问题
I have simple RabbitMQ cluster with 2 physical identical linux nodes: (CentOS, RabbitMQ 3.1.5, Erlang R15B, 2GB Ram, CPU 1xCore). Mirroring and synchronization of nodes is turned on.
I have two problems which bothers me:
In a normal situation everything is fine, but after restarting one of the nodes(by stop_app and start_app in the commandline) the whole cluster becomes unavaible to producers and consumers - I can't produce or receive messages from a queue during synchronization. Is this situation normal?
During synchronization I observed very high CPU load (almost 100%) on the slave node(that which was restarted). I measured the speed of synchronization - it's dramatic low (synchronization of 2 millions of messages takes above 3 hours). It's strange because producing of such amount takes much less. Is this situation normal too?
回答1:
I've recently been tasked with looking into RabbitMQ at work and so have been deep in the documentation.
- When synchronising this is the case. This is an extract from the RabbitMQ HA documentation here.
If a queue is set to automatically synchronise it will synchronise whenever a new slave joins - becoming unresponsive until it has done so.
- If the messages are being read-from and persisted-to disk (either through choice or through memory limitations) there may be overhead there. You can see a chart on this blog entry (it's the last chart before the comments) which indicates that there are performance changes when reading from and writing to queues of that many messages. These charts are for older versions of RabbitMQ but I've not seen anything more recent.
来源：https://stackoverflow.com/questions/19016479/rabbitmq-strange-synchronization-behavior