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server_state.go
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server_state.go
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// Copyright (c) 2018 Palantir Technologies. All rights reserved.
//
// 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 witchcraft
import (
"context"
"net/http"
"strconv"
"sync/atomic"
werror "github.com/palantir/witchcraft-go-error"
"github.com/palantir/witchcraft-go-server/conjure/witchcraft/api/health"
)
type ServerState int32
const (
ServerIdle ServerState = iota
ServerInitializing
ServerRunning
)
func (s ServerState) String() string {
switch s {
case ServerIdle:
return "idle"
case ServerInitializing:
return "initializing"
case ServerRunning:
return "running"
default:
return "unknown state: " + strconv.Itoa(int(s))
}
}
type serverStateManager struct {
serverRunning int32
}
func (s *serverStateManager) Start() error {
// state went from Idle to Initializing: OK
if atomic.CompareAndSwapInt32(&s.serverRunning, int32(ServerIdle), int32(ServerInitializing)) {
return nil
}
// error if current state is not idle/failed to transition to initializing
switch s.State() {
case ServerInitializing:
return werror.Error("server is already initializing and must be stopped before it can be started again")
case ServerRunning:
return werror.Error("server is already running and must be stopped before it can be started again")
default:
return werror.Error("server is in an unknown state and must be stopped before it can be started again")
}
}
func (s *serverStateManager) Running() bool {
return s.State() == ServerRunning
}
func (s *serverStateManager) State() ServerState {
return ServerState(atomic.LoadInt32(&s.serverRunning))
}
func (s *serverStateManager) setState(state ServerState) {
atomic.StoreInt32(&s.serverRunning, int32(state))
}
func (s *serverStateManager) Status() (int, interface{}) {
if !s.Running() {
return http.StatusServiceUnavailable, nil
}
return http.StatusOK, nil
}
func (s *serverStateManager) HealthStatus(ctx context.Context) health.HealthStatus {
state := health.HealthStateHealthy
if !s.Running() {
state = health.HealthStateTerminal
}
return health.HealthStatus{
Checks: map[health.CheckType]health.HealthCheckResult{
"SERVER_STATUS": {
Type: "SERVER_STATUS",
State: state,
},
},
}
}