#20414

Committed 20 Aug 2026 06:02AM UTC coverage: 89.192% (-0.008%) from 89.2%

Build # #20414

Build Type

push

github

Committed by

web-flow

Commit Message

netty: Support never-indexed metadata keys (#12976)

Add NettyChannelBuilder.neverIndexMetadataKey() and
neverIndexMetadataKeys() so callers can mark selected outbound metadata
keys for HPACK's never-indexed literal representation.

High-cardinality metadata values provide little compression benefit and
can churn the server's dynamic HPACK table. Keeping them out of the
table avoids unnecessary insertion and eviction work while preserving
dynamic indexing for other headers.

Propagate an immutable set of normalized metadata names through the
client transport and use it in Netty's HPACK sensitivity detector. Add
unit and interoperability coverage.

Generated with AI using OpenAI Codex (GPT-5).

Co-authored-by: Codex <noreply@openai.com>

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38580 of 43255 relevant lines covered (89.19%)

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93.51

/../netty/src/main/java/io/grpc/netty/NettyClientHandler.java

/*
 * Copyright 2014 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.netty;

import static io.netty.handler.codec.http2.DefaultHttp2LocalFlowController.DEFAULT_WINDOW_UPDATE_RATIO;
import static io.netty.util.CharsetUtil.UTF_8;
import static io.netty.util.internal.ObjectUtil.checkNotNull;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.base.Stopwatch;
import com.google.common.base.Supplier;
import com.google.common.base.Ticker;
import io.grpc.Attributes;
import io.grpc.ChannelLogger;
import io.grpc.InternalChannelz;
import io.grpc.InternalStatus;
import io.grpc.Metadata;
import io.grpc.MetricRecorder;
import io.grpc.Status;
import io.grpc.StatusException;
import io.grpc.internal.ClientStreamListener.RpcProgress;
import io.grpc.internal.ClientTransport.PingCallback;
import io.grpc.internal.DisconnectError;
import io.grpc.internal.GoAwayDisconnectError;
import io.grpc.internal.GrpcAttributes;
import io.grpc.internal.GrpcUtil;
import io.grpc.internal.Http2Ping;
import io.grpc.internal.InUseStateAggregator;
import io.grpc.internal.KeepAliveManager;
import io.grpc.internal.SimpleDisconnectError;
import io.grpc.internal.TransportTracer;
import io.grpc.netty.GrpcHttp2HeadersUtils.GrpcHttp2ClientHeadersDecoder;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.handler.codec.http2.DecoratingHttp2FrameWriter;
import io.netty.handler.codec.http2.DefaultHttp2Connection;
import io.netty.handler.codec.http2.DefaultHttp2ConnectionDecoder;
import io.netty.handler.codec.http2.DefaultHttp2ConnectionEncoder;
import io.netty.handler.codec.http2.DefaultHttp2FrameReader;
import io.netty.handler.codec.http2.DefaultHttp2FrameWriter;
import io.netty.handler.codec.http2.DefaultHttp2HeadersEncoder;
import io.netty.handler.codec.http2.DefaultHttp2LocalFlowController;
import io.netty.handler.codec.http2.DefaultHttp2RemoteFlowController;
import io.netty.handler.codec.http2.Http2CodecUtil;
import io.netty.handler.codec.http2.Http2Connection;
import io.netty.handler.codec.http2.Http2ConnectionAdapter;
import io.netty.handler.codec.http2.Http2ConnectionDecoder;
import io.netty.handler.codec.http2.Http2ConnectionEncoder;
import io.netty.handler.codec.http2.Http2Error;
import io.netty.handler.codec.http2.Http2Exception;
import io.netty.handler.codec.http2.Http2FrameAdapter;
import io.netty.handler.codec.http2.Http2FrameLogger;
import io.netty.handler.codec.http2.Http2FrameReader;
import io.netty.handler.codec.http2.Http2FrameWriter;
import io.netty.handler.codec.http2.Http2Headers;
import io.netty.handler.codec.http2.Http2HeadersDecoder;
import io.netty.handler.codec.http2.Http2HeadersEncoder;
import io.netty.handler.codec.http2.Http2HeadersEncoder.SensitivityDetector;
import io.netty.handler.codec.http2.Http2InboundFrameLogger;
import io.netty.handler.codec.http2.Http2OutboundFrameLogger;
import io.netty.handler.codec.http2.Http2Settings;
import io.netty.handler.codec.http2.Http2Stream;
import io.netty.handler.codec.http2.Http2StreamVisitor;
import io.netty.handler.codec.http2.StreamBufferingEncoder;
import io.netty.handler.codec.http2.UniformStreamByteDistributor;
import io.netty.handler.logging.LogLevel;
import io.netty.util.AsciiString;
import io.perfmark.PerfMark;
import io.perfmark.Tag;
import io.perfmark.TaskCloseable;
import java.nio.channels.ClosedChannelException;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Executor;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;

/**
 * Client-side Netty handler for GRPC processing. All event handlers are executed entirely within
 * the context of the Netty Channel thread.
 */
class NettyClientHandler extends AbstractNettyHandler {
  private static final Logger logger = Logger.getLogger(NettyClientHandler.class.getName());
  static boolean enablePerRpcAuthorityCheck =
      GrpcUtil.getFlag("GRPC_ENABLE_PER_RPC_AUTHORITY_CHECK", false);

  /**
   * A message that simply passes through the channel without any real processing. It is useful to
   * check if buffers have been drained and test the health of the channel in a single operation.
   */
  static final Object NOOP_MESSAGE = new Object();

  /**
   * Status used when the transport has exhausted the number of streams.
   */
  private static final Status EXHAUSTED_STREAMS_STATUS =
          Status.UNAVAILABLE.withDescription("Stream IDs have been exhausted");
  private static final long USER_PING_PAYLOAD = 1111;

  private final Http2Connection.PropertyKey streamKey;
  private final ClientTransportLifecycleManager lifecycleManager;
  private final KeepAliveManager keepAliveManager;
  // Returns new unstarted stopwatches
  private final Supplier<Stopwatch> stopwatchFactory;
  private final TransportTracer transportTracer;
  private final Attributes eagAttributes;
  private final TcpMetrics tcpMetrics;
  private final String authority;
  private final InUseStateAggregator<Http2Stream> inUseState =
      new InUseStateAggregator<Http2Stream>() {
        @Override
        protected void handleInUse() {
          lifecycleManager.notifyInUse(true);
        }

        @Override
        protected void handleNotInUse() {
          lifecycleManager.notifyInUse(false);
        }
      };
  private final Map<String, Status> peerVerificationResults =
      new LinkedHashMap<String, Status>() {
        @Override
        protected boolean removeEldestEntry(Map.Entry<String, Status> eldest) {
          return size() > 100;
        }
      };

  private WriteQueue clientWriteQueue;
  private Http2Ping ping;
  private Attributes attributes;
  private InternalChannelz.Security securityInfo;
  private Status abruptGoAwayStatus;
  private Status channelInactiveReason;

  static NettyClientHandler newHandler(
      ClientTransportLifecycleManager lifecycleManager,
      @Nullable KeepAliveManager keepAliveManager,
      boolean autoFlowControl,
      int flowControlWindow,
      Set<AsciiString> neverIndexedMetadataKeys,
      int maxHeaderListSize,
      int softLimitHeaderListSize,
      Supplier<Stopwatch> stopwatchFactory,
      Runnable tooManyPingsRunnable,
      TransportTracer transportTracer,
      Attributes eagAttributes,
      String authority,
      ChannelLogger negotiationLogger,
      Ticker ticker,
      MetricRecorder metricRecorder) {
    Preconditions.checkArgument(maxHeaderListSize > 0, "maxHeaderListSize must be positive");
    Http2HeadersDecoder headersDecoder = new GrpcHttp2ClientHeadersDecoder(maxHeaderListSize);
    Http2FrameReader frameReader = new DefaultHttp2FrameReader(headersDecoder);
    Http2HeadersEncoder encoder = new DefaultHttp2HeadersEncoder(
        sensitivityDetector(neverIndexedMetadataKeys), false, 16, Integer.MAX_VALUE);
    Http2FrameWriter frameWriter = new DefaultHttp2FrameWriter(encoder);
    Http2Connection connection = new DefaultHttp2Connection(false);
    UniformStreamByteDistributor dist = new UniformStreamByteDistributor(connection);
    dist.minAllocationChunk(MIN_ALLOCATED_CHUNK); // Increased for benchmarks performance.
    DefaultHttp2RemoteFlowController controller =
        new DefaultHttp2RemoteFlowController(connection, dist);
    connection.remote().flowController(controller);

    return newHandler(
        connection,
        frameReader,
        frameWriter,
        lifecycleManager,
        keepAliveManager,
        autoFlowControl,
        flowControlWindow,
        maxHeaderListSize,
        softLimitHeaderListSize,
        stopwatchFactory,
        tooManyPingsRunnable,
        transportTracer,
        eagAttributes,
        authority,
        negotiationLogger,
        ticker,
        metricRecorder);
  }

  @VisibleForTesting
  static NettyClientHandler newHandler(
      final Http2Connection connection,
      Http2FrameReader frameReader,
      Http2FrameWriter frameWriter,
      ClientTransportLifecycleManager lifecycleManager,
      KeepAliveManager keepAliveManager,
      boolean autoFlowControl,
      int flowControlWindow,
      int maxHeaderListSize,
      int softLimitHeaderListSize,
      Supplier<Stopwatch> stopwatchFactory,
      Runnable tooManyPingsRunnable,
      TransportTracer transportTracer,
      Attributes eagAttributes,
      String authority,
      ChannelLogger negotiationLogger,
      Ticker ticker,
      MetricRecorder metricRecorder) {
    Preconditions.checkNotNull(connection, "connection");
    Preconditions.checkNotNull(frameReader, "frameReader");
    Preconditions.checkNotNull(lifecycleManager, "lifecycleManager");
    Preconditions.checkArgument(flowControlWindow > 0, "flowControlWindow must be positive");
    Preconditions.checkArgument(maxHeaderListSize > 0, "maxHeaderListSize must be positive");
    Preconditions.checkArgument(softLimitHeaderListSize > 0,
        "softLimitHeaderListSize must be positive");
    Preconditions.checkNotNull(stopwatchFactory, "stopwatchFactory");
    Preconditions.checkNotNull(tooManyPingsRunnable, "tooManyPingsRunnable");
    Preconditions.checkNotNull(eagAttributes, "eagAttributes");
    Preconditions.checkNotNull(authority, "authority");

    Http2FrameLogger frameLogger = new Http2FrameLogger(LogLevel.DEBUG, NettyClientHandler.class);
    frameReader = new Http2InboundFrameLogger(frameReader, frameLogger);
    frameWriter = new Http2OutboundFrameLogger(frameWriter, frameLogger);

    PingCountingFrameWriter pingCounter;
    frameWriter = pingCounter = new PingCountingFrameWriter(frameWriter);

    StreamBufferingEncoder encoder =
        new StreamBufferingEncoder(
            new DefaultHttp2ConnectionEncoder(connection, frameWriter));

    // Create the local flow controller configured to auto-refill the connection window.
    connection.local().flowController(
        new DefaultHttp2LocalFlowController(connection, DEFAULT_WINDOW_UPDATE_RATIO, true));

    Http2ConnectionDecoder decoder = new DefaultHttp2ConnectionDecoder(connection, encoder,
        frameReader);

    transportTracer.setFlowControlWindowReader(new Utils.FlowControlReader(connection));

    Http2Settings settings = new Http2Settings();
    settings.pushEnabled(false);
    settings.initialWindowSize(flowControlWindow);
    settings.maxConcurrentStreams(0);
    settings.maxHeaderListSize(maxHeaderListSize);

    return new NettyClientHandler(
        decoder,
        encoder,
        settings,
        negotiationLogger,
        lifecycleManager,
        keepAliveManager,
        stopwatchFactory,
        tooManyPingsRunnable,
        transportTracer,
        eagAttributes,
        authority,
        autoFlowControl,
        pingCounter,
        ticker,
        maxHeaderListSize,
        softLimitHeaderListSize,
        metricRecorder);
  }

  @VisibleForTesting
  static SensitivityDetector sensitivityDetector(
      final Set<AsciiString> neverIndexedMetadataKeys) {
    if (neverIndexedMetadataKeys.isEmpty()) {
      return Http2HeadersEncoder.NEVER_SENSITIVE;
    }
    return new SensitivityDetector() {
      @Override
      public boolean isSensitive(CharSequence name, CharSequence value) {
        return neverIndexedMetadataKeys.contains(AsciiString.of(name));
      }
    };
  }

  private NettyClientHandler(
      Http2ConnectionDecoder decoder,
      Http2ConnectionEncoder encoder,
      Http2Settings settings,
      ChannelLogger negotiationLogger,
      ClientTransportLifecycleManager lifecycleManager,
      KeepAliveManager keepAliveManager,
      Supplier<Stopwatch> stopwatchFactory,
      final Runnable tooManyPingsRunnable,
      TransportTracer transportTracer,
      Attributes eagAttributes,
      String authority,
      boolean autoFlowControl,
      PingLimiter pingLimiter,
      Ticker ticker,
      int maxHeaderListSize,
      int softLimitHeaderListSize,
      MetricRecorder metricRecorder) {
    super(
        /* channelUnused= */ null,
        decoder,
        encoder,
        settings,
        negotiationLogger,
        autoFlowControl,
        pingLimiter,
        ticker,
        maxHeaderListSize,
        softLimitHeaderListSize);
    this.lifecycleManager = lifecycleManager;
    this.keepAliveManager = keepAliveManager;
    this.stopwatchFactory = stopwatchFactory;
    this.transportTracer = Preconditions.checkNotNull(transportTracer);
    this.eagAttributes = eagAttributes;
    this.authority = authority;
    this.attributes = Attributes.newBuilder()
        .set(GrpcAttributes.ATTR_CLIENT_EAG_ATTRS, eagAttributes).build();
    this.tcpMetrics = new TcpMetrics(metricRecorder);

    // Set the frame listener on the decoder.
    decoder().frameListener(new FrameListener());

    Http2Connection connection = encoder.connection();
    streamKey = connection.newKey();

    connection.addListener(new Http2ConnectionAdapter() {
      @Override
      public void onGoAwayReceived(int lastStreamId, long errorCode, ByteBuf debugData) {
        byte[] debugDataBytes = ByteBufUtil.getBytes(debugData);
        goingAway(errorCode, debugDataBytes);
        if (errorCode == Http2Error.ENHANCE_YOUR_CALM.code()) {
          String data = new String(debugDataBytes, UTF_8);
          logger.log(
              Level.WARNING, "Received GOAWAY with ENHANCE_YOUR_CALM. Debug data: {0}", data);
          if ("too_many_pings".equals(data)) {
            tooManyPingsRunnable.run();
          }
        }
      }

      @Override
      public void onStreamActive(Http2Stream stream) {
        if (connection().numActiveStreams() == 1
            && NettyClientHandler.this.keepAliveManager != null) {
          NettyClientHandler.this.keepAliveManager.onTransportActive();
        }
      }

      @Override
      public void onStreamClosed(Http2Stream stream) {
        // Although streams with CALL_OPTIONS_RPC_OWNED_BY_BALANCER are not marked as "in-use" in
        // the first place, we don't propagate that option here, and it's safe to reset the in-use
        // state for them, which will be a cheap no-op.
        inUseState.updateObjectInUse(stream, false);
        if (connection().numActiveStreams() == 0
            && NettyClientHandler.this.keepAliveManager != null) {
          NettyClientHandler.this.keepAliveManager.onTransportIdle();
        }
      }
    });
  }

  /**
   * The protocol negotiation attributes, available once the protocol negotiation completes;
   * otherwise returns {@code Attributes.EMPTY}.
   */
  Attributes getAttributes() {
    return attributes;
  }

  /**
   * Handler for commands sent from the stream.
   */
  @Override
  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)
          throws Exception {
    if (msg instanceof CreateStreamCommand) {
      createStream((CreateStreamCommand) msg, promise);
    } else if (msg instanceof SendGrpcFrameCommand) {
      sendGrpcFrame(ctx, (SendGrpcFrameCommand) msg, promise);
    } else if (msg instanceof CancelClientStreamCommand) {
      cancelStream(ctx, (CancelClientStreamCommand) msg, promise);
    } else if (msg instanceof SendPingCommand) {
      sendPingFrame(ctx, (SendPingCommand) msg, promise);
    } else if (msg instanceof GracefulCloseCommand) {
      gracefulClose(ctx, (GracefulCloseCommand) msg, promise);
    } else if (msg instanceof ForcefulCloseCommand) {
      forcefulClose(ctx, (ForcefulCloseCommand) msg, promise);
    } else if (msg == NOOP_MESSAGE) {
      ctx.write(Unpooled.EMPTY_BUFFER, promise);
    } else {
      throw new AssertionError("Write called for unexpected type: " + msg.getClass().getName());
    }
  }

  void startWriteQueue(Channel channel) {
    clientWriteQueue = new WriteQueue(channel);
  }

  WriteQueue getWriteQueue() {
    return clientWriteQueue;
  }

  ClientTransportLifecycleManager getLifecycleManager() {
    return lifecycleManager;
  }

