RabbitMQ HA fine tuning of mirroring synchronization

Question

I use rabbitmq-server-3.6.1.

It seems there are two options how to set synchronization batch size. First one is policy option "ha-sync-batch-size". It is described in RabbitMQ documentation here. Second one is configuration file option "mirroring_sync_batch_size", which I cannot find described anywhere and do not understand from RabbitMQ source code how it works.

The question is related to the mirroring synchronisation and consists of several subquestions:

1. Does "mirroring_sync_batch_size" influence the synchronisation batch size in the same way as "ha-sync-batch-size" does?
2. If answer to question #1 is yes, which of the options takes precedence when both are present?
3. If answer to question #1 is no, what does "mirroring_sync_batch_size" do?
4. What is purpose and function of configuration file option "mirroring_flow_control"?

Thanks in advance for your answers.

Answer 1

mirroring_sync_batch_size configuration variable is used as default value if no policy is set. mirroring_flow_control option enables or disables flow control mechanism between channel and mirror slave processes. Flow control is described in this blog post