TAO_Transport Class Reference

Generic definitions for the Transport class. More...

#include <Transport.h>

Inheritance diagram for TAO_Transport:

[legend]Collaboration diagram for TAO_Transport:

[legend]List of all members.

Template methods
The Transport class uses the Template Method Pattern to implement the protocol specific functionality. Implementors of a pluggable protocol should override the following methods with the semantics documented below.
enum	{ TAO_ONEWAY_REQUEST = 0, TAO_TWOWAY_REQUEST = 1, TAO_REPLY }
virtual ACE_Event_Handler *	event_handler_i (void)=0
bool	is_connected (void) const
	Is this transport really connected.
bool	post_open (size_t id)
	Perform all the actions when this transport get opened.
TAO_Connection_Handler *	connection_handler (void)
	Get the connection handler for this transport.
TAO_OutputCDR &	out_stream (void)
	Accessor for the output CDR stream.
int	generate_locate_request (TAO_Target_Specification &spec, TAO_Operation_Details &opdetails, TAO_OutputCDR &output)
virtual int	generate_request_header (TAO_Operation_Details &opd, TAO_Target_Specification &spec, TAO_OutputCDR &msg)
int	recache_transport (TAO_Transport_Descriptor_Interface *desc)
	Recache ourselves in the cache.
virtual int	handle_input (TAO_Resume_Handle &rh, ACE_Time_Value *max_wait_time=0, int block=0)
	Callback to read incoming data.
virtual int	send_request (TAO_Stub *stub, TAO_ORB_Core *orb_core, TAO_OutputCDR &stream, int message_semantics, ACE_Time_Value *max_time_wait)=0
virtual int	send_message (TAO_OutputCDR &stream, TAO_Stub *stub=0, int message_semantics=TAO_Transport::TAO_TWOWAY_REQUEST, ACE_Time_Value *max_time_wait=0)=0
virtual int	send_message_shared (TAO_Stub *stub, int message_semantics, const ACE_Message_Block *message_block, ACE_Time_Value *max_wait_time)
	Sent the contents of message_block.
int	format_queue_message (TAO_OutputCDR &stream)
	Format and queue a message for stream.
int	send_message_block_chain (const ACE_Message_Block *message_block, size_t &bytes_transferred, ACE_Time_Value *max_wait_time=0)
	Send a message block chain,.
int	send_message_block_chain_i (const ACE_Message_Block *message_block, size_t &bytes_transferred, ACE_Time_Value *max_wait_time)
	Send a message block chain, assuming the lock is held.
int	purge_entry (void)
	Cache management.
int	make_idle (void)
	Cache management.
int	update_transport (void)
	Cache management.
int	handle_timeout (const ACE_Time_Value &current_time, const void *act)
size_t	recv_buffer_size (void)
	Accessor to recv_buffer_size_.
size_t	sent_byte_count (void)
	Accessor to sent_byte_count_.
TAO_Codeset_Translator_Base *	char_translator (void) const
	CodeSet Negotiation - Get the char codeset translator factory.
TAO_Codeset_Translator_Base *	wchar_translator (void) const
	CodeSet Negotiation - Get the wchar codeset translator factory.
void	char_translator (TAO_Codeset_Translator_Base *)
	CodeSet negotiation - Set the char codeset translator factory.
void	wchar_translator (TAO_Codeset_Translator_Base *)
	CodeSet negotiation - Set the wchar codeset translator factory.
void	assign_translators (TAO_InputCDR *, TAO_OutputCDR *)
void	clear_translators (TAO_InputCDR *, TAO_OutputCDR *)
CORBA::Boolean	is_tcs_set () const
	Return true if the tcs has been set.
void	first_request_sent ()
	Set the state of the first_request_ flag to 0.
void	send_connection_closed_notifications (void)
virtual TAO_Connection_Handler *	connection_handler_i (void)=0
int	parse_consolidate_messages (ACE_Message_Block &bl, TAO_Resume_Handle &rh, ACE_Time_Value *time=0)
int	parse_incoming_messages (ACE_Message_Block &message_block)
size_t	missing_data (ACE_Message_Block &message_block)
virtual int	consolidate_message (ACE_Message_Block &incoming, ssize_t missing_data, TAO_Resume_Handle &rh, ACE_Time_Value *max_wait_time)
int	consolidate_fragments (TAO_Queued_Data *qd, TAO_Resume_Handle &rh)
	@Bala: Docu???
int	consolidate_message_queue (ACE_Message_Block &incoming, ssize_t missing_data, TAO_Resume_Handle &rh, ACE_Time_Value *max_wait_time)
int	consolidate_extra_messages (ACE_Message_Block &incoming, TAO_Resume_Handle &rh)
int	process_parsed_messages (TAO_Queued_Data *qd, TAO_Resume_Handle &rh)
TAO_Queued_Data *	make_queued_data (ACE_Message_Block &incoming)
	Make a queued data from the incoming message block.
int	send_message_shared_i (TAO_Stub *stub, int message_semantics, const ACE_Message_Block *message_block, ACE_Time_Value *max_wait_time)
int	queue_message_i (const ACE_Message_Block *message_block)
	Queue a message for message_block.
CORBA::ULong	tag_
	IOP protocol tag.
TAO_ORB_Core *	orb_core_
	Global orbcore resource.
TAO::Transport_Cache_Manager::HASH_MAP_ENTRY *	cache_map_entry_
TAO_Transport_Mux_Strategy *	tms_
TAO_Wait_Strategy *	ws_
	Strategy for waiting for the reply after sending the request.
int	bidirectional_flag_
TAO::Connection_Role	opening_connection_role_
TAO_Queued_Message *	head_
	Implement the outgoing data queue.
TAO_Queued_Message *	tail_
TAO_Incoming_Message_Queue	incoming_message_queue_
	Queue of the incoming messages..
ACE_Time_Value	current_deadline_
long	flush_timer_id_
	The timer ID.
TAO_Transport_Timer	transport_timer_
	The adapter used to receive timeout callbacks from the Reactor.
ACE_Lock *	handler_lock_
size_t	id_