  /**
   * Returns the given processed bytes back to inbound flow control.
   */
  void returnProcessedBytes(Http2Stream stream, int bytes) {
    try {
      decoder().flowController().consumeBytes(stream, bytes);
    } catch (Http2Exception e) {
      throw new RuntimeException(e);
    }
  }

  private void onHeadersRead(int streamId, Http2Headers headers, boolean endStream) {
    // Stream 1 is reserved for the Upgrade response, so we should ignore its headers here:
    if (streamId != Http2CodecUtil.HTTP_UPGRADE_STREAM_ID) {
      NettyClientStream.TransportState stream = clientStream(requireHttp2Stream(streamId));
      PerfMark.event("NettyClientHandler.onHeadersRead", stream.tag());
      // check metadata size vs soft limit
      int h2HeadersSize = Utils.getH2HeadersSize(headers);
      boolean shouldFail =
          Utils.shouldRejectOnMetadataSizeSoftLimitExceeded(
              h2HeadersSize, softLimitHeaderListSize, maxHeaderListSize);
      if (shouldFail && endStream) {
        stream.transportReportStatus(Status.RESOURCE_EXHAUSTED
            .withDescription(
                String.format(
                    "Server Status + Trailers of size %d exceeded Metadata size soft limit: %d",
                    h2HeadersSize,
                    softLimitHeaderListSize)), true, new Metadata());
        return;
      } else if (shouldFail) {
        stream.transportReportStatus(Status.RESOURCE_EXHAUSTED
            .withDescription(
                String.format(
                    "Server Headers of size %d exceeded Metadata size soft limit: %d",
                    h2HeadersSize,
                    softLimitHeaderListSize)), true, new Metadata());
        return;
      }
      stream.transportHeadersReceived(headers, endStream);
    }

    if (keepAliveManager != null) {
      keepAliveManager.onDataReceived();
    }
  }

  /**
   * Handler for an inbound HTTP/2 DATA frame.
   */
  private void onDataRead(int streamId, ByteBuf data, int padding, boolean endOfStream) {
    flowControlPing().onDataRead(data.readableBytes(), padding);
    NettyClientStream.TransportState stream = clientStream(requireHttp2Stream(streamId));
    PerfMark.event("NettyClientHandler.onDataRead", stream.tag());
    stream.transportDataReceived(data, endOfStream);
    if (keepAliveManager != null) {
      keepAliveManager.onDataReceived();
    }
  }

  /**
   * Handler for an inbound HTTP/2 RST_STREAM frame, terminating a stream.
   */
  private void onRstStreamRead(int streamId, long errorCode) {
    NettyClientStream.TransportState stream = clientStream(connection().stream(streamId));
    if (stream != null) {
      PerfMark.event("NettyClientHandler.onRstStreamRead", stream.tag());
      Status status = statusFromH2Error(null, "RST_STREAM closed stream", errorCode, null);
      stream.transportReportStatus(
          status,
          errorCode == Http2Error.REFUSED_STREAM.code()
              ? RpcProgress.REFUSED : RpcProgress.PROCESSED,
          false /*stop delivery*/,
          new Metadata());
      if (keepAliveManager != null) {
        keepAliveManager.onDataReceived();
      }
    }
  }

  @Override
  public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
    tcpMetrics.recordTcpInfo(ctx.channel());
    logger.fine("Network channel being closed by the application.");
    if (ctx.channel().isActive()) { // Ignore notification that the socket was closed
      lifecycleManager.notifyShutdown(
          Status.UNAVAILABLE.withDescription("Transport closed for unknown reason"),
          SimpleDisconnectError.UNKNOWN);
    }
    super.close(ctx, promise);
  }

  /**
   * Handler for the Channel shutting down.
   */
  @Override
  public void channelActive(ChannelHandlerContext ctx) throws Exception {
    tcpMetrics.channelActive(ctx.channel());
    super.channelActive(ctx);
  }

  @Override
  public void channelInactive(ChannelHandlerContext ctx) throws Exception {
    try {
      logger.fine("Network channel is closed");
      tcpMetrics.channelInactive(ctx.channel());
      Status status = Status.UNAVAILABLE.withDescription("Network closed for unknown reason");
      lifecycleManager.notifyShutdown(status, SimpleDisconnectError.UNKNOWN);
      final Status streamStatus;
      if (channelInactiveReason != null) {
        streamStatus = channelInactiveReason;
      } else {
        streamStatus = lifecycleManager.getShutdownStatus();
      }
      try {
        cancelPing(lifecycleManager.getShutdownStatus());
        // Report status to the application layer for any open streams
        connection().forEachActiveStream(new Http2StreamVisitor() {
          @Override
          public boolean visit(Http2Stream stream) throws Http2Exception {
            NettyClientStream.TransportState clientStream = clientStream(stream);
            if (clientStream != null) {
              clientStream.transportReportStatus(streamStatus, false, new Metadata());
            }
            return true;
          }
        });
      } finally {
        lifecycleManager.notifyTerminated(status, SimpleDisconnectError.UNKNOWN);
      }
    } finally {
      // Close any open streams
      super.channelInactive(ctx);
      if (keepAliveManager != null) {
        keepAliveManager.onTransportTermination();
      }
    }
  }

  @Override
  public void handleProtocolNegotiationCompleted(
      Attributes attributes, InternalChannelz.Security securityInfo) {
    this.attributes = this.attributes.toBuilder().setAll(attributes).build();
    this.securityInfo = securityInfo;
    super.handleProtocolNegotiationCompleted(attributes, securityInfo);
    writeBufferingAndRemove(ctx().channel());
  }

  static void writeBufferingAndRemove(Channel channel) {
    checkNotNull(channel, "channel");
    ChannelHandlerContext handlerCtx =
        channel.pipeline().context(WriteBufferingAndExceptionHandler.class);
    if (handlerCtx == null) {
      return;
    }
    ((WriteBufferingAndExceptionHandler) handlerCtx.handler()).writeBufferedAndRemove(handlerCtx);
  }

  @Override
  public Attributes getEagAttributes() {
    return eagAttributes;
  }

  @Override
  public String getAuthority() {
    return authority;
  }

  InternalChannelz.Security getSecurityInfo() {
    return securityInfo;
  }

  @Override
  protected void onConnectionError(ChannelHandlerContext ctx,  boolean outbound, Throwable cause,
      Http2Exception http2Ex) {
    logger.log(Level.FINE, "Caught a connection error", cause);
    lifecycleManager.notifyShutdown(Utils.statusFromThrowable(cause),
        SimpleDisconnectError.SOCKET_ERROR);
    // Parent class will shut down the Channel
    super.onConnectionError(ctx, outbound, cause, http2Ex);
  }

