c - 消息在 RabbitMQ C master 中丢失

Question

我正在使用alanxz的RabbitMQ C master。链接如下: https://github.com/alanxz/rabbitmq-c

在 amqp_sendstring.c 和 amqp_listen.c 示例中，当我关闭 amqp_listen.c 并仍然继续使用 amqp_sendstring.c 发送字符串时，消息会丢失。因此，当我重新启动 amqp_listen.c 时，它没有收到消息。我希望 amqp_listen.c 在前者处于非事件状态时接收 amqp_sendstring.c 发送的消息。我该怎么办？

amqp_sendstring.c:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <stdint.h>
#include <amqp_tcp_socket.h>
#include <amqp.h>
#include <amqp_framing.h>

#include "utils.h"

int main(int argc, char const *const *argv)
{
  char const *hostname;
  int port, status;
  char const *exchange;
  char const *routingkey;
  char const *messagebody;
  amqp_socket_t *socket = NULL;
  amqp_connection_state_t conn;

  if (argc < 6) {
    fprintf(stderr, "Usage: amqp_sendstring host port exchange routingkey messagebody\n");
    return 1;
  }

  hostname = argv[1];
  port = atoi(argv[2]);
  exchange = argv[3];
  routingkey = argv[4];
  messagebody = argv[5];

  conn = amqp_new_connection();

  socket = amqp_tcp_socket_new(conn);
  if (!socket) {
    die("creating TCP socket");
  }

  status = amqp_socket_open(socket, hostname, port);
  if (status) {
    die("opening TCP socket");
  }

  die_on_amqp_error(amqp_login(conn, "/", 0, 131072, 0, AMQP_SASL_METHOD_PLAIN, "guest", "guest"),
                    "Logging in");
  amqp_channel_open(conn, 1);
  die_on_amqp_error(amqp_get_rpc_reply(conn), "Opening channel");

  {
    amqp_basic_properties_t props;
    props._flags = AMQP_BASIC_CONTENT_TYPE_FLAG | AMQP_BASIC_DELIVERY_MODE_FLAG;
    props.content_type = amqp_cstring_bytes("text/plain");
    props.delivery_mode = 2; /* persistent delivery mode */
    die_on_error(amqp_basic_publish(conn,
                                    1,
                                    amqp_cstring_bytes(exchange),
                                    amqp_cstring_bytes(routingkey),
                                    0,
                                    0,
                                    &props,
                                    amqp_cstring_bytes(messagebody)),
                 "Publishing");
  }

  die_on_amqp_error(amqp_channel_close(conn, 1, AMQP_REPLY_SUCCESS), "Closing channel");
  die_on_amqp_error(amqp_connection_close(conn, AMQP_REPLY_SUCCESS), "Closing connection");
  die_on_error(amqp_destroy_connection(conn), "Ending connection");
  return 0;
}

amqp_listen.c:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <stdint.h>
#include <amqp_tcp_socket.h>
#include <amqp.h>
#include <amqp_framing.h>

#include <assert.h>

#include "utils.h"

int main(int argc, char const *const *argv)
{
  char const *hostname;
  int port, status;
  char const *exchange;
  char const *bindingkey;
  amqp_socket_t *socket = NULL;
  amqp_connection_state_t conn;

  amqp_bytes_t queuename;

  if (argc < 5) {
    fprintf(stderr, "Usage: amqp_listen host port exchange bindingkey\n");
    return 1;
  }

  hostname = argv[1];
  port = atoi(argv[2]);
  exchange = argv[3];
  bindingkey = argv[4];

  conn = amqp_new_connection();

  socket = amqp_tcp_socket_new(conn);
  if (!socket) {
    die("creating TCP socket");
  }

  status = amqp_socket_open(socket, hostname, port);
  if (status) {
    die("opening TCP socket");
  }

  die_on_amqp_error(amqp_login(conn, "/", 0, 131072, 0, AMQP_SASL_METHOD_PLAIN, "guest", "guest"),
                    "Logging in");
  amqp_channel_open(conn, 1);
  die_on_amqp_error(amqp_get_rpc_reply(conn), "Opening channel");

  {
    amqp_queue_declare_ok_t *r = amqp_queue_declare(conn, 1, amqp_empty_bytes, 0, 0, 0, 1,
                                 amqp_empty_table);
    die_on_amqp_error(amqp_get_rpc_reply(conn), "Declaring queue");
    queuename = amqp_bytes_malloc_dup(r->queue);
    if (queuename.bytes == NULL) {
      fprintf(stderr, "Out of memory while copying queue name");
      return 1;
    }
  }

  amqp_queue_bind(conn, 1, queuename, amqp_cstring_bytes(exchange), amqp_cstring_bytes(bindingkey),
                  amqp_empty_table);
  die_on_amqp_error(amqp_get_rpc_reply(conn), "Binding queue");

  amqp_basic_consume(conn, 1, queuename, amqp_empty_bytes, 0, 1, 0, amqp_empty_table);
  die_on_amqp_error(amqp_get_rpc_reply(conn), "Consuming");

  {
    for (;;) {
      amqp_rpc_reply_t res;
      amqp_envelope_t envelope;

      amqp_maybe_release_buffers(conn);

      res = amqp_consume_message(conn, &envelope, NULL, 0);

      if (AMQP_RESPONSE_NORMAL != res.reply_type) {
        break;
      }

      printf("Delivery %u, exchange %.*s routingkey %.*s\n",
             (unsigned) envelope.delivery_tag,
             (int) envelope.exchange.len, (char *) envelope.exchange.bytes,
             (int) envelope.routing_key.len, (char *) envelope.routing_key.bytes);

      if (envelope.message.properties._flags & AMQP_BASIC_CONTENT_TYPE_FLAG) {
        printf("Content-type: %.*s\n",
               (int) envelope.message.properties.content_type.len,
               (char *) envelope.message.properties.content_type.bytes);
      }
      printf("----\n");

      amqp_dump(envelope.message.body.bytes, envelope.message.body.len);

      amqp_destroy_envelope(&envelope);
    }
  }

  die_on_amqp_error(amqp_channel_close(conn, 1, AMQP_REPLY_SUCCESS), "Closing channel");
  die_on_amqp_error(amqp_connection_close(conn, AMQP_REPLY_SUCCESS), "Closing connection");
  die_on_error(amqp_destroy_connection(conn), "Ending connection");

  return 0;
}

请建议我如何以正确的顺序检索丢失的消息。

Answer 1

由 amqp_listen.c 声明的队列是通过设置 auto_delete 标志来声明的。这意味着当队列上的使用者终止时(通常是通过关闭底层连接)，队列将被删除。如果您希望队列持续存在，请将 amqp_queue_declare 中的 auto_delete 参数设置为 0。

此外，当未指定队列名称时(例如，使用 amqp_empty_bytes 作为 queue 参数)，代理会在您每次调用该队列时创建一个新的唯一队列名称。更改 amqp_queue_declare 函数，以便每次调用它时都使用相同的队列名称。

另请参阅:https://www.rabbitmq.com/amqp-0-9-1-reference.html#queue.declare