#19653

Committed 18 Jan 2025 01:16AM CUT coverage: 88.576% (+0.006%) from 88.57%

Build # #19653

Build Type

push

github

Committed by

ejona86

Commit Message

xds: Rename grpc.xds.cluster to grpc.lb.backend_service

The name is being changed to allow the value to be used in more metrics
where xds-specifics are awkward.

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33719 of 38068 relevant lines covered (88.58%)

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/../core/src/main/java/io/grpc/internal/DelayedClientTransport.java

/*
 * Copyright 2015 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.internal;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import io.grpc.CallOptions;
import io.grpc.ClientStreamTracer;
import io.grpc.Context;
import io.grpc.InternalChannelz.SocketStats;
import io.grpc.InternalLogId;
import io.grpc.LoadBalancer.PickResult;
import io.grpc.LoadBalancer.PickSubchannelArgs;
import io.grpc.LoadBalancer.SubchannelPicker;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import io.grpc.Status;
import io.grpc.SynchronizationContext;
import io.grpc.internal.ClientStreamListener.RpcProgress;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.concurrent.Executor;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;

/**
 * A client transport that queues requests before a real transport is available. When {@link
 * #reprocess} is called, this class applies the provided {@link SubchannelPicker} to pick a
 * transport for each pending stream.
 *
 * <p>This transport owns every stream that it has created until a real transport has been picked
 * for that stream, at which point the ownership of the stream is transferred to the real transport,
 * thus the delayed transport stops owning the stream.
 */
final class DelayedClientTransport implements ManagedClientTransport {
  // lazily allocated, since it is infrequently used.
  private final InternalLogId logId =
      InternalLogId.allocate(DelayedClientTransport.class, /*details=*/ null);

  private final Object lock = new Object();

  private final Executor defaultAppExecutor;
  private final SynchronizationContext syncContext;

  private Runnable reportTransportInUse;
  private Runnable reportTransportNotInUse;
  private Runnable reportTransportTerminated;
  private Listener listener;

  @Nonnull
  @GuardedBy("lock")
  private Collection<PendingStream> pendingStreams = new LinkedHashSet<>();

  /** Immutable state needed for picking. 'lock' must be held for writing. */
  private volatile PickerState pickerState = new PickerState(null, null);

  /**
   * Creates a new delayed transport.
   *
   * @param defaultAppExecutor pending streams will create real streams and run buffered operations
   *        in an application executor, which will be this executor, unless there is on provided in
   *        {@link CallOptions}.
   * @param syncContext all listener callbacks of the delayed transport will be run from this
   *        SynchronizationContext.
   */
  DelayedClientTransport(Executor defaultAppExecutor, SynchronizationContext syncContext) {
    this.defaultAppExecutor = defaultAppExecutor;
    this.syncContext = syncContext;
  }

  @Override
  public final Runnable start(final Listener listener) {
    this.listener = listener;
    reportTransportInUse = new Runnable() {
        @Override
        public void run() {
          listener.transportInUse(true);
        }
      };
    reportTransportNotInUse = new Runnable() {
        @Override
        public void run() {
          listener.transportInUse(false);
        }
      };
    reportTransportTerminated = new Runnable() {
        @Override
        public void run() {
          listener.transportTerminated();
        }
      };
    return null;
  }