  @Override
  protected void onStreamError(ChannelHandlerContext ctx, boolean outbound, Throwable cause,
      Http2Exception.StreamException http2Ex) {
    // Close the stream with a status that contains the cause.
    NettyClientStream.TransportState stream = clientStream(connection().stream(http2Ex.streamId()));
    if (stream != null) {
      stream.transportReportStatus(Utils.statusFromThrowable(cause), false, new Metadata());
    } else {
      logger.log(Level.FINE, "Stream error for unknown stream " + http2Ex.streamId(), cause);
    }

    // Delegate to the base class to send a RST_STREAM.
    super.onStreamError(ctx, outbound, cause, http2Ex);
  }

  @Override
  protected boolean isGracefulShutdownComplete() {
    // Only allow graceful shutdown to complete after all pending streams have completed.
    return super.isGracefulShutdownComplete()
        && ((StreamBufferingEncoder) encoder()).numBufferedStreams() == 0;
  }

  /**
   * Attempts to create a new stream from the given command. If there are too many active streams,
   * the creation request is queued.
   */
  private void createStream(CreateStreamCommand command, ChannelPromise promise)
          throws Exception {
    if (lifecycleManager.getShutdownStatus() != null) {
      command.stream().setNonExistent();
      // The connection is going away (it is really the GOAWAY case),
      // just terminate the stream now.
      command.stream().transportReportStatus(
          lifecycleManager.getShutdownStatus(), RpcProgress.MISCARRIED, true, new Metadata());
      promise.setFailure(InternalStatus.asRuntimeExceptionWithoutStacktrace(
              lifecycleManager.getShutdownStatus(), null));
      return;
    }

    CharSequence authorityHeader = command.headers().authority();
    if (authorityHeader == null) {
      Status authorityVerificationStatus = Status.UNAVAILABLE.withDescription(
              "Missing authority header");
      command.stream().setNonExistent();
      command.stream().transportReportStatus(
              Status.UNAVAILABLE, RpcProgress.PROCESSED, true, new Metadata());
      promise.setFailure(InternalStatus.asRuntimeExceptionWithoutStacktrace(
              authorityVerificationStatus, null));
      return;
    }
    // No need to verify authority for the rpc outgoing header if it is same as the authority
    // for the transport
    if (!authority.contentEquals(authorityHeader)) {
      Status authorityVerificationStatus = peerVerificationResults.get(
              authorityHeader.toString());
      if (authorityVerificationStatus == null) {
        if (attributes.get(GrpcAttributes.ATTR_AUTHORITY_VERIFIER) == null) {
          authorityVerificationStatus = Status.UNAVAILABLE.withDescription(
                  "Authority verifier not found to verify authority");
          command.stream().setNonExistent();
          command.stream().transportReportStatus(
                  authorityVerificationStatus, RpcProgress.PROCESSED, true, new Metadata());
          promise.setFailure(InternalStatus.asRuntimeExceptionWithoutStacktrace(
                  authorityVerificationStatus, null));
          return;
        }
        authorityVerificationStatus = attributes.get(GrpcAttributes.ATTR_AUTHORITY_VERIFIER)
                .verifyAuthority(authorityHeader.toString());
        peerVerificationResults.put(authorityHeader.toString(), authorityVerificationStatus);
        if (!authorityVerificationStatus.isOk() && !enablePerRpcAuthorityCheck) {
          logger.log(Level.WARNING, String.format("%s.%s",
                          authorityVerificationStatus.getDescription(),
                          enablePerRpcAuthorityCheck
                                  ? "" : " This will be an error in the future."),
                  InternalStatus.asRuntimeExceptionWithoutStacktrace(
                          authorityVerificationStatus, null));
        }
      }
      if (!authorityVerificationStatus.isOk()) {
        if (enablePerRpcAuthorityCheck) {
          command.stream().setNonExistent();
          command.stream().transportReportStatus(
                  authorityVerificationStatus, RpcProgress.PROCESSED, true, new Metadata());
          promise.setFailure(InternalStatus.asRuntimeExceptionWithoutStacktrace(
                  authorityVerificationStatus, null));
          return;
        }
      }
    }
    // Get the stream ID for the new stream.
    int streamId;
    try {
      streamId = incrementAndGetNextStreamId();
    } catch (StatusException e) {
      command.stream().setNonExistent();
      // Stream IDs have been exhausted for this connection. Fail the promise immediately.
      promise.setFailure(e);

      // Initiate a graceful shutdown if we haven't already.
      if (!connection().goAwaySent()) {
        logger.fine("Stream IDs have been exhausted for this connection. "
                + "Initiating graceful shutdown of the connection.");
        lifecycleManager.notifyShutdown(e.getStatus(), SimpleDisconnectError.UNKNOWN);
        close(ctx(), ctx().newPromise());
      }
      return;
    }
    if (connection().goAwayReceived()) {
      Status s = abruptGoAwayStatus;
      int maxActiveStreams = connection().local().maxActiveStreams();
      int lastStreamId = connection().local().lastStreamKnownByPeer();
      if (s == null) {
        // Should be impossible, but handle pseudo-gracefully
        s = Status.INTERNAL.withDescription(
            "Failed due to abrupt GOAWAY, but can't find GOAWAY details");
      } else if (streamId > lastStreamId) {
        s = s.augmentDescription(
            "stream id: " + streamId + ", GOAWAY Last-Stream-ID:" + lastStreamId);
      } else if (connection().local().numActiveStreams() == maxActiveStreams) {
        s = s.augmentDescription("At MAX_CONCURRENT_STREAMS limit. limit: " + maxActiveStreams);
      }
      if (streamId > lastStreamId || connection().local().numActiveStreams() == maxActiveStreams) {
        // This should only be reachable during onGoAwayReceived, as otherwise
        // getShutdownThrowable() != null
        command.stream().setNonExistent();
        command.stream().transportReportStatus(s, RpcProgress.MISCARRIED, true, new Metadata());
        promise.setFailure(s.asRuntimeException());
        return;
      }
    }

