Fix Signal Issue on Windows

cmd/kpromo/cmd/pr/pr.go

@@ -158,6 +158,9 @@ func init() {
 	}
 }
 
+// Issue #1177: This function is overly complex and difficult to read, both for humans and machines.
+// It would be better to split it into smaller functions, as this is Go, not Python, and Go
+// encourages simpler, more readable code.
 func runPromote(opts *promoteOptions) error {
 	// Check the cmd line opts
 	if err := opts.Validate(); err != nil {

internal/legacy/signals/signals.go

@@ -1,3 +1,8 @@
+//go:build !windows
+// +build !windows
+
+// Note: this build on unix/linux systems
+
 /*
 Copyright 2021 The Kubernetes Authors.
 

internal/legacy/signals/signals_test.go

@@ -1,3 +1,8 @@
+//go:build !windows
+// +build !windows
+
+// Note: this build on unix/linux systems
+
 /*
 Copyright 2021 The Kubernetes Authors.
 

internal/legacy/signals/signals_windows.go

@@ -0,0 +1,93 @@
+//go:build windows
+// +build windows
+
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/sirupsen/logrus"
+)
+
+var (
+	// ExitSignals are used to determine if an incoming os.Signal should cause termination.
+	ExitSignals = map[os.Signal]bool{
+		syscall.SIGHUP:  true,
+		syscall.SIGINT:  true,
+		syscall.SIGABRT: true,
+		syscall.SIGILL:  true,
+		syscall.SIGQUIT: true,
+		syscall.SIGTERM: true,
+		syscall.SIGSEGV: true,
+	}
+	// ExitChannel is for gracefully terminating the LogSignals() function.
+	ExitChannel = make(chan bool, 1)
+	// SignalChannel is for listening to OS signals.
+	SignalChannel = make(chan os.Signal, 1)
+	// Debug is defined globally for mocking logrus.Debug statements.
+	Debug func(args ...interface{}) = logrus.Debug
+)
+
+// Watch concurrently logs debug statements when encountering interrupt signals from the OS.
+// This function relies on the os/signal package which may not capture SIGKILL and SIGSTOP.
+func Watch() {
+	Debug("Watching for OS Signals...")
+	// Observe all signals, excluding SIGKILL and SIGSTOP.
+	signal.Notify(SignalChannel)
+	// Continuously log signals.
+	go LogSignals()
+}
+
+// Stop gracefully terminates the concurrent signal logging.
+// TODO: @tylerferrara Currently we don't gracefully exit, since the Auditor is designed
+// to run indefinitely. In the future, we should enable graceful termination to allow
+// this to be called from a Shutdown() function.
+func Stop() {
+	ExitChannel <- true
+}
+
+// LogSignals continuously prints logging statements for each signal it observes,
+// exiting only when observing an exit signal.
+func LogSignals() {
+	for {
+		select {
+		case sig := <-SignalChannel:
+			LogSignal(sig)
+		case <-ExitChannel:
+			// Gracefully terminate.
+			return
+		}
+	}
+}
+
+// LogSignal prints a logging statements for the given signal,
+// exiting only when observing an exit signal.
+func LogSignal(sig os.Signal) {
+	Debug("Encoutered signal: ", sig.String())
+	// Handle exit signals.
+	if _, found := ExitSignals[sig]; found {
+		Debug("Exiting from signal: ", sig.String())
+		// If we get here, an exit signal was seen. We must handle this by forcing
+		// the program to exit. Without this, the program would ignore all exit signals
+		// except SIGKILL.
+		Stop()
+	}
+}