  /**
   * If a {@link SubchannelPicker} is being, or has been provided via {@link #reprocess}, the last
   * picker will be consulted.
   *
   * <p>Otherwise, if the delayed transport is not shutdown, then a {@link PendingStream} is
   * returned; if the transport is shutdown, then a {@link FailingClientStream} is returned.
   */
  @Override
  public final ClientStream newStream(
      MethodDescriptor<?, ?> method, Metadata headers, CallOptions callOptions,
      ClientStreamTracer[] tracers) {
    try {
      PickSubchannelArgs args = new PickSubchannelArgsImpl(
          method, headers, callOptions, new PickDetailsConsumerImpl(tracers));
      PickerState state = pickerState;
      while (true) {
        if (state.shutdownStatus != null) {
          return new FailingClientStream(state.shutdownStatus, tracers);
        }
        if (state.lastPicker != null) {
          PickResult pickResult = state.lastPicker.pickSubchannel(args);
          callOptions = args.getCallOptions();
          // User code provided authority takes precedence over the LB provided one.
          if (callOptions.getAuthority() == null
              && pickResult.getAuthorityOverride() != null) {
            callOptions = callOptions.withAuthority(pickResult.getAuthorityOverride());
          }
          ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult,
              callOptions.isWaitForReady());
          if (transport != null) {
            return transport.newStream(
                args.getMethodDescriptor(), args.getHeaders(), callOptions,
                tracers);
          }
        }
        // This picker's conclusion is "buffer".  If there hasn't been a newer picker set (possible
        // race with reprocess()), we will buffer the RPC.  Otherwise, will try with the new picker.
        synchronized (lock) {
          PickerState newerState = pickerState;
          if (state == newerState) {
            return createPendingStream(args, tracers);
          }
          state = newerState;
        }
      }
    } finally {
      syncContext.drain();
    }
  }

  /**
   * Caller must call {@code syncContext.drain()} outside of lock because this method may
   * schedule tasks on syncContext.
   */
  @GuardedBy("lock")
  private PendingStream createPendingStream(
      PickSubchannelArgs args, ClientStreamTracer[] tracers) {
    PendingStream pendingStream = new PendingStream(args, tracers);
    pendingStreams.add(pendingStream);
    if (getPendingStreamsCount() == 1) {
      syncContext.executeLater(reportTransportInUse);
    }
    for (ClientStreamTracer streamTracer : tracers) {
      streamTracer.createPendingStream();
    }
    return pendingStream;
  }

  @Override
  public final void ping(final PingCallback callback, Executor executor) {
    throw new UnsupportedOperationException("This method is not expected to be called");
  }

  @Override
  public ListenableFuture<SocketStats> getStats() {
    SettableFuture<SocketStats> ret = SettableFuture.create();
    ret.set(null);
    return ret;
  }

  /**
   * Prevents creating any new streams.  Buffered streams are not failed and may still proceed
   * when {@link #reprocess} is called.  The delayed transport will be terminated when there is no
   * more buffered streams.
   */
  @Override
  public final void shutdown(final Status status) {
    synchronized (lock) {
      if (pickerState.shutdownStatus != null) {
        return;
      }
      pickerState = pickerState.withShutdownStatus(status);
      syncContext.executeLater(new Runnable() {
          @Override
          public void run() {
            listener.transportShutdown(status);
          }
        });
      if (!hasPendingStreams() && reportTransportTerminated != null) {
        syncContext.executeLater(reportTransportTerminated);
        reportTransportTerminated = null;
      }
    }
    syncContext.drain();
  }

  /**
   * Shuts down this transport and cancels all streams that it owns, hence immediately terminates
   * this transport.
   */
  @Override
  public final void shutdownNow(Status status) {
    shutdown(status);
    Collection<PendingStream> savedPendingStreams;
    Runnable savedReportTransportTerminated;
    synchronized (lock) {
      savedPendingStreams = pendingStreams;
      savedReportTransportTerminated = reportTransportTerminated;
      reportTransportTerminated = null;
      if (!pendingStreams.isEmpty()) {
        pendingStreams = Collections.emptyList();
      }
    }
    if (savedReportTransportTerminated != null) {
      for (PendingStream stream : savedPendingStreams) {
        Runnable runnable = stream.setStream(
            new FailingClientStream(status, RpcProgress.REFUSED, stream.tracers));
        if (runnable != null) {
          // Drain in-line instead of using an executor as failing stream just throws everything
          // away. This is essentially the same behavior as DelayedStream.cancel() but can be done
          // before stream.start().
          runnable.run();
        }
      }
      syncContext.execute(savedReportTransportTerminated);
    }
    // If savedReportTransportTerminated == null, transportTerminated() has already been called in
    // shutdown().
  }

  public final boolean hasPendingStreams() {
    synchronized (lock) {
      return !pendingStreams.isEmpty();
    }
  }