	A unique identifier for the transport.
unsigned long	purging_order_
	Used by the LRU, LFU and FIFO Connection Purging Strategies.
size_t	recv_buffer_size_
	Size of the buffer received.
size_t	sent_byte_count_
	Number of bytes sent.
bool	is_connected_
TAO::Transport_Cache_Manager &	transport_cache_manager (void)
	Helper method that returns the Transport Cache Manager.
int	drain_queue (void)
	Send some of the data in the queue.
int	drain_queue_i (void)
	Implement drain_queue() assuming the lock is held.
int	queue_is_empty_i (void)
	Check if there are messages pending in the queue.
int	drain_queue_helper (int &iovcnt, iovec iov[])
	A helper routine used in drain_queue_i().
int	schedule_output_i (void)
	Schedule handle_output() callbacks.
int	cancel_output_i (void)
	Cancel handle_output() callbacks.
void	cleanup_queue (size_t byte_count)
	Cleanup the queue.
void	cleanup_queue_i ()
	Cleanup the complete queue.
int	check_buffering_constraints_i (TAO_Stub *stub, int &must_flush)
	Check if the buffering constraints have been reached.
int	send_synchronous_message_i (const ACE_Message_Block *message_block, ACE_Time_Value *max_wait_time)
int	send_reply_message_i (const ACE_Message_Block *message_block, ACE_Time_Value *max_wait_time)
int	send_synch_message_helper_i (TAO_Synch_Queued_Message &s, ACE_Time_Value *max_wait_time)
int	flush_timer_pending (void) const
	Check if the flush timer is still pending.
void	reset_flush_timer (void)
void	report_invalid_event_handler (const char *caller)
	Print out error messages if the event handler is not valid.
int	process_queue_head (TAO_Resume_Handle &rh)
int	notify_reactor (void)
void	send_connection_closed_notifications_i (void)
	Assume the lock is held.
void	process_fragment (TAO_Queued_Data *fragment_message, TAO_Queued_Data *queueable_message, CORBA::Octet major, CORBA::Octet minor, TAO_Resume_Handle &rh)
void	allocate_partial_message_block (void)
	TAO_Transport (const TAO_Transport &)
	Prohibited.
void	operator= (const TAO_Transport &)
TAO_Codeset_Translator_Base *	char_translator_
	Additional member values required to support codeset translation.
TAO_Codeset_Translator_Base *	wchar_translator_
CORBA::Boolean	tcs_set_
CORBA::Boolean	first_request_
ACE_Message_Block *	partial_message_
	Holds the partial GIOP message (if there is one).
class	TAO_Block_Flushing_Strategy
class	TAO_Reactive_Flushing_Strategy
class	TAO_Leader_Follower_Flushing_Strategy
class	TAO_Thread_Per_Connection_Handler
Public Member Functions
	TAO_Transport (CORBA::ULong tag, TAO_ORB_Core *orb_core)
	Default creator, requires the tag value be supplied.
virtual	~TAO_Transport (void)
	Destructor.
CORBA::ULong	tag (void) const
	Return the protocol tag.
TAO_ORB_Core *	orb_core (void) const
	Access the ORB that owns this connection.
TAO_Transport_Mux_Strategy *	tms (void) const
	Get the TAO_Tranport_Mux_Strategy used by this object.
TAO_Wait_Strategy *	wait_strategy (void) const
	Return the TAO_Wait_Strategy used by this object.
int	handle_output (void)
	Callback method to reactively drain the outgoing data queue.
int	bidirectional_flag (void) const
	Get the bidirectional flag.
void	bidirectional_flag (int flag)
	Set the bidirectional flag.
void	cache_map_entry (TAO::Transport_Cache_Manager::HASH_MAP_ENTRY *entry)
	Set the Cache Map entry.
TAO::Transport_Cache_Manager::HASH_MAP_ENTRY *	cache_map_entry (void)
	Get the Cache Map entry.
size_t	id (void) const
	Set and Get the identifier for this transport instance.
void	id (size_t id)
TAO::Connection_Role	opened_as (void) const
void	opened_as (TAO::Connection_Role)
unsigned long	purging_order (void) const
void	purging_order (unsigned long value)
int	queue_is_empty (void)
	Check if there are messages pending in the queue.
void	provide_handler (TAO::Connection_Handler_Set &handlers)
	Added event handler to the handlers set.
bool	provide_blockable_handler (TAO::Connection_Handler_Set &handlers)
virtual int	register_handler (void)
	Register the handler with the reactor.
virtual ssize_t	send (iovec *iov, int iovcnt, size_t &bytes_transferred, const ACE_Time_Value *timeout=0)=0
	Write the complete Message_Block chain to the connection.
virtual ssize_t	recv (char *buffer, size_t len, const ACE_Time_Value *timeout=0)=0
	Read len bytes from into buf.
Control connection lifecycle
These methods are routed through the TMS object. The TMS strategies implement them correctly.
bool	idle_after_send (void)
bool	idle_after_reply (void)
virtual void	close_connection (void)
	Call the implementation method after obtaining the lock.
Template methods
The Transport class uses the Template Method Pattern to implement the protocol specific functionality. Implementors of a pluggable protocol should override the following methods with the semantics documented below.
virtual int	messaging_init (CORBA::Octet major, CORBA::Octet minor)=0
virtual int	tear_listen_point_list (TAO_InputCDR &cdr)
virtual bool	post_connect_hook (void)
	Hooks that can be overridden in concrete transports.
ACE_Event_Handler::Reference_Count	add_reference (void)
	Memory management routines.
ACE_Event_Handler::Reference_Count	remove_reference (void)
virtual TAO_Pluggable_Messaging *	messaging_object (void)=0

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Detailed Description

Generic definitions for the Transport class.

