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supervisor.go
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supervisor.go
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/*
Copyright 2015 Gravitational, Inc.
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 service
import (
"os"
"sync"
log "github.com/Sirupsen/logrus"
"github.com/gravitational/trace"
)
// Supervisor implements the simple service logic - registering
// service functions and de-registering the service goroutines
type Supervisor interface {
// Register adds the service to the pool, if supervisor is in
// the started state, the service will be started immediatelly
// otherwise, it will be started after Start() has been called
Register(srv Service)
// RegisterFunc creates a service from function spec and registers
// it within the system
RegisterFunc(fn ServiceFunc)
// Start starts all unstarted services
Start() error
// Wait waits until all services exit
Wait() error
// Run starts and waits for the service to complete
// it's a combinatioin Start() and Wait()
Run() error
}
type LocalSupervisor struct {
state int
sync.Mutex
wg *sync.WaitGroup
services []Service
errors []error
}
func (s *LocalSupervisor) Register(srv Service) {
s.Lock()
defer s.Unlock()
s.services = append(s.services, srv)
if s.state == stateStarted {
s.serve(srv)
}
}
func (s *LocalSupervisor) RegisterFunc(fn ServiceFunc) {
s.Register(fn)
}
func (s *LocalSupervisor) serve(srv Service) {
s.wg.Add(1)
go func() {
defer s.wg.Done()
err := srv.Serve()
if err != nil {
log.Errorf("srv.Serve() error: %v", err)
os.Exit(1)
}
}()
}
func (s *LocalSupervisor) Start() error {
s.Lock()
defer s.Unlock()
s.state = stateStarted
if len(s.services) == 0 {
log.Infof("no services registered, returning")
return nil
}
for _, srv := range s.services {
s.serve(srv)
}
return nil
}
func (s *LocalSupervisor) Wait() error {
s.wg.Wait()
return nil
}
func (s *LocalSupervisor) Run() error {
if err := s.Start(); err != nil {
return trace.Wrap(err)
}
return s.Wait()
}
func NewSupervisor() Supervisor {
return &LocalSupervisor{
services: []Service{},
wg: &sync.WaitGroup{},
}
}
type Service interface {
Serve() error
}
type ServiceFunc func() error
func (s ServiceFunc) Serve() error {
return s()
}
const (
stateCreated = iota
stateStarted = iota
)