  @VisibleForTesting
  final int getPendingStreamsCount() {
    synchronized (lock) {
      return pendingStreams.size();
    }
  }

  /**
   * Use the picker to try picking a transport for every pending stream, proceed the stream if the
   * pick is successful, otherwise keep it pending.
   *
   * <p>This method may be called concurrently with {@code newStream()}, and it's safe.  All pending
   * streams will be served by the latest picker (if a same picker is given more than once, they are
   * considered different pickers) as soon as possible.
   *
   * <p>This method <strong>must not</strong> be called concurrently with itself.
   */
  final void reprocess(@Nullable SubchannelPicker picker) {
    ArrayList<PendingStream> toProcess;
    synchronized (lock) {
      pickerState = pickerState.withPicker(picker);
      if (picker == null || !hasPendingStreams()) {
        return;
      }
      toProcess = new ArrayList<>(pendingStreams);
    }
    ArrayList<PendingStream> toRemove = new ArrayList<>();

    for (final PendingStream stream : toProcess) {
      PickResult pickResult = picker.pickSubchannel(stream.args);
      CallOptions callOptions = stream.args.getCallOptions();
      // User code provided authority takes precedence over the LB provided one.
      if (callOptions.getAuthority() == null && pickResult.getAuthorityOverride() != null) {
        stream.setAuthority(pickResult.getAuthorityOverride());
      }
      final ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult,
          callOptions.isWaitForReady());
      if (transport != null) {
        Executor executor = defaultAppExecutor;
        // createRealStream may be expensive. It will start real streams on the transport. If
        // there are pending requests, they will be serialized too, which may be expensive. Since
        // we are now on transport thread, we need to offload the work to an executor.
        if (callOptions.getExecutor() != null) {
          executor = callOptions.getExecutor();
        }
        Runnable runnable = stream.createRealStream(transport);
        if (runnable != null) {
          executor.execute(runnable);
        }
        toRemove.add(stream);
      }  // else: stay pending
    }

    synchronized (lock) {
      // Between this synchronized and the previous one:
      //   - Streams may have been cancelled, which may turn pendingStreams into emptiness.
      //   - shutdown() may be called, which may turn pendingStreams into null.
      if (!hasPendingStreams()) {
        return;
      }
      pendingStreams.removeAll(toRemove);
      // Because delayed transport is long-lived, we take this opportunity to down-size the
      // hashmap.
      if (pendingStreams.isEmpty()) {
        pendingStreams = new LinkedHashSet<>();
      }
      if (!hasPendingStreams()) {
        // There may be a brief gap between delayed transport clearing in-use state, and first real
        // transport starting streams and setting in-use state.  During the gap the whole channel's
        // in-use state may be false. However, it shouldn't cause spurious switching to idleness
        // (which would shutdown the transports and LoadBalancer) because the gap should be shorter
        // than IDLE_MODE_DEFAULT_TIMEOUT_MILLIS (1 second).
        syncContext.executeLater(reportTransportNotInUse);
        if (pickerState.shutdownStatus != null && reportTransportTerminated != null) {
          syncContext.executeLater(reportTransportTerminated);
          reportTransportTerminated = null;
        }
      }
    }
    syncContext.drain();
  }

  @Override
  public InternalLogId getLogId() {
    return logId;
  }

  private class PendingStream extends DelayedStream {
    private final PickSubchannelArgs args;
    private final Context context = Context.current();
    private final ClientStreamTracer[] tracers;

    private PendingStream(PickSubchannelArgs args, ClientStreamTracer[] tracers) {
      this.args = args;
      this.tracers = tracers;
    }

