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// Copyright 2017 Canonical Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package raftmembership
import (
"fmt"
"time"
"github.com/hashicorp/raft"
)
// ChangeRequest represents a request to change a server's membership in
// a raft cluster (either join or leave).
//
// A requesting server uses an implementation of the membership Changer
// interface to connect to a target server through some network transport layer
// and to ask to join or leave the target server's cluster. The target server
// internally uses ChangeRequest and HandleChangeRequests as helpers to
// implement handlers to process such requests coming from the network
// transport layer.
type ChangeRequest struct {
id raft.ServerID // ID of the server requesting the membership change
address raft.ServerAddress // Address of the server requesting the membership change
kind ChangeRequestKind // Kind of membership change being requested
done chan error // Notify client code of request success or failure
}
// NewJoinRequest creates a new membership ChangeRequest to join a
// cluster.
func NewJoinRequest(id raft.ServerID, address raft.ServerAddress) *ChangeRequest {
return &ChangeRequest{
id: id,
address: address,
kind: JoinRequest,
done: make(chan error, 1),
}
}
// NewLeaveRequest creates a new membership ChangeRequest to leave a
// cluster.
func NewLeaveRequest(id raft.ServerID) *ChangeRequest {
return &ChangeRequest{
id: id,
kind: LeaveRequest,
done: make(chan error, 1),
}
}
// ID of the server requesting to change its membership.
func (r *ChangeRequest) ID() raft.ServerID {
return r.id
}
// Address of the server requesting to change its membership.
func (r *ChangeRequest) Address() raft.ServerAddress {
return r.address
}
// Kind is the type of membership change requested, either join leave.
func (r *ChangeRequest) Kind() ChangeRequestKind {
return r.kind
}
// Error blocks until this ChangeRequest is fully processed or the given
// timeout is reached and returns any error hit while handling the request, or
// nil if none was met.
func (r *ChangeRequest) Error(timeout time.Duration) error {
var err error
select {
case err = <-r.done:
case <-time.After(timeout):
err = fmt.Errorf("timeout waiting for membership change")
}
return err
}
// Done should be invoked by the code handling this request (such as
// HandleChangeRequests) to notify callers that the it has been
// processed, either successfully or not.
func (r *ChangeRequest) Done(err error) {
r.done <- err
close(r.done)
}
// ChangeRequestKind is kind of membership change being requested.
type ChangeRequestKind int
func (k ChangeRequestKind) String() string {
return changeRequestKindToString[k]
}
// Possible values for ChangeRequestKind
const (
JoinRequest ChangeRequestKind = iota
LeaveRequest
)
var changeRequestKindToString = []string{
JoinRequest: "join",
LeaveRequest: "leave",
}
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