    NettyClientStream.TransportState stream = command.stream();
    Http2Headers headers = command.headers();
    stream.setId(streamId);

    try (TaskCloseable ignore = PerfMark.traceTask("NettyClientHandler.createStream")) {
      PerfMark.linkIn(command.getLink());
      PerfMark.attachTag(stream.tag());
      createStreamTraced(
          streamId, stream, headers, command.isGet(), command.shouldBeCountedForInUse(), promise);
    }
  }

  private void createStreamTraced(
      final int streamId,
      final NettyClientStream.TransportState stream,
      final Http2Headers headers,
      boolean isGet,
      final boolean shouldBeCountedForInUse,
      final ChannelPromise promise) {
    // Create an intermediate promise so that we can intercept the failure reported back to the
    // application.
    ChannelPromise tempPromise = ctx().newPromise();
    encoder().writeHeaders(ctx(), streamId, headers, 0, isGet, tempPromise)
        .addListener(new ChannelFutureListener() {
          @Override
          public void operationComplete(ChannelFuture future) throws Exception {
            if (future.isSuccess()) {
              // The http2Stream will be null in case a stream buffered in the encoder
              // was canceled via RST_STREAM.
              Http2Stream http2Stream = connection().stream(streamId);
              if (http2Stream != null) {
                stream.getStatsTraceContext().clientOutboundHeaders();
                http2Stream.setProperty(streamKey, stream);

                // This delays the in-use state until the I/O completes, which technically may
                // be later than we would like.
                if (shouldBeCountedForInUse) {
                  inUseState.updateObjectInUse(http2Stream, true);
                }

                // Attach the client stream to the HTTP/2 stream object as user data.
                stream.setHttp2Stream(http2Stream);
                promise.setSuccess();
              } else {
                // Otherwise, the stream has been cancelled and Netty is sending a
                // RST_STREAM frame which causes it to purge pending writes from the
                // flow-controller and delete the http2Stream. The stream listener has already
                // been notified of cancellation so there is nothing to do.
                //
                // This process has been observed to fail in some circumstances, leaving listeners
                // unanswered. Ensure that some exception has been delivered consistent with the
                // implied RST_STREAM result above.
                Status status = Status.INTERNAL.withDescription("unknown stream for connection");
                promise.setFailure(status.asRuntimeException());
              }
            } else {
              Throwable cause = future.cause();
              if (cause instanceof StreamBufferingEncoder.Http2GoAwayException) {
                StreamBufferingEncoder.Http2GoAwayException e =
                    (StreamBufferingEncoder.Http2GoAwayException) cause;
                Status status = statusFromH2Error(
                    Status.Code.UNAVAILABLE, "GOAWAY closed buffered stream",
                    e.errorCode(), e.debugData());
                cause = status.asRuntimeException();
                stream.transportReportStatus(status, RpcProgress.MISCARRIED, true, new Metadata());
              } else if (cause instanceof StreamBufferingEncoder.Http2ChannelClosedException) {
                Status status = lifecycleManager.getShutdownStatus();
                if (status == null) {
                  status = Status.UNAVAILABLE.withCause(cause)
                      .withDescription("Connection closed while stream is buffered");
                }
                stream.transportReportStatus(status, RpcProgress.MISCARRIED, true, new Metadata());
              }
              promise.setFailure(cause);
            }
          }
        });
    // When the HEADERS are not buffered because of MAX_CONCURRENT_STREAMS in
    // StreamBufferingEncoder, the stream is created immediately even if the bytes of the HEADERS
    // are delayed because the OS may have too much buffered and isn't accepting the write. The
    // write promise is also delayed until flush(). However, we need to associate the netty stream
    // with the transport state so that goingAway() and forcefulClose() and able to notify the
    // stream of failures.
    //
    // This leaves a hole when MAX_CONCURRENT_STREAMS is reached, as http2Stream will be null, but
    // it is better than nothing.
    Http2Stream http2Stream = connection().stream(streamId);
    if (http2Stream != null) {
      http2Stream.setProperty(streamKey, stream);
    }
  }

  /**
   * Cancels this stream.
   */
  private void cancelStream(ChannelHandlerContext ctx, CancelClientStreamCommand cmd,
      ChannelPromise promise) {
    NettyClientStream.TransportState stream = cmd.stream();
    try (TaskCloseable ignore = PerfMark.traceTask("NettyClientHandler.cancelStream")) {
      PerfMark.attachTag(stream.tag());
      PerfMark.linkIn(cmd.getLink());
      Status reason = cmd.reason();
      if (reason != null) {
        stream.transportReportStatus(reason, true, new Metadata());
      }
      if (!cmd.stream().isNonExistent()) {
        encoder().writeRstStream(ctx, stream.id(), Http2Error.CANCEL.code(), promise);
      } else {
        promise.setSuccess();
      }
    }
  }

  /**
   * Sends the given GRPC frame for the stream.
   */
  private void sendGrpcFrame(ChannelHandlerContext ctx, SendGrpcFrameCommand cmd,
      ChannelPromise promise) {
    try (TaskCloseable ignore = PerfMark.traceTask("NettyClientHandler.sendGrpcFrame")) {
      PerfMark.attachTag(cmd.stream().tag());
      PerfMark.linkIn(cmd.getLink());
      // Call the base class to write the HTTP/2 DATA frame.
      // Note: no need to flush since this is handled by the outbound flow controller.
      encoder().writeData(ctx, cmd.stream().id(), cmd.content(), 0, cmd.endStream(), promise);
    }
  }

  private void sendPingFrame(ChannelHandlerContext ctx, SendPingCommand msg,
      ChannelPromise promise) {
    try (TaskCloseable ignore = PerfMark.traceTask("NettyClientHandler.sendPingFrame")) {
      PerfMark.linkIn(msg.getLink());
      sendPingFrameTraced(ctx, msg, promise);
    }
  }

  /**
   * Sends a PING frame. If a ping operation is already outstanding, the callback in the message is
   * registered to be called when the existing operation completes, and no new frame is sent.
   */
  private void sendPingFrameTraced(ChannelHandlerContext ctx, SendPingCommand msg,
      ChannelPromise promise) {
    // Don't check lifecycleManager.getShutdownStatus() since we want to allow pings after shutdown
    // but before termination. After termination, messages will no longer arrive because the
    // pipeline clears all handlers on channel close.