    /** Runnable may be null. */
    private Runnable createRealStream(ClientTransport transport) {
      ClientStream realStream;
      Context origContext = context.attach();
      try {
        realStream = transport.newStream(
            args.getMethodDescriptor(), args.getHeaders(), args.getCallOptions(),
            tracers);
      } finally {
        context.detach(origContext);
      }
      return setStream(realStream);
    }

    @Override
    public void cancel(Status reason) {
      super.cancel(reason);
      synchronized (lock) {
        if (reportTransportTerminated != null) {
          boolean justRemovedAnElement = pendingStreams.remove(this);
          if (!hasPendingStreams() && justRemovedAnElement) {
            syncContext.executeLater(reportTransportNotInUse);
            if (pickerState.shutdownStatus != null) {
              syncContext.executeLater(reportTransportTerminated);
              reportTransportTerminated = null;
            }
          }
        }
      }
      syncContext.drain();
    }

    @Override
    protected void onEarlyCancellation(Status reason) {
      for (ClientStreamTracer tracer : tracers) {
        tracer.streamClosed(reason);
      }
    }

    @Override
    public void appendTimeoutInsight(InsightBuilder insight) {
      if (args.getCallOptions().isWaitForReady()) {
        insight.append("wait_for_ready");
      }
      super.appendTimeoutInsight(insight);
    }
  }

  static final class PickerState {
    /**
     * The last picker that {@link #reprocess} has used. May be set to null when the channel has
     * moved to idle.
     */
    @Nullable
    final SubchannelPicker lastPicker;
    /**
     * When {@code shutdownStatus != null && !hasPendingStreams()}, then the transport is considered
     * terminated.
     */
    @Nullable
    final Status shutdownStatus;

    private PickerState(SubchannelPicker lastPicker, Status shutdownStatus) {
      this.lastPicker = lastPicker;
      this.shutdownStatus = shutdownStatus;
    }

    public PickerState withPicker(SubchannelPicker newPicker) {
      return new PickerState(newPicker, this.shutdownStatus);
    }

    public PickerState withShutdownStatus(Status newShutdownStatus) {
      return new PickerState(this.lastPicker, newShutdownStatus);
    }
  }
}

