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package nl.topicus.jdbc.shaded.io.grpc.internal;
import nl.topicus.jdbc.shaded.com.google.nl.topicus.jdbc.shaded.com.on.annotations.VisibleForTesting;
import nl.topicus.jdbc.shaded.io.grpc.CallOptions;
import nl.topicus.jdbc.shaded.io.grpc.Context;
import nl.topicus.jdbc.shaded.io.grpc.LoadBalancer.PickResult;
import nl.topicus.jdbc.shaded.io.grpc.LoadBalancer.PickSubchannelArgs;
import nl.topicus.jdbc.shaded.io.grpc.LoadBalancer.SubchannelPicker;
import nl.topicus.jdbc.shaded.io.grpc.Metadata;
import nl.topicus.jdbc.shaded.io.grpc.MethodDescriptor;
import nl.topicus.jdbc.shaded.io.grpc.Status;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.concurrent.Executor;
import nl.topicus.jdbc.shaded.javax.annotation.Nullable;
import nl.topicus.jdbc.shaded.javax.annotation.concurrent.GuardedBy;
/**
* 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.
*
* 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 {
private final LogId lodId = LogId.allocate(getClass().getName());
private final Object lock = new Object();
private final Executor defaultAppExecutor;
private final ChannelExecutor channelExecutor;
private Runnable reportTransportInUse;
private Runnable reportTransportNotInUse;
private Runnable reportTransportShutdown;
private Runnable reportTransportTerminated;
@GuardedBy("lock")
private Collection pendingStreams = new LinkedHashSet();
/**
* When shutdown == true and pendingStreams == null, then the transport is considered terminated.
*/
@GuardedBy("lock")
private boolean shutdown;
/**
* The last picker that {@link #reprocess} has used.
*/
@GuardedBy("lock")
@Nullable
private SubchannelPicker lastPicker;
@GuardedBy("lock")
private long lastPickerVersion;
/**
* Creates a new delayed transport.
*
* @param defaultAppExecutor pending streams will create real streams and run bufferred operations
* in an application executor, which will be this executor, unless there is on provided in
* {@link CallOptions}.
* @param channelExecutor all listener callbacks of the delayed transport will be run from this
* ChannelExecutor.
*/
DelayedClientTransport(Executor defaultAppExecutor, ChannelExecutor channelExecutor) {
this.defaultAppExecutor = defaultAppExecutor;
this.channelExecutor = channelExecutor;
}
@Override
public final Runnable start(final Listener listener) {
reportTransportInUse = new Runnable() {
@Override
public void run() {
listener.transportInUse(true);
}
};
reportTransportNotInUse = new Runnable() {
@Override
public void run() {
listener.transportInUse(false);
}
};
reportTransportShutdown = new Runnable() {
@Override
public void run() {
listener.transportShutdown(
Status.UNAVAILABLE.withDescription("Channel requested transport to shut down"));
}
};
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.
*
* 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) {
try {
SubchannelPicker picker = null;
PickSubchannelArgs args = new PickSubchannelArgsImpl(method, headers, callOptions);
long pickerVersion = -1;
synchronized (lock) {
if (!shutdown) {
if (lastPicker == null) {
return createPendingStream(args);
}
picker = lastPicker;
pickerVersion = lastPickerVersion;
}
}
if (picker != null) {
while (true) {
PickResult pickResult = picker.pickSubchannel(args);
ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult,
callOptions.isWaitForReady());
if (transport != null) {
return transport.newStream(
args.getMethodDescriptor(), args.getHeaders(), args.getCallOptions());
}
// This picker's conclusion is "buffer". If there hasn't been a newer picker set
// (possible race with reprocess()), we will buffer it. Otherwise, will try with the new
// picker.
synchronized (lock) {
if (shutdown) {
break;
}
if (pickerVersion == lastPickerVersion) {
return createPendingStream(args);
}
picker = lastPicker;
pickerVersion = lastPickerVersion;
}
}
}
return new FailingClientStream(Status.UNAVAILABLE.withDescription(
"Channel has shutdown (reported by delayed transport)"));
} finally {
channelExecutor.drain();
}
}
@Override
public final ClientStream newStream(MethodDescriptor method, Metadata headers) {
return newStream(method, headers, CallOptions.DEFAULT);
}
/**
* Caller must call {@code channelExecutor.drain()} outside of lock because this method may
* schedule tasks on channelExecutor.
