Implement ErrorGroup and update tests and examples

CHANGELOG.md

@@ -0,0 +1,9 @@
+# CHANGELOG
+
+## v2.0.0
+
+* 
+
+## v1.0.0
+
+* Initial implementation

README.md

@@ -20,35 +20,35 @@ import (
 )
 ```
 
-Instantiate the error group and main context in the main goroutine.
+Instantiate the main context in the main goroutine.
 
 ```Go
 func main() {
-	mainCtx, cancel := relax.MainContext()
+	mainCtx := relax.Context()
 ```
 
-This ensures that the main goroutine is relaxed against SIGINT and SIGTERM.
+This ensures that SIGINT/SIGTERM will cause all contexts used in the application to be `Done()`.
 
-If you have multiple, long running processes to run in your program, you can use errgroup to launch them.
+If you have multiple, long running processes to run in your program, you can use ErrorGroup to launch them.
 
 ```Go
-	g, ctx := errgroup.WithContext(mainCtx)
+	g, ctx := relax.NewErrorGroup(mainCtx)
 ```
 
-Launch your goroutines and make sure to `defer relax.Recover(cancel)` so that any panics do not get in the way of graceful shutdown of the program.
+You can use the `ErrorGroup` to launch goroutines which will return an error if they encounter a panic.
 ```Go
 	g.Go(func() error {
-		defer relax.Recover(cancel)
-		return myLongRunningProcess(ctx)
+		// An error containing "failed" will be returned
+		panic("failed")
 	})
 ```
 
 Finally, in the main goroutine, make sure to wait for the error group:
 