The transport object is created in the Service handler constructor and deleted in the Service Handler's destructor!!

The main responsability of a Transport object is to encapsulate a connection, and provide a transport independent way to send and receive data. Since TAO is heavily based on the Reactor for all if not all its I/O the Transport class is usually implemented with a helper Connection Handler that adapts the generic Transport interface to the Reactor types.

The outgoing data path:

One of the responsibilities of the TAO_Transport class is to send out GIOP messages as efficiently as possible. In most cases messages are put out in FIFO order, the transport object will put out the message using a single system call and return control to the application. However, for oneways and AMI requests it may be more efficient (or required if the SYNC_NONE policy is in effect) to queue the messages until a large enough data set is available. Another reason to queue is that some applications cannot block for I/O, yet they want to send messages so large that a single write() operation would not be able to cope with them. In such cases we need to queue the data and use the Reactor to drain the queue.

Therefore, the Transport class may need to use a queue to temporarily hold the messages, and, in some configurations, it may need to use the Reactor to concurrently drain such queues.

Out of order messages:

TAO provides explicit policies to send 'urgent' messages. Such messages may put at the head of the queue. However, they cannot be sent immediately because the transport may already be sending another message in a reactive fashion.

Consequently, the Transport must also know if the head of the queue has been partially sent. In that case new messages can only follow the head. Only once the head is completely sent we can start sending new messages.

Waiting threads:

One or more threads can be blocked waiting for the connection to completely send the message. The thread should return as soon as its message has been sent, so a per-thread condition is required. This suggest that simply using a ACE_Message_Queue would not be enough: there is a significant amount of ancillary information, to keep on each message that the Message_Block class does not provide room for.

Blocking I/O is still attractive for some applications. First, my eliminating the Reactor overhead performance is improved when sending large blocks of data. Second, using the Reactor to send out data opens the door for nested upcalls, yet some applications cannot deal with the reentrancy issues in this case.

Timeouts:

Some or all messages could have a timeout period attached to them. The timeout source could either be some high-level policy or maybe some strategy to prevent denial of service attacks. In any case the timeouts are per-message, and later messages could have shorter timeouts. In fact, some kind of scheduling (such as EDF) could be required in a few applications.

Conclusions:

The outgoing data path consist in several components:

• A queue of pending messages
• A message currently being transmitted
• A per-transport 'send strategy' to choose between blocking on write, blocking on the reactor or blockin on leader/follower.
• A per-message 'waiting object'
• A per-message timeout

The Transport object provides a single method to send request messages (send_request_message ()).

The incoming data path:

One of the main responsibilities of the transport is to read and process the incoming GIOP message as quickly and efficiently as possible. There are other forces that needs to be given due consideration. They are

• Multiple threads should be able to traverse along the same data path but should not be able to read from the same handle at the same time ie. the handle should not be shared between threads at any instant.
• Reads on the handle could give one or more messages.
• Minimise locking and copying overhead when trying to attack the above.

Parsing messages (GIOP) & processing the message:

The messages should be checked for validity and the right information should be sent to the higher layer for processing. The process of doing a sanity check and preparing the messages for the higher layers of the ORB are done by the messaging protocol.

Design forces and Challenges

To keep things as efficient as possible for medium sized requests, it would be good to minimise data copying and locking along the incoming path ie. from the time of reading the data from the handle to the application. We achieve this by creating a buffer on stack and reading the data from the handle into the buffer. We then pass the same data block (the buffer is encapsulated into a data block) to the higher layers of the ORB. The problems stem from the following (a) Data is bigger than the buffer that we have on stack (b) Transports like TCP do not guarantee availability of the whole chunk of data in one shot. Data could trickle in byte by byte. (c) Single read gives multiple messages

We solve the problems as follows

(a) First do a read with the buffer on stack. Query the underlying messaging object whether the message has any incomplete portion. If so, we just grow the buffer for the missing size and read the rest of the message. We free the handle and then send the message to the higher layers of the ORB for processing.

(b) If we block (ie. if we receive a EWOULDBLOCK) while trying to do the above (ie. trying to read after growing the buffer size) we put the message in a queue and return back to the reactor. The reactor would call us back when the handle becomes read ready.

(c) If we get multiple messages (possible if the client connected to the server sends oneways or AMI requests), we parse and split the messages. Every message is put in the queue. Once the messages are queued, the thread picks up one message to send to the higher layers of the ORB. Before doing that, if it finds more messages, it sends a notify to the reactor without resuming the handle. The next thread picks up a message from the queue and processes that. Once the queue is drained the last thread resumes the handle.

