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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2017 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed 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.jboss.ejb.protocol.remote;

import static java.security.AccessController.doPrivileged;
import static org.jboss.ejb.client.EJBClientContext.FILTER_ATTR_EJB_MODULE;
import static org.jboss.ejb.client.EJBClientContext.FILTER_ATTR_EJB_MODULE_DISTINCT;
import static org.jboss.ejb.client.EJBClientContext.FILTER_ATTR_NODE;
import static org.jboss.ejb.client.EJBClientContext.getCurrent;

import java.io.IOException;
import java.net.ConnectException;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.UnknownHostException;
import java.security.GeneralSecurityException;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import javax.net.ssl.SSLContext;

import org.jboss.ejb._private.Logs;
import org.jboss.ejb.client.DiscoveryEJBClientInterceptor;
import org.jboss.ejb.client.EJBClientConnection;
import org.jboss.ejb.client.EJBClientContext;
import org.jboss.ejb.client.EJBModuleIdentifier;
import org.jboss.logging.Logger;
import org.jboss.remoting3.ConnectionPeerIdentity;
import org.jboss.remoting3.Endpoint;
import org.wildfly.common.Assert;
import org.wildfly.common.net.CidrAddressTable;
import org.wildfly.common.net.Inet;
import org.wildfly.discovery.AllFilterSpec;
import org.wildfly.discovery.AttributeValue;
import org.wildfly.discovery.EqualsFilterSpec;
import org.wildfly.discovery.FilterSpec;
import org.wildfly.discovery.ServiceType;
import org.wildfly.discovery.ServiceURL;
import org.wildfly.discovery.spi.DiscoveryProvider;
import org.wildfly.discovery.spi.DiscoveryRequest;
import org.wildfly.discovery.spi.DiscoveryResult;
import org.wildfly.security.auth.client.AuthenticationConfiguration;
import org.wildfly.security.auth.client.AuthenticationContext;
import org.wildfly.security.auth.client.AuthenticationContextConfigurationClient;
import org.xnio.FailedIoFuture;
import org.xnio.IoFuture;
import org.xnio.OptionMap;

/**
 * Provides discovery service based on all known EJBClientChannel service registry entries.
 *
 * @author David M. Lloyd
 */
final class RemotingEJBDiscoveryProvider implements DiscoveryProvider, DiscoveredNodeRegistry {

    static final AuthenticationContextConfigurationClient AUTH_CONFIGURATION_CLIENT = doPrivileged(AuthenticationContextConfigurationClient.ACTION);

    private final ConcurrentHashMap nodes = new ConcurrentHashMap<>();

    private final ConcurrentHashMap failedDestinations = new ConcurrentHashMap();

    private final ConcurrentHashMap> clusterNodes = new ConcurrentHashMap<>();

    private final ConcurrentHashMap effectiveAuthURIs = new ConcurrentHashMap<>();
    
    private static final long DESTINATION_RECHECK_INTERVAL = TimeUnit.MILLISECONDS.toNanos(SecurityUtils.getLong(SystemProperties.DESTINATION_RECHECK_INTERVAL, 5000L));

    public RemotingEJBDiscoveryProvider() {
        Endpoint.getCurrent(); //this will blow up if remoting is not present, preventing this from being registered
    }

    public NodeInformation getNodeInformation(final String nodeName) {
        return nodes.computeIfAbsent(nodeName, NodeInformation::new);
    }

    public List getAllNodeInformation() {
        return new ArrayList<>(nodes.values());
    }

    public void addNode(final String clusterName, final String nodeName, URI registeredBy) {
        effectiveAuthURIs.putIfAbsent(clusterName, registeredBy);
        clusterNodes.computeIfAbsent(clusterName, ignored -> Collections.newSetFromMap(new ConcurrentHashMap<>())).add(nodeName);
    }

    public void removeNode(final String clusterName, final String nodeName) {
        clusterNodes.getOrDefault(clusterName, Collections.emptySet()).remove(nodeName);
    }

    public void removeCluster(final String clusterName) {
        final Set removed = clusterNodes.remove(clusterName);
        if (removed != null) removed.clear();
        effectiveAuthURIs.remove(clusterName);
    }

