github.com/bazelbuild/bazel-watcher@v0.25.2/internal/ibazel/command/command.go (about)

     1  // Copyright 2017 The Bazel Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //    http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package command
    16  
    17  import (
    18  	"bytes"
    19  	"flag"
    20  	"fmt"
    21  	"io/ioutil"
    22  	"os"
    23  	"os/exec"
    24  	"runtime"
    25  	"strings"
    26  	"syscall"
    27  	"time"
    28  
    29  	"github.com/bazelbuild/bazel-watcher/internal/bazel"
    30  	"github.com/bazelbuild/bazel-watcher/internal/ibazel/log"
    31  	"github.com/bazelbuild/bazel-watcher/internal/ibazel/process_group"
    32  )
    33  
    34  var (
    35  	execCommand  = process_group.Command
    36  	bazelNew     = bazel.New
    37  	waitDuration = flag.Duration(
    38  		"graceful_termination_wait_duration",
    39  		10*time.Second,
    40  		"Specify the duration to wait for a graceful termination before sending SIGKILL to the subprocess")
    41  )
    42  
    43  // Command is an object that wraps the logic of running a task in Bazel and
    44  // manipulating it.
    45  type Command interface {
    46  	Start() (*bytes.Buffer, error)
    47  	Terminate()
    48  	Kill()
    49  	NotifyOfChanges() *bytes.Buffer
    50  	IsSubprocessRunning() bool
    51  }
    52  
    53  // start will be called by most implementations since this logic is extremely
    54  // common.
    55  func start(b bazel.Bazel, target string, args []string) (*bytes.Buffer, process_group.ProcessGroup) {
    56  	var filePattern strings.Builder
    57  	filePattern.WriteString("bazel_script_path*")
    58  	if runtime.GOOS == "windows" {
    59  		filePattern.WriteString(".bat")
    60  	}
    61  
    62  	tmpfile, err := ioutil.TempFile("", filePattern.String())
    63  	if err != nil {
    64  		fmt.Print(err)
    65  	}
    66  	// Close the file so bazel can write over it
    67  	if err := tmpfile.Close(); err != nil {
    68  		fmt.Print(err)
    69  	}
    70  
    71  	// Start by building the binary
    72  	_, outputBuffer, _ := b.Run("--script_path="+tmpfile.Name(), target)
    73  
    74  	runScriptPath := tmpfile.Name()
    75  
    76  	// Now that we have built the target, construct a executable form of it for
    77  	// execution in a go routine.
    78  	cmd := execCommand(runScriptPath, args...)
    79  	cmd.RootProcess().Stdout = os.Stdout
    80  	cmd.RootProcess().Stderr = os.Stderr
    81  
    82  	return outputBuffer, cmd
    83  }
    84  
    85  func subprocessRunning(cmd *exec.Cmd) bool {
    86  	if cmd == nil {
    87  		return false
    88  	}
    89  	if cmd.Process == nil {
    90  		return false
    91  	}
    92  	if cmd.ProcessState != nil {
    93  		if cmd.ProcessState.Exited() {
    94  			return false
    95  		}
    96  	}
    97  
    98  	return true
    99  }
   100  
   101  func terminate(pg process_group.ProcessGroup) {
   102  	pg.Signal(syscall.SIGTERM)
   103  	done := make(chan bool, 1)
   104  	go func() {
   105  		select {
   106  		case <-time.After(*waitDuration):
   107  			log.Logf("The subprocess wasn't terminated within %s. Forcing to close.", *waitDuration)
   108  			kill(pg)
   109  		case <-done:
   110  			// The subprocess was terminated with SIGTERM
   111  		}
   112  	}()
   113  	pg.Wait()
   114  	done <- true
   115  	pg.Close()
   116  }
   117  
   118  func kill(pg process_group.ProcessGroup) {
   119  	if subprocessRunning(pg.RootProcess()) {
   120  		log.Logf("Sending SIGKILL to the subprocess")
   121  		pg.Signal(syscall.SIGKILL)
   122  	}
   123  }