k8s.io/apiserver@v0.31.1/pkg/server/signal.go (about)

     1  /*
     2  Copyright 2017 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package server
    18  
    19  import (
    20  	"context"
    21  	"os"
    22  	"os/signal"
    23  )
    24  
    25  var onlyOneSignalHandler = make(chan struct{})
    26  var shutdownHandler chan os.Signal
    27  
    28  // SetupSignalHandler registered for SIGTERM and SIGINT. A stop channel is returned
    29  // which is closed on one of these signals. If a second signal is caught, the program
    30  // is terminated with exit code 1.
    31  // Only one of SetupSignalContext and SetupSignalHandler should be called, and only can
    32  // be called once.
    33  func SetupSignalHandler() <-chan struct{} {
    34  	return SetupSignalContext().Done()
    35  }
    36  
    37  // SetupSignalContext is same as SetupSignalHandler, but a context.Context is returned.
    38  // Only one of SetupSignalContext and SetupSignalHandler should be called, and only can
    39  // be called once.
    40  func SetupSignalContext() context.Context {
    41  	close(onlyOneSignalHandler) // panics when called twice
    42  
    43  	shutdownHandler = make(chan os.Signal, 2)
    44  
    45  	ctx, cancel := context.WithCancel(context.Background())
    46  	signal.Notify(shutdownHandler, shutdownSignals...)
    47  	go func() {
    48  		<-shutdownHandler
    49  		cancel()
    50  		<-shutdownHandler
    51  		os.Exit(1) // second signal. Exit directly.
    52  	}()
    53  
    54  	return ctx
    55  }
    56  
    57  // RequestShutdown emulates a received event that is considered as shutdown signal (SIGTERM/SIGINT)
    58  // This returns whether a handler was notified
    59  func RequestShutdown() bool {
    60  	if shutdownHandler != nil {
    61  		select {
    62  		case shutdownHandler <- shutdownSignals[0]:
    63  			return true
    64  		default:
    65  		}
    66  	}
    67  
    68  	return false
    69  }