return ephemeralId.hashCode();
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        if (nodeName.length() > 0) {
            sb.append('{').append(nodeName).append('}');
        }
        sb.append('{').append(nodeId).append('}');
        sb.append('{').append(ephemeralId).append('}');
        sb.append('{').append(hostName).append('}');
        sb.append('{').append(address).append('}');
        if (roles.isEmpty() == false) {
            sb.append('{');
            roles.stream().map(DiscoveryNodeRole::roleNameAbbreviation).sorted().forEach(sb::append);
            sb.append('}');
        }
        if (!attributes.isEmpty()) {
            sb.append(
                attributes.entrySet()
                    .stream()
                    .filter(entry -> !entry.getKey().startsWith(REMOTE_STORE_NODE_ATTRIBUTE_KEY_PREFIX)) // filter remote_store attributes
                                                                                                         // from logging to reduce noise.
                    .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue))
            );
        }
        return sb.toString();
    }

    @Override
    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startObject(getId());
        builder.field("name", getName());
        builder.field("ephemeral_id", getEphemeralId());
        builder.field("transport_address", getAddress().toString());

        builder.startObject("attributes");
        for (Map.Entry<String, String> entry : attributes.entrySet()) {
            builder.field(entry.getKey(), entry.getValue());
        }
        builder.endObject();

        builder.endObject();
        return builder;
    }

    private static Map<String, DiscoveryNodeRole> rolesToMap(final Stream<DiscoveryNodeRole> roles) {
        return Collections.unmodifiableMap(roles.collect(Collectors.toMap(DiscoveryNodeRole::roleName, Function.identity())));
    }

    private static Map<String, DiscoveryNodeRole> roleMap = rolesToMap(DiscoveryNodeRole.BUILT_IN_ROLES.stream());

    public static DiscoveryNodeRole getRoleFromRoleName(final String roleName) {
        // As we are supporting dynamic role, should make role name case-insensitive to avoid confusion of role name like "Data"/"DATA"
        String lowerCasedRoleName = Objects.requireNonNull(roleName).toLowerCase(Locale.ROOT);
        if (roleMap.containsKey(lowerCasedRoleName)) {
            return roleMap.get(lowerCasedRoleName);
        }
        return new DiscoveryNodeRole.DynamicRole(lowerCasedRoleName, lowerCasedRoleName, false);
    }

    public static Set<DiscoveryNodeRole> getPossibleRoles() {
        return Collections.unmodifiableSet(new HashSet<>(roleMap.values()));
    }

    public static void setAdditionalRoles(final Set<DiscoveryNodeRole> additionalRoles) {
        assert additionalRoles.stream().allMatch(r -> r.legacySetting() == null || r.legacySetting().isDeprecated()) : additionalRoles;
        final Map<String, DiscoveryNodeRole> roleNameToPossibleRoles = rolesToMap(
            Stream.concat(DiscoveryNodeRole.BUILT_IN_ROLES.stream(), additionalRoles.stream())
        );
        // collect the abbreviation names into a map to ensure that there are not any duplicate abbreviations
        final Map<String, DiscoveryNodeRole> roleNameAbbreviationToPossibleRoles = Collections.unmodifiableMap(
            roleNameToPossibleRoles.values()
                .stream()
                .collect(Collectors.toMap(DiscoveryNodeRole::roleNameAbbreviation, Function.identity()))
        );
        assert roleNameToPossibleRoles.size() == roleNameAbbreviationToPossibleRoles.size() : "roles by name ["
            + roleNameToPossibleRoles
            + "], roles by name abbreviation ["
            + roleNameAbbreviationToPossibleRoles
            + "]";
        roleMap = roleNameToPossibleRoles;
    }

    /**
     * Load the deprecated {@link DiscoveryNodeRole#MASTER_ROLE}.
     * Master role is not added into BUILT_IN_ROLES, because {@link #setAdditionalRoles(Set)} check role name abbreviation duplication,
     * and CLUSTER_MANAGER_ROLE has the same abbreviation name with MASTER_ROLE.
     */
    public static void setDeprecatedMasterRole() {
        final Map<String, DiscoveryNodeRole> modifiableRoleMap = new HashMap<>(roleMap);
        modifiableRoleMap.put(DiscoveryNodeRole.MASTER_ROLE.roleName(), DiscoveryNodeRole.MASTER_ROLE);
        roleMap = Collections.unmodifiableMap(modifiableRoleMap);
    }

    public static Set<String> getPossibleRoleNames() {
        return roleMap.keySet();
    }

    /**
     * Enum that holds all the possible roles that a node can fulfill in a cluster.
     * Each role has its name and a corresponding abbreviation used by cat apis.
     */
    private enum LegacyRole {
        MASTER("master"),
        DATA("data"),
        INGEST("ingest");

        private final String roleName;

        LegacyRole(final String roleName) {
            this.roleName = roleName;
        }

        public String roleName() {
            return roleName;
        }

    }

}