    private boolean haveNotExpiredFailedDestination(URI uri) {
        Long failureTimestamp = failedDestinations.get(uri);
        if(failureTimestamp == null) {
            return false;
        }
        else {
            long delta = System.nanoTime() - failureTimestamp.longValue();
            return delta < DESTINATION_RECHECK_INTERVAL;
        }
    }

    public DiscoveryRequest discover(final ServiceType serviceType, final FilterSpec filterSpec, final DiscoveryResult result) {
        if (! serviceType.implies(ServiceType.of("ejb", "jboss"))) {
            // only respond to requests for JBoss Enterprise Beans services
            Logs.INVOCATION.tracef("EJB discovery provider: wrong service type(%s), returning!", serviceType.toString());
            result.complete();
            return DiscoveryRequest.NULL;
        }
        final EJBClientContext ejbClientContext = getCurrent();
        final RemoteEJBReceiver ejbReceiver = ejbClientContext.getAttachment(RemoteTransportProvider.ATTACHMENT_KEY);
        if (ejbReceiver == null) {
            // ???
            Logs.INVOCATION.tracef("EJB discovery provider: no EJBReceiver available, returning!");
            result.complete();
            return DiscoveryRequest.NULL;
        }

        final List configuredConnections = ejbClientContext.getConfiguredConnections();

        final DiscoveryAttempt discoveryAttempt = new DiscoveryAttempt(serviceType, filterSpec, result, ejbReceiver, AuthenticationContext.captureCurrent());

        boolean ok = false;
        boolean discoveryConnections = false;
        // first pass
        for (EJBClientConnection connection : configuredConnections) {
            if (! connection.isForDiscovery()) {
                Logs.INVOCATION.tracef("EJB discovery provider: found non-discovery connection, skipping");
                continue;
            }
            discoveryConnections = true;
            final URI uri = connection.getDestination();
            if (haveNotExpiredFailedDestination(uri)) {
                Logs.INVOCATION.tracef("EJB discovery provider: attempting to connect to configured connection %s, skipping because marked as failed", uri);
                continue;
            }
            ok = true;
            Logs.INVOCATION.tracef("EJB discovery provider: attempting to connect to configured connection %s", uri);
            discoveryAttempt.connectAndDiscover(uri, null);
        }
        // also establish cluster nodes if known
        for (Map.Entry> entry : clusterNodes.entrySet()) {
            final String clusterName = entry.getKey();
            final Set nodeSet = entry.getValue();
            int maxConnections = ejbClientContext.getMaximumConnectedClusterNodes();
            nodeLoop: for (String nodeName : nodeSet) {
                if (maxConnections <= 0) break;
                final NodeInformation nodeInformation = nodes.get(nodeName);
                if (nodeInformation != null) {
                    final NodeInformation.ClusterNodeInformation clusterInfo = nodeInformation.getClustersByName().get(clusterName);
                    if (clusterInfo != null) {
                        final Map> tables = clusterInfo.getAddressTablesByProtocol();
                        for (Map.Entry> entry2 : tables.entrySet()) {
                            final String protocol = entry2.getKey();
                            final CidrAddressTable addressTable = entry2.getValue();
                            for (CidrAddressTable.Mapping mapping : addressTable) {
                                try {
                                    final InetSocketAddress destination = Inet.getResolved(mapping.getValue());
                                    final InetSocketAddress source = ejbReceiver.getSourceAddress(destination);
                                    if (source == null ? mapping.getRange().getNetmaskBits() == 0 : source.equals(destination)) {
                                        final InetAddress destinationAddress = destination.getAddress();
                                        String hostName = Inet.getHostNameIfResolved(destinationAddress);
                                        if (hostName == null) {
                                            if (destinationAddress instanceof Inet6Address) {
                                                hostName = '[' + Inet.toOptimalString(destinationAddress) + ']';
                                            } else {
                                                hostName = Inet.toOptimalString(destinationAddress);
                                            }
                                        }
                                        final URI uri = new URI(protocol, null, hostName, destination.getPort(), null, null, null);
                                        if (haveNotExpiredFailedDestination(uri)) {
                                            Logs.INVOCATION.tracef("EJB discovery provider: attempting to connect to cluster connection %s, skipping because marked as failed", uri);
                                        } else {
                                            maxConnections--;
                                            Logs.INVOCATION.tracef("EJB discovery provider: attempting to connect to cluster %s connection %s", clusterName, uri);
                                            discoveryAttempt.connectAndDiscover(uri, clusterName);
                                            ok = true;
                                            continue nodeLoop;
                                        }
                                    }
                                } catch (URISyntaxException e) {
                                    // ignore URI and try the next one
                                } catch (UnknownHostException e) {
                                    Logs.MAIN.logf(Logger.Level.DEBUG, "Cannot resolve %s host during discovery attempt, skipping", mapping.getValue());
                                }