*/
@GuardedBy("lock")
private PendingStream createPendingStream(PickSubchannelArgs args) {
PendingStream pendingStream = new PendingStream(args);
pendingStreams.add(pendingStream);
if (pendingStreams.size() == 1) {
channelExecutor.executeLater(reportTransportInUse);
}
return pendingStream;
}
@Override
public final void ping(final PingCallback callback, Executor executor) {
throw new UnsupportedOperationException("This method is not expected to be called");
}
/**
* 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() {
synchronized (lock) {
if (shutdown) {
return;
}
shutdown = true;
channelExecutor.executeLater(reportTransportShutdown);
if (pendingStreams == null || pendingStreams.isEmpty()) {
pendingStreams = null;
channelExecutor.executeLater(reportTransportTerminated);
}
}
channelExecutor.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();
Collection savedPendingStreams = null;
synchronized (lock) {
if (pendingStreams != null) {
savedPendingStreams = pendingStreams;
pendingStreams = null;
}
}
if (savedPendingStreams != null) {
for (PendingStream stream : savedPendingStreams) {
stream.cancel(status);
}
channelExecutor.executeLater(reportTransportTerminated).drain();
}
// If savedPendingStreams == null, transportTerminated() has already been called in shutdown().
}
public final boolean hasPendingStreams() {
synchronized (lock) {
return pendingStreams != null && !pendingStreams.isEmpty();
}
}
@VisibleForTesting
final int getPendingStreamsCount() {
synchronized (lock) {
return pendingStreams == null ? 0 : 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.
*
* 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.
*
*
This method must not be called concurrently with itself.
*/
final void reprocess(SubchannelPicker picker) {
ArrayList toProcess;
ArrayList toRemove = new ArrayList();
synchronized (lock) {
lastPicker = picker;
lastPickerVersion++;
if (pendingStreams == null || pendingStreams.isEmpty()) {
return;
}
toProcess = new ArrayList(pendingStreams);
}
for (final PendingStream stream : toProcess) {
PickResult pickResult = picker.pickSubchannel(stream.args);
CallOptions callOptions = stream.args.getCallOptions();
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();
}
executor.execute(new Runnable() {
@Override
public void run() {
stream.createRealStream(transport);
}
});
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 (pendingStreams == null || pendingStreams.isEmpty()) {
return;
}
pendingStreams.removeAll(toRemove);
if (pendingStreams.isEmpty()) {
// 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).
channelExecutor.executeLater(reportTransportNotInUse);
if (shutdown) {
pendingStreams = null;
channelExecutor.executeLater(reportTransportTerminated);
} else {
// Because delayed transport is long-lived, we take this opportunity to down-size the
// hashmap.
pendingStreams = new LinkedHashSet();
}
}
}
channelExecutor.drain();
}
// TODO(carl-mastrangelo): remove this once the Subchannel change is in.
@Override
public LogId getLogId() {
return lodId;
}
private class PendingStream extends DelayedStream {
private final PickSubchannelArgs args;
private final Context context = Context.current();
private PendingStream(PickSubchannelArgs args) {
this.args = args;
}
private void createRealStream(ClientTransport transport) {
ClientStream realStream;
Context origContext = context.attach();
try {
realStream = transport.newStream(
args.getMethodDescriptor(), args.getHeaders(), args.getCallOptions());
} finally {
context.detach(origContext);
}
setStream(realStream);
}
@Override
public void cancel(Status reason) {
super.cancel(reason);
synchronized (lock) {
if (pendingStreams != null) {
boolean justRemovedAnElement = pendingStreams.remove(this);
if (pendingStreams.isEmpty() && justRemovedAnElement) {
channelExecutor.executeLater(reportTransportNotInUse);
if (shutdown) {
pendingStreams = null;
channelExecutor.executeLater(reportTransportTerminated);
}
}
}
}
channelExecutor.drain();
}
}
}