Sending Replies

We could use the outgoing path of the ORB to send replies. This would allow us to reuse most of the code in the outgoing data path. We were doing this till TAO-1.2.3. We run in to problems. When writing the reply the ORB gets flow controlled, and the ORB tries to flush the message by going into the reactor. This resulted in unnecessary nesting. The thread that gets into the Reactor could potentially handle other messages (incoming or outgoing) and the stack starts growing leading to crashes.

Solution to the nesting problem

The solution that we (plan to) adopt is pretty straight forward. The thread sending replies will not block to send the replies but queue the replies and return to the Reactor. (Note the careful usages of the terms "blocking in the Reactor" as opposed to "return back to the Reactor".

See Also:

http://cvs.doc.wustl.edu/ace-latest.cgi/ACE_wrappers/TAO/docs/pluggable_protocols/index.html

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Member Enumeration Documentation

anonymous enum

Enumeration values: TAO_ONEWAY_REQUEST  TAO_TWOWAY_REQUEST  TAO_REPLY

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Constructor & Destructor Documentation

TAO_Transport::TAO_Transport (  CORBA::ULong  tag, TAO_ORB_Core *  orb_core )

Default creator, requires the tag value be supplied.

TAO_Transport::~TAO_Transport (  void   )  [virtual]

Destructor.

TAO_Transport::TAO_Transport (  const TAO_Transport &   )  [private]

Prohibited.

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Member Function Documentation

ACE_Event_Handler::Reference_Count TAO_Transport::add_reference (  void   )

Memory management routines.

void TAO_Transport::allocate_partial_message_block (  void   )  [private]

Allocate a partial message block and store it in our partial_message_ data member.

void TAO_Transport::assign_translators (  TAO_InputCDR *  , TAO_OutputCDR *  )

Use the Transport's codeset factories to set the translator for input and output CDRs.

ACE_INLINE void TAO_Transport::bidirectional_flag (  int  flag  )

Set the bidirectional flag.

ACE_INLINE int TAO_Transport::bidirectional_flag (  void   )  const

Get the bidirectional flag.

ACE_INLINE TAO::Transport_Cache_Manager::HASH_MAP_ENTRY * TAO_Transport::cache_map_entry (  void   )

Get the Cache Map entry.

ACE_INLINE void TAO_Transport::cache_map_entry (  TAO::Transport_Cache_Manager::HASH_MAP_ENTRY *  entry  )

Set the Cache Map entry.

int TAO_Transport::cancel_output_i (  void   )  [private]

Cancel handle_output() callbacks.

ACE_INLINE void TAO_Transport::char_translator (  TAO_Codeset_Translator_Base *   )

CodeSet negotiation - Set the char codeset translator factory.

ACE_INLINE TAO_Codeset_Translator_Base * TAO_Transport::char_translator (  void   )  const

CodeSet Negotiation - Get the char codeset translator factory.

int TAO_Transport::check_buffering_constraints_i (  TAO_Stub *  stub, int &  must_flush )  [private]

Check if the buffering constraints have been reached.

void TAO_Transport::cleanup_queue (  size_t  byte_count  )  [private]

Cleanup the queue. Exactly byte_count bytes have been sent, the queue must be cleaned up as potentially several messages have been completely sent out. It leaves on head_ the next message to send out.

void TAO_Transport::cleanup_queue_i (   )  [private]

Cleanup the complete queue.

void TAO_Transport::clear_translators (  TAO_InputCDR *  , TAO_OutputCDR *  )

It is necessary to clear the codeset translator when a CDR stream is used for more than one GIOP message. This is required since the header must not be translated, whereas the body must be.

void TAO_Transport::close_connection (  void   )  [virtual]

Call the implementation method after obtaining the lock.

ACE_INLINE TAO_Connection_Handler * TAO_Transport::connection_handler (  void   )

Get the connection handler for this transport.

virtual TAO_Connection_Handler* TAO_Transport::connection_handler_i (  void   )  [protected, pure virtual]

Implemented in TAO_IIOP_Transport.

int TAO_Transport::consolidate_extra_messages (  ACE_Message_Block &  incoming, TAO_Resume_Handle &  rh )  [protected]

Called by parse_consolidate_message () if we have more messages in one read. Queue up the messages and try to process one of them, atleast at the head of them.

int TAO_Transport::consolidate_fragments (  TAO_Queued_Data *  qd, TAO_Resume_Handle &  rh )  [protected]

@Bala: Docu???

int TAO_Transport::consolidate_message (  ACE_Message_Block &  incoming, ssize_t  missing_data, TAO_Resume_Handle &  rh, ACE_Time_Value *  max_wait_time )  [protected, virtual]

Consolidate the currently read message or consolidate the last message in the queue. The consolidation of the last message in the queue is done by calling consolidate_message_queue ().

int TAO_Transport::consolidate_message_queue (  ACE_Message_Block &  incoming, ssize_t  missing_data, TAO_Resume_Handle &  rh, ACE_Time_Value *  max_wait_time )  [protected]

First consolidate the message queue. If the message is still not complete, try to read from the handle again to make it complete. If these dont help put the message back in the queue and try to check the queue if we have message to process. (the thread needs to do some work anyway :-))

int TAO_Transport::drain_queue (  void   )  [private]

Send some of the data in the queue. As the outgoing data is drained this method is invoked to send as much of the current message as possible. Returns 0 if there is more data to send, -1 if there was an error and 1 if the message was completely sent.

int TAO_Transport::drain_queue_helper (  int &  iovcnt, iovec  iov[] )  [private]

A helper routine used in drain_queue_i().

int TAO_Transport::drain_queue_i (  void   )  [private]

Implement drain_queue() assuming the lock is held.

virtual ACE_Event_Handler* TAO_Transport::event_handler_i (  void   )  [pure virtual]

Normally a concrete TAO_Transport object has-a ACE_Event_Handler member that functions as an adapter between the ACE_Reactor framework and the TAO pluggable protocol framework. In all the protocols implemented so far this role is fullfilled by an instance of ACE_Svc_Handler. Todo: Since we only use a limited functionality of ACE_Svc_Handler we could probably implement a generic adapter class (TAO_Transport_Event_Handler or something), this will reduce footprint and simplify the process of implementing a pluggable protocol. This method has to be renamed to event_handler() Implemented in TAO_IIOP_Transport.

ACE_INLINE void TAO_Transport::first_request_sent (   )

Set the state of the first_request_ flag to 0.

ACE_INLINE int TAO_Transport::flush_timer_pending (  void   )  const [private]

Check if the flush timer is still pending.

int TAO_Transport::format_queue_message (  TAO_OutputCDR &  stream  )

Format and queue a message for stream.

int TAO_Transport::generate_locate_request (  TAO_Target_Specification &  spec, TAO_Operation_Details &  opdetails, TAO_OutputCDR &  output )

This is a request for the transport object to write a LocateRequest header before it is sent out.

int TAO_Transport::generate_request_header (  TAO_Operation_Details &  opd, TAO_Target_Specification &  spec, TAO_OutputCDR &  msg )  [virtual]

This is a request for the transport object to write a request header before it sends out the request Reimplemented in TAO_IIOP_Transport.

int TAO_Transport::handle_input (  TAO_Resume_Handle &  rh, ACE_Time_Value *  max_wait_time = 0, int  block = 0 )  [virtual]

Callback to read incoming data. The ACE_Event_Handler adapter invokes this method as part of its handle_input() operation. Todo: the method name is confusing! Calling it handle_input() would probably make things easier to understand and follow! Once a complete message is read the Transport class delegates on the Messaging layer to invoke the right upcall (on the server) or the TAO_Reply_Dispatcher (on the client side). Parameters: max_wait_time  In some cases the I/O is synchronous, e.g. a thread-per-connection server or when Wait_On_Read is enabled. In those cases a maximum read time can be specified. block  Is deprecated and ignored.

int TAO_Transport::handle_output (  void   )

Callback method to reactively drain the outgoing data queue.

int TAO_Transport::handle_timeout (  const ACE_Time_Value &  current_time, const void *  act )

Parameters: current_time  The current time as reported from the Reactor act  The Asynchronous Completion Token. Currently it is interpreted as follows: If the ACT is the address of this->current_deadline_ the queueing timeout has expired and the queue should start flushing. Returns: Returns 0 if there are no problems, -1 if there is an error Todo: In the future this function could be used to expire messages (oneways) that have been sitting for too long on the queue.

ACE_INLINE void TAO_Transport::id (  size_t  id  )

ACE_INLINE size_t TAO_Transport::id (  void   )  const

Set and Get the identifier for this transport instance. If not set, this will return an integer representation of the this pointer for the instance on which it's called.

bool TAO_Transport::idle_after_reply (  void   )

Request is sent and the reply is received. Idle the transport now.

bool TAO_Transport::idle_after_send (  void   )

Request has been just sent, but the reply is not received. Idle the transport now.

ACE_INLINE bool TAO_Transport::is_connected (  void   )  const

Is this transport really connected.

ACE_INLINE CORBA::Boolean TAO_Transport::is_tcs_set (   )  const

Return true if the tcs has been set.

int TAO_Transport::make_idle (  void   )

Cache management.

TAO_Queued_Data * TAO_Transport::make_queued_data (  ACE_Message_Block &  incoming  )  [protected]

Make a queued data from the incoming message block.

virtual int TAO_Transport::messaging_init (  CORBA::Octet  major, CORBA::Octet  minor )  [pure virtual]

Initialising the messaging object. This would be used by the connector side. On the acceptor side the connection handler would take care of the messaging objects. Implemented in TAO_IIOP_Transport.

virtual TAO_Pluggable_Messaging* TAO_Transport::messaging_object (  void   )  [pure virtual]

Return the messaging object that is used to format the data that needs to be sent. Implemented in TAO_IIOP_Transport.

size_t TAO_Transport::missing_data (  ACE_Message_Block &  message_block  )  [protected]

Return if we have any missing data in the queue of messages or determine if we have more information left out in the presently read message to make it complete.

int TAO_Transport::notify_reactor (  void   )  [private]

ACE_INLINE void TAO_Transport::opened_as (  TAO::Connection_Role   )

ACE_INLINE TAO::Connection_Role TAO_Transport::opened_as (  void   )  const

Methods dealing with the role of the connection, e.g., CLIENT or SERVER. See CORBA 2.6 Specification, Section 15.5.1 for origin of definitions.

void TAO_Transport::operator= (  const TAO_Transport &   )  [private]

ACE_INLINE TAO_ORB_Core * TAO_Transport::orb_core (  void   )  const

Access the ORB that owns this connection.