                            }
                        }
                    }
                }
            }
        }
        // special second pass - retry everything because all were marked failed
        if (discoveryConnections && ! ok) {
            Logs.INVOCATION.tracef("EJB discovery provider: all discovery-enabled configured connections marked failed, retrying configured connections ...");
            for (EJBClientConnection connection : configuredConnections) {
                if (! connection.isForDiscovery()) {
                    continue;
                }
                URI destination = connection.getDestination();
                Logs.INVOCATION.tracef("EJB discovery provider: attempting to connect to connection %s", destination);
                discoveryAttempt.connectAndDiscover(destination, null);
            }
        }

        discoveryAttempt.countDown();
        return discoveryAttempt;
    }

    static EJBModuleIdentifier getIdentifierForAttribute(String attribute, AttributeValue value) {
        if (! value.isString()) {
            return null;
        }
        final String stringVal = value.toString();
        switch (attribute) {
            case FILTER_ATTR_EJB_MODULE: {
                final String[] segments = stringVal.split("/");
                final String app, module;
                if (segments.length == 2) {
                    app = segments[0];
                    module = segments[1];
                } else if (segments.length == 1) {
                    app = "";
                    module = segments[0];
                } else {
                    return null;
                }
                return new EJBModuleIdentifier(app, module, "");
            }
            case FILTER_ATTR_EJB_MODULE_DISTINCT: {
                final String[] segments = stringVal.split("/");
                final String app, module, distinct;
                if (segments.length == 3) {
                    app = segments[0];
                    module = segments[1];
                    distinct = segments[2];
                } else if (segments.length == 2) {
                    app = "";
                    module = segments[0];
                    distinct = segments[1];
                } else {
                    return null;
                }
                return new EJBModuleIdentifier(app, module, distinct);
            }
            default: {
                return null;
            }
        }
    }

    static final FilterSpec.Visitor MI_EXTRACTOR = new FilterSpec.Visitor() {
        public EJBModuleIdentifier handle(final EqualsFilterSpec filterSpec, final Void parameter) throws RuntimeException {
            return getIdentifierForAttribute(filterSpec.getAttribute(), filterSpec.getValue());
        }

        public EJBModuleIdentifier handle(final AllFilterSpec filterSpec, final Void parameter) throws RuntimeException {
            for (FilterSpec child : filterSpec) {
                final EJBModuleIdentifier match = child.accept(this);
                if (match != null) {
                    return match;
                }
            }
            return null;
        }
    };

    static final FilterSpec.Visitor NODE_EXTRACTOR = new FilterSpec.Visitor() {
        public String handle(final EqualsFilterSpec filterSpec, final Void parameter) throws RuntimeException {
            final AttributeValue value = filterSpec.getValue();
            return filterSpec.getAttribute().equals(FILTER_ATTR_NODE) && value.isString() ? value.toString() : null;
        }

        public String handle(final AllFilterSpec filterSpec, final Void parameter) throws RuntimeException {
            for (FilterSpec child : filterSpec) {
                final String match = child.accept(this);
                if (match != null) {
                    return match;
                }
            }
            return null;
        }
    };

    /**
     * This method gets a ConnectionPeerIdentity object for a remote connection to a destination, similar to Endpoint.getConnectedIdentity().
     * However, if we call it with a cluster name, indicating that we are connecting to a cluster, instead of looking up the AuthenticationContext
     * for the cluster member destination, it instead uses the AuthenticationContext for the URI which first connected to the cluster.
     * This is the cluster effective URI, in the sense that it is an effective URI (i.e. resolved) for a cluster - the same credentials will be used
     * no matter which cluster member we connect to.
     */
    IoFuture getConnectedIdentityUsingClusterEffective(Endpoint endpoint, URI destination, String abstractType, String abstractTypeAuthority, AuthenticationContext context, String clusterName) {
        Assert.checkNotNullParam("destination", destination);
        Assert.checkNotNullParam("context", context);

