#20170

Committed 09 Feb 2026 10:46AM UTC coverage: 88.695% (+0.001%) from 88.694%

Build # #20170

Build Type

push

github

Committed by

web-flow

Commit Message

fix(xds): Allow and normalize trailing dot (FQDN) in matchHostName (#12644)

## Summary

`matchHostName` in `RoutingUtils` and `XdsNameResolver` currently
rejects hostnames and patterns
with a trailing dot (`.`) via `checkArgument`. A trailing dot denotes a
**Fully Qualified Domain Name (FQDN)** as defined in
[RFC 1034 Section
3.1](https://www.rfc-editor.org/rfc/rfc1034#section-3.1), and is a
valid,
well-defined representation of an absolute domain name. Rejecting it is
inconsistent with the RFC.

This change removes the trailing-dot rejection and adds normalization to
strip the trailing dot
before matching, making `example.com.` and `example.com` match
equivalently.

## Background

Per [RFC 1034 Section
3.1](https://www.rfc-editor.org/rfc/rfc1034#section-3.1):

> "If the name ends with a dot, it is an absolute name ... For example,
`poneria.ISI.EDU.`"

A trailing dot simply indicates that the name is rooted at the DNS root
and is semantically
equivalent to the same name without the trailing dot. Treating it as
invalid prevents legitimate
FQDNs from being used as hostnames or virtual host domain patterns in
xDS routing configuration.

## Motivation

This was discovered when using gRPC Proxyless Service Mesh on a
Kubernetes cluster with Istio.
The issue surfaced after upgrading Istio from 1.26.8 to 1.28.3. The
Istio change
[istio/istio#56008](https://github.com/istio/istio/pull/56008) began
sending FQDN-style domain
names (with trailing dots) in xDS route configuration, which caused
grpc-java to throw an
`IllegalArgumentException` in `matchHostName`:

```text
java.lang.IllegalArgumentException: Invalid pattern/domain name
    at com.google.common.base.Preconditions.checkArgument(Preconditions.java:143)
```

The root cause is that grpc-java's `matchHostName` was not RFC-compliant
in rejecting trailing dots — the Istio upgrade merely made it visible.
The fix here is to bring grpc-java into compliance with RFC 1034,
independent of any specific Istio versi... (continued)

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92.11

/../xds/src/main/java/io/grpc/xds/XdsNameResolver.java

/*
 * Copyright 2019 The gRPC Authors
 *
 * 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 io.grpc.xds;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static io.grpc.xds.client.Bootstrapper.XDSTP_SCHEME;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Joiner;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Sets;
import com.google.gson.Gson;
import com.google.protobuf.util.Durations;
import io.grpc.Attributes;
import io.grpc.CallOptions;
import io.grpc.Channel;
import io.grpc.ClientCall;
import io.grpc.ClientInterceptor;
import io.grpc.ClientInterceptors;
import io.grpc.ForwardingClientCall.SimpleForwardingClientCall;
import io.grpc.ForwardingClientCallListener.SimpleForwardingClientCallListener;
import io.grpc.InternalConfigSelector;
import io.grpc.InternalLogId;
import io.grpc.LoadBalancer.PickSubchannelArgs;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import io.grpc.MetricRecorder;
import io.grpc.NameResolver;
import io.grpc.Status;
import io.grpc.Status.Code;
import io.grpc.StatusOr;
import io.grpc.SynchronizationContext;
import io.grpc.internal.GrpcUtil;
import io.grpc.internal.ObjectPool;
import io.grpc.xds.ClusterSpecifierPlugin.PluginConfig;
import io.grpc.xds.Filter.FilterConfig;
import io.grpc.xds.Filter.NamedFilterConfig;
import io.grpc.xds.RouteLookupServiceClusterSpecifierPlugin.RlsPluginConfig;
import io.grpc.xds.ThreadSafeRandom.ThreadSafeRandomImpl;
import io.grpc.xds.VirtualHost.Route;
import io.grpc.xds.VirtualHost.Route.RouteAction;
import io.grpc.xds.VirtualHost.Route.RouteAction.ClusterWeight;
import io.grpc.xds.VirtualHost.Route.RouteAction.HashPolicy;
import io.grpc.xds.VirtualHost.Route.RouteAction.RetryPolicy;
import io.grpc.xds.VirtualHost.Route.RouteMatch;
import io.grpc.xds.XdsNameResolverProvider.CallCounterProvider;
import io.grpc.xds.client.Bootstrapper.AuthorityInfo;
import io.grpc.xds.client.Bootstrapper.BootstrapInfo;
import io.grpc.xds.client.XdsClient;
import io.grpc.xds.client.XdsInitializationException;
import io.grpc.xds.client.XdsLogger;
import io.grpc.xds.client.XdsLogger.XdsLogLevel;
import java.net.URI;
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.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Supplier;
import javax.annotation.Nullable;

