Question

我使用mosquitto服务器作为mqtt经纪人。我测试mosquitto的性能，我需要订阅$ SYS层次结构来获取某些数据，例如当前从$SYS/broker/clients/active主题连接的数量。我有以下mosquitto配置文件。

# Place your local configuration in /etc/mosquitto/conf.d/
#
# A full description of the configuration file is at
# /usr/share/doc/mosquitto/examples/mosquitto.conf.example

pid_file /var/run/mosquitto.pid

persistence true
persistence_location /var/lib/mosquitto/

log_dest file /var/log/mosquitto/mosquitto.log

include_dir /etc/mosquitto/conf.d

listener 1884
protocol websockets

listener 1883

sys_interval 1

max_connections -1

我订阅$SYS/broker/clients/active这样的主题

ubuntu@linux-box:/etc/mosquitto$ mosquitto_sub -d -t $SYS/broker/clients/active
Client mosqsub/28715-ip-172-31 sending CONNECT
Client mosqsub/28715-ip-172-31 received CONNACK
Client mosqsub/28715-ip-172-31 sending SUBSCRIBE (Mid: 1, Topic: /broker/clients/active, QoS: 0)
Client mosqsub/28715-ip-172-31 received SUBACK
Subscribed (mid: 1): 0

配置文件中的sys_interval为1，但我没有收到上述订阅的任何更新。我也试过这个订阅一些替代主题，但仍然没有收到任何东西。 Mosquitto服务器托管在具有Linux操作系统的AWS微实例上。

Answer 1

$SYS被shell解释为环境变量，并且在mosquito_sub看到之前被替换。您可以通过它在SUBSCRIBE日志语句中报告的主题字符串看到这种情况。

您应该在主题字符串周围添加引号：

 $ mosquitto_sub -d -t '$SYS/broker/clients/active'

Mosquitto没有发布SYS主题

1 个答案: