Allow signal bootstrap sends to commands on cancel to be customized

agent/job_runner.go

@@ -509,6 +509,11 @@ func (r *JobRunner) createEnvironment() ([]string, error) {
 	env["BUILDKITE_AGENT_EXPERIMENT"] = strings.Join(experiments.Enabled(), ",")
 	env["BUILDKITE_REDACTED_VARS"] = strings.Join(r.conf.AgentConfiguration.RedactedVars, ",")
 
+	// propagate CancelSignal to bootstrap, unless it's the default SIGTERM
+	if r.conf.CancelSignal != process.SIGTERM {
+		env["BUILDKITE_CANCEL_SIGNAL"] = r.conf.CancelSignal.String()
+	}
+
 	// Whether to enable profiling in the bootstrap
 	if r.conf.AgentConfiguration.Profile != "" {
 		env["BUILDKITE_AGENT_PROFILE"] = r.conf.AgentConfiguration.Profile

bootstrap/bootstrap.go

@@ -85,6 +85,7 @@ func (b *Bootstrap) Run(ctx context.Context) (exitCode int) {
 
 		b.shell.PTY = b.Config.RunInPty
 		b.shell.Debug = b.Config.Debug
+		b.shell.InterruptSignal = b.Config.CancelSignal
 	}
 
 	// Listen for cancellation

bootstrap/config.go

@@ -7,6 +7,7 @@ import (
 	"log"
 
 	"github.com/buildkite/agent/v3/env"
+	"github.com/buildkite/agent/v3/process"
 )
 
 // Config provides the configuration for the Bootstrap. Some of the keys are
@@ -127,6 +128,9 @@ type Config struct {
 	// Phases to execute, defaults to all phases
 	Phases []string
 
+	// What signal to use for command cancellation
+	CancelSignal process.Signal
+
 	// List of environment variable globs to redact from job output
 	RedactedVars []string
 

bootstrap/shell/shell.go

@@ -64,6 +64,9 @@ type Shell struct {
 	// Currently running command
 	cmd     *command
 	cmdLock sync.Mutex
+
+	// The signal to use to interrupt the command
+	InterruptSignal process.Signal
 }
 
 // New returns a new Shell
@@ -102,12 +105,13 @@ func (s *Shell) WithStdin(r io.Reader) *Shell {
 	defer s.cmdLock.Unlock()
 	// Can't copy struct like `newsh := *s` because sync.Mutex can't be copied.
 	return &Shell{
-		Logger: s.Logger,
-		Env:    s.Env,
-		stdin:  r, // our new stdin
-		Writer: s.Writer,
-		wd:     s.wd,
-		ctx:    s.ctx,
+		Logger:          s.Logger,
+		Env:             s.Env,
+		stdin:           r, // our new stdin
+		Writer:          s.Writer,
+		wd:              s.wd,
+		ctx:             s.ctx,
+		InterruptSignal: s.InterruptSignal,
 	}
 }
 
@@ -375,11 +379,12 @@ func (s *Shell) buildCommand(ctx context.Context, name string, arg ...string) (*
 	}
 
 	cfg := process.Config{
-		Path:  absPath,
-		Args:  arg,
-		Env:   s.Env.ToSlice(),
-		Stdin: s.stdin,
-		Dir:   s.wd,
+		Path:            absPath,
+		Args:            arg,
+		Env:             s.Env.ToSlice(),
+		Stdin:           s.stdin,
+		Dir:             s.wd,
+		InterruptSignal: s.InterruptSignal,
 	}
 
 	// Create a sub-context so that shell.Cancel() can interrupt

clicommand/bootstrap.go

@@ -12,6 +12,7 @@ import (
 	"github.com/buildkite/agent/v3/cliconfig"
 	"github.com/buildkite/agent/v3/experiments"
 	"github.com/buildkite/agent/v3/logger"
+	"github.com/buildkite/agent/v3/process"
 	"github.com/urfave/cli"
 )
 
@@ -81,6 +82,7 @@ type BootstrapConfig struct {
 	Experiments                  []string `cli:"experiment" normalize:"list"`
 	Phases                       []string `cli:"phases" normalize:"list"`
 	Profile                      string   `cli:"profile"`
+	CancelSignal                 string   `cli:"cancel-signal"`
 	RedactedVars                 []string `cli:"redacted-vars" normalize:"list"`
 	TracingBackend               string   `cli:"tracing-backend"`
 }
@@ -297,6 +299,12 @@ var BootstrapCommand = cli.Command{
 			Usage:  "The specific phases to execute. The order they're defined is irrelevant.",
 			EnvVar: "BUILDKITE_BOOTSTRAP_PHASES",
 		},
+		cli.StringFlag{
+			Name:   "cancel-signal",
+			Usage:  "The signal to use for cancellation",
+			EnvVar: "BUILDKITE_CANCEL_SIGNAL",
+			Value:  "SIGTERM",
+		},
 		cli.StringSliceFlag{
 			Name:   "redacted-vars",
 			Usage:  "Pattern of environment variable names containing sensitive values",
@@ -353,6 +361,11 @@ var BootstrapCommand = cli.Command{
 			}
 		}
 
+		cancelSig, err := process.ParseSignal(cfg.CancelSignal)
+		if err != nil {
+			l.Fatal("Failed to parse cancel-signal: %v", err)
+		}
+
 		// Configure the bootstraper
 		bootstrap := bootstrap.New(bootstrap.Config{
 			Command:                      cfg.Command,
@@ -392,6 +405,7 @@ var BootstrapCommand = cli.Command{
 			SSHKeyscan:                   cfg.SSHKeyscan,
 			Shell:                        cfg.Shell,
 			Phases:                       cfg.Phases,
+			CancelSignal:                 cancelSig,
 			RedactedVars:                 cfg.RedactedVars,
 			TracingBackend:               cfg.TracingBackend,
 		})