/**
 * A {@link NameResolver} for resolving gRPC target names with "xds:" scheme.
 *
 * <p>Resolving a gRPC target involves contacting the control plane management server via xDS
 * protocol to retrieve service information and produce a service config to the caller.
 *
 * @see XdsNameResolverProvider
 */
final class XdsNameResolver extends NameResolver {
  static final CallOptions.Key<String> CLUSTER_SELECTION_KEY =
      CallOptions.Key.create("io.grpc.xds.CLUSTER_SELECTION_KEY");
  static final CallOptions.Key<XdsConfig> XDS_CONFIG_CALL_OPTION_KEY =
      CallOptions.Key.create("io.grpc.xds.XDS_CONFIG_CALL_OPTION_KEY");
  static final CallOptions.Key<Long> RPC_HASH_KEY =
      CallOptions.Key.create("io.grpc.xds.RPC_HASH_KEY");
  static final CallOptions.Key<Boolean> AUTO_HOST_REWRITE_KEY =
      CallOptions.Key.create("io.grpc.xds.AUTO_HOST_REWRITE_KEY");
  @VisibleForTesting
  static boolean enableTimeout =
      Strings.isNullOrEmpty(System.getenv("GRPC_XDS_EXPERIMENTAL_ENABLE_TIMEOUT"))
          || Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_ENABLE_TIMEOUT"));

  private final InternalLogId logId;
  private final XdsLogger logger;
  @Nullable
  private final String targetAuthority;
  private final String target;
  private final String serviceAuthority;
  // Encoded version of the service authority as per 
  // https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.
  private final String encodedServiceAuthority;
  private final String overrideAuthority;
  private final ServiceConfigParser serviceConfigParser;
  private final SynchronizationContext syncContext;
  private final ScheduledExecutorService scheduler;
  private final XdsClientPool xdsClientPool;
  private final ThreadSafeRandom random;
  private final FilterRegistry filterRegistry;
  private final XxHash64 hashFunc = XxHash64.INSTANCE;
  // Clusters (with reference counts) to which new/existing requests can be/are routed.
  // put()/remove() must be called in SyncContext, and get() can be called in any thread.
  private final ConcurrentMap<String, ClusterRefState> clusterRefs = new ConcurrentHashMap<>();
  private final ConfigSelector configSelector = new ConfigSelector();
  private final long randomChannelId;
  private final Args nameResolverArgs;
  // Must be accessed in syncContext.
  // Filter instances are unique per channel, and per filter (name+typeUrl).
  // NamedFilterConfig.filterStateKey -> filter_instance.
  private final HashMap<String, Filter> activeFilters = new HashMap<>();

  private volatile RoutingConfig routingConfig;
  private Listener2 listener;
  private XdsClient xdsClient;
  private CallCounterProvider callCounterProvider;
  private ResolveState resolveState;

  XdsNameResolver(
      URI targetUri, String name, @Nullable String overrideAuthority,
      ServiceConfigParser serviceConfigParser,
      SynchronizationContext syncContext, ScheduledExecutorService scheduler,
      @Nullable Map<String, ?> bootstrapOverride,
      MetricRecorder metricRecorder, Args nameResolverArgs) {
    this(targetUri, targetUri.getAuthority(), name, overrideAuthority, serviceConfigParser,
        syncContext, scheduler,
        bootstrapOverride == null
          ? SharedXdsClientPoolProvider.getDefaultProvider()
          : new SharedXdsClientPoolProvider(),
        ThreadSafeRandomImpl.instance, FilterRegistry.getDefaultRegistry(), bootstrapOverride,
        metricRecorder, nameResolverArgs);
  }

  @VisibleForTesting
  XdsNameResolver(
      URI targetUri, @Nullable String targetAuthority, String name,
      @Nullable String overrideAuthority, ServiceConfigParser serviceConfigParser,
      SynchronizationContext syncContext, ScheduledExecutorService scheduler,
      XdsClientPoolFactory xdsClientPoolFactory, ThreadSafeRandom random,
      FilterRegistry filterRegistry, @Nullable Map<String, ?> bootstrapOverride,
      MetricRecorder metricRecorder, Args nameResolverArgs) {
    this.targetAuthority = targetAuthority;
    target = targetUri.toString();

    // The name might have multiple slashes so encode it before verifying.
    serviceAuthority = checkNotNull(name, "name");
    this.encodedServiceAuthority = 
      GrpcUtil.checkAuthority(GrpcUtil.AuthorityEscaper.encodeAuthority(serviceAuthority));

    this.overrideAuthority = overrideAuthority;
    this.serviceConfigParser = checkNotNull(serviceConfigParser, "serviceConfigParser");
    this.syncContext = checkNotNull(syncContext, "syncContext");
    this.scheduler = checkNotNull(scheduler, "scheduler");
    Supplier<XdsClient> xdsClientSupplierArg =
        nameResolverArgs.getArg(XdsNameResolverProvider.XDS_CLIENT_SUPPLIER);
    if (xdsClientSupplierArg != null) {
      this.xdsClientPool = new SupplierXdsClientPool(xdsClientSupplierArg);
    } else {
      checkNotNull(xdsClientPoolFactory, "xdsClientPoolFactory");
      this.xdsClientPool = new BootstrappingXdsClientPool(
          xdsClientPoolFactory, target, bootstrapOverride, metricRecorder);
    }
    this.random = checkNotNull(random, "random");
    this.filterRegistry = checkNotNull(filterRegistry, "filterRegistry");
    this.nameResolverArgs = checkNotNull(nameResolverArgs, "nameResolverArgs");

    randomChannelId = random.nextLong();
    logId = InternalLogId.allocate("xds-resolver", name);
    logger = XdsLogger.withLogId(logId);
    logger.log(XdsLogLevel.INFO, "Created resolver for {0}", name);
  }

  @Override
  public String getServiceAuthority() {
    return encodedServiceAuthority;
  }

