nats.zig/deps/nats.c/examples/subscriber.c

// Copyright 2015-2018 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "examples.h"

static const char *usage = ""\
"-gd            use global message delivery thread pool\n" \
"-sync          receive synchronously (default is asynchronous)\n" \
"-count         number of expected messages\n";

static void
onMsg(natsConnection *nc, natsSubscription *sub, natsMsg *msg, void *closure)
{
    if (print)
        printf("Received msg: %s - %.*s\n",
               natsMsg_GetSubject(msg),
               natsMsg_GetDataLength(msg),
               natsMsg_GetData(msg));

    if (start == 0)
        start = nats_Now();

    // We should be using a mutex to protect those variables since
    // they are used from the subscription's delivery and the main
    // threads. For demo purposes, this is fine.
    if (++count == total)
        elapsed = nats_Now() - start;

    natsMsg_Destroy(msg);
}

static void
asyncCb(natsConnection *nc, natsSubscription *sub, natsStatus err, void *closure)
{
    if (print)
        printf("Async error: %u - %s\n", err, natsStatus_GetText(err));

    natsSubscription_GetDropped(sub, (int64_t*) &dropped);
}

int main(int argc, char **argv)
{
    natsConnection      *conn = NULL;
    natsOptions         *opts  = NULL;
    natsSubscription    *sub   = NULL;
    natsStatistics      *stats = NULL;
    natsMsg             *msg   = NULL;
    natsStatus          s;

    opts = parseArgs(argc, argv, usage);

    printf("Listening %ssynchronously on '%s'.\n",
           (async ? "a" : ""), subj);

    s = natsOptions_SetErrorHandler(opts, asyncCb, NULL);

    if (s == NATS_OK)
        s = natsConnection_Connect(&conn, opts);

    if (s == NATS_OK)
    {
        if (async)
            s = natsConnection_Subscribe(&sub, conn, subj, onMsg, NULL);
        else
            s = natsConnection_SubscribeSync(&sub, conn, subj);
    }

    // For maximum performance, set no limit on the number of pending messages.
    if (s == NATS_OK)
        s = natsSubscription_SetPendingLimits(sub, -1, -1);

    if (s == NATS_OK)
        s = natsSubscription_AutoUnsubscribe(sub, (int) total);

    if (s == NATS_OK)
        s = natsStatistics_Create(&stats);

    if ((s == NATS_OK) && async)
    {
        while (s == NATS_OK)
        {
            s = printStats(STATS_IN|STATS_COUNT, conn, sub, stats);

            if (count + dropped == total)
                break;

            if (s == NATS_OK)
                nats_Sleep(1000);
        }
    }
    else if (s == NATS_OK)
    {
        int64_t last = 0;

        for (count = 0; (s == NATS_OK) && (count < total); count++)
        {
            s = natsSubscription_NextMsg(&msg, sub, 10000);
            if (s != NATS_OK)
                break;

            if (start == 0)
                start = nats_Now();

            if (nats_Now() - last >= 1000)
            {
                s = printStats(STATS_IN|STATS_COUNT, conn, sub, stats);
                last = nats_Now();
            }

            natsMsg_Destroy(msg);
        }
    }

    if (s == NATS_OK)
    {
        printStats(STATS_IN|STATS_COUNT,conn, sub, stats);
        printPerf("Received");
    }
    else
    {
        printf("Error: %u - %s\n", s, natsStatus_GetText(s));
        nats_PrintLastErrorStack(stderr);
    }

    // Destroy all our objects to avoid report of memory leak
    natsStatistics_Destroy(stats);
    natsSubscription_Destroy(sub);
    natsConnection_Destroy(conn);
    natsOptions_Destroy(opts);

    // To silence reports of memory still in used with valgrind
    nats_Close();

    return 0;
}