TAO_OutputCDR & TAO_Transport::out_stream (  void   )

Accessor for the output CDR stream.

int TAO_Transport::parse_consolidate_messages (  ACE_Message_Block &  bl, TAO_Resume_Handle &  rh, ACE_Time_Value *  time = 0 )  [protected]

Called by the handle_input_i(). This method is used to parse message read by the handle_input_i() call. It also decides whether the message needs consolidation before processing.

int TAO_Transport::parse_incoming_messages (  ACE_Message_Block &  message_block  )  [protected]

Method does parsing of the message if we have a fresh message in the message_block or just returns if we have read part of the previously stored message.

bool TAO_Transport::post_connect_hook (  void   )  [virtual]

Hooks that can be overridden in concrete transports. These hooks are invoked just after connection establishment (or after a connection is fetched from cache). The return value signifies whether the invoker should proceed with post connection establishment activities. Protocols like SSLIOP need this to verify whether connections already established have valid certificates. There are no pre_connect_hooks () since the transport doesn't exist before a connection establishment. :-) @NOTE: The methods are not made const with a reason.

bool TAO_Transport::post_open (  size_t  id  )

Perform all the actions when this transport get opened.

void TAO_Transport::process_fragment (  TAO_Queued_Data *  fragment_message, TAO_Queued_Data *  queueable_message, CORBA::Octet  major, CORBA::Octet  minor, TAO_Resume_Handle &  rh )  [private]

Process a non-version specific fragment by either consolidating the fragments or enqueuing the queueable message

int TAO_Transport::process_parsed_messages (  TAO_Queued_Data *  qd, TAO_Resume_Handle &  rh )  [protected]

Process the message by sending it to the higher layers of the ORB.

int TAO_Transport::process_queue_head (  TAO_Resume_Handle &  rh  )  [private]

bool TAO_Transport::provide_blockable_handler (  TAO::Connection_Handler_Set &  handlers  )

Called by the cache when the ORB is shuting down. Parameters: handlers  The TAO_Connection_Handler_Set into which the transport should place its handler if the transport has RW strategy on. Returns: true indicates a handler was added to the handler set. false indocates that the transport did not have a blockable handler that could be added.

void TAO_Transport::provide_handler (  TAO::Connection_Handler_Set &  handlers  )

Added event handler to the handlers set. Called by the cache when the cache is closing. Parameters: handlers  The TAO_Connection_Handler_Set into which the transport should place its handler

int TAO_Transport::purge_entry (  void   )

Cache management.

ACE_INLINE void TAO_Transport::purging_order (  unsigned long  value  )

ACE_INLINE unsigned long TAO_Transport::purging_order (  void   )  const

Get and Set the purging order. The purging strategy uses the set version to set the purging order.

ACE_INLINE int TAO_Transport::queue_is_empty (  void   )

Check if there are messages pending in the queue. Returns: 1 if the queue is empty

int TAO_Transport::queue_is_empty_i (  void   )  [private]

Check if there are messages pending in the queue. This version assumes that the lock is already held. Use with care! Returns: 1 if the queue is empty

int TAO_Transport::queue_message_i (  const ACE_Message_Block *  message_block  )  [protected]

Queue a message for message_block.

int TAO_Transport::recache_transport (  TAO_Transport_Descriptor_Interface *  desc  )

Recache ourselves in the cache. Todo: Ideally the following should be inline. purge_entry has a return value, use it

virtual ssize_t TAO_Transport::recv (  char *  buffer, size_t  len, const ACE_Time_Value *  timeout = 0 )  [pure virtual]

Read len bytes from into buf. This method serializes on handler_lock_, guaranteeing that only thread can execute it on the same instance concurrently. Parameters: buffer  ORB allocated buffer where the data should be @ The ACE_Time_Value *s is just a place holder for now. It is not clear this this is the best place to specify this. The actual timeout values will be kept in the Policies. Implemented in TAO_IIOP_Transport.

size_t TAO_Transport::recv_buffer_size (  void   )

Accessor to recv_buffer_size_.

int TAO_Transport::register_handler (  void   )  [virtual]

Register the handler with the reactor. Register the handler with the reactor. This method is used by the Wait_On_Reactor strategy. The transport must register its event handler with the ORB's Reactor. Todo: I think this method is pretty much useless, the connections are *always* registered with the Reactor, except in thread-per-connection mode. In that case putting the connection in the Reactor would produce unpredictable results anyway.

ACE_Event_Handler::Reference_Count TAO_Transport::remove_reference (  void   )

Initialising the messaging object. This would be used by the connector side. On the acceptor side the connection handler would take care of the messaging objects.

void TAO_Transport::report_invalid_event_handler (  const char *  caller  )  [private]

Print out error messages if the event handler is not valid.

ACE_INLINE void TAO_Transport::reset_flush_timer (  void   )  [private]

The flush timer expired or was explicitly cancelled, mark it as not pending

int TAO_Transport::schedule_output_i (  void   )  [private]

Schedule handle_output() callbacks.

virtual ssize_t TAO_Transport::send (  iovec *  iov, int  iovcnt, size_t &  bytes_transferred, const ACE_Time_Value *  timeout = 0 )  [pure virtual]

Write the complete Message_Block chain to the connection. This method serializes on handler_lock_, guaranteeing that only thread can execute it on the same instance concurrently. Often the implementation simply forwards the arguments to the underlying ACE_Svc_Handler class. Using the code factored out into ACE. Be careful with protocols that perform non-trivial transformations of the data, such as SSLIOP or protocols that compress the stream. Parameters: mblk  contains the data that must be sent. For each message block in the cont() chain all the data between rd_ptr() and wr_ptr() should be delivered to the remote peer. timeout  is the maximum time that the application is willing to wait for the data to be sent, useful in platforms that implement timed writes. The timeout value is obtained from the policies set by the application. bytes_transferred  should return the total number of bytes successfully transferred before the connection blocked. This is required because in some platforms and/or protocols multiple system calls may be required to send the chain of message blocks. The first few calls can work successfully, but the final one can fail or signal a flow control situation (via EAGAIN). In this case the ORB expects the function to return -1, errno to be appropriately set and this argument to return the number of bytes already on the OS I/O subsystem. This call can also fail if the transport instance is no longer associated with a connection (e.g., the connection handler closed down). In that case, it returns -1 and sets errno to ENOENT. Implemented in TAO_IIOP_Transport.