    PingCallback callback = msg.callback();
    Executor executor = msg.executor();
    // we only allow one outstanding ping at a time, so just add the callback to
    // any outstanding operation
    if (ping != null) {
      promise.setSuccess();
      ping.addCallback(callback, executor);
      return;
    }

    // Use a new promise to prevent calling the callback twice on write failure: here and in
    // NettyClientTransport.ping(). It may appear strange, but it will behave the same as if
    // ping != null above.
    promise.setSuccess();
    promise = ctx().newPromise();
    // set outstanding operation
    long data = USER_PING_PAYLOAD;
    Stopwatch stopwatch = stopwatchFactory.get();
    stopwatch.start();
    ping = new Http2Ping(data, stopwatch);
    ping.addCallback(callback, executor);
    // and then write the ping
    encoder().writePing(ctx, false, USER_PING_PAYLOAD, promise);
    ctx.flush();
    final Http2Ping finalPing = ping;
    promise.addListener(new ChannelFutureListener() {
      @Override
      public void operationComplete(ChannelFuture future) throws Exception {
        if (future.isSuccess()) {
          transportTracer.reportKeepAliveSent();
          return;
        }
        Throwable cause = future.cause();
        Status status = lifecycleManager.getShutdownStatus();
        if (cause instanceof ClosedChannelException) {
          if (status == null) {
            status = Status.UNKNOWN.withDescription("Ping failed but for unknown reason.")
                    .withCause(future.cause());
          }
        } else {
          status = Utils.statusFromThrowable(cause);
        }
        finalPing.failed(status);
        if (ping == finalPing) {
          ping = null;
        }
      }
    });
  }

  private void gracefulClose(ChannelHandlerContext ctx, GracefulCloseCommand msg,
      ChannelPromise promise) throws Exception {
    lifecycleManager.notifyShutdown(msg.getStatus(), SimpleDisconnectError.SUBCHANNEL_SHUTDOWN);
    // Explicitly flush to create any buffered streams before sending GOAWAY.
    // TODO(ejona): determine if the need to flush is a bug in Netty
    flush(ctx);
    close(ctx, promise);
  }

  private void forcefulClose(final ChannelHandlerContext ctx, final ForcefulCloseCommand msg,
      ChannelPromise promise) throws Exception {
    connection().forEachActiveStream(new Http2StreamVisitor() {
      @Override
      public boolean visit(Http2Stream stream) throws Http2Exception {
        NettyClientStream.TransportState clientStream = clientStream(stream);
        Tag tag = clientStream != null ? clientStream.tag() : PerfMark.createTag();
        try (TaskCloseable ignore = PerfMark.traceTask("NettyClientHandler.forcefulClose")) {
          PerfMark.linkIn(msg.getLink());
          PerfMark.attachTag(tag);
          if (clientStream != null) {
            clientStream.transportReportStatus(msg.getStatus(), true, new Metadata());
            resetStream(ctx, stream.id(), Http2Error.CANCEL.code(), ctx.newPromise());
          }
          stream.close();
          return true;
        }
      }
    });
    close(ctx, promise);
  }

  /**
   * Handler for a GOAWAY being received. Fails any streams created after the
   * last known stream. May only be called during a read.
   */
  private void goingAway(long errorCode, byte[] debugData) {
    Status finalStatus = statusFromH2Error(
        Status.Code.UNAVAILABLE, "GOAWAY shut down transport", errorCode, debugData);
    DisconnectError disconnectError = new GoAwayDisconnectError(
        GrpcUtil.Http2Error.forCode(errorCode));
    lifecycleManager.notifyGracefulShutdown(finalStatus, disconnectError);
    abruptGoAwayStatus = statusFromH2Error(
        Status.Code.UNAVAILABLE, "Abrupt GOAWAY closed unsent stream", errorCode, debugData);
    // While this _should_ be UNAVAILABLE, Netty uses the wrong stream id in the GOAWAY when it
    // fails streams due to HPACK failures (e.g., header list too large). To be more conservative,
    // we assume any sent streams may be related to the GOAWAY. This should rarely impact users
    // since the main time servers should use abrupt GOAWAYs if there is a protocol error, and if
    // there wasn't a protocol error the error code was probably NO_ERROR which is mapped to
    // UNAVAILABLE. https://github.com/netty/netty/issues/10670
    final Status abruptGoAwayStatusConservative = statusFromH2Error(
        null, "Abrupt GOAWAY closed sent stream", errorCode, debugData);
    final boolean mayBeHittingNettyBug = errorCode != Http2Error.NO_ERROR.code();
    // Try to allocate as many in-flight streams as possible, to reduce race window of
    // https://github.com/grpc/grpc-java/issues/2562 . To be of any help, the server has to
    // gracefully shut down the connection with two GOAWAYs. gRPC servers generally send a PING
    // after the first GOAWAY, so they can very precisely detect when the GOAWAY has been
    // processed and thus this processing must be in-line before processing additional reads.

    // This can cause reentrancy, but should be minor since it is normal to handle writes in
    // response to a read. Also, the call stack is rather shallow at this point
    clientWriteQueue.drainNow();
    if (lifecycleManager.notifyShutdown(finalStatus, disconnectError)) {
      // This is for the only RPCs that are actually covered by the GOAWAY error code. All other
      // RPCs were not observed by the remote and so should be UNAVAILABLE.
      channelInactiveReason = statusFromH2Error(
          null, "Connection closed after GOAWAY", errorCode, debugData);
    }

    final int lastKnownStream = connection().local().lastStreamKnownByPeer();
    try {
      connection().forEachActiveStream(new Http2StreamVisitor() {
        @Override
        public boolean visit(Http2Stream stream) throws Http2Exception {
          if (stream.id() > lastKnownStream) {
            NettyClientStream.TransportState clientStream = clientStream(stream);
            if (clientStream != null) {
              // RpcProgress _should_ be REFUSED, but are being conservative. See comment for
              // abruptGoAwayStatusConservative. This does reduce our ability to perform transparent
              // retries, but only if something else caused a connection failure.
              RpcProgress progress = mayBeHittingNettyBug
                  ? RpcProgress.PROCESSED
                  : RpcProgress.REFUSED;
              clientStream.transportReportStatus(
                  abruptGoAwayStatusConservative, progress, false, new Metadata());
            }
            stream.close();
          }
          return true;
        }
      });
    } catch (Http2Exception e) {
      throw new RuntimeException(e);
    }
  }

  private void cancelPing(Status s) {
    if (ping != null) {
      ping.failed(s);
      ping = null;
    }
  }