  @Override
  public void start(Listener2 listener) {
    this.listener = checkNotNull(listener, "listener");
    try {
      xdsClient = xdsClientPool.getObject();
    } catch (Exception e) {
      listener.onError(
          Status.UNAVAILABLE.withDescription("Failed to initialize xDS").withCause(e));
      return;
    }
    BootstrapInfo bootstrapInfo = xdsClient.getBootstrapInfo();
    String listenerNameTemplate;
    if (targetAuthority == null) {
      listenerNameTemplate = bootstrapInfo.clientDefaultListenerResourceNameTemplate();
    } else {
      AuthorityInfo authorityInfo = bootstrapInfo.authorities().get(targetAuthority);
      if (authorityInfo == null) {
        listener.onError(Status.INVALID_ARGUMENT.withDescription(
            "invalid target URI: target authority not found in the bootstrap"));
        return;
      }
      listenerNameTemplate = authorityInfo.clientListenerResourceNameTemplate();
    }
    String replacement = serviceAuthority;
    if (listenerNameTemplate.startsWith(XDSTP_SCHEME)) {
      replacement = XdsClient.percentEncodePath(replacement);
    }
    String ldsResourceName = expandPercentS(listenerNameTemplate, replacement);
    if (!XdsClient.isResourceNameValid(ldsResourceName, XdsListenerResource.getInstance().typeUrl())
        ) {
      listener.onError(Status.INVALID_ARGUMENT.withDescription(
          "invalid listener resource URI for service authority: " + serviceAuthority));
      return;
    }
    ldsResourceName = XdsClient.canonifyResourceName(ldsResourceName);
    callCounterProvider = SharedCallCounterMap.getInstance();

    resolveState = new ResolveState(ldsResourceName);
    resolveState.start();
  }

  @Override
  public void refresh() {
    if (resolveState != null) {
      resolveState.refresh();
    }
  }

  private static String expandPercentS(String template, String replacement) {
    return template.replace("%s", replacement);
  }

  @Override
  public void shutdown() {
    logger.log(XdsLogLevel.INFO, "Shutdown");
    if (resolveState != null) {
      resolveState.shutdown();
    }
    if (xdsClient != null) {
      xdsClient = xdsClientPool.returnObject(xdsClient);
    }
  }

  @VisibleForTesting
  static Map<String, ?> generateServiceConfigWithMethodConfig(
      @Nullable Long timeoutNano, @Nullable RetryPolicy retryPolicy) {
    if (timeoutNano == null
        && (retryPolicy == null || retryPolicy.retryableStatusCodes().isEmpty())) {
      return Collections.emptyMap();
    }
    ImmutableMap.Builder<String, Object> methodConfig = ImmutableMap.builder();
    methodConfig.put(
        "name", Collections.singletonList(Collections.emptyMap()));
    if (retryPolicy != null && !retryPolicy.retryableStatusCodes().isEmpty()) {
      ImmutableMap.Builder<String, Object> rawRetryPolicy = ImmutableMap.builder();
      rawRetryPolicy.put("maxAttempts", (double) retryPolicy.maxAttempts());
      rawRetryPolicy.put("initialBackoff", Durations.toString(retryPolicy.initialBackoff()));
      rawRetryPolicy.put("maxBackoff", Durations.toString(retryPolicy.maxBackoff()));
      rawRetryPolicy.put("backoffMultiplier", 2D);
      List<String> codes = new ArrayList<>(retryPolicy.retryableStatusCodes().size());
      for (Code code : retryPolicy.retryableStatusCodes()) {
        codes.add(code.name());
      }
      rawRetryPolicy.put(
          "retryableStatusCodes", Collections.unmodifiableList(codes));
      if (retryPolicy.perAttemptRecvTimeout() != null) {
        rawRetryPolicy.put(
            "perAttemptRecvTimeout", Durations.toString(retryPolicy.perAttemptRecvTimeout()));
      }
      methodConfig.put("retryPolicy", rawRetryPolicy.buildOrThrow());
    }
    if (timeoutNano != null) {
      String timeout = timeoutNano / 1_000_000_000.0 + "s";
      methodConfig.put("timeout", timeout);
    }
    return Collections.singletonMap(
        "methodConfig", Collections.singletonList(methodConfig.buildOrThrow()));
  }

  @VisibleForTesting
  XdsClient getXdsClient() {
    return xdsClient;
  }

  // called in syncContext
  private void updateResolutionResult(XdsConfig xdsConfig) {
    syncContext.throwIfNotInThisSynchronizationContext();

    ImmutableMap.Builder<String, Object> childPolicy = new ImmutableMap.Builder<>();
    for (String name : clusterRefs.keySet()) {
      Map<String, ?> lbPolicy = clusterRefs.get(name).toLbPolicy();
      childPolicy.put(name, ImmutableMap.of("lbPolicy", ImmutableList.of(lbPolicy)));
    }
    Map<String, ?> rawServiceConfig = ImmutableMap.of(
        "loadBalancingConfig",
        ImmutableList.of(ImmutableMap.of(
            XdsLbPolicies.CLUSTER_MANAGER_POLICY_NAME,
            ImmutableMap.of("childPolicy", childPolicy.buildOrThrow()))));