void TAO_Transport::send_connection_closed_notifications (  void   )

Notify all the components inside a Transport when the underlying connection is closed.

void TAO_Transport::send_connection_closed_notifications_i (  void   )  [private]

Assume the lock is held.

virtual int TAO_Transport::send_message (  TAO_OutputCDR &  stream, TAO_Stub *  stub = 0, int  message_semantics = TAO_Transport::TAO_TWOWAY_REQUEST, ACE_Time_Value *  max_time_wait = 0 )  [pure virtual]

Once the ORB is prepared to receive a reply (see send_request() above), and all the arguments have been marshaled the CDR stream must be 'formatted', i.e. the message_size field in the GIOP header can finally be set to the proper value. Implemented in TAO_IIOP_Transport.

int TAO_Transport::send_message_block_chain (  const ACE_Message_Block *  message_block, size_t &  bytes_transferred, ACE_Time_Value *  max_wait_time = 0 )

Send a message block chain,.

int TAO_Transport::send_message_block_chain_i (  const ACE_Message_Block *  message_block, size_t &  bytes_transferred, ACE_Time_Value *  max_wait_time )

Send a message block chain, assuming the lock is held.

int TAO_Transport::send_message_shared (  TAO_Stub *  stub, int  message_semantics, const ACE_Message_Block *  message_block, ACE_Time_Value *  max_wait_time )  [virtual]

Sent the contents of message_block. Parameters: stub  The object reference used for this operation, useful to obtain the current policies. message_semantics  If this is set to TAO_TWO_REQUEST this method will block until the operation is completely written on the wire. If it is set to other values this operation could return. message_block  The CDR encapsulation of the GIOP message that must be sent. The message may consist of multiple Message Blocks chained through the cont() field. max_wait_time  The maximum time that the operation can block, used in the implementation of timeouts. Reimplemented in TAO_IIOP_Transport.

int TAO_Transport::send_message_shared_i (  TAO_Stub *  stub, int  message_semantics, const ACE_Message_Block *  message_block, ACE_Time_Value *  max_wait_time )  [protected]

Implement send_message_shared() assuming the handler_lock_ is held.

int TAO_Transport::send_reply_message_i (  const ACE_Message_Block *  message_block, ACE_Time_Value *  max_wait_time )  [private]

Send a reply message, i.e. do not block until the message is on the wire, but just return after adding them to the queue.

virtual int TAO_Transport::send_request (  TAO_Stub *  stub, TAO_ORB_Core *  orb_core, TAO_OutputCDR &  stream, int  message_semantics, ACE_Time_Value *  max_time_wait )  [pure virtual]

Preparing the ORB to receive the reply only once the request is completely sent opens the system to some subtle race conditions: suppose the ORB is running in a multi-threaded configuration, thread A makes a request while thread B is using the Reactor to process all incoming requests. Thread A could be implemented as follows: 1) send the request 2) setup the ORB to receive the reply 3) wait for the request but in this case thread B may receive the reply between step (1) and (2), and drop it as an invalid or unexpected message. Consequently the correct implementation is: 1) setup the ORB to receive the reply 2) send the request 3) wait for the reply The following method encapsulates this idiom. Todo: This is generic code, it should be factored out into the Transport class. Implemented in TAO_IIOP_Transport.

int TAO_Transport::send_synch_message_helper_i (  TAO_Synch_Queued_Message &  s, ACE_Time_Value *  max_wait_time )  [private]

A helper method used by send_synchronous_message_i() and send_reply_message_i(). Reusable code that could be used by both the methods.

int TAO_Transport::send_synchronous_message_i (  const ACE_Message_Block *  message_block, ACE_Time_Value *  max_wait_time )  [private]

Send a synchronous message, i.e. block until the message is on the wire

size_t TAO_Transport::sent_byte_count (  void   )

Accessor to sent_byte_count_.

ACE_INLINE CORBA::ULong TAO_Transport::tag (  void   )  const

Return the protocol tag. The OMG assigns unique tags (a 32-bit unsigned number) to each protocol. New protocol tags can be obtained free of charge from the OMG, check the documents in corbafwd.h for more details.

int TAO_Transport::tear_listen_point_list (  TAO_InputCDR &  cdr  )  [virtual]

Extracts the list of listen points from the cdr stream. The list would have the protocol specific details of the ListenPoints Reimplemented in TAO_IIOP_Transport.

ACE_INLINE TAO_Transport_Mux_Strategy * TAO_Transport::tms (  void   )  const

Get the TAO_Tranport_Mux_Strategy used by this object. The role of the TAO_Transport_Mux_Strategy is described in more detail in that class' documentation. Enough is to say that the class is used to control how many threads can have pending requests over the same connection. Multiplexing multiple threads over the same connection conserves resources and is almost required for AMI, but having only one pending request per connection is more efficient and reduces the possibilities of priority inversions.

TAO::Transport_Cache_Manager & TAO_Transport::transport_cache_manager (  void   )  [private]

Helper method that returns the Transport Cache Manager.

int TAO_Transport::update_transport (  void   )

Cache management.