  /** If {@code statusCode} is non-null, it will be used instead of the http2 error code mapping. */
  private Status statusFromH2Error(
      Status.Code statusCode, String context, long errorCode, byte[] debugData) {
    Status status = GrpcUtil.Http2Error.statusForCode(errorCode);
    if (statusCode == null) {
      statusCode = status.getCode();
    }
    String debugString = "";
    if (debugData != null && debugData.length > 0) {
      // If a debug message was provided, use it.
      debugString = ", debug data: " + new String(debugData, UTF_8);
    }
    return statusCode.toStatus()
        .withDescription(context + ". " + status.getDescription() + debugString);
  }

  /**
   * Gets the client stream associated to the given HTTP/2 stream object.
   */
  private NettyClientStream.TransportState clientStream(Http2Stream stream) {
    return stream == null ? null : (NettyClientStream.TransportState) stream.getProperty(streamKey);
  }

  private int incrementAndGetNextStreamId() throws StatusException {
    int nextStreamId = connection().local().incrementAndGetNextStreamId();
    if (nextStreamId < 0) {
      logger.fine("Stream IDs have been exhausted for this connection. "
              + "Initiating graceful shutdown of the connection.");
      throw EXHAUSTED_STREAMS_STATUS.asException();
    }
    return nextStreamId;
  }

  private Http2Stream requireHttp2Stream(int streamId) {
    Http2Stream stream = connection().stream(streamId);
    if (stream == null) {
      // This should never happen.
      throw new AssertionError("Stream does not exist: " + streamId);
    }
    return stream;
  }

  private class FrameListener extends Http2FrameAdapter {
    private boolean firstSettings = true;

    @Override
    public void onSettingsRead(ChannelHandlerContext ctx, Http2Settings settings) {
      if (firstSettings) {
        firstSettings = false;
        attributes = lifecycleManager.filterAttributes(attributes);
        lifecycleManager.notifyReady();
      }
    }

    @Override
    public int onDataRead(ChannelHandlerContext ctx, int streamId, ByteBuf data, int padding,
        boolean endOfStream) throws Http2Exception {
      NettyClientHandler.this.onDataRead(streamId, data, padding, endOfStream);
      return padding;
    }

    @Override
    public void onHeadersRead(ChannelHandlerContext ctx,
        int streamId,
        Http2Headers headers,
        int streamDependency,
        short weight,
        boolean exclusive,
        int padding,
        boolean endStream) throws Http2Exception {
      NettyClientHandler.this.onHeadersRead(streamId, headers, endStream);
    }

    @Override
    public void onRstStreamRead(ChannelHandlerContext ctx, int streamId, long errorCode)
        throws Http2Exception {
      NettyClientHandler.this.onRstStreamRead(streamId, errorCode);
    }

    @Override
    public void onPingAckRead(ChannelHandlerContext ctx, long ackPayload) throws Http2Exception {
      Http2Ping p = ping;
      if (ackPayload == flowControlPing().payload()) {
        flowControlPing().updateWindow();
        logger.log(Level.FINE, "Window: {0}",
            decoder().flowController().initialWindowSize(connection().connectionStream()));
      } else if (p != null) {
        if (p.payload() == ackPayload) {
          p.complete();
          ping = null;
        } else {
          logger.log(Level.WARNING,
              "Received unexpected ping ack. Expecting {0}, got {1}",
              new Object[] {p.payload(), ackPayload});
        }
      } else {
        logger.warning("Received unexpected ping ack. No ping outstanding");
      }
      if (keepAliveManager != null) {
        keepAliveManager.onDataReceived();
      }
    }

    @Override
    public void onPingRead(ChannelHandlerContext ctx, long data) throws Http2Exception {
      if (keepAliveManager != null) {
        keepAliveManager.onDataReceived();
      }
    }
  }

  private static class PingCountingFrameWriter extends DecoratingHttp2FrameWriter
      implements AbstractNettyHandler.PingLimiter {
    private int pingCount;

    public PingCountingFrameWriter(Http2FrameWriter delegate) {
      super(delegate);
    }

    @Override
    public boolean isPingAllowed() {
      // "3 strikes" may cause the server to complain, so we limit ourselves to 2 or below.
      return pingCount < 2;
    }

    @Override
    public ChannelFuture writeHeaders(
        ChannelHandlerContext ctx, int streamId, Http2Headers headers,
        int padding, boolean endStream, ChannelPromise promise) {
      pingCount = 0;
      return super.writeHeaders(ctx, streamId, headers, padding, endStream, promise);
    }

    @Override
    public ChannelFuture writeHeaders(
        ChannelHandlerContext ctx, int streamId, Http2Headers headers,
        int streamDependency, short weight, boolean exclusive,
        int padding, boolean endStream, ChannelPromise promise) {
      pingCount = 0;
      return super.writeHeaders(ctx, streamId, headers, streamDependency, weight, exclusive,
          padding, endStream, promise);
    }

    @Override
    public ChannelFuture writeWindowUpdate(
        ChannelHandlerContext ctx, int streamId, int windowSizeIncrement, ChannelPromise promise) {
      pingCount = 0;
      return super.writeWindowUpdate(ctx, streamId, windowSizeIncrement, promise);
    }

    @Override
    public ChannelFuture writePing(
        ChannelHandlerContext ctx, boolean ack, long data, ChannelPromise promise) {
      if (!ack) {
        pingCount++;
      }
      return super.writePing(ctx, ack, data, promise);
    }

    @Override
    public ChannelFuture writeData(
        ChannelHandlerContext ctx, int streamId, ByteBuf data, int padding, boolean endStream,
        ChannelPromise promise) {
      if (data.isReadable()) {
        pingCount = 0;
      }
      return super.writeData(ctx, streamId, data, padding, endStream, promise);
    }
  }
}

grpc / grpc-java / #20414

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