Use contexts for new async demo.

1 files changed, 179 insertions, 0 deletions

diff --git a/demo/async/server.c b/demo/async/server.c
new file mode 100644
index 00000000..fe884b3e
--- /dev/null
+++ b/demo/async/server.c
@@ -0,0 +1,179 @@
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitoar.com>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+// This program serves as an example for how to write an async RPC service,
+// using the request/reply pattern and contexts (nng_ctx(5)).  The server
+// allocates a number of contexts up front, which determines the amount of
+// parallelism possible.  The callbacks are handled asynchronously, so
+// this could be done by threads, or something similar.  For our uses we
+// make use of an event driven architecture that we already have available.
+
+// Our demonstration application layer protocol is simple.  The client sends
+// a number of milliseconds to wait before responding.  The server just gives
+// back an empty reply after waiting that long.
+
+// To run this program, start the server as async_demo <url> -s
+// Then connect to it with the client as async_client <url> <msec>.
+//
+//  For example:
+//
+//  % ./server tcp://127.0.0.1:5555 &
+//  % ./client tcp://127.0.0.1:5555 323
+//  Request took 324 milliseconds.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+#include <time.h>
+
+#include <nng/nng.h>
+#include <nng/protocol/reqrep0/rep.h>
+#include <nng/supplemental/util/platform.h>
+
+// Parallel is the maximum number of outstanding requests we can handle.
+// This is *NOT* the number of threads in use, but instead represents
+// outstanding work items.  Select a small number to reduce memory size.
+// (Each one of these can be thought of as a request-reply loop.)  Note
+// that you will probably run into limitations on the number of open file
+// descriptors if you set this too high. (If not for that limit, this could
+// be set in the thousands, each context consumes a couple of KB.)
+#ifndef PARALLEL
+#define PARALLEL 128
+#endif
+
+// The server keeps a list of work items, sorted by expiration time,
+// so that we can use this to set the timeout to the correct value for
+// use in poll.
+struct work {
+	enum { INIT, RECV, WAIT, SEND } state;
+	nng_aio *aio;
+	nng_msg *msg;
+	nng_ctx  ctx;
+};
+
+void
+fatal(const char *func, int rv)
+{
+	fprintf(stderr, "%s: %s\n", func, nng_strerror(rv));
+	exit(1);
+}
+
+void
+server_cb(void *arg)
+{
+	struct work *work = arg;
+	nng_msg *    msg;
+	int          rv;
+	uint32_t     when;
+
+	switch (work->state) {
+	case INIT:
+		work->state = RECV;
+		nng_ctx_recv(work->ctx, work->aio);
+		break;
+	case RECV:
+		if ((rv = nng_aio_result(work->aio)) != 0) {
+			fatal("nng_ctx_recv", rv);
+		}
+		msg = nng_aio_get_msg(work->aio);
+		if ((rv = nng_msg_trim_u32(msg, &when)) != 0) {
+			// bad message, just ignore it.
+			nng_msg_free(msg);
+			nng_ctx_recv(work->ctx, work->aio);
+			return;
+		}
+		work->msg   = msg;
+		work->state = WAIT;
+		nng_sleep_aio(when, work->aio);
+		break;
+	case WAIT:
+		// We could add more data to the message here.
+		nng_aio_set_msg(work->aio, work->msg);
+		work->msg   = NULL;
+		work->state = SEND;
+		nng_ctx_send(work->ctx, work->aio);
+		break;
+	case SEND:
+		if ((rv = nng_aio_result(work->aio)) != 0) {
+			nng_msg_free(work->msg);
+			fatal("nng_ctx_send", rv);
+		}
+		work->state = RECV;
+		nng_ctx_recv(work->ctx, work->aio);
+		break;
+	default:
+		fatal("bad state!", NNG_ESTATE);
+		break;
+	}
+}
+
+struct work *
+alloc_work(nng_socket sock)
+{
+	struct work *w;
+	int          rv;
+
+	if ((w = nng_alloc(sizeof(*w))) == NULL) {
+		fatal("nng_alloc", NNG_ENOMEM);
+	}
+	if ((rv = nng_aio_alloc(&w->aio, server_cb, w)) != 0) {
+		fatal("nng_aio_alloc", rv);
+	}
+	if ((rv = nng_ctx_open(&w->ctx, sock)) != 0) {
+		fatal("nng_ctx_open", rv);
+	}
+	w->state = INIT;
+	return (w);
+}
+
+// The server runs forever.
+int
+server(const char *url)
+{
+	nng_socket   sock;
+	struct work *works[PARALLEL];
+	int          rv;
+	int          i;
+
+	/*  Create the socket. */
+	rv = nng_rep0_open(&sock);
+	if (rv != 0) {
+		fatal("nng_rep0_open", rv);
+	}
+
+	for (i = 0; i < PARALLEL; i++) {
+		works[i] = alloc_work(sock);
+	}
+
+	if ((rv = nng_listen(sock, url, NULL, 0)) != 0) {
+		fatal("nng_listen", rv);
+	}
+
+	for (i = 0; i < PARALLEL; i++) {
+		server_cb(works[i]); // this starts them going (INIT state)
+	}
+
+	for (;;) {
+		nng_msleep(3600000); // neither pause() nor sleep() portable
+	}
+}
+
+int
+main(int argc, char **argv)
+{
+	int rc;
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s <url>\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+	rc = server(argv[1]);
+	exit(rc == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
+}