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Source file src/k8s.io/kubernetes/pkg/windows/service/service.go

Documentation: k8s.io/kubernetes/pkg/windows/service

     1  //go:build windows
     2  // +build windows
     3  
     4  /*
     5  Copyright 2018 The Kubernetes Authors.
     6  
     7  Licensed under the Apache License, Version 2.0 (the "License");
     8  you may not use this file except in compliance with the License.
     9  You may obtain a copy of the License at
    10  
    11      http://www.apache.org/licenses/LICENSE-2.0
    12  
    13  Unless required by applicable law or agreed to in writing, software
    14  distributed under the License is distributed on an "AS IS" BASIS,
    15  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    16  See the License for the specific language governing permissions and
    17  limitations under the License.
    18  */
    19  
    20  package service
    21  
    22  import (
    23  	"os"
    24  	"time"
    25  
    26  	"k8s.io/apiserver/pkg/server"
    27  	"k8s.io/klog/v2"
    28  
    29  	"golang.org/x/sys/windows"
    30  	"golang.org/x/sys/windows/svc"
    31  )
    32  
    33  type handler struct {
    34  	tosvc   chan bool
    35  	fromsvc chan error
    36  }
    37  
    38  // InitService is the entry point for running the daemon as a Windows
    39  // service. It returns an indication of whether it is running as a service;
    40  // and an error.
    41  func InitService(serviceName string) error {
    42  	h := &handler{
    43  		tosvc:   make(chan bool),
    44  		fromsvc: make(chan error),
    45  	}
    46  
    47  	var err error
    48  	go func() {
    49  		err = svc.Run(serviceName, h)
    50  		h.fromsvc <- err
    51  	}()
    52  
    53  	// Wait for the first signal from the service handler.
    54  	err = <-h.fromsvc
    55  	if err != nil {
    56  		return err
    57  	}
    58  	klog.Infof("Running %s as a Windows service!", serviceName)
    59  	return nil
    60  }
    61  
    62  func (h *handler) Execute(_ []string, r <-chan svc.ChangeRequest, s chan<- svc.Status) (bool, uint32) {
    63  	s <- svc.Status{State: svc.StartPending, Accepts: 0}
    64  	// Unblock initService()
    65  	h.fromsvc <- nil
    66  
    67  	s <- svc.Status{State: svc.Running, Accepts: svc.AcceptStop | svc.AcceptShutdown | svc.Accepted(windows.SERVICE_ACCEPT_PARAMCHANGE)}
    68  	klog.Infof("Service running")
    69  Loop:
    70  	for {
    71  		select {
    72  		case <-h.tosvc:
    73  			break Loop
    74  		case c := <-r:
    75  			switch c.Cmd {
    76  			case svc.Cmd(windows.SERVICE_CONTROL_PARAMCHANGE):
    77  				s <- c.CurrentStatus
    78  			case svc.Interrogate:
    79  				s <- c.CurrentStatus
    80  			case svc.Stop, svc.Shutdown:
    81  				klog.Infof("Service stopping")
    82  				// We need to translate this request into a signal that can be handled by the signal handler
    83  				// handling shutdowns normally (currently apiserver/pkg/server/signal.go).
    84  				// If we do not do this, our main threads won't be notified of the upcoming shutdown.
    85  				// Since Windows services do not use any console, we cannot simply generate a CTRL_BREAK_EVENT
    86  				// but need a dedicated notification mechanism.
    87  				graceful := server.RequestShutdown()
    88  
    89  				// Free up the control handler and let us terminate as gracefully as possible.
    90  				// If that takes too long, the service controller will kill the remaining threads.
    91  				// As per https://docs.microsoft.com/en-us/windows/desktop/services/service-control-handler-function
    92  				s <- svc.Status{State: svc.StopPending}
    93  
    94  				// If we cannot exit gracefully, we really only can exit our process, so at least the
    95  				// service manager will think that we gracefully exited. At the time of writing this comment this is
    96  				// needed for applications that do not use signals (e.g. kube-proxy)
    97  				if !graceful {
    98  					go func() {
    99  						// Ensure the SCM was notified (The operation above (send to s) was received and communicated to the
   100  						// service control manager - so it doesn't look like the service crashes)
   101  						time.Sleep(1 * time.Second)
   102  						os.Exit(0)
   103  					}()
   104  				}
   105  				break Loop
   106  			}
   107  		}
   108  	}
   109  
   110  	return false, 0
   111  }
   112  

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