View Source RaftedValue.Data behaviour (rafted_value v0.11.2)
A behaviour that defines data to be replicated by RaftedValue servers.
It is required to implement a callback module of this behaviour to run a consensus group.
Concrete implementations of all callback functions of this behaviour must be pure,
so that all members of a consensus group can reproduce the data by replicating only command_arg.
Therefore, for example, if you want to use "current time" in your command implementation,
you must not obtain current time in command/1 implementation; you have to pass it by embedding in command_arg.
This is a design decision made to support arbitrary data structure while keeping Raft logs compact.
Link to this section Summary
Callbacks
Generic read/write operation on the stored value.
Creates an initial value to be stored.
Read-only operation on the stored value.
Link to this section Types
Link to this section Callbacks
@callback command(data(), command_arg()) :: {command_ret(), data()}
Generic read/write operation on the stored value.
This callback function is invoked by RaftedValue.command/4.
Commands are replicated across members of the consensus group and executed in all members
in order to reproduce the same history of stored value.
This function should return a pair of "return value to client" and "next version of stored data".
@callback new() :: data()
Creates an initial value to be stored.
Whenever a new consensus group is started by RaftedValue.start_link/2 (called with :create_new_consensus_group),
this function is called to initialize the stored value.
Read-only operation on the stored value.
This callback function is invoked by RaftedValue.query/3.
This function should return "return value to client".