docs/rmr_send_msg.3.rst - oransc/ric-plt/lib/rmr - Gitiles



 .. This work is licensed under a Creative Commons Attribution 4.0 International License.
 .. SPDX-License-Identifier: CC-BY-4.0
 .. CAUTION: this document is generated from source in doc/src/rtd.
 .. To make changes edit the source and recompile the document.
 .. Do NOT make changes directly to .rst or .md files.


 ============================================================================================
 Man Page: rmr_send_msg
 ============================================================================================

 RMR Library Functions
 ============================================================================================


 NAME
 --------------------------------------------------------------------------------------------

 rmr_send_msg

 SYNOPSIS
 --------------------------------------------------------------------------------------------


 ::

  #include <rmr/rmr.h>
  rmr_mbuf_t* rmr_send_msg( void* vctx, rmr_mbuf_t* msg );


 DESCRIPTION
 --------------------------------------------------------------------------------------------

 The rmr_send_msg function accepts a message buffer from the
 user application and attempts to send it. The destination of
 the message is selected based on the message type specified
 in the message buffer, and the matching information in the
 routing tables which are currently in use by the RMR library.
 This may actually result in the sending of the message to
 multiple destinations which could degrade expected overall
 performance of the user application. (Limiting excessive
 sending of messages is the responsibility of the
 application(s) responsible for building the routing table
 used by the RMR library, and not the responsibility of the
 library.)

 Retries
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 The send operations in RMR will retry *soft* send failures
 until one of three conditions occurs:


 1.

   The message is sent without error


 2.

   The underlying transport reports a *hard* failure


 3.

   The maximum number of retry loops has been attempted


 A retry loop consists of approximately 1000 send attempts
 **without** any intervening calls to *sleep()* or *usleep().*
 The number of retry loops defaults to 1, thus a maximum of
 1000 send attempts is performed before returning to the user
 application. This value can be set at any point after RMr
 initialisation using the *rmr_set_stimeout()* function
 allowing the user application to completely disable retires
 (set to 0), or to increase the number of retry loops.

 Transport Level Blocking
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 The underlying transport mechanism used to send messages is
 configured in *non-blocking* mode. This means that if a
 message cannot be sent immediately the transport mechanism
 will **not** pause with the assumption that the inability to
 send will clear quickly (within a few milliseconds). This
 means that when the retry loop is completely disabled (set to
 0), that the failure to accept a message for sending by the
 underlying mechanisms (software or hardware) will be reported
 immediately to the user application.

 It should be noted that depending on the underlying transport
 mechanism being used, it is extremely likely that retry
 conditions will happen during normal operations. These are
 completely out of RMR's control, and there is nothing that
 RMR can do to avoid or mitigate these other than by allowing
 RMR to retry the send operation, and even then it is possible
 (e.g., during connection reattempts), that a single retry
 loop is not enough to guarantee a successful send.

 RETURN VALUE
 --------------------------------------------------------------------------------------------

 On success, a new message buffer, with an empty payload, is
 returned for the application to use for the next send. The
 state in this buffer will reflect the overall send operation
 state and will be RMR_OK when the send was successful.

 When the message cannot be successfully sent this function
 will return the unsent (original) message buffer with the
 state set to indicate the reason for failure. The value of
 *errno* may also be set to reflect a more detailed failure
 reason if it is known.

 In the event of extreme failure, a nil pointer is returned.
 In this case the value of errno might be of some use, for
 documentation, but there will be little that the user
 application can do other than to move on.

 **CAUTION:** In some cases it is extremely likely that the
 message returned by the send function does **not** reference
 the same memory structure. Thus is important for the user
 programme to capture the new pointer for future use or to be
 passed to rmr_free(). If you are experiencing either double
 free errors or segment faults in either rmr_free() or
 rmr_send_msg(), ensure that the return value from this
 function is being captured and used.

 ERRORS
 --------------------------------------------------------------------------------------------

 The following values may be passed back in the *state* field
 of the returned message buffer.


 RMR_RETRY

   The message could not be sent, but the underlying
   transport mechanism indicates that the failure is
   temporary. If the send operation is tried again it might
   be successful.

 RMR_SEND_FAILED

   The send operation was not successful and the underlying
   transport mechanism indicates a permanent (hard) failure;
   retrying the send is not possible.

 RMR_ERR_BADARG

   The message buffer pointer did not refer to a valid
   message.

 RMR_ERR_NOHDR

   The header in the message buffer was not valid or
   corrupted.

 RMR_ERR_NOENDPT

   The message type in the message buffer did not map to a
   known endpoint.