    if (logger.isLoggable(XdsLogLevel.INFO)) {
      logger.log(
          XdsLogLevel.INFO, "Generated service config: {0}", new Gson().toJson(rawServiceConfig));
    }
    ConfigOrError parsedServiceConfig = serviceConfigParser.parseServiceConfig(rawServiceConfig);
    Attributes attrs =
        Attributes.newBuilder()
            .set(XdsAttributes.XDS_CLIENT, xdsClient)
            .set(XdsAttributes.XDS_CONFIG, xdsConfig)
            .set(XdsAttributes.XDS_CLUSTER_SUBSCRIPT_REGISTRY, resolveState.xdsDependencyManager)
            .set(XdsAttributes.CALL_COUNTER_PROVIDER, callCounterProvider)
            .set(InternalConfigSelector.KEY, configSelector)
            .build();
    ResolutionResult result =
        ResolutionResult.newBuilder()
            .setAttributes(attrs)
            .setServiceConfig(parsedServiceConfig)
            .build();
    if (!listener.onResult2(result).isOk()) {
      resolveState.xdsDependencyManager.requestReresolution();
    }
  }

  private final class ConfigSelector extends InternalConfigSelector {
    @Override
    public Result selectConfig(PickSubchannelArgs args) {
      RoutingConfig routingCfg;
      RouteData selectedRoute;
      String cluster;
      ClientInterceptor filters;
      Metadata headers = args.getHeaders();
      String path = "/" + args.getMethodDescriptor().getFullMethodName();
      do {
        routingCfg = routingConfig;
        if (routingCfg.errorStatus != null) {
          return Result.forError(routingCfg.errorStatus);
        }
        selectedRoute = null;
        for (RouteData route : routingCfg.routes) {
          if (RoutingUtils.matchRoute(route.routeMatch, path, headers, random)) {
            selectedRoute = route;
            break;
          }
        }
        if (selectedRoute == null) {
          return Result.forError(
              Status.UNAVAILABLE.withDescription("Could not find xDS route matching RPC"));
        }
        if (selectedRoute.routeAction == null) {
          return Result.forError(Status.UNAVAILABLE.withDescription(
              "Could not route RPC to Route with non-forwarding action"));
        }
        RouteAction action = selectedRoute.routeAction;
        if (action.cluster() != null) {
          cluster = prefixedClusterName(action.cluster());
          filters = selectedRoute.filterChoices.get(0);
        } else if (action.weightedClusters() != null) {
          // XdsRouteConfigureResource verifies the total weight will not be 0 or exceed uint32
          long totalWeight = 0;
          for (ClusterWeight weightedCluster : action.weightedClusters()) {
            totalWeight += weightedCluster.weight();
          }
          long select = random.nextLong(totalWeight);
          long accumulator = 0;
          for (int i = 0; ; i++) {
            ClusterWeight weightedCluster = action.weightedClusters().get(i);
            accumulator += weightedCluster.weight();
            if (select < accumulator) {
              cluster = prefixedClusterName(weightedCluster.name());
              filters = selectedRoute.filterChoices.get(i);
              break;
            }
          }
        } else if (action.namedClusterSpecifierPluginConfig() != null) {
          cluster =
              prefixedClusterSpecifierPluginName(action.namedClusterSpecifierPluginConfig().name());
          filters = selectedRoute.filterChoices.get(0);
        } else {
          // updateRoutes() discards routes with unknown actions
          throw new AssertionError();
        }
      } while (!retainCluster(cluster));

      final RouteAction routeAction = selectedRoute.routeAction;
      Long timeoutNanos = null;
      if (enableTimeout) {
        timeoutNanos = routeAction.timeoutNano();
        if (timeoutNanos == null) {
          timeoutNanos = routingCfg.fallbackTimeoutNano;
        }
        if (timeoutNanos <= 0) {
          timeoutNanos = null;
        }
      }
      RetryPolicy retryPolicy = routeAction.retryPolicy();
      // TODO(chengyuanzhang): avoid service config generation and parsing for each call.
      Map<String, ?> rawServiceConfig =
          generateServiceConfigWithMethodConfig(timeoutNanos, retryPolicy);
      ConfigOrError parsedServiceConfig = serviceConfigParser.parseServiceConfig(rawServiceConfig);
      Object config = parsedServiceConfig.getConfig();
      if (config == null) {
        releaseCluster(cluster);
        return Result.forError(
            parsedServiceConfig.getError().augmentDescription(
                "Failed to parse service config (method config)"));
      }
      final String finalCluster = cluster;
      final XdsConfig xdsConfig = routingCfg.xdsConfig;
      final long hash = generateHash(routeAction.hashPolicies(), headers);
      class ClusterSelectionInterceptor implements ClientInterceptor {
        @Override
        public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
            final MethodDescriptor<ReqT, RespT> method, CallOptions callOptions,
            final Channel next) {
          CallOptions callOptionsForCluster =
              callOptions.withOption(CLUSTER_SELECTION_KEY, finalCluster)
                  .withOption(XDS_CONFIG_CALL_OPTION_KEY, xdsConfig)
                  .withOption(RPC_HASH_KEY, hash);
          if (routeAction.autoHostRewrite()) {
            callOptionsForCluster = callOptionsForCluster.withOption(AUTO_HOST_REWRITE_KEY, true);
          }
          return new SimpleForwardingClientCall<ReqT, RespT>(
              next.newCall(method, callOptionsForCluster)) {
            @Override
            public void start(Listener<RespT> listener, Metadata headers) {
              listener = new SimpleForwardingClientCallListener<RespT>(listener) {
                boolean committed;

                @Override
                public void onHeaders(Metadata headers) {
                  committed = true;
                  releaseCluster(finalCluster);
                  delegate().onHeaders(headers);
                }

