Package io.grpc.internal

Class DelayedClientTransport

java.lang.Object

io.grpc.internal.DelayedClientTransport

All Implemented Interfaces:

ClientTransport, ManagedClientTransport, InternalInstrumented<InternalChannelz.SocketStats>, InternalWithLogId

final class DelayedClientTransport
extends java.lang.Object
implements ManagedClientTransport

A client transport that queues requests before a real transport is available. When reprocess(io.grpc.LoadBalancer.SubchannelPicker) is called, this class applies the provided LoadBalancer.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.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private class	DelayedClientTransport.PendingStream
(package private) static class	DelayedClientTransport.PickerState

Nested classes/interfaces inherited from interface io.grpc.internal.ClientTransport

ClientTransport.PingCallback

Nested classes/interfaces inherited from interface io.grpc.internal.ManagedClientTransport

ManagedClientTransport.Listener

Field Summary

Fields

Modifier and Type	Field	Description
private java.util.concurrent.Executor	defaultAppExecutor
private ManagedClientTransport.Listener	listener
private java.lang.Object	lock
private InternalLogId	logId
private java.util.Collection<DelayedClientTransport.PendingStream>	pendingStreams
private DelayedClientTransport.PickerState	pickerState	Immutable state needed for picking.
private java.lang.Runnable	reportTransportInUse
private java.lang.Runnable	reportTransportNotInUse
private java.lang.Runnable	reportTransportTerminated
private SynchronizationContext	syncContext

Constructor Summary

Constructors

Constructor	Description
DelayedClientTransport(java.util.concurrent.Executor defaultAppExecutor, SynchronizationContext syncContext)	Creates a new delayed transport.

Method Summary

Modifier and Type	Method	Description
private DelayedClientTransport.PendingStream	createPendingStream(LoadBalancer.PickSubchannelArgs args, ClientStreamTracer[] tracers)	Caller must call syncContext.drain() outside of lock because this method may schedule tasks on syncContext.
InternalLogId	getLogId()	Returns an ID that is primarily used in debug logs.
(package private) int	getPendingStreamsCount()
com.google.common.util.concurrent.ListenableFuture<InternalChannelz.SocketStats>	getStats()	Returns the stats object.
boolean	hasPendingStreams()
ClientStream	newStream(MethodDescriptor<?,?> method, Metadata headers, CallOptions callOptions, ClientStreamTracer[] tracers)	If a LoadBalancer.SubchannelPicker is being, or has been provided via reprocess(io.grpc.LoadBalancer.SubchannelPicker), the last picker will be consulted.
void	ping(ClientTransport.PingCallback callback, java.util.concurrent.Executor executor)	Pings a remote endpoint.
(package private) void	reprocess(LoadBalancer.SubchannelPicker picker)	Use the picker to try picking a transport for every pending stream, proceed the stream if the pick is successful, otherwise keep it pending.
void	shutdown(Status status)	Prevents creating any new streams.
void	shutdownNow(Status status)	Shuts down this transport and cancels all streams that it owns, hence immediately terminates this transport.
java.lang.Runnable	start(ManagedClientTransport.Listener listener)	Starts transport.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

logId

private final InternalLogId logId

lock

private final java.lang.Object lock

defaultAppExecutor

private final java.util.concurrent.Executor defaultAppExecutor

syncContext

private final SynchronizationContext syncContext

reportTransportInUse

private java.lang.Runnable reportTransportInUse

reportTransportNotInUse

private java.lang.Runnable reportTransportNotInUse

reportTransportTerminated

private java.lang.Runnable reportTransportTerminated

listener

private ManagedClientTransport.Listener listener

pendingStreams

@Nonnull
private java.util.Collection<DelayedClientTransport.PendingStream> pendingStreams

pickerState

private volatile DelayedClientTransport.PickerState pickerState

Immutable state needed for picking. 'lock' must be held for writing.

Constructor Detail

DelayedClientTransport

DelayedClientTransport(java.util.concurrent.Executor defaultAppExecutor,
                       SynchronizationContext syncContext)

Creates a new delayed transport.

Parameters:

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 CallOptions.

syncContext - all listener callbacks of the delayed transport will be run from this SynchronizationContext.

Method Detail

start

public final java.lang.Runnable start(ManagedClientTransport.Listener listener)

Description copied from interface: ManagedClientTransport

Starts transport. This method may only be called once.

This method and the returned Runnable should not throw any exceptions.

Specified by:

start in interface ManagedClientTransport

Parameters:

listener - non-null listener of transport events

Returns:

a Runnable that is executed after-the-fact by the original caller, typically after locks are released

newStream

public final ClientStream newStream(MethodDescriptor<?,?> method,
                                    Metadata headers,
                                    CallOptions callOptions,
                                    ClientStreamTracer[] tracers)

If a LoadBalancer.SubchannelPicker is being, or has been provided via reprocess(io.grpc.LoadBalancer.SubchannelPicker), the last picker will be consulted.

Otherwise, if the delayed transport is not shutdown, then a DelayedClientTransport.PendingStream is returned; if the transport is shutdown, then a FailingClientStream is returned.

Specified by:

newStream in interface ClientTransport

Parameters:

method - the descriptor of the remote method to be called for this stream.

headers - to send at the beginning of the call

callOptions - runtime options of the call

tracers - a non-empty array of tracers. The last element in it is reserved to be set by the load balancer's pick result and otherwise is a no-op tracer.

Returns:

the newly created stream.

createPendingStream

private DelayedClientTransport.PendingStream createPendingStream(LoadBalancer.PickSubchannelArgs args,
                                                                 ClientStreamTracer[] tracers)

Caller must call syncContext.drain() outside of lock because this method may schedule tasks on syncContext.

ping

public final void ping(ClientTransport.PingCallback callback,
                       java.util.concurrent.Executor executor)

Description copied from interface: ClientTransport

Pings a remote endpoint. When an acknowledgement is received, the given callback will be invoked using the given executor.

Pings are not necessarily sent to the same endpoint, thus a successful ping only means at least one endpoint responded, but doesn't imply the availability of other endpoints (if there is any).

This is an optional method. Transports that do not have any mechanism by which to ping the remote endpoint may throw UnsupportedOperationException.

Specified by:

ping in interface ClientTransport

getStats

public com.google.common.util.concurrent.ListenableFuture<InternalChannelz.SocketStats> getStats()

Description copied from interface: InternalInstrumented

Returns the stats object.

Specified by:

getStats in interface InternalInstrumented<InternalChannelz.SocketStats>

shutdown

public final void shutdown(Status status)

Prevents creating any new streams. Buffered streams are not failed and may still proceed when reprocess(io.grpc.LoadBalancer.SubchannelPicker) is called. The delayed transport will be terminated when there is no more buffered streams.

Specified by:

shutdown in interface ManagedClientTransport

shutdownNow

public final void shutdownNow(Status status)

Shuts down this transport and cancels all streams that it owns, hence immediately terminates this transport.

Specified by:

shutdownNow in interface ManagedClientTransport

hasPendingStreams

public final boolean hasPendingStreams()

getPendingStreamsCount

final int getPendingStreamsCount()

reprocess

final void reprocess(@Nullable
                     LoadBalancer.SubchannelPicker picker)

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 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.

getLogId

public InternalLogId getLogId()

Description copied from interface: InternalWithLogId

Returns an ID that is primarily used in debug logs. It usually contains the class name and a numeric ID that is unique among the instances.

The subclasses of this interface usually want to include the log ID in their Object.toString() results.

Specified by:

getLogId in interface InternalWithLogId