Submodule box.ctl
The box.ctl
submodule contains two functions: wait_ro
(wait until read-only)
and wait_rw
(wait until read-write).
The functions are useful during initialization of a server.
A particular use is for box.once().
For example, when a replica is initializing, it may call
a box.once()
function while the server is still in
read-only mode, and fail to make changes that are necessary
only once before the replica is fully initialized.
This could cause conflicts between a master and a replica
if the master is in read-write mode and the replica is in
read-only mode.
Waiting until “read only mode = false” solves this problem.
To see whether a function is already in read-only or read-write mode, check box.info.ro.
Below is a list of all box.ctl
functions.
Name | Use |
---|---|
box.ctl.wait_ro() | Wait until box.info.ro is true |
box.ctl.wait_rw() | Wait until box.info.ro is false |