                @Override
                public void onClose(Status status, Metadata trailers) {
                  if (!committed) {
                    releaseCluster(finalCluster);
                  }
                  delegate().onClose(status, trailers);
                }
              };
              delegate().start(listener, headers);
            }
          };
        }
      }

      return
          Result.newBuilder()
              .setConfig(config)
              .setInterceptor(combineInterceptors(
                  ImmutableList.of(new ClusterSelectionInterceptor(), filters)))
              .build();
    }

    private boolean retainCluster(String cluster) {
      ClusterRefState clusterRefState = clusterRefs.get(cluster);
      if (clusterRefState == null) {
        return false;
      }
      AtomicInteger refCount = clusterRefState.refCount;
      int count;
      do {
        count = refCount.get();
        if (count == 0) {
          return false;
        }
      } while (!refCount.compareAndSet(count, count + 1));
      return true;
    }

    private void releaseCluster(final String cluster) {
      int count = clusterRefs.get(cluster).refCount.decrementAndGet();
      if (count < 0) {
        throw new AssertionError();
      }
      if (count == 0) {
        syncContext.execute(new Runnable() {
          @Override
          public void run() {
            if (clusterRefs.get(cluster).refCount.get() != 0) {
              throw new AssertionError();
            }
            clusterRefs.remove(cluster).close();
            if (resolveState.lastConfigOrStatus.hasValue()) {
              updateResolutionResult(resolveState.lastConfigOrStatus.getValue());
            } else {
              resolveState.cleanUpRoutes(resolveState.lastConfigOrStatus.getStatus());
            }
          }
        });
      }
    }

    private long generateHash(List<HashPolicy> hashPolicies, Metadata headers) {
      Long hash = null;
      for (HashPolicy policy : hashPolicies) {
        Long newHash = null;
        if (policy.type() == HashPolicy.Type.HEADER) {
          String value = getHeaderValue(headers, policy.headerName());
          if (value != null) {
            if (policy.regEx() != null && policy.regExSubstitution() != null) {
              value = policy.regEx().matcher(value).replaceAll(policy.regExSubstitution());
            }
            newHash = hashFunc.hashAsciiString(value);
          }
        } else if (policy.type() == HashPolicy.Type.CHANNEL_ID) {
          newHash = hashFunc.hashLong(randomChannelId);
        }
        if (newHash != null ) {
          // Rotating the old value prevents duplicate hash rules from cancelling each other out
          // and preserves all of the entropy.
          long oldHash = hash != null ? ((hash << 1L) | (hash >> 63L)) : 0;
          hash = oldHash ^ newHash;
        }
        // If the policy is a terminal policy and a hash has been generated, ignore
        // the rest of the hash policies.
        if (policy.isTerminal() && hash != null) {
          break;
        }
      }
      return hash == null ? random.nextLong() : hash;
    }
  }

  static final class PassthroughClientInterceptor implements ClientInterceptor {
    @Override
    public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
        MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
      return next.newCall(method, callOptions);
    }
  }

  private static ClientInterceptor combineInterceptors(final List<ClientInterceptor> interceptors) {
    if (interceptors.size() == 0) {
      return new PassthroughClientInterceptor();
    }
    if (interceptors.size() == 1) {
      return interceptors.get(0);
    }
    return new ClientInterceptor() {
      @Override
      public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
          MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
        next = ClientInterceptors.interceptForward(next, interceptors);
        return next.newCall(method, callOptions);
      }
    };
  }

  @Nullable
  private static String getHeaderValue(Metadata headers, String headerName) {
    if (headerName.endsWith(Metadata.BINARY_HEADER_SUFFIX)) {
      return null;
    }
    if (headerName.equals("content-type")) {
      return "application/grpc";
    }
    Metadata.Key<String> key;
    try {
      key = Metadata.Key.of(headerName, Metadata.ASCII_STRING_MARSHALLER);
    } catch (IllegalArgumentException e) {
      return null;
    }
    Iterable<String> values = headers.getAll(key);
    return values == null ? null : Joiner.on(",").join(values);
  }

  private static String prefixedClusterName(String name) {
    return "cluster:" + name;
  }

  private static String prefixedClusterSpecifierPluginName(String pluginName) {
    return "cluster_specifier_plugin:" + pluginName;
  }

  class ResolveState implements XdsDependencyManager.XdsConfigWatcher {
    private final ConfigOrError emptyServiceConfig =
        serviceConfigParser.parseServiceConfig(Collections.<String, Object>emptyMap());
    private final String authority;
    private final XdsDependencyManager xdsDependencyManager;
    private boolean stopped;
    @Nullable
    private Set<String> existingClusters;  // clusters to which new requests can be routed
    private StatusOr<XdsConfig> lastConfigOrStatus;

    private ResolveState(String ldsResourceName) {
      authority = overrideAuthority != null ? overrideAuthority : encodedServiceAuthority;
      xdsDependencyManager =
          new XdsDependencyManager(xdsClient, syncContext, authority, ldsResourceName,
              nameResolverArgs);
    }

    void start() {
      xdsDependencyManager.start(this);
    }

    void refresh() {
      xdsDependencyManager.requestReresolution();
    }

    private void shutdown() {
      if (stopped) {
        return;
      }

      stopped = true;
      xdsDependencyManager.shutdown();
      updateActiveFilters(null);
    }

    @Override
    public void onUpdate(StatusOr<XdsConfig> updateOrStatus) {
      if (stopped) {
        return;
      }
      logger.log(XdsLogLevel.INFO, "Receive XDS resource update: {0}", updateOrStatus);

      lastConfigOrStatus = updateOrStatus;
      if (!updateOrStatus.hasValue()) {
        updateActiveFilters(null);
        cleanUpRoutes(updateOrStatus.getStatus());
        return;
      }