1	/*
2	* Copyright 2015 The gRPC Authors
3	*
4	* Licensed under the Apache License, Version 2.0 (the "License");
5	* you may not use this file except in compliance with the License.
6	* You may obtain a copy of the License at
7	*
8	* http://www.apache.org/licenses/LICENSE-2.0
9	*
10	* Unless required by applicable law or agreed to in writing, software
11	* distributed under the License is distributed on an "AS IS" BASIS,
12	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13	* See the License for the specific language governing permissions and
14	* limitations under the License.
15	*/
16
17	package io.grpc.internal;
18
19	import com.google.common.annotations.VisibleForTesting;
20	import com.google.common.util.concurrent.ListenableFuture;
21	import com.google.common.util.concurrent.SettableFuture;
22	import com.google.errorprone.annotations.concurrent.GuardedBy;
23	import io.grpc.CallOptions;
24	import io.grpc.ClientStreamTracer;
25	import io.grpc.Context;
26	import io.grpc.InternalChannelz.SocketStats;
27	import io.grpc.InternalLogId;
28	import io.grpc.LoadBalancer.PickResult;
29	import io.grpc.LoadBalancer.PickSubchannelArgs;
30	import io.grpc.LoadBalancer.SubchannelPicker;
31	import io.grpc.Metadata;
32	import io.grpc.MethodDescriptor;
33	import io.grpc.Status;
34	import io.grpc.SynchronizationContext;
35	import io.grpc.internal.ClientStreamListener.RpcProgress;
36	import java.util.ArrayList;
37	import java.util.Collection;
38	import java.util.Collections;
39	import java.util.LinkedHashSet;
40	import java.util.concurrent.Executor;
41	import javax.annotation.Nonnull;
42	import javax.annotation.Nullable;
43
44	/**
45	* A client transport that queues requests before a real transport is available. When {@link
46	* #reprocess} is called, this class applies the provided {@link SubchannelPicker} to pick a
47	* transport for each pending stream.
48	*
49	* <p>This transport owns every stream that it has created until a real transport has been picked
50	* for that stream, at which point the ownership of the stream is transferred to the real transport,
51	* thus the delayed transport stops owning the stream.
52	*/
53	final class DelayedClientTransport implements ManagedClientTransport {
54	// lazily allocated, since it is infrequently used.
55	private final InternalLogId logId =	1✔
56	InternalLogId.allocate(DelayedClientTransport.class, /details=/ null);	1✔
57
58	private final Object lock = new Object();	1✔
59
60	private final Executor defaultAppExecutor;
61	private final SynchronizationContext syncContext;
62
63	private Runnable reportTransportInUse;
64	private Runnable reportTransportNotInUse;
65	private Runnable reportTransportTerminated;
66	private Listener listener;
67
68	@Nonnull	1✔
69	@GuardedBy("lock")
70	private Collection<PendingStream> pendingStreams = new LinkedHashSet<>();
71
72	/** Immutable state needed for picking. 'lock' must be held for writing. */
73	private volatile PickerState pickerState = new PickerState(null, null);	1✔
74
75	/**
76	* Creates a new delayed transport.
77	*
78	* @param defaultAppExecutor pending streams will create real streams and run buffered operations
79	* in an application executor, which will be this executor, unless there is on provided in
80	* {@link CallOptions}.
81	* @param syncContext all listener callbacks of the delayed transport will be run from this
82	* SynchronizationContext.
83	*/
84	DelayedClientTransport(Executor defaultAppExecutor, SynchronizationContext syncContext) {	1✔
85	this.defaultAppExecutor = defaultAppExecutor;	1✔
86	this.syncContext = syncContext;	1✔
87	}	1✔
88
89	@Override
90	public final Runnable start(final Listener listener) {
91	this.listener = listener;	1✔
92	reportTransportInUse = new Runnable() {	1✔
93	@Override
94	public void run() {
95	listener.transportInUse(true);	1✔
96	}	1✔
97	};
98	reportTransportNotInUse = new Runnable() {	1✔
99	@Override
100	public void run() {
101	listener.transportInUse(false);	1✔
