128 lines
3.6 KiB
Go
128 lines
3.6 KiB
Go
// Copyright 2016 The etcd Authors
|
|
//
|
|
// 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 concurrency
|
|
|
|
import (
|
|
"time"
|
|
|
|
v3 "github.com/coreos/etcd/clientv3"
|
|
"golang.org/x/net/context"
|
|
)
|
|
|
|
const defaultSessionTTL = 60
|
|
|
|
// Session represents a lease kept alive for the lifetime of a client.
|
|
// Fault-tolerant applications may use sessions to reason about liveness.
|
|
type Session struct {
|
|
client *v3.Client
|
|
opts *sessionOptions
|
|
id v3.LeaseID
|
|
|
|
cancel context.CancelFunc
|
|
donec <-chan struct{}
|
|
}
|
|
|
|
// NewSession gets the leased session for a client.
|
|
func NewSession(client *v3.Client, opts ...SessionOption) (*Session, error) {
|
|
ops := &sessionOptions{ttl: defaultSessionTTL, ctx: client.Ctx()}
|
|
for _, opt := range opts {
|
|
opt(ops)
|
|
}
|
|
|
|
resp, err := client.Grant(ops.ctx, int64(ops.ttl))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
id := v3.LeaseID(resp.ID)
|
|
|
|
ctx, cancel := context.WithCancel(ops.ctx)
|
|
keepAlive, err := client.KeepAlive(ctx, id)
|
|
if err != nil || keepAlive == nil {
|
|
return nil, err
|
|
}
|
|
|
|
donec := make(chan struct{})
|
|
s := &Session{client: client, opts: ops, id: id, cancel: cancel, donec: donec}
|
|
|
|
// keep the lease alive until client error or cancelled context
|
|
go func() {
|
|
defer close(donec)
|
|
for range keepAlive {
|
|
// eat messages until keep alive channel closes
|
|
}
|
|
}()
|
|
|
|
return s, nil
|
|
}
|
|
|
|
// Client is the etcd client that is attached to the session.
|
|
func (s *Session) Client() *v3.Client {
|
|
return s.client
|
|
}
|
|
|
|
// Lease is the lease ID for keys bound to the session.
|
|
func (s *Session) Lease() v3.LeaseID { return s.id }
|
|
|
|
// Done returns a channel that closes when the lease is orphaned, expires, or
|
|
// is otherwise no longer being refreshed.
|
|
func (s *Session) Done() <-chan struct{} { return s.donec }
|
|
|
|
// Orphan ends the refresh for the session lease. This is useful
|
|
// in case the state of the client connection is indeterminate (revoke
|
|
// would fail) or when transferring lease ownership.
|
|
func (s *Session) Orphan() {
|
|
s.cancel()
|
|
<-s.donec
|
|
}
|
|
|
|
// Close orphans the session and revokes the session lease.
|
|
func (s *Session) Close() error {
|
|
s.Orphan()
|
|
// if revoke takes longer than the ttl, lease is expired anyway
|
|
ctx, cancel := context.WithTimeout(s.opts.ctx, time.Duration(s.opts.ttl)*time.Second)
|
|
_, err := s.client.Revoke(ctx, s.id)
|
|
cancel()
|
|
return err
|
|
}
|
|
|
|
type sessionOptions struct {
|
|
ttl int
|
|
ctx context.Context
|
|
}
|
|
|
|
// SessionOption configures Session.
|
|
type SessionOption func(*sessionOptions)
|
|
|
|
// WithTTL configures the session's TTL in seconds.
|
|
// If TTL is <= 0, the default 60 seconds TTL will be used.
|
|
func WithTTL(ttl int) SessionOption {
|
|
return func(so *sessionOptions) {
|
|
if ttl > 0 {
|
|
so.ttl = ttl
|
|
}
|
|
}
|
|
}
|
|
|
|
// WithContext assigns a context to the session instead of defaulting to
|
|
// using the client context. This is useful for canceling NewSession and
|
|
// Close operations immediately without having to close the client. If the
|
|
// context is canceled before Close() completes, the session's lease will be
|
|
// abandoned and left to expire instead of being revoked.
|
|
func WithContext(ctx context.Context) SessionOption {
|
|
return func(so *sessionOptions) {
|
|
so.ctx = ctx
|
|
}
|
|
}
|