X-Git-Url: https://gerrit.o-ran-sc.org/r/gitweb?a=blobdiff_plain;ds=inline;f=docs%2Frmr_wh_call.3.rst;fp=docs%2Frmr_wh_call.3.rst;h=3d6ac315c28828b128a51d2b298d7260b855ecac;hb=117030c67f7a3722e64f1ecc3305a5862b3b7ce9;hp=0000000000000000000000000000000000000000;hpb=2d9d6784b306047e94ca9816813e5007b00fd17e;p=ric-plt%2Flib%2Frmr.git diff --git a/docs/rmr_wh_call.3.rst b/docs/rmr_wh_call.3.rst new file mode 100644 index 0000000..3d6ac31 --- /dev/null +++ b/docs/rmr_wh_call.3.rst @@ -0,0 +1,214 @@ + + +.. 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_wh_call +============================================================================================ + +RMR Library Functions +============================================================================================ + + +NAME +-------------------------------------------------------------------------------------------- + +rmr_wh_call + +SYNOPSIS +-------------------------------------------------------------------------------------------- + + +:: + + #include + rmr_mbuf_t* rmr_wh_call( void* vctx, rmr_whid_t whid, rmr_mbuf_t* msg, int call_id, int max_wait ) + + + +DESCRIPTION +-------------------------------------------------------------------------------------------- + +The rmr_wh_call function accepts a message buffer (msg) from +the user application and attempts to send it using the +wormhole ID provided (whid). If the send is successful, the +call will block until either a response message is received, +or the max_wait number of milliseconds has passed. In order +for the response to be recognised as a response, the remote +process **must** use rmr_rts_msg() to send their response. + +Like *rmr_wh_send_msg,* this function attempts to send the +message directly to a process at the other end of a wormhole +which was created with *rmr_wh_open().* When sending message +via wormholes, the normal RMR routing based on message type +is ignored, and the caller may leave the message type +unspecified in the message buffer (unless it is needed by the +receiving process). The call_id parameter is a number in the +range of 2 through 255 and is used to identify the calling +thread in order to properly match a response message when it +arrives. Providing this value, and ensuring the proper +uniqueness, is the responsibility of the user application and +as such the ability to use the rmr_wh_call() function from +potentially non-threaded concurrent applications (such as +Go's goroutines) is possible. + +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, new message buffer, with the payload containing +the response from the remote endpoint is returned. The state +in this buffer will reflect the overall send operation state +and should be RMR_OK. + +If a message is returned with a state which is anything other +than RMR_OK, the indication is that the send was not +successful. The user application must check the state and +determine the course of action. If the return value is NULL, +no message, the indication is that there was no response +received within the timeout (max_wait) period of time. + +ERRORS +-------------------------------------------------------------------------------------------- + +The following values may be passed back in the *state* field +of the returned message buffer. + + + +RMR_ERR_WHID + + The wormhole ID passed in was not associated with an open + wormhole, or was out of range for a valid ID. + +RMR_ERR_NOWHOPEN + + No wormholes exist, further attempt to validate the ID are + skipped. + +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. + + +EXAMPLE +-------------------------------------------------------------------------------------------- + +The following is a simple example of how the a wormhole is +created (rmr_wh_open) and then how rmr_wh_send_msg function +is used to send messages. Some error checking is omitted for +clarity. + + +:: + + #include // system headers omitted for clarity + int main() { + rmr_whid_t whid = -1; // wormhole id for sending + void* mrc; //msg router context + int i; + rmr_mbuf_t* sbuf; // send buffer + int count = 0; + int norm_msg_size = 1500; // most messages fit in this size + mrc = rmr_init( "43086", norm_msg_size, RMRFL_NONE ); + if( mrc == NULL ) { + fprintf( stderr, "[FAIL] unable to initialise RMR environment\\n" ); + exit( 1 ); + } + while( ! rmr_ready( mrc ) ) { // wait for routing table info + sleep( 1 ); + } + sbuf = rmr_alloc_msg( mrc, 2048 ); + while( 1 ) { + if( whid < 0 ) { + whid = rmr_wh_open( mrc, "localhost:6123" ); // open fails if endpoint refuses conn + if( RMR_WH_CONNECTED( wh ) ) { + snprintf( sbuf->payload, 1024, "periodic update from sender: %d", count++ ); + sbuf->len = strlen( sbuf->payload ); + sbuf = rmr_wh_call( mrc, whid, sbuf, 1000 ); // expect a response in 1s or less + if( sbuf != NULL && sbuf->state = RMR_OK ) { + sprintf( stderr, "response: %s\\n", sbuf->payload ); // assume they sent a string + } else { + sprintf( stderr, "response not received, or send error\\n" ); + } + } + } + sleep( 5 ); + } + } + + + +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_fib(3), rmr_has_str(3), +rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), +rmr_set_stimeout(3), rmr_wh_open(3), rmr_wh_close(3), +rmr_wh_state(3)