102	}	1✔
103	};
104	reportTransportTerminated = new Runnable() {	1✔
105	@Override
106	public void run() {
107	listener.transportTerminated();	1✔
108	}	1✔
109	};
110	return null;	1✔
111	}
112
113	/**
114	* If a {@link SubchannelPicker} is being, or has been provided via {@link #reprocess}, the last
115	* picker will be consulted.
116	*
117	* <p>Otherwise, if the delayed transport is not shutdown, then a {@link PendingStream} is
118	* returned; if the transport is shutdown, then a {@link FailingClientStream} is returned.
119	*/
120	@Override
121	public final ClientStream newStream(
122	MethodDescriptor<?, ?> method, Metadata headers, CallOptions callOptions,
123	ClientStreamTracer[] tracers) {
124	try {
125	PickSubchannelArgs args = new PickSubchannelArgsImpl(	1✔
126	method, headers, callOptions, new PickDetailsConsumerImpl(tracers));
127	PickerState state = pickerState;	1✔
128	while (true) {
129	if (state.shutdownStatus != null) {	1✔
130	return new FailingClientStream(state.shutdownStatus, tracers);	1✔
131	}
132	if (state.lastPicker != null) {	1✔
133	PickResult pickResult = state.lastPicker.pickSubchannel(args);	1✔
134	callOptions = args.getCallOptions();	1✔
135	// User code provided authority takes precedence over the LB provided one.
136	if (callOptions.getAuthority() == null	1✔
137	&& pickResult.getAuthorityOverride() != null) {	1✔
138	callOptions = callOptions.withAuthority(pickResult.getAuthorityOverride());	1✔
139	}
140	ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult,	1✔
141	callOptions.isWaitForReady());	1✔
142	if (transport != null) {	1✔
143	return transport.newStream(	1✔
144	args.getMethodDescriptor(), args.getHeaders(), callOptions,	1✔
145	tracers);
146	}
147	}
148	// This picker's conclusion is "buffer". If there hasn't been a newer picker set (possible
149	// race with reprocess()), we will buffer the RPC. Otherwise, will try with the new picker.
150	synchronized (lock) {	1✔
151	PickerState newerState = pickerState;	1✔
152	if (state == newerState) {	1✔
153	return createPendingStream(args, tracers);	1✔
154	}
155	state = newerState;	1✔
156	}	1✔
157	}
158	} finally {
159	syncContext.drain();	1✔
160	}
161	}
162
163	/**
164	* Caller must call {@code syncContext.drain()} outside of lock because this method may
165	* schedule tasks on syncContext.
166	*/
167	@GuardedBy("lock")
168	private PendingStream createPendingStream(
169	PickSubchannelArgs args, ClientStreamTracer[] tracers) {
170	PendingStream pendingStream = new PendingStream(args, tracers);	1✔
171	pendingStreams.add(pendingStream);	1✔
172	if (getPendingStreamsCount() == 1) {	1✔
173	syncContext.executeLater(reportTransportInUse);	1✔
174	}
175	for (ClientStreamTracer streamTracer : tracers) {	1✔
176	streamTracer.createPendingStream();	1✔
177	}
178	return pendingStream;	1✔
179	}
180
181	@Override
182	public final void ping(final PingCallback callback, Executor executor) {
183	throw new UnsupportedOperationException("This method is not expected to be called");	×
184	}
185
186	@Override
187	public ListenableFuture<SocketStats> getStats() {
188	SettableFuture<SocketStats> ret = SettableFuture.create();	×
189	ret.set(null);	×
190	return ret;	×
191	}
192
193	/**
194	* Prevents creating any new streams. Buffered streams are not failed and may still proceed
195	* when {@link #reprocess} is called. The delayed transport will be terminated when there is no
196	* more buffered streams.
197	*/
198	@Override
199	public final void shutdown(final Status status) {
200	synchronized (lock) {	1✔
201	if (pickerState.shutdownStatus != null) {	1✔
202	return;	1✔
203	}
204	pickerState = pickerState.withShutdownStatus(status);	1✔
205	syncContext.executeLater(new Runnable() {	1✔
206	@Override
207	public void run() {
208	listener.transportShutdown(status);	1✔
209	}	1✔
210	});
211	if (!hasPendingStreams() && reportTransportTerminated != null) {	1✔
212	syncContext.executeLater(reportTransportTerminated);	1✔
213	reportTransportTerminated = null;	1✔