      // Process Route
      XdsConfig update = updateOrStatus.getValue();
      HttpConnectionManager httpConnectionManager = update.getListener().httpConnectionManager();
      if (httpConnectionManager == null) {
        logger.log(XdsLogLevel.INFO, "API Listener: httpConnectionManager does not exist.");
        updateActiveFilters(null);
        cleanUpRoutes(updateOrStatus.getStatus());
        return;
      }

      VirtualHost virtualHost = update.getVirtualHost();
      ImmutableList<NamedFilterConfig> filterConfigs = httpConnectionManager.httpFilterConfigs();
      long streamDurationNano = httpConnectionManager.httpMaxStreamDurationNano();

      updateActiveFilters(filterConfigs);
      updateRoutes(update, virtualHost, streamDurationNano, filterConfigs);
    }

    // called in syncContext
    private void updateActiveFilters(@Nullable List<NamedFilterConfig> filterConfigs) {
      if (filterConfigs == null) {
        filterConfigs = ImmutableList.of();
      }
      Set<String> filtersToShutdown = new HashSet<>(activeFilters.keySet());
      for (NamedFilterConfig namedFilter : filterConfigs) {
        String typeUrl = namedFilter.filterConfig.typeUrl();
        String filterKey = namedFilter.filterStateKey();

        Filter.Provider provider = filterRegistry.get(typeUrl);
        checkNotNull(provider, "provider %s", typeUrl);
        Filter filter = activeFilters.computeIfAbsent(
            filterKey, k -> provider.newInstance(namedFilter.name));
        checkNotNull(filter, "filter %s", filterKey);
        filtersToShutdown.remove(filterKey);
      }

      // Shutdown filters not present in current HCM.
      for (String filterKey : filtersToShutdown) {
        Filter filterToShutdown = activeFilters.remove(filterKey);
        checkNotNull(filterToShutdown, "filterToShutdown %s", filterKey);
        filterToShutdown.close();
      }
    }

    private void updateRoutes(
        XdsConfig xdsConfig,
        @Nullable VirtualHost virtualHost,
        long httpMaxStreamDurationNano,
        @Nullable List<NamedFilterConfig> filterConfigs) {
      List<Route> routes = virtualHost.routes();
      ImmutableList.Builder<RouteData> routesData = ImmutableList.builder();

      // Populate all clusters to which requests can be routed to through the virtual host.
      Set<String> clusters = new HashSet<>();
      // uniqueName -> clusterName
      Map<String, String> clusterNameMap = new HashMap<>();
      // uniqueName -> pluginConfig
      Map<String, RlsPluginConfig> rlsPluginConfigMap = new HashMap<>();
      for (Route route : routes) {
        RouteAction action = route.routeAction();
        String prefixedName;
        if (action == null) {
          routesData.add(new RouteData(route.routeMatch(), null, ImmutableList.of()));
        } else if (action.cluster() != null) {
          prefixedName = prefixedClusterName(action.cluster());
          clusters.add(prefixedName);
          clusterNameMap.put(prefixedName, action.cluster());
          ClientInterceptor filters = createFilters(filterConfigs, virtualHost, route, null);
          routesData.add(new RouteData(route.routeMatch(), route.routeAction(), filters));
        } else if (action.weightedClusters() != null) {
          ImmutableList.Builder<ClientInterceptor> filterList = ImmutableList.builder();
          for (ClusterWeight weightedCluster : action.weightedClusters()) {
            prefixedName = prefixedClusterName(weightedCluster.name());
            clusters.add(prefixedName);
            clusterNameMap.put(prefixedName, weightedCluster.name());
            filterList.add(createFilters(filterConfigs, virtualHost, route, weightedCluster));
          }
          routesData.add(
              new RouteData(route.routeMatch(), route.routeAction(), filterList.build()));
        } else if (action.namedClusterSpecifierPluginConfig() != null) {
          PluginConfig pluginConfig = action.namedClusterSpecifierPluginConfig().config();
          if (pluginConfig instanceof RlsPluginConfig) {
            prefixedName = prefixedClusterSpecifierPluginName(
                action.namedClusterSpecifierPluginConfig().name());
            clusters.add(prefixedName);
            rlsPluginConfigMap.put(prefixedName, (RlsPluginConfig) pluginConfig);
          }
          ClientInterceptor filters = createFilters(filterConfigs, virtualHost, route, null);
          routesData.add(new RouteData(route.routeMatch(), route.routeAction(), filters));
        } else {
          // Discard route
        }
      }