 ```Go
 	if err := g.Wait(); err != nil {
-		fmt.Println("error from group", err)
+		fmt.Println(err)
 	}
 ```
 
-For more detailed usage, see [examples](./examples/).
+For more detailed usage, see [examples](./examples/) and the `*_test.go` files.

context.go

@@ -0,0 +1,31 @@
+package relax
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+// Context instantiates a context that is cancelled only when
+// the SIGINT/SIGTERM signals are received.
+// This context should be set up in main() of your application.
+func Context() context.Context {
+	// Instantiate cancellable context
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		// Cancel context on signals
+		signalChan := make(chan os.Signal, 1)
+		signal.Notify(signalChan, Signals()...)
+		// Wait for signal
+		<-signalChan
+		// Cancel context
+		cancel()
+	}()
+	return ctx
+}
+
+// Signals returns the signals that will cause the context to be cancelled.
+func Signals() []os.Signal {
+	return []os.Signal{syscall.SIGINT, syscall.SIGTERM}
+}

context_test.go

@@ -0,0 +1,27 @@
+package relax
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestContext_Signals_CancelContext(t *testing.T) {
+	for _, signal := range Signals() {
+		t.Run(signal.String(), func(t *testing.T) {
+			ctx := Context()
+			go func() {
+				cmd := exec.Command("kill", "-SIGINT", fmt.Sprint(os.Getpid()))
+				cmd.Stderr = os.Stderr
+				cmd.Stdout = os.Stdout
+				require.NoError(t, cmd.Run())
+			}()
+			// Exit only if signal causes cancel
+			<-ctx.Done()
+			t.Log("Exiting gracefully")
+		})
+	}
+}

errgroup.go

@@ -0,0 +1,48 @@
+package relax
+
+import (
+	"context"
+	"fmt"
+
+	"golang.org/x/sync/errgroup"
+)
+
+var (
+	// PanicError is returned when a panic is recovered
+	// during the execution of a goroutine
+	PanicError = fmt.Errorf("recovered from panic")
+)
+
+// ErrorGroup is a wrapper around golang.org/x/sync/errgroup.Group that
+// recovers from panics and returns them as errors
+type ErrorGroup struct {
+	*errgroup.Group
+}
+
+// NewErrorGroup instantiates an ErrorGroup and corresponding context.
+// This function should be used the same way as errgroup.WithContext() from
+// golang.org/x/sync/errgroup
+func NewErrorGroup(ctx context.Context) (*ErrorGroup, context.Context) {
+	errgroup, groupCtx := errgroup.WithContext(ctx)
+	return &ErrorGroup{
+		Group: errgroup,
+	}, groupCtx
+}
+
+// Go runs a provided func in a goroutine while ensuring that
+// any panic is recovered and returned as an error
+func (g *ErrorGroup) Go(f func() error) {
+	g.Group.Go(func() (err error) {
+		// Define a recover func that converts a panic to an error
+		recoverFunc := func() {
+			if r := recover(); r != nil {
+				// Assign the panic content to returned error
+				err = fmt.Errorf("%w: %v", PanicError, r)
+			}
+		}
+		// Handle panics
+		defer recoverFunc()
+		// Call the provided func
+		return f()
+	})
+}

errgroup_test.go

@@ -0,0 +1,60 @@
+package relax
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestErrGroup_CancelParentContext_ChildContextDone(t *testing.T) {
+	// Root context to cancel
+	ctx, cancel := context.WithCancel(context.Background())
+
+	// Group to wait on root and group context Done()
+	e, gCtx := NewErrorGroup(ctx)
+	e.Go(func() error {
+		<-ctx.Done()
+		<-gCtx.Done()
+		return nil
+	})
+
+	// Cancel root context
+	cancel()
+
+	// Validate
+	assert.NoError(t, e.Wait())
+}
+
+func TestErrGroup_Panic_Error(t *testing.T) {
+	// Group
+	e, ctx := NewErrorGroup(context.Background())
+
+	// Routine that panics
+	panicMsg := "testing content is returned as error"
+	e.Go(func() error {
+		panic(panicMsg)
+	})
+
+	// Sibling routine that blocks on Group context
+	e.Go(func() error {
+		<-ctx.Done()
+		return nil
+	})
+
+	// Wait for all goroutines
+	err := e.Wait()
+	assert.Error(t, err)
+	// Verify panic message/error is returned
+	assert.Contains(t, err.Error(), panicMsg)
+	assert.True(t, errors.Is(err, PanicError))
+}
+
+func TestErrGroup_NoPanic_NoError(t *testing.T) {
+	e, _ := NewErrorGroup(context.Background())
+	e.Go(func() error {
+		return nil
+	})
+	assert.NoError(t, e.Wait())
+}

examples/context/main.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+
+	"github.com/sergerad/relax"
+)
+
+func main() {
+	// Main context that is cancelled on SIGINT/SIGTERM
+	ctx := relax.Context()
+
+	// Indicate how to exit the app gracefully
+	println("Either of the following commands would exit the app gracefully:")
+	println("kill -SIGINT", os.Getpid())
+	println("kill -SIGTERM", os.Getpid())
+
+	// Exit the app automatically. Comment this out to try manually
+	// sending signals
+	go func() {
+		cmd := exec.Command("kill", "-SIGINT", fmt.Sprint(os.Getpid()))
+		cmd.Stderr = os.Stderr
+		cmd.Stdout = os.Stdout
+		if err := cmd.Run(); err != nil {
+			log.Fatal(err)
+		}
+	}()
+
+	// Wait for context to be cancelled
+	<-ctx.Done()
+	println("Exiting gracefully")
+}

examples/errgroup/main.go

@@ -3,60 +3,33 @@ package main
 import (
 	"context"
 	"fmt"
-	"time"
 
 	"github.com/sergerad/relax"
-	"golang.org/x/sync/errgroup"
 )
 
 func main() {
-	// Instantiate the main context
-	mainCtx, cancel := relax.MainContext()
-
-	// Use the main context for errgroup
-	g, ctx := errgroup.WithContext(mainCtx)
+	// Instantiate the main context and error group
+	g, ctx := relax.NewErrorGroup(relax.Context())
 
 	// Launch goroutine that blocks on context
 	g.Go(func() error {
-		// Relax panics
-		defer relax.Recover(cancel)
-		// Block
-		select {
-		case <-ctx.Done():
-			fmt.Println("blocking routine done")
-		}
+		<-ctx.Done()
+		fmt.Println("blocking routine done")
 		return nil
 	})
+
 	// Launch goroutine that resembles a long running processor
 	g.Go(func() error {
 		return exampleProcessor(ctx)
 	})
 
 	// Wait for errgroup
 	if err := g.Wait(); err != nil {
-		fmt.Println("error from group", err)
+		fmt.Println(err)
 	}
 	fmt.Println("shutting down")
-
-	// Sleep to give all goroutines a chance to exit due to ctx.Done()
-	time.Sleep(1)
 }
 
 func exampleProcessor(ctx context.Context) error {
-	childCtx, cancel := context.WithCancel(ctx)
-	go func() {
-		defer relax.Recover(cancel)
-		panic(1)
-	}()
-	go func() {
-		select {
-		case <-childCtx.Done():
-		}
-		fmt.Println("processor goroutine done")
-	}()
-	select {
-	case <-childCtx.Done():
-		fmt.Println("processor done")
-		return childCtx.Err()
-	}
+	panic("processor failed")
 }