ACE_INLINE TAO_Wait_Strategy * TAO_Transport::wait_strategy (  void   )  const

Return the TAO_Wait_Strategy used by this object. The role of the TAO_Wait_Strategy is described in more detail in that class' documentation. Enough is to say that the ORB can wait for a reply blocking on read(), using the Reactor to wait for multiple events concurrently or using the Leader/Followers protocol.

ACE_INLINE void TAO_Transport::wchar_translator (  TAO_Codeset_Translator_Base *   )

CodeSet negotiation - Set the wchar codeset translator factory.

ACE_INLINE TAO_Codeset_Translator_Base * TAO_Transport::wchar_translator (  void   )  const

CodeSet Negotiation - Get the wchar codeset translator factory.

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Friends And Related Function Documentation

friend class TAO_Block_Flushing_Strategy [friend]

This class needs priviledged access to queue_is_empty_i() drain_queue_i()

friend class TAO_Leader_Follower_Flushing_Strategy [friend]

friend class TAO_Reactive_Flushing_Strategy [friend]

These classes need privileged access to: schedule_output_i() cancel_output_i()

friend class TAO_Thread_Per_Connection_Handler [friend]

Needs priveleged access to event_handler_i ()

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Member Data Documentation

int TAO_Transport::bidirectional_flag_ [protected]

Have we sent any info on bidirectional information or have we received any info regarding making the connection served by this transport bidirectional. The flag is used as follows: + We dont want to send the bidirectional context info more than once on the connection. Why? Waste of marshalling and demarshalling time on the client. + On the server side -- once a client that has established the connection asks the server to use the connection both ways, we *dont* want the server to pack service info to the client. That is not allowed. We need a flag to prevent such a things from happening. The value of this flag will be 0 if the client sends info and 1 if the server receives the info.

TAO::Transport_Cache_Manager::HASH_MAP_ENTRY* TAO_Transport::cache_map_entry_ [protected]

Our entry in the cache. We dont own this. It is here for our convenience. We cannot just change things around.

TAO_Codeset_Translator_Base* TAO_Transport::char_translator_ [private]

Additional member values required to support codeset translation. @Phil, I think it would be nice if we could think of a way to do the following. We have been trying to use the transport for marking about translator factories and such! IMHO this is a wrong encapulation ie. trying to populate the transport object with these details. We should probably have a class something like TAO_Message_Property or TAO_Message_Translator or whatever (I am sure you get the idea) and encapsulate all these details. Coupling these seems odd. if I have to be more cynical we can move this to the connection_handler and it may more sense with the DSCP stuff around there. Do you agree?

ACE_Time_Value TAO_Transport::current_deadline_ [protected]

The queue will start draining no later than <queing_deadline_> if* the deadline is

CORBA::Boolean TAO_Transport::first_request_ [private]

First_request_ is true until the first request is sent or received. This is necessary since codeset context information is necessary only on the first request. After that, the translators are fixed for the life of the connection.

long TAO_Transport::flush_timer_id_ [protected]

The timer ID.

ACE_Lock* TAO_Transport::handler_lock_ [mutable, protected]

This is an ACE_Lock that gets initialized from TAO_ORB_Core::resource_factory()->create_cached_connection_lock(). This way, one can use a lock appropriate for the type of system, i.e., a null lock for single-threaded systems, and a real lock for multi-threaded systems.

TAO_Queued_Message* TAO_Transport::head_ [protected]

Implement the outgoing data queue.

size_t TAO_Transport::id_ [protected]

A unique identifier for the transport. This never *never* changes over the lifespan, so we don't have to worry about locking it. HINT: Protocol-specific transports that use connection handler might choose to set this to the handle for their connection.

TAO_Incoming_Message_Queue TAO_Transport::incoming_message_queue_ [protected]

Queue of the incoming messages..

bool TAO_Transport::is_connected_ [protected]

Is this transport really connected or not. In case of oneways with SYNC_NONE Policy we don't wait until the connection is ready and we buffer the requests in this transport until the connection is ready

TAO::Connection_Role TAO_Transport::opening_connection_role_ [protected]

TAO_ORB_Core* TAO_Transport::orb_core_ [protected]

Global orbcore resource.

ACE_Message_Block* TAO_Transport::partial_message_ [private]

Holds the partial GIOP message (if there is one).

unsigned long TAO_Transport::purging_order_ [protected]

Used by the LRU, LFU and FIFO Connection Purging Strategies.

size_t TAO_Transport::recv_buffer_size_ [protected]

Size of the buffer received.

size_t TAO_Transport::sent_byte_count_ [protected]

Number of bytes sent.

CORBA::ULong TAO_Transport::tag_ [protected]

IOP protocol tag.

TAO_Queued_Message* TAO_Transport::tail_ [protected]

CORBA::Boolean TAO_Transport::tcs_set_ [private]

The tcs_set_ flag indicates that negotiation has occured and so the translators are correct, since a null translator is valid if both ends are using the same codeset, whatever that codeset might be.

TAO_Transport_Mux_Strategy* TAO_Transport::tms_ [protected]

Strategy to decide whether multiple requests can be sent over the same connection or the connection is exclusive for a request.

TAO_Transport_Timer TAO_Transport::transport_timer_ [protected]

The adapter used to receive timeout callbacks from the Reactor.

TAO_Codeset_Translator_Base* TAO_Transport::wchar_translator_ [private]

TAO_Wait_Strategy* TAO_Transport::ws_ [protected]

Strategy for waiting for the reply after sending the request.

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The documentation for this class was generated from the following files:

• Transport.h
• Transport.cpp
• Transport.inl

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