      // Updates channel's load balancing config whenever the set of selectable clusters changes.
      boolean shouldUpdateResult = existingClusters == null;
      Set<String> addedClusters =
          existingClusters == null ? clusters : Sets.difference(clusters, existingClusters);
      Set<String> deletedClusters =
          existingClusters == null
              ? Collections.emptySet() : Sets.difference(existingClusters, clusters);
      existingClusters = clusters;
      for (String cluster : addedClusters) {
        if (clusterRefs.containsKey(cluster)) {
          clusterRefs.get(cluster).refCount.incrementAndGet();
        } else {
          if (clusterNameMap.containsKey(cluster)) {
            assert cluster.startsWith("cluster:");
            XdsConfig.Subscription subscription =
                xdsDependencyManager.subscribeToCluster(cluster.substring("cluster:".length()));
            clusterRefs.put(
                cluster,
                ClusterRefState.forCluster(
                    new AtomicInteger(1), clusterNameMap.get(cluster), subscription));
          }
          if (rlsPluginConfigMap.containsKey(cluster)) {
            clusterRefs.put(
                cluster,
                ClusterRefState.forRlsPlugin(
                    new AtomicInteger(1), rlsPluginConfigMap.get(cluster)));
          }
          shouldUpdateResult = true;
        }
      }
      for (String cluster : clusters) {
        RlsPluginConfig rlsPluginConfig = rlsPluginConfigMap.get(cluster);
        if (!Objects.equals(rlsPluginConfig, clusterRefs.get(cluster).rlsPluginConfig)) {
          ClusterRefState newClusterRefState =
              ClusterRefState.forRlsPlugin(clusterRefs.get(cluster).refCount, rlsPluginConfig);
          clusterRefs.put(cluster, newClusterRefState);
          shouldUpdateResult = true;
        }
      }
      // Update service config to include newly added clusters.
      if (shouldUpdateResult && routingConfig != null) {
        updateResolutionResult(xdsConfig);
        shouldUpdateResult = false;
      } else {
        // Need to update at least once
        shouldUpdateResult = true;
      }
      // Make newly added clusters selectable by config selector and deleted clusters no longer
      // selectable.
      routingConfig = new RoutingConfig(xdsConfig, httpMaxStreamDurationNano, routesData.build());
      for (String cluster : deletedClusters) {
        int count = clusterRefs.get(cluster).refCount.decrementAndGet();
        if (count == 0) {
          clusterRefs.remove(cluster).close();
          shouldUpdateResult = true;
        }
      }
      if (shouldUpdateResult) {
        updateResolutionResult(xdsConfig);
      }
    }

    private ClientInterceptor createFilters(
        @Nullable List<NamedFilterConfig> filterConfigs,
        VirtualHost virtualHost,
        Route route,
        @Nullable ClusterWeight weightedCluster) {
      if (filterConfigs == null) {
        return new PassthroughClientInterceptor();
      }

      Map<String, FilterConfig> selectedOverrideConfigs =
          new HashMap<>(virtualHost.filterConfigOverrides());
      selectedOverrideConfigs.putAll(route.filterConfigOverrides());
      if (weightedCluster != null) {
        selectedOverrideConfigs.putAll(weightedCluster.filterConfigOverrides());
      }

      ImmutableList.Builder<ClientInterceptor> filterInterceptors = ImmutableList.builder();
      for (NamedFilterConfig namedFilter : filterConfigs) {
        String name = namedFilter.name;
        FilterConfig config = namedFilter.filterConfig;
        FilterConfig overrideConfig = selectedOverrideConfigs.get(name);
        String filterKey = namedFilter.filterStateKey();

        Filter filter = activeFilters.get(filterKey);
        checkNotNull(filter, "activeFilters.get(%s)", filterKey);
        ClientInterceptor interceptor =
            filter.buildClientInterceptor(config, overrideConfig, scheduler);

        if (interceptor != null) {
          filterInterceptors.add(interceptor);
        }
      }

      // Combine interceptors produced by different filters into a single one that executes
      // them sequentially. The order is preserved.
      return combineInterceptors(filterInterceptors.build());
    }

    private void cleanUpRoutes(Status error) {
      routingConfig = new RoutingConfig(error);
      if (existingClusters != null) {
        for (String cluster : existingClusters) {
          int count = clusterRefs.get(cluster).refCount.decrementAndGet();
          if (count == 0) {
            clusterRefs.remove(cluster).close();
          }
        }
        existingClusters = null;
      }

      // Without addresses the default LB (normally pick_first) should become TRANSIENT_FAILURE, and
      // the config selector handles the error message itself.
      listener.onResult2(ResolutionResult.newBuilder()
          .setAttributes(Attributes.newBuilder()
            .set(InternalConfigSelector.KEY, configSelector)
            .build())
          .setServiceConfig(emptyServiceConfig)
          .build());
    }
  }

  /**
   * VirtualHost-level configuration for request routing.
   */
  private static class RoutingConfig {
    final XdsConfig xdsConfig;
    final long fallbackTimeoutNano;
    final ImmutableList<RouteData> routes;
    final Status errorStatus;

    private RoutingConfig(
        XdsConfig xdsConfig, long fallbackTimeoutNano, ImmutableList<RouteData> routes) {
      this.xdsConfig = checkNotNull(xdsConfig, "xdsConfig");
      this.fallbackTimeoutNano = fallbackTimeoutNano;
      this.routes = checkNotNull(routes, "routes");
      this.errorStatus = null;
    }

    private RoutingConfig(Status errorStatus) {
      this.xdsConfig = null;
      this.fallbackTimeoutNano = 0;
      this.routes = null;
      this.errorStatus = checkNotNull(errorStatus, "errorStatus");
      checkArgument(!errorStatus.isOk(), "errorStatus should not be okay");
    }
  }

  static final class RouteData {
    final RouteMatch routeMatch;
    /** null implies non-forwarding action. */
    @Nullable
    final RouteAction routeAction;
    /**
     * Only one of these interceptors should be used per-RPC. There are only multiple values in the
     * list for weighted clusters, in which case the order of the list mirrors the weighted
     * clusters.
     */
    final ImmutableList<ClientInterceptor> filterChoices;

    RouteData(RouteMatch routeMatch, @Nullable RouteAction routeAction, ClientInterceptor filter) {
      this(routeMatch, routeAction, ImmutableList.of(filter));
    }