214	}
215	}	1✔
216	syncContext.drain();	1✔
217	}	1✔
218
219	/**
220	* Shuts down this transport and cancels all streams that it owns, hence immediately terminates
221	* this transport.
222	*/
223	@Override
224	public final void shutdownNow(Status status) {
225	shutdown(status);	1✔
226	Collection<PendingStream> savedPendingStreams;
227	Runnable savedReportTransportTerminated;
228	synchronized (lock) {	1✔
229	savedPendingStreams = pendingStreams;	1✔
230	savedReportTransportTerminated = reportTransportTerminated;	1✔
231	reportTransportTerminated = null;	1✔
232	if (!pendingStreams.isEmpty()) {	1✔
233	pendingStreams = Collections.emptyList();	1✔
234	}
235	}	1✔
236	if (savedReportTransportTerminated != null) {	1✔
237	for (PendingStream stream : savedPendingStreams) {	1✔
238	Runnable runnable = stream.setStream(	1✔
239	new FailingClientStream(status, RpcProgress.REFUSED, stream.tracers));	1✔
240	if (runnable != null) {	1✔
241	// Drain in-line instead of using an executor as failing stream just throws everything
242	// away. This is essentially the same behavior as DelayedStream.cancel() but can be done
243	// before stream.start().
244	runnable.run();	1✔
245	}
246	}	1✔
247	syncContext.execute(savedReportTransportTerminated);	1✔
248	}
249	// If savedReportTransportTerminated == null, transportTerminated() has already been called in
250	// shutdown().
251	}	1✔
252
253	public final boolean hasPendingStreams() {
254	synchronized (lock) {	1✔
255	return !pendingStreams.isEmpty();	1✔
256	}
257	}
258
259	@VisibleForTesting
260	final int getPendingStreamsCount() {
261	synchronized (lock) {	1✔
262	return pendingStreams.size();	1✔
263	}
264	}
265
266	/**
267	* Use the picker to try picking a transport for every pending stream, proceed the stream if the
268	* pick is successful, otherwise keep it pending.
269	*
270	* <p>This method may be called concurrently with {@code newStream()}, and it's safe. All pending
271	* streams will be served by the latest picker (if a same picker is given more than once, they are
272	* considered different pickers) as soon as possible.
273	*
274	* <p>This method <strong>must not</strong> be called concurrently with itself.
275	*/
276	final void reprocess(@Nullable SubchannelPicker picker) {
277	ArrayList<PendingStream> toProcess;
278	synchronized (lock) {	1✔
279	pickerState = pickerState.withPicker(picker);	1✔
280	if (picker == null \|\| !hasPendingStreams()) {	1✔
281	return;	1✔
282	}
283	toProcess = new ArrayList<>(pendingStreams);	1✔
284	}	1✔
285	ArrayList<PendingStream> toRemove = new ArrayList<>();	1✔
286
287	for (final PendingStream stream : toProcess) {	1✔
288	PickResult pickResult = picker.pickSubchannel(stream.args);	1✔
289	CallOptions callOptions = stream.args.getCallOptions();	1✔
290	// User code provided authority takes precedence over the LB provided one.
291	if (callOptions.getAuthority() == null && pickResult.getAuthorityOverride() != null) {	1✔
292	stream.setAuthority(pickResult.getAuthorityOverride());	1✔
293	}
294	final ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult,	1✔
295	callOptions.isWaitForReady());	1✔
296	if (transport != null) {	1✔
297	Executor executor = defaultAppExecutor;	1✔
298	// createRealStream may be expensive. It will start real streams on the transport. If
299	// there are pending requests, they will be serialized too, which may be expensive. Since
300	// we are now on transport thread, we need to offload the work to an executor.
301	if (callOptions.getExecutor() != null) {	1✔
302	executor = callOptions.getExecutor();	1✔
303	}
304	Runnable runnable = stream.createRealStream(transport);	1✔
305	if (runnable != null) {	1✔
306	executor.execute(runnable);	1✔
307	}
308	toRemove.add(stream);	1✔
309	} // else: stay pending
310	}	1✔
311
312	synchronized (lock) {	1✔
313	// Between this synchronized and the previous one:
314	// - Streams may have been cancelled, which may turn pendingStreams into emptiness.
