X-Git-Url: https://gerrit.o-ran-sc.org/r/gitweb?a=blobdiff_plain;f=docs%2Frmr_mt_call.3.rst;h=60d343c4f95ad08455791ed501a95336b288af4c;hb=a3a121ca4a0426ec964fa684fb27c397f2ee9e24;hp=b090e04b51e32e272a22a66ecba0e239ab6c2e83;hpb=2b3c393e660c5e1037191f43cc70537da8316b89;p=ric-plt%2Flib%2Frmr.git diff --git a/docs/rmr_mt_call.3.rst b/docs/rmr_mt_call.3.rst index b090e04..60d343c 100644 --- a/docs/rmr_mt_call.3.rst +++ b/docs/rmr_mt_call.3.rst @@ -1,50 +1,53 @@ - - .. 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_mt_call ============================================================================================ -RMR Library Functions -============================================================================================ - - -NAME --------------------------------------------------------------------------------------------- + + +RMR LIBRARY FUNCTIONS +===================== + + + +NAME +---- + rmr_mt_call - -SYNOPSIS --------------------------------------------------------------------------------------------- - + + +SYNOPSIS +-------- + :: - + #include + extern rmr_mbuf_t* rmr_mt_call( void* vctx, rmr_mbuf_t* msg, int id, int timeout ); - - -DESCRIPTION --------------------------------------------------------------------------------------------- - -The rmr_mt_call function sends the user application message -to a remote endpoint, and waits for a corresponding response -message before returning control to the user application. The -user application supplies a completed message buffer, as it -would for a rmr_send_msg call, but unlike with a send, the -buffer returned will have the response from the application -that received the message. The thread invoking the -*rmr_mt_call()* will block until a message arrives or until -*timeout* milliseconds has passed; which ever comes first. -Using a timeout value of zero (0) will cause the thread to -block without a timeout. + + +DESCRIPTION +----------- + +The ``rmr_mt_call`` function sends the user application +message to a remote endpoint, and waits for a corresponding +response message before returning control to the user +application. The user application supplies a completed +message buffer, as it would for a ``rmr_send_msg`` call, but +unlike with a send, the buffer returned will have the +response from the application that received the message. The +thread invoking the *rmr_mt_call()* will block until a +message arrives or until *timeout* milliseconds has passed; +which ever comes first. Using a timeout value of zero (0) +will cause the thread to block without a timeout. The *id* supplied as the third parameter is an integer in the range of 2 through 255 inclusive. This is a caller defined @@ -57,46 +60,39 @@ Messages which are received while waiting for the response are queued on a *normal* receive queue and will be delivered to the user application with the next invocation of *rmr_mt_rcv()* or *rmr_rvv_msg().* by RMR, and are returned -to the user application when rmr_rcv_msg is invoked. These -messages are returned in the order received, one per call to -rmr_rcv_msg. - -The Transaction ID -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - +to the user application when ``rmr_rcv_msg`` is invoked. +These messages are returned in the order received, one per +call to ``rmr_rcv_msg.`` + + +The Transaction ID +------------------ + The user application is responsible for setting the value of the transaction ID field before invoking *rmr_mt_call.* The -transaction ID is a RMR_MAX_XID byte field that is used to -match the response message when it arrives. RMR will compare -**all** of the bytes in the field, so the caller must ensure -that they are set correctly to avoid missing the response -message. The application which returns the response message -is also expected to ensure that the return buffer has the -matching transaction ID. This can be done transparently if -the application uses the *rmr_rts_msg()* function and does +transaction ID is a ``RMR_MAX_XID`` byte field that is used +to match the response message when it arrives. RMR will +compare **all** of the bytes in the field, so the caller must +ensure that they are set correctly to avoid missing the +response message. The application which returns the response +message is also expected to ensure that the return buffer has +the matching transaction ID. This can be done transparently +if the application uses the *rmr_rts_msg()* function and does not adjust the transaction ID. - -Retries -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - + + +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 + &item The message is sent without error + + &item The underlying transport reports a *hard* failure + + &item The maximum number of retry loops has been attempted A retry loop consists of approximately 1000 send attempts @@ -107,10 +103,11 @@ 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 -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - + + +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 @@ -129,55 +126,58 @@ 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 --------------------------------------------------------------------------------------------- - -The rmr_mt_call function returns a pointer to a message + + +RETURN VALUE +------------ + +The ``rmr_mt_call`` function returns a pointer to a message buffer with the state set to reflect the overall state of -call processing. If the state is RMR_OK then the buffer +call processing. If the state is ``RMR_OK`` then the buffer contains the response message; otherwise the state indicates the error encountered while attempting to send the message. If no response message is received when the timeout period has expired, a nil pointer will be returned (NULL). - -ERRORS --------------------------------------------------------------------------------------------- - + + +ERRORS +------ + These values are reflected in the state field of the returned message. - -RMR_OK - - The call was successful and the message buffer references - the response message. - - -RMR_ERR_BADARG - - An argument passed to the function was invalid. - - -RMR_ERR_CALLFAILED - - The call failed and the value of *errno,* as described - below, should be checked for the specific reason. - - -RMR_ERR_NOENDPT - - An endpoint associated with the message type could not be - found in the route table. - - -RMR_ERR_RETRY - - The underlying transport mechanism was unable to accept - the message for sending. The user application can retry - the call operation if appropriate to do so. + .. list-table:: + :widths: auto + :header-rows: 0 + :class: borderless + + * - **RMR_OK** + - + The call was successful and the message buffer references the + response message. + + * - **RMR_ERR_BADARG** + - + An argument passed to the function was invalid. + + * - **RMR_ERR_CALLFAILED** + - + The call failed and the value of *errno,* as described below, + should be checked for the specific reason. + + * - **RMR_ERR_NOENDPT** + - + An endpoint associated with the message type could not be + found in the route table. + + * - **RMR_ERR_RETRY** + - + The underlying transport mechanism was unable to accept the + message for sending. The user application can retry the call + operation if appropriate to do so. + The global "variable" *errno* will be set to one of the @@ -185,73 +185,83 @@ following values if the overall call processing was not successful. - -ETIMEDOUT - - Too many messages were queued before receiving the - expected response - - -ENOBUFS - - The queued message ring is full, messages were dropped - - -EINVAL - - A parameter was not valid - - -EAGAIN - - The underlying message system wsa interrupted or the - device was busy; the message was **not** sent, and user - application should call this function with the message - again. - - -EXAMPLE --------------------------------------------------------------------------------------------- - -The following code bit shows one way of using the rmr_mt_call -function, and illustrates how the transaction ID must be set. + .. list-table:: + :widths: auto + :header-rows: 0 + :class: borderless + + * - **ETIMEDOUT** + - + Too many messages were queued before receiving the expected + response + + * - **ENOBUFS** + - + The queued message ring is full, messages were dropped + + * - **EINVAL** + - + A parameter was not valid + + * - **EAGAIN** + - + The underlying message system wsa interrupted or the device + was busy; the message was **not** sent, and user application + should call this function with the message again. + + + + +EXAMPLE +------- + +The following code bit shows one way of using the +``rmr_mt_call`` function, and illustrates how the transaction +ID must be set. :: - + int retries_left = 5; // max retries on dev not available static rmr_mbuf_t* mbuf = NULL; // response msg msg_t* pm; // appl message struct (payload) + // get a send buffer and reference the payload mbuf = rmr_alloc_msg( mr, sizeof( pm->req ) ); pm = (msg_t*) mbuf->payload; + // generate an xaction ID and fill in payload with data and msg type rmr_bytes2xact( mbuf, xid, RMR_MAX_XID ); snprintf( pm->req, sizeof( pm->req ), "{ \\"req\\": \\"num users\\"}" ); mbuf->mtype = MT_USR_RESP; + msg = rmr_mt_call( mr, msg, my_id, 100 ); // wait up to 100ms if( ! msg ) { // probably a timeout and no msg received return NULL; // let errno trickle up } + if( mbuf->state != RMR_OK ) { while( retries_left-- > 0 && // loop as long as eagain mbuf->state == RMR_ERR_RETRY && (msg = rmr_mt_call( mr, msg )) != NULL && mbuf->state != RMR_OK ) { + usleep( retry_delay ); } + if( mbuf == NULL || mbuf->state != RMR_OK ) { rmr_free_msg( mbuf ); // safe if nil return NULL; } } + // do something with mbuf - - -SEE ALSO --------------------------------------------------------------------------------------------- - + + +SEE ALSO +-------- + rmr_alloc_msg(3), rmr_free_msg(3), rmr_init(3), rmr_mt_rcv(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3),