 The following values may be assigned to errno on failure.


 INVAL

   Parameter(s) passed to the function were not valid, or the
   underlying message processing environment was unable to
   interpret the message.


 ENOKEY

   The header information in the message buffer was invalid.


 ENXIO

   No known endpoint for the message could be found.


 EMSGSIZE

   The underlying transport refused to accept the message
   because of a size value issue (message was not attempted
   to be sent).


 EFAULT

   The message referenced by the message buffer is corrupt
   (nil pointer or bad internal length).


 EBADF

   Internal RMR error; information provided to the message
   transport environment was not valid.


 ENOTSUP

   Sending was not supported by the underlying message
   transport.


 EFSM

   The device is not in a state that can accept the message.


 EAGAIN

   The device is not able to accept a message for sending.
   The user application should attempt to resend.


 EINTR

   The operation was interrupted by delivery of a signal
   before the message was sent.


 ETIMEDOUT

   The underlying message environment timed out during the
   send process.


 ETERM

   The underlying message environment is in a shutdown state.


 EXAMPLE
 --------------------------------------------------------------------------------------------

 The following is a simple example of how the rmr_send_msg
 function is called. In this example, the send message buffer
 is saved between calls and reused eliminating alloc/free
 cycles.


 ::

      static rmr_mbuf_t*  send_msg = NULL;        // message to send; reused on each call
      msg_t*  send_pm;                            // payload for send
      msg_t*  pm;                                 // our message format in the received payload
      if( send_msg  == NULL ) {
          send_msg = rmr_alloc_msg( mr, MAX_SIZE ); // new buffer to send
      }
      // reference payload and fill in message type
      pm = (msg_t*) send_msg->payload;
      send_msg->mtype = MT_ANSWER;
      msg->len = generate_data( pm );       // something that fills the payload in
      msg = rmr_send_msg( mr, send_msg );   // ensure new pointer used after send
      if( ! msg ) {
          return ERROR;
      } else {
          if( msg->state != RMR_OK ) {
              // check for RMR_ERR_RETRY, and resend if needed
              // else return error
          }
      }
      return OK;


 SEE ALSO
 --------------------------------------------------------------------------------------------

 rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3),
 rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3),
 rmr_rts_msg(3), rmr_ready(3), rmr_mk_ring(3),
 rmr_ring_free(3), rmr_torcv_rcv(3), rmr_wh_send_msg(3)


	.. This work is licensed under a Creative Commons Attribution 4.0 International License.
	.. SPDX-License-Identifier: CC-BY-4.0
	.. CAUTION: this document is generated from source in doc/src/rtd.
	.. To make changes edit the source and recompile the document.
	.. Do NOT make changes directly to .rst or .md files.


	============================================================================================
	Man Page: rmr_send_msg
	============================================================================================

	RMR Library Functions
	============================================================================================


	NAME
	--------------------------------------------------------------------------------------------

	rmr_send_msg

	SYNOPSIS
	--------------------------------------------------------------------------------------------


	::

	#include <rmr/rmr.h>
	rmr_mbuf_t* rmr_send_msg( void* vctx, rmr_mbuf_t* msg );



	DESCRIPTION
	--------------------------------------------------------------------------------------------

	The rmr_send_msg function accepts a message buffer from the
	user application and attempts to send it. The destination of
	the message is selected based on the message type specified
	in the message buffer, and the matching information in the
	routing tables which are currently in use by the RMR library.
	This may actually result in the sending of the message to
	multiple destinations which could degrade expected overall
	performance of the user application. (Limiting excessive
	sending of messages is the responsibility of the
	application(s) responsible for building the routing table
	used by the RMR library, and not the responsibility of the
	library.)

	Retries
	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	The send operations in RMR will retry soft send failures
	until one of three conditions occurs:



	1.

	The message is sent without error


	2.

	The underlying transport reports a hard failure


	3.

	The maximum number of retry loops has been attempted


	A retry loop consists of approximately 1000 send attempts
	without any intervening calls to sleep() or usleep().
	The number of retry loops defaults to 1, thus a maximum of
	1000 send attempts is performed before returning to the user
	application. This value can be set at any point after RMr
	initialisation using the rmr_set_stimeout() function
	allowing the user application to completely disable retires
	(set to 0), or to increase the number of retry loops.

	Transport Level Blocking
	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	The underlying transport mechanism used to send messages is
	configured in non-blocking mode. This means that if a
	message cannot be sent immediately the transport mechanism
	will not pause with the assumption that the inability to
	send will clear quickly (within a few milliseconds). This
	means that when the retry loop is completely disabled (set to
	0), that the failure to accept a message for sending by the
	underlying mechanisms (software or hardware) will be reported
	immediately to the user application.