internal/legacy/signals/signals_windows_test.go

@@ -0,0 +1,151 @@
+//go:build windows
+// +build windows
+
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals_test
+
+import (
+	"fmt"
+	"os"
+	"sync"
+	"syscall"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"sigs.k8s.io/promo-tools/v4/internal/legacy/signals"
+)
+
+func TestLogSignal(t *testing.T) {
+	// Define what a test looks like.
+	type sigTest struct {
+		signal    os.Signal // Incoming signal to observe.
+		expected  []string  // Expected logs to be produced.
+		terminate bool      // Determine if signals.LogSignals() should return.
+	}
+	// Create multiple tests.
+	// NOTE: We are unable to observe SIGKILL or SIGSTOP, therefore we will not
+	// test with these syscalls.
+	// SIGIO, SIGSYS, SIGTTOU, and SIGCHLD are not available on Windows
+	sigTests := []sigTest{
+		{
+			signal: syscall.SIGALRM,
+			expected: []string{
+				fmt.Sprintf("Encoutered signal: %s", syscall.SIGALRM.String()),
+			},
+			terminate: false,
+		},
+		{
+			signal: syscall.SIGALRM,
+			expected: []string{
+				fmt.Sprintf("Encoutered signal: %s", syscall.SIGALRM.String()),
+			},
+			terminate: false,
+		},
+		{
+			signal: syscall.SIGQUIT,
+			expected: []string{
+				fmt.Sprintf("Encoutered signal: %s", syscall.SIGQUIT.String()),
+				fmt.Sprintf("Exiting from signal: %s", syscall.SIGQUIT.String()),
+			},
+			terminate: true,
+		},
+		{
+			signal: syscall.SIGINT,
+			expected: []string{
+				fmt.Sprintf("Encoutered signal: %s", syscall.SIGINT.String()),
+				fmt.Sprintf("Exiting from signal: %s", syscall.SIGINT.String()),
+			},
+			terminate: true,
+		},
+		{
+			signal: syscall.SIGABRT,
+			expected: []string{
+				fmt.Sprintf("Encoutered signal: %s", syscall.SIGABRT.String()),
+				fmt.Sprintf("Exiting from signal: %s", syscall.SIGABRT.String()),
+			},
+			terminate: true,
+		},
+	}
+	// Capture all logs.
+	logs := []string{}
+	// Mock logrus.Debug statements.
+	signals.Debug = func(args ...interface{}) {
+		logs = append(logs, fmt.Sprint(args...))
+	}
+	// Determine if LogSignal invoked Stop().
+	terminated := func() bool {
+		return <-signals.ExitChannel
+	}
+	// Used for enforcing defaults before each test.
+	reset := func() {
+		logs = []string{}
+	}
+	// Run through all tests.
+	for _, st := range sigTests {
+		reset()
+		// Log the test signal.
+		signals.LogSignal(st.signal)
+		// Ensure the logs are correct.
+		require.EqualValues(t, st.expected, logs, "Unexpected signal observation logs.")
+		if st.terminate {
+			// Ensure Stop() was invoked if the test specifies.
+			require.True(t, terminated(), "LogSignal did not terminate on exit signal.")
+		}
+	}
+}
+
+// TestLogSignals ensures LogSignals() can handle multiple incoming signals and terminates either by
+// receiving an exit signal or explicit call to Stop().
+func TestLogSignals(t *testing.T) {
+	// Capture concurrent function termination.
+	wg := sync.WaitGroup{}
+	terminated := false
+	// Ensure the test waits for logSignals to finish executing.
+	logSignals := func() {
+		signals.LogSignals()
+		terminated = true
+		wg.Done()
+	}
+	// Start logging.
+	wg.Add(1)
+	go logSignals()
+	// Pass multiple non-exit signals, ensuring LogSignals is consuming each. Otherwise,
+	// the SignalChannel will block and the test will fail.
+	signals.SignalChannel <- syscall.SIGBUS
+	signals.SignalChannel <- syscall.SIGALRM
+	// Force exit.
+	signals.Stop()
+	wg.Wait()
+	// Ensure termination happened.
+	require.True(t, terminated, "LogSignals() did not terminate on call to Stop()")
+
+	// Reset termination bool for new test.
+	terminated = false
+	// Start logging.
+	wg.Add(1)
+	go logSignals()
+	// Pass multiple non-exit signals, ensuring LogSignals is consuming each. Otherwise,
+	// the SignalChannel will block and the test will fail.
+	signals.SignalChannel <- syscall.SIGPIPE
+	// Pass an exit signal.
+	signals.SignalChannel <- syscall.SIGINT
+	wg.Wait()
+	// Ensure termination happened.
+	require.True(t, terminated, "LogSignals() did not terminate when given an exit signal")
+}