315	// - shutdown() may be called, which may turn pendingStreams into null.
316	if (!hasPendingStreams()) {	1✔
317	return;	×
318	}
319	pendingStreams.removeAll(toRemove);	1✔
320	// Because delayed transport is long-lived, we take this opportunity to down-size the
321	// hashmap.
322	if (pendingStreams.isEmpty()) {	1✔
323	pendingStreams = new LinkedHashSet<>();	1✔
324	}
325	if (!hasPendingStreams()) {	1✔
326	// There may be a brief gap between delayed transport clearing in-use state, and first real
327	// transport starting streams and setting in-use state. During the gap the whole channel's
328	// in-use state may be false. However, it shouldn't cause spurious switching to idleness
329	// (which would shutdown the transports and LoadBalancer) because the gap should be shorter
330	// than IDLE_MODE_DEFAULT_TIMEOUT_MILLIS (1 second).
331	syncContext.executeLater(reportTransportNotInUse);	1✔
332	if (pickerState.shutdownStatus != null && reportTransportTerminated != null) {	1✔
333	syncContext.executeLater(reportTransportTerminated);	1✔
334	reportTransportTerminated = null;	1✔
335	}
336	}
337	}	1✔
338	syncContext.drain();	1✔
339	}	1✔
340
341	@Override
342	public InternalLogId getLogId() {
343	return logId;	×
344	}
345
346	private class PendingStream extends DelayedStream {
347	private final PickSubchannelArgs args;
348	private final Context context = Context.current();	1✔
349	private final ClientStreamTracer[] tracers;
350
351	private PendingStream(PickSubchannelArgs args, ClientStreamTracer[] tracers) {	1✔
352	this.args = args;	1✔
353	this.tracers = tracers;	1✔
354	}	1✔
355
356	/** Runnable may be null. */
357	private Runnable createRealStream(ClientTransport transport) {
358	ClientStream realStream;
359	Context origContext = context.attach();	1✔
360	try {
361	realStream = transport.newStream(	1✔
362	args.getMethodDescriptor(), args.getHeaders(), args.getCallOptions(),	1✔
363	tracers);
364	} finally {
365	context.detach(origContext);	1✔
366	}
367	return setStream(realStream);	1✔
368	}
369
370	@Override
371	public void cancel(Status reason) {
372	super.cancel(reason);	1✔
373	synchronized (lock) {	1✔
374	if (reportTransportTerminated != null) {	1✔
375	boolean justRemovedAnElement = pendingStreams.remove(this);	1✔
376	if (!hasPendingStreams() && justRemovedAnElement) {	1✔
377	syncContext.executeLater(reportTransportNotInUse);	1✔
378	if (pickerState.shutdownStatus != null) {	1✔
379	syncContext.executeLater(reportTransportTerminated);	1✔
380	reportTransportTerminated = null;	1✔
381	}
382	}
383	}
384	}	1✔
385	syncContext.drain();	1✔
386	}	1✔
387
388	@Override
389	protected void onEarlyCancellation(Status reason) {
390	for (ClientStreamTracer tracer : tracers) {	1✔
391	tracer.streamClosed(reason);	1✔
392	}
393	}	1✔
394
395	@Override
396	public void appendTimeoutInsight(InsightBuilder insight) {
397	if (args.getCallOptions().isWaitForReady()) {	1✔
398	insight.append("wait_for_ready");	1✔
399	}
400	super.appendTimeoutInsight(insight);	1✔
401	}	1✔
402	}
403
404	static final class PickerState {
405	/**
406	* The last picker that {@link #reprocess} has used. May be set to null when the channel has
407	* moved to idle.
408	*/
409	@Nullable
410	final SubchannelPicker lastPicker;
411	/**
412	* When {@code shutdownStatus != null && !hasPendingStreams()}, then the transport is considered
413	* terminated.
414	*/
415	@Nullable
416	final Status shutdownStatus;
417
418	private PickerState(SubchannelPicker lastPicker, Status shutdownStatus) {	1✔
419	this.lastPicker = lastPicker;	1✔
420	this.shutdownStatus = shutdownStatus;	1✔
421	}	1✔
422
423	public PickerState withPicker(SubchannelPicker newPicker) {
424	return new PickerState(newPicker, this.shutdownStatus);	1✔
425	}
426
427	public PickerState withShutdownStatus(Status newShutdownStatus) {
428	return new PickerState(this.lastPicker, newShutdownStatus);	1✔
429	}
430	}
431	}

grpc / grpc-java / #19653

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