    RouteData(
        RouteMatch routeMatch,
        @Nullable RouteAction routeAction,
        ImmutableList<ClientInterceptor> filterChoices) {
      this.routeMatch = checkNotNull(routeMatch, "routeMatch");
      checkArgument(
          routeAction == null || !filterChoices.isEmpty(),
          "filter may be empty only for non-forwarding action");
      this.routeAction = routeAction;
      if (routeAction != null && routeAction.weightedClusters() != null) {
        checkArgument(
            routeAction.weightedClusters().size() == filterChoices.size(),
            "filter choices must match size of weighted clusters");
      }
      for (ClientInterceptor filter : filterChoices) {
        checkNotNull(filter, "entry in filterChoices is null");
      }
      this.filterChoices = checkNotNull(filterChoices, "filterChoices");
    }
  }

  private static class ClusterRefState {
    final AtomicInteger refCount;
    @Nullable
    final String traditionalCluster;
    @Nullable
    final RlsPluginConfig rlsPluginConfig;
    @Nullable
    final XdsConfig.Subscription subscription;

    private ClusterRefState(
        AtomicInteger refCount, @Nullable String traditionalCluster,
        @Nullable RlsPluginConfig rlsPluginConfig, @Nullable XdsConfig.Subscription subscription) {
      this.refCount = refCount;
      checkArgument(traditionalCluster == null ^ rlsPluginConfig == null,
          "There must be exactly one non-null value in traditionalCluster and pluginConfig");
      this.traditionalCluster = traditionalCluster;
      this.rlsPluginConfig = rlsPluginConfig;
      this.subscription = subscription;
    }

    private Map<String, ?> toLbPolicy() {
      if (traditionalCluster != null) {
        return ImmutableMap.of(
            XdsLbPolicies.CDS_POLICY_NAME,
            ImmutableMap.of("cluster", traditionalCluster));
      } else {
        ImmutableMap<String, ?> rlsConfig = new ImmutableMap.Builder<String, Object>()
            .put("routeLookupConfig", rlsPluginConfig.config())
            .put(
                "childPolicy",
                ImmutableList.of(ImmutableMap.of(XdsLbPolicies.CDS_POLICY_NAME, ImmutableMap.of(
                    "is_dynamic", true))))
            .put("childPolicyConfigTargetFieldName", "cluster")
            .buildOrThrow();
        return ImmutableMap.of("rls_experimental", rlsConfig);
      }
    }

    private void close() {
      if (subscription != null) {
        subscription.close();
      }
    }

    static ClusterRefState forCluster(
        AtomicInteger refCount, String name, XdsConfig.Subscription subscription) {
      return new ClusterRefState(refCount, name, null, checkNotNull(subscription, "subscription"));
    }

    static ClusterRefState forRlsPlugin(
        AtomicInteger refCount,
        RlsPluginConfig rlsPluginConfig) {
      return new ClusterRefState(refCount, null, rlsPluginConfig, null);
    }
  }

  /** An ObjectPool, except it can throw an exception. */
  private interface XdsClientPool {
    XdsClient getObject() throws XdsInitializationException;

    XdsClient returnObject(XdsClient xdsClient);
  }

  private static final class BootstrappingXdsClientPool implements XdsClientPool {
    private final XdsClientPoolFactory xdsClientPoolFactory;
    private final String target;
    private final @Nullable Map<String, ?> bootstrapOverride;
    private final @Nullable MetricRecorder metricRecorder;
    private ObjectPool<XdsClient> xdsClientPool;

    BootstrappingXdsClientPool(
        XdsClientPoolFactory xdsClientPoolFactory,
        String target,
        @Nullable Map<String, ?> bootstrapOverride,
        @Nullable MetricRecorder metricRecorder) {
      this.xdsClientPoolFactory = checkNotNull(xdsClientPoolFactory, "xdsClientPoolFactory");
      this.target = checkNotNull(target, "target");
      this.bootstrapOverride = bootstrapOverride;
      this.metricRecorder = metricRecorder;
    }

    @Override
    public XdsClient getObject() throws XdsInitializationException {
      if (xdsClientPool == null) {
        BootstrapInfo bootstrapInfo;
        if (bootstrapOverride == null) {
          bootstrapInfo = GrpcBootstrapperImpl.defaultBootstrap();
        } else {
          bootstrapInfo = new GrpcBootstrapperImpl().bootstrap(bootstrapOverride);
        }
        this.xdsClientPool =
            xdsClientPoolFactory.getOrCreate(target, bootstrapInfo, metricRecorder);
      }
      return xdsClientPool.getObject();
    }

    @Override
    public XdsClient returnObject(XdsClient xdsClient) {
      return xdsClientPool.returnObject(xdsClient);
    }
  }

  private static final class SupplierXdsClientPool implements XdsClientPool {
    private final Supplier<XdsClient> xdsClientSupplier;

    SupplierXdsClientPool(Supplier<XdsClient> xdsClientSupplier) {
      this.xdsClientSupplier = checkNotNull(xdsClientSupplier, "xdsClientSupplier");
    }

    @Override
    public XdsClient getObject() throws XdsInitializationException {
      XdsClient xdsClient = xdsClientSupplier.get();
      if (xdsClient == null) {
        throw new XdsInitializationException("Caller failed to initialize XDS_CLIENT_SUPPLIER");
      }
      return xdsClient;
    }

    @Override
    public XdsClient returnObject(XdsClient xdsClient) {
      return null;
    }
  }
}

grpc / grpc-java / #20170

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