minio/cmd/service.go
Harshavardhana 9ca25bd48f
fix: atomic.Value should be a concrete type to avoid panics (#13740)
Go's atomic.Value does not support `nil` type,
concrete type is necessary to avoid any panics with
the current implementation.

Also remove boolean to turn-off tracking of freezeCount.
2021-11-23 16:09:28 -08:00

105 lines
3.6 KiB
Go

// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package cmd
import (
"context"
"os"
"os/exec"
"syscall"
)
// Type of service signals currently supported.
type serviceSignal int
const (
serviceRestart serviceSignal = iota // Restarts the server.
serviceStop // Stops the server.
serviceReloadDynamic // Reload dynamic config values.
serviceFreeze // Freeze all S3 API calls.
serviceUnFreeze // Un-Freeze previously frozen S3 API calls.
// Add new service requests here.
)
// Global service signal channel.
var globalServiceSignalCh chan serviceSignal
// GlobalContext context that is canceled when server is requested to shut down.
var GlobalContext context.Context
// cancelGlobalContext can be used to indicate server shutdown.
var cancelGlobalContext context.CancelFunc
func initGlobalContext() {
GlobalContext, cancelGlobalContext = context.WithCancel(context.Background())
globalServiceSignalCh = make(chan serviceSignal)
}
// restartProcess starts a new process passing it the active fd's. It
// doesn't fork, but starts a new process using the same environment and
// arguments as when it was originally started. This allows for a newly
// deployed binary to be started. It returns the pid of the newly started
// process when successful.
func restartProcess() error {
// Use the original binary location. This works with symlinks such that if
// the file it points to has been changed we will use the updated symlink.
argv0, err := exec.LookPath(os.Args[0])
if err != nil {
return err
}
// Invokes the execve system call.
// Re-uses the same pid. This preserves the pid over multiple server-respawns.
return syscall.Exec(argv0, os.Args, os.Environ())
}
// freezeServices will freeze all incoming S3 API calls.
// For each call, unfreezeServices must be called once.
func freezeServices() {
// Use atomics for globalServiceFreeze, so we can read without locking.
// We need a lock since we are need the 2 atomic values to remain in sync.
globalServiceFreezeMu.Lock()
// If multiple calls, first one creates channel.
globalServiceFreezeCnt++
if globalServiceFreezeCnt == 1 {
globalServiceFreeze.Store(make(chan struct{}))
}
globalServiceFreezeMu.Unlock()
}
// unfreezeServices will unfreeze all incoming S3 API calls.
// For each call, unfreezeServices must be called once.
func unfreezeServices() {
// We need a lock since we need the 2 atomic values to remain in sync.
globalServiceFreezeMu.Lock()
// Close when we reach 0
globalServiceFreezeCnt--
if globalServiceFreezeCnt <= 0 {
// Ensure we only close once.
if val := globalServiceFreeze.Load(); val != nil {
var _ch chan struct{}
if ch, ok := val.(chan struct{}); ok {
globalServiceFreeze.Store(_ch)
close(ch)
}
}
globalServiceFreezeCnt = 0 // Don't risk going negative.
}
globalServiceFreezeMu.Unlock()
}