	It should be noted that depending on the underlying transport
	mechanism being used, it is extremely likely that retry
	conditions will happen during normal operations. These are
	completely out of RMR's control, and there is nothing that
	RMR can do to avoid or mitigate these other than by allowing
	RMR to retry the send operation, and even then it is possible
	(e.g., during connection reattempts), that a single retry
	loop is not enough to guarantee a successful send.

	RETURN VALUE
	--------------------------------------------------------------------------------------------

	On success, a new message buffer, with an empty payload, is
	returned for the application to use for the next send. The
	state in this buffer will reflect the overall send operation
	state and will be RMR_OK when the send was successful.

	When the message cannot be successfully sent this function
	will return the unsent (original) message buffer with the
	state set to indicate the reason for failure. The value of
	errno may also be set to reflect a more detailed failure
	reason if it is known.

	In the event of extreme failure, a nil pointer is returned.
	In this case the value of errno might be of some use, for
	documentation, but there will be little that the user
	application can do other than to move on.

	CAUTION: In some cases it is extremely likely that the
	message returned by the send function does not reference
	the same memory structure. Thus is important for the user
	programme to capture the new pointer for future use or to be
	passed to rmr_free(). If you are experiencing either double
	free errors or segment faults in either rmr_free() or
	rmr_send_msg(), ensure that the return value from this
	function is being captured and used.

	ERRORS
	--------------------------------------------------------------------------------------------

	The following values may be passed back in the state field
	of the returned message buffer.



	RMR_RETRY

	The message could not be sent, but the underlying
	transport mechanism indicates that the failure is
	temporary. If the send operation is tried again it might
	be successful.

	RMR_SEND_FAILED

	The send operation was not successful and the underlying
	transport mechanism indicates a permanent (hard) failure;
	retrying the send is not possible.

	RMR_ERR_BADARG

	The message buffer pointer did not refer to a valid
	message.

	RMR_ERR_NOHDR

	The header in the message buffer was not valid or
	corrupted.

	RMR_ERR_NOENDPT

	The message type in the message buffer did not map to a
	known endpoint.


	The following values may be assigned to errno on failure.


	INVAL

	Parameter(s) passed to the function were not valid, or the
	underlying message processing environment was unable to
	interpret the message.


	ENOKEY

	The header information in the message buffer was invalid.


	ENXIO

	No known endpoint for the message could be found.


	EMSGSIZE

	The underlying transport refused to accept the message
	because of a size value issue (message was not attempted
	to be sent).


	EFAULT

	The message referenced by the message buffer is corrupt
	(nil pointer or bad internal length).


	EBADF

	Internal RMR error; information provided to the message
	transport environment was not valid.


	ENOTSUP

	Sending was not supported by the underlying message
	transport.


	EFSM

	The device is not in a state that can accept the message.


	EAGAIN

	The device is not able to accept a message for sending.
	The user application should attempt to resend.


	EINTR

	The operation was interrupted by delivery of a signal
	before the message was sent.


	ETIMEDOUT

	The underlying message environment timed out during the
	send process.


	ETERM

	The underlying message environment is in a shutdown state.


	EXAMPLE
	--------------------------------------------------------------------------------------------

	The following is a simple example of how the rmr_send_msg
	function is called. In this example, the send message buffer
	is saved between calls and reused eliminating alloc/free
	cycles.


	::

	static rmr_mbuf_t* send_msg = NULL; // message to send; reused on each call
	msg_t* send_pm; // payload for send
	msg_t* pm; // our message format in the received payload
	if( send_msg == NULL ) {
	send_msg = rmr_alloc_msg( mr, MAX_SIZE ); // new buffer to send
	}
	// reference payload and fill in message type
	pm = (msg_t*) send_msg->payload;
	send_msg->mtype = MT_ANSWER;
	msg->len = generate_data( pm ); // something that fills the payload in
	msg = rmr_send_msg( mr, send_msg ); // ensure new pointer used after send
	if( ! msg ) {
	return ERROR;
	} else {
	if( msg->state != RMR_OK ) {
	// check for RMR_ERR_RETRY, and resend if needed
	// else return error
	}
	}
	return OK;



	SEE ALSO
	--------------------------------------------------------------------------------------------

	rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3),
	rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3),
	rmr_rts_msg(3), rmr_ready(3), rmr_mk_ring(3),
	rmr_ring_free(3), rmr_torcv_rcv(3), rmr_wh_send_msg(3)