rocksdb/thrift/lib/cpp/async/TAsyncTransport.h

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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
#ifndef THRIFT_ASYNC_TASYNCTRANSPORT_H_
#define THRIFT_ASYNC_TASYNCTRANSPORT_H_ 1
#include "thrift/lib/cpp/thrift_config.h"
#include <sys/uio.h>
#include <inttypes.h>
#include <memory>
namespace folly {
class IOBuf;
}
namespace apache { namespace thrift {
namespace transport {
class TSocketAddress;
class TTransportException;
}
namespace async {
class TEventBase;
/**
* TAsyncTransport defines an asynchronous API for streaming I/O.
*
* This class provides an API to for asynchronously waiting for data
* on a streaming transport, and for asynchronously sending data.
*
* The APIs for reading and writing are intentionally asymmetric. Waiting for
* data to read is a persistent API: a callback is installed, and is notified
* whenever new data is available. It continues to be notified of new events
* until it is uninstalled.
*
* TAsyncTransport does not provide read timeout functionality, because it
* typically cannot determine when the timeout should be active. Generally, a
* timeout should only be enabled when processing is blocked waiting on data
* from the remote endpoint. For server-side applications, the timeout should
* not be active if the server is currently processing one or more outstanding
* requests on this transport. For client-side applications, the timeout
* should not be active if there are no requests pending on the transport.
* Additionally, if a client has multiple pending requests, it will ususally
* want a separate timeout for each request, rather than a single read timeout.
*
* The write API is fairly intuitive: a user can request to send a block of
* data, and a callback will be informed once the entire block has been
* transferred to the kernel, or on error. TAsyncTransport does provide a send
* timeout, since most callers want to give up if the remote end stops
* responding and no further progress can be made sending the data.
*/
class TAsyncTransport {
public:
class ReadCallback {
public:
virtual ~ReadCallback() {}
/**
* When data becomes available, getReadBuffer() will be invoked to get the
* buffer into which data should be read.
*
* This method allows the ReadCallback to delay buffer allocation until
* data becomes available. This allows applications to manage large
* numbers of idle connections, without having to maintain a separate read
* buffer for each idle connection.
*
* It is possible that in some cases, getReadBuffer() may be called
* multiple times before readDataAvailable() is invoked. In this case, the
* data will be written to the buffer returned from the most recent call to
* readDataAvailable(). If the previous calls to readDataAvailable()
* returned different buffers, the ReadCallback is responsible for ensuring
* that they are not leaked.
*
* If getReadBuffer() throws an exception, returns a NULL buffer, or
* returns a 0 length, the ReadCallback will be uninstalled and its
* readError() method will be invoked.
*
* getReadBuffer() is not allowed to change the transport state before it
* returns. (For example, it should never uninstall the read callback, or
* set a different read callback.)
*
* @param bufReturn getReadBuffer() should update *bufReturn to contain the
* address of the read buffer. This parameter will never
* be NULL.
* @param lenReturn getReadBuffer() should update *lenReturn to contain the
* maximum number of bytes that may be written to the read
* buffer. This parameter will never be NULL.
*/
virtual void getReadBuffer(void** bufReturn, size_t* lenReturn) = 0;
/**
* readDataAvailable() will be invoked when data has been successfully read
* into the buffer returned by the last call to getReadBuffer().
*
* The read callback remains installed after readDataAvailable() returns.
* It must be explicitly uninstalled to stop receiving read events.
* getReadBuffer() will be called at least once before each call to
* readDataAvailable(). getReadBuffer() will also be called before any
* call to readEOF().
*
* @param len The number of bytes placed in the buffer.
*/
virtual void readDataAvailable(size_t len) THRIFT_NOEXCEPT = 0;
/**
* readEOF() will be invoked when the transport is closed.
*
* The read callback will be automatically uninstalled immediately before
* readEOF() is invoked.
*/
virtual void readEOF() THRIFT_NOEXCEPT = 0;
/**
* readError() will be invoked if an error occurs reading from the
* transport.
*
* The read callback will be automatically uninstalled immediately before
* readError() is invoked.
*
* @param ex An exception describing the error that occurred.
*/
virtual void readError(const transport::TTransportException& ex)
THRIFT_NOEXCEPT = 0;
};
class WriteCallback {
public:
virtual ~WriteCallback() {}
/**
* writeSuccess() will be invoked when all of the data has been
* successfully written.
*
* Note that this mainly signals that the buffer containing the data to
* write is no longer needed and may be freed or re-used. It does not
* guarantee that the data has been fully transmitted to the remote
* endpoint. For example, on socket-based transports, writeSuccess() only
* indicates that the data has been given to the kernel for eventual
* transmission.
*/
virtual void writeSuccess() THRIFT_NOEXCEPT = 0;
/**
* writeError() will be invoked if an error occurs writing the data.
*
* @param bytesWritten The number of bytes that were successfull
* @param ex An exception describing the error that occurred.
*/
virtual void writeError(size_t bytesWritten,
const transport::TTransportException& ex)
THRIFT_NOEXCEPT = 0;
};
virtual ~TAsyncTransport() {}
/**
* Set the read callback.
*
* See the documentation for ReadCallback above for a description of how the
* callback will be invoked. Note that the callback remains installed until
* it is explicitly uninstalled, or until an error occurs.
*
* If a ReadCallback is already installed, it is replaced with the new
* callback.
*
* Note that setReadCallback() may invoke the ReadCallback immediately,
* before returning.
*
* @param callback The callback to invoke when data is available.
* This parameter may be NULL to uninstall the current
* read callback.
*/
virtual void setReadCallback(ReadCallback* callback) = 0;
/**
* Get the currently installed read callback.
*
* @return Returns a pointer to the installed ReadCallback, or NULL if no
* ReadCallback is installed.
*/
virtual ReadCallback* getReadCallback() const = 0;
/**
* Write data to the transport.
*
* write() will always return immediately. The WriteCallback will later be
* invoked from the main TEventBase loop when the write has completed.
*
* Additional write attempts may be started before the first write completes.
* The subsequent write requests will be queued, and processed in the order
* in which they were called.
*
* @param callback The callback to invoke when the data has been written.
* The callback may not be NULL.
* @param buf The buffer containing the data to write. The caller is
* responsible for ensuring that this buffer remains valid
* until the callback is invoked. This parameter may not
* be NULL.
* @param bytes The number of bytes to write.
*/
virtual void write(WriteCallback* callback,
const void* buf, size_t bytes) = 0;
/**
* Write non-contiguous data to the transport.
*
* writev() will always return immediately. The WriteCallback will later be
* invoked from the main TEventBase loop when the write has completed.
*
* Additional write attempts may be started before the first write completes.
* The subsequent write requests will be queued, and processed in the order
* in which they were called.
*
* @param callback The callback to invoke when the data has been written.
* The callback may not be NULL.
* @param vec A pointer to an array of iovec objects. The caller is
* responsible for ensuring that the buffers remain valid
* until the callback is invoked. This parameter may not
* be NULL.
* @param count The number of iovec objects in the vec array.
*/
virtual void writev(WriteCallback* callback,
const iovec* vec, size_t count) = 0;
/**
* Write a chain of IOBufs to the transport.
*
* writeChain() will always return immediately. The WriteCallback will
* later be invoked from the main TEventBase loop when the write has
* completed.
*
* Additional write attempts may be started before the first write completes.
* The subsequent write requests will be queued, and processed in the order
* in which they were called.
*
* @param callback The callback to invoke when the data has been written.
* The callback may not be NULL.
* @param iob The head of an IOBuf chain. The TAsyncTransport
* will take ownership of this chain and delete it
* after writing.
* @param cork Whether to delay the write until the next non-corked
* write operation. (Note: may not be supported in all
* subclasses or on all platforms.)
*/
virtual void writeChain(WriteCallback* callback,
std::unique_ptr<folly::IOBuf>&& iob,
bool cork = false) = 0;
/**
* Close the transport.
*
* This gracefully closes the transport, waiting for all pending write
* requests to complete before actually closing the underlying transport.
*
* If a read callback is set, readEOF() will be called immediately. If there
* are outstanding write requests, the close will be delayed until all
* remaining writes have completed. No new writes may be started after
* close() has been called.
*/
virtual void close() = 0;
/**
* Close the transport immediately.
*
* This closes the transport immediately, dropping any outstanding data
* waiting to be written.
*
* If a read callback is set, readEOF() will be called immediately.
* If there are outstanding write requests, these requests will be aborted
* and writeError() will be invoked immediately on all outstanding write
* callbacks.
*/
virtual void closeNow() = 0;
/**
* Reset the transport immediately.
*
* This closes the transport immediately, sending a reset to the remote peer
* if possible to indicate abnormal shutdown.
*
* Note that not all subclasses implement this reset functionality: some
* subclasses may treat reset() the same as closeNow(). Subclasses that use
* TCP transports should terminate the connection with a TCP reset.
*/
virtual void closeWithReset() {
closeNow();
}
/**
* Perform a half-shutdown of the write side of the transport.
*
* The caller should not make any more calls to write() or writev() after
* shutdownWrite() is called. Any future write attempts will fail
* immediately.
*
* Not all transport types support half-shutdown. If the underlying
* transport does not support half-shutdown, it will fully shutdown both the
* read and write sides of the transport. (Fully shutting down the socket is
* better than doing nothing at all, since the caller may rely on the
* shutdownWrite() call to notify the other end of the connection that no
* more data can be read.)
*
* If there is pending data still waiting to be written on the transport,
* the actual shutdown will be delayed until the pending data has been
* written.
*
* Note: There is no corresponding shutdownRead() equivalent. Simply
* uninstall the read callback if you wish to stop reading. (On TCP sockets
* at least, shutting down the read side of the socket is a no-op anyway.)
*/
virtual void shutdownWrite() = 0;
/**
* Perform a half-shutdown of the write side of the transport.
*
* shutdownWriteNow() is identical to shutdownWrite(), except that it
* immediately performs the shutdown, rather than waiting for pending writes
* to complete. Any pending write requests will be immediately failed when
* shutdownWriteNow() is called.
*/
virtual void shutdownWriteNow() = 0;
/**
* Determine if transport is open and ready to read or write.
*
* Note that this function returns false on EOF; you must also call error()
* to distinguish between an EOF and an error.
*
* @return true iff the transport is open and ready, false otherwise.
*/
virtual bool good() const = 0;
/**
* Determine if the transport is readable or not.
*
* @return true iff the transport is readable, false otherwise.
*/
virtual bool readable() const = 0;
/**
* Determine if transport is connected to the endpoint
*
* @return false iff the transport is connected, otherwise true
*/
virtual bool connecting() const = 0;
/**
* Determine if an error has occurred with this transport.
*
* @return true iff an error has occurred (not EOF).
*/
virtual bool error() const = 0;
/**
* Attach the transport to a TEventBase.
*
* This may only be called if the transport is not currently attached to a
* TEventBase (by an earlier call to detachEventBase()).
*
* This method must be invoked in the TEventBase's thread.
*/
virtual void attachEventBase(TEventBase* eventBase) = 0;
/**
* Detach the transport from its TEventBase.
*
* This may only be called when the transport is idle and has no reads or
* writes pending. Once detached, the transport may not be used again until
* it is re-attached to a TEventBase by calling attachEventBase().
*
* This method must be called from the current TEventBase's thread.
*/
virtual void detachEventBase() = 0;
/**
* Get the TEventBase used by this transport.
*
* Returns NULL if this transport is not currently attached to a TEventBase.
*/
virtual TEventBase* getEventBase() const = 0;
/**
* Set the send timeout.
*
* If write requests do not make any progress for more than the specified
* number of milliseconds, fail all pending writes and close the transport.
*
* If write requests are currently pending when setSendTimeout() is called,
* the timeout interval is immediately restarted using the new value.
*
* @param milliseconds The timeout duration, in milliseconds. If 0, no
* timeout will be used.
*/
virtual void setSendTimeout(uint32_t milliseconds) = 0;
/**
* Get the send timeout.
*
* @return Returns the current send timeout, in milliseconds. A return value
* of 0 indicates that no timeout is set.
*/
virtual uint32_t getSendTimeout() const = 0;
/**
* Get the address of the local endpoint of this transport.
*
* This function may throw TTransportException on error.
*
* @param address The local address will be stored in the specified
* TSocketAddress.
*/
virtual void getLocalAddress(transport::TSocketAddress* address) const = 0;
/**
* Get the address of the remote endpoint to which this transport is
* connected.
*
* This function may throw TTransportException on error.
*
* @param address The remote endpoint's address will be stored in the
* specified TSocketAddress.
*/
virtual void getPeerAddress(transport::TSocketAddress* address) const = 0;
};
}}} // apache::thrift::async
#endif // #ifndef THRIFT_ASYNC_TASYNCTRANSPORT_H_