        URI effectiveAuth = clusterName != null ? effectiveAuthURIs.get(clusterName) : null;
        boolean updateAuth = effectiveAuth != null;

        if (!updateAuth) {
            effectiveAuth = destination;
        }

        final AuthenticationContextConfigurationClient client = AUTH_CONFIGURATION_CLIENT;
        final SSLContext sslContext;
        try {
            sslContext = client.getSSLContext(destination, context);
        } catch (GeneralSecurityException e) {
            return new FailedIoFuture<>(Logs.REMOTING.failedToConfigureSslContext(e));
        }
        final AuthenticationConfiguration authenticationConfiguration = client.getAuthenticationConfiguration(effectiveAuth, context, -1, abstractType, abstractTypeAuthority);
        return endpoint.getConnectedIdentity(destination, sslContext, updateAuth ? fixupOverrides(authenticationConfiguration, destination) : authenticationConfiguration);
    }

    // TODO remove this hack once ELY-1399 is fully completed, and nothing else
    // (e.g. naming) registers an override. This also works around REM3-315.
    private AuthenticationConfiguration fixupOverrides(AuthenticationConfiguration config, URI target) {
        return config.useProtocol(target.getScheme()).useHost(target.getHost()).usePort(target.getPort());
    }

    final class DiscoveryAttempt implements DiscoveryRequest, DiscoveryResult {
        private final ServiceType serviceType;
        private final FilterSpec filterSpec;
        private final DiscoveryResult discoveryResult;
        private final RemoteEJBReceiver ejbReceiver;
        private final AuthenticationContext authenticationContext;

        private final Endpoint endpoint;
        private final AtomicInteger outstandingCount = new AtomicInteger(1); // this is '1' so that we don't finish until all connections are searched
        private volatile boolean phase2;
        private final List cancellers = Collections.synchronizedList(new ArrayList<>());
        private final IoFuture.HandlingNotifier outerNotifier;
        private final IoFuture.HandlingNotifier innerNotifier;
        // keep a record of URIs we try to connect to for each cluster
        private final ConcurrentHashMap> urisByCluster = new ConcurrentHashMap<>();
        private final Set connectFailedURIs = new HashSet<>();
        /**
         * nodes that have already been provided to the discovery provider eagerly
         */
        private final Set eagerNodes;

        DiscoveryAttempt(final ServiceType serviceType, final FilterSpec filterSpec, final DiscoveryResult discoveryResult, final RemoteEJBReceiver ejbReceiver, final AuthenticationContext authenticationContext) {
            this.serviceType = serviceType;
            this.filterSpec = filterSpec;
            this.discoveryResult = discoveryResult;
            this.ejbReceiver = ejbReceiver;

            this.authenticationContext = authenticationContext;
            endpoint = Endpoint.getCurrent();
            outerNotifier = new IoFuture.HandlingNotifier() {
                public void handleCancelled(final URI destination) {
                    countDown();
                }

                public void handleFailed(final IOException exception, final URI destination) {
                    DiscoveryAttempt.this.discoveryResult.reportProblem(exception);
                    failedDestinations.put(destination, System.nanoTime());
                    if (exception instanceof ConnectException) {
                        connectFailedURIs.add(destination);
                        Logs.INVOCATION.tracef("DiscoveryAttempt: got ConnectException on node with destination = %s", destination);
                    }
                    countDown();
                }

                public void handleDone(final ConnectionPeerIdentity data, final URI destination) {
                    final IoFuture future = DiscoveryAttempt.this.ejbReceiver.serviceHandle.getClientService(data.getConnection(), OptionMap.EMPTY);
                    onCancel(future::cancel);
                    future.addNotifier(innerNotifier, destination);
                }
            };
            innerNotifier = new IoFuture.HandlingNotifier() {
                public void handleCancelled(final URI destination) {
                    countDown();
                }

