72 lines
1.9 KiB
Go
72 lines
1.9 KiB
Go
package raft
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import (
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"fmt"
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"reflect"
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)
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//------------------------------------------------------------------------------
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//
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// Globals
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//
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//------------------------------------------------------------------------------
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var commandTypes map[string]Command
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func init() {
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commandTypes = map[string]Command{}
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}
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//------------------------------------------------------------------------------
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//
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// Typedefs
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//
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//------------------------------------------------------------------------------
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// A command represents an action to be taken on the replicated state machine.
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type Command interface {
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CommandName() string
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Apply(server *Server) ([]byte, error)
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}
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//------------------------------------------------------------------------------
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//
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// Functions
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//
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//------------------------------------------------------------------------------
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//--------------------------------------
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// Instantiation
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//--------------------------------------
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// Creates a new instance of a command by name.
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func NewCommand(name string) (Command, error) {
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// Find the registered command.
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command := commandTypes[name]
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if command == nil {
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return nil, fmt.Errorf("raft.Command: Unregistered command type: %s", name)
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}
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// Make a copy of the command.
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v := reflect.New(reflect.Indirect(reflect.ValueOf(command)).Type()).Interface()
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copy, ok := v.(Command)
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if !ok {
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panic(fmt.Sprintf("raft: Unable to copy command: %s (%v)", command.CommandName(), reflect.ValueOf(v).Kind().String()))
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}
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return copy, nil
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}
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//--------------------------------------
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// Registration
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//--------------------------------------
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// Registers a command by storing a reference to an instance of it.
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func RegisterCommand(command Command) {
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if command == nil {
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panic(fmt.Sprintf("raft: Cannot register nil"))
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} else if commandTypes[command.CommandName()] != nil {
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panic(fmt.Sprintf("raft: Duplicate registration: %s", command.CommandName()))
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}
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commandTypes[command.CommandName()] = command
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}
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