                public void handleFailed(final IOException exception, final URI destination) {
                    DiscoveryAttempt.this.discoveryResult.reportProblem(exception);
                    failedDestinations.put(destination, System.nanoTime());
                    countDown();
                }

                public void handleDone(final EJBClientChannel clientChannel, final URI destination) {
                    failedDestinations.remove(destination);
                    countDown();
                }
            };

            eagerNodes = DiscoveryEJBClientInterceptor.getDiscoveryAdditionalTimeout() == 0 ? null : Collections.synchronizedSet(new HashSet<>());
        }

        void connectAndDiscover(URI uri, String clusterEffective) {
            final String scheme = uri.getScheme();
            if (scheme == null || ! ejbReceiver.getRemoteTransportProvider().supportsProtocol(scheme) || ! endpoint.isValidUriScheme(scheme)) {
                countDown();
                return;
            }
            outstandingCount.getAndIncrement();

            // keep a record of this URI if it has an associated cluster (EJBCLIENT-325)
            if (clusterEffective != null) {
                urisByCluster.computeIfAbsent(clusterEffective, ignored -> Collections.newSetFromMap(new ConcurrentHashMap<>())).add(uri);
            }

            final IoFuture future;
            if(System.getSecurityManager() == null) {
                future = getConnectedIdentityUsingClusterEffective(endpoint, uri, "ejb", "jboss", authenticationContext, clusterEffective);
            } else {
                future = doPrivileged((PrivilegedAction>) () -> getConnectedIdentityUsingClusterEffective(endpoint, uri, "ejb", "jboss", authenticationContext, clusterEffective));
            }
            onCancel(future::cancel);
            future.addNotifier(outerNotifier, uri);
        }

        void countDown() {
            if (outstandingCount.decrementAndGet() == 0) {

                // before calculating the search result, update DNR to remove crashed last members of clusters (EJBCLIENT-325)
                for (String cluster : urisByCluster.keySet()) {
                    Set uris = urisByCluster.get(cluster);
                      if (uris != null && uris.size() == 1) {
                        // get the URI and check if it represents a failed last cluster member
                        URI uri = uris.iterator().next();
                        if (connectFailedURIs.contains(uri)) {
                            Logs.INVOCATION.tracef("DiscoveryAttempt: countDown() found a cluster %s with one failed destination, %s, removing cluster", cluster, uri);
                            removeCluster(cluster);
                            for (NodeInformation nodeInformation : getAllNodeInformation()) {
                                nodeInformation.removeCluster(cluster);
                            }
                        }
                    }
                }

                final DiscoveryResult result = this.discoveryResult;
                final String node = filterSpec.accept(NODE_EXTRACTOR);
                final EJBModuleIdentifier module = filterSpec.accept(MI_EXTRACTOR);
                if (phase2) {
                    if (node != null) {
                        if (eagerNodes == null || !eagerNodes.contains(node)) {
                            final NodeInformation information = nodes.get(node);
                            if (information != null) information.discover(serviceType, filterSpec, result);
                        }
                    } else for (NodeInformation information : nodes.values()) {
                        if (eagerNodes == null || !eagerNodes.contains(information.getNodeName())) {
                            information.discover(serviceType, filterSpec, result);
                        }
                    }
                    result.complete();
                } else {
                    boolean ok = false;
                    // optimize for simple module identifier and node name queries
                    if (node != null) {
                        if (eagerNodes == null || !eagerNodes.contains(node)) {
                            final NodeInformation information = nodes.get(node);
                            if (information != null) {
                                if (information.discover(serviceType, filterSpec, result)) {
                                    ok = true;
                                }
                            }
                        }
                    } else for (NodeInformation information : nodes.values()) {
                        if (eagerNodes == null || !eagerNodes.contains(information.getNodeName())) {
                            if (information.discover(serviceType, filterSpec, result)) {
                                ok = true;
                            }
                        }
                    }
                    if (ok || (eagerNodes != null && !eagerNodes.isEmpty())) {
                        result.complete();
                    } else {
                        // everything failed.  We have to reconnect everything.
                        Set everything = new HashSet<>();
                        Map effectiveAuthMappings = new HashMap<>();
                        for (EJBClientConnection connection : ejbReceiver.getReceiverContext().getClientContext().getConfiguredConnections()) {
                            if (connection.isForDiscovery()) {
                                everything.add(connection.getDestination());
                            }
                        }
                        outer: for (NodeInformation information : nodes.values()) {
                            for (Map.Entry entry : information.getClustersByName().entrySet()) {
                                String clusterName = entry.getKey();
                                NodeInformation.ClusterNodeInformation cni = entry.getValue();
                                final Map> atm = cni.getAddressTablesByProtocol();
                                for (Map.Entry> entry2 : atm.entrySet()) {
                                    final String protocol = entry2.getKey();
                                    final CidrAddressTable addressTable = entry2.getValue();
                                    for (CidrAddressTable.Mapping mapping : addressTable) {
                                        try {
                                            final InetSocketAddress destination = Inet.getResolved(mapping.getValue());
                                            final InetSocketAddress source = ejbReceiver.getSourceAddress(destination);
                                            if (source == null ? mapping.getRange().getNetmaskBits() == 0 : source.equals(destination)) {

                                                final InetAddress destinationAddress = destination.getAddress();
                                                String hostName = Inet.getHostNameIfResolved(destinationAddress);
                                                if (hostName == null) {
                                                    if (destinationAddress instanceof Inet6Address) {
                                                        hostName = '[' + Inet.toOptimalString(destinationAddress) + ']';
                                                    } else {
                                                        hostName = Inet.toOptimalString(destinationAddress);
                                                    }
                                                }
                                                URI location = new URI(protocol, null, hostName, destination.getPort(), null, null, null);
                                                effectiveAuthMappings.put(location, clusterName);
                                                everything.add(location);
                                                continue outer;
                                            }
                                        } catch (URISyntaxException | UnknownHostException e) {
                                            // ignore URI and try the next one
                                        }
                                    }
                                }
                            }
                        }
                        // now connect them ALL
                        phase2 = true;
                        outstandingCount.incrementAndGet();
                        for (URI uri : everything) {
                            if(!failedDestinations.containsKey(uri)) {
                                connectAndDiscover(uri, effectiveAuthMappings.get(uri));
                            }
                        }
                        countDown();
                    }
                }
            } else if (eagerNodes != null) {
                final DiscoveryResult result = this.discoveryResult;
                final String node = filterSpec.accept(NODE_EXTRACTOR);
                if (node != null) {
                    if (!eagerNodes.contains(node)) {
                        final NodeInformation information = nodes.get(node);
                        if (information != null) {
                            if (information.discover(serviceType, filterSpec, result)) {
                                eagerNodes.add(node);
                            }
                        }
                    }
                } else for (NodeInformation information : nodes.values()) {
                    if (!eagerNodes.contains(information.getNodeName())) {
                        if (information.discover(serviceType, filterSpec, result)) {
                            eagerNodes.add(information.getNodeName());
                        }
                    }
                }
            }
        }

        // discovery result methods

        public void complete() {
            countDown();
        }

        public void reportProblem(final Throwable description) {
            discoveryResult.reportProblem(description);
        }

        public void addMatch(final ServiceURL serviceURL) {
            discoveryResult.addMatch(serviceURL);
        }

        // discovery request methods

        public void cancel() {
            final List cancellers = this.cancellers;
            final List cancellersCopy;
            synchronized (cancellers) {
                /*
                 In scenario in which the last node performs a cancel operation and discovery fails a retry is
                 attempted (see phase2 in countdown method above). This triggers opening new connections and,
                 as a result, adding cancellers, which are being iterated over in this method leading to
                 ConcurrentModificationException. To avoid this the copy is created.

                 See https://issues.redhat.com/browse/JBEAP-24568
                 */
                cancellersCopy = new ArrayList<>(cancellers);
            }
            /*
             * EJBCLIENT-536 - since we are iterating the copy we can safely do it outside synchronized block; running
             * the cancellers synchronized may cause deadlocks
             */
            for (Runnable canceller : cancellersCopy) {
                canceller.run();
            }
        }

        void onCancel(final Runnable action) {
            final List cancellers = this.cancellers;
            synchronized (cancellers) {
                cancellers.add(action);
            }
        }
    }
}




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