Implement timeouts and graceful shutdown

cmd/main.go

@@ -1,14 +1,19 @@
 package main
 
 import (
+	"context"
 	"flag"
 	"fmt"
 	"log"
+	"net"
 	"os"
+	"os/signal"
+	"syscall"
 	"time"
 
 	"github.com/localhots/bocadillo/reader"
 	"github.com/localhots/bocadillo/reader/slave"
+	"github.com/pkg/errors"
 )
 
 func main() {
@@ -31,12 +36,29 @@ func main() {
 		log.Fatalf("Failed to create reader: %v", err)
 	}
 
-	// for i := 0; i < 100; i++ {
+	done := handleShutdown()
+	ctx := context.Background()
 	for {
-		evt, err := reader.ReadEvent()
+		ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
+		defer cancel()
+		select {
+		case <-done:
+			log.Println("Closing reader")
+			err := reader.Close()
 			if err != nil {
+				log.Fatalf("Failed to close reader: %v", err)
+			}
+			return
+		default:
+			evt, err := reader.ReadEvent(ctx)
+			if err != nil {
+				if isTimeout(err) {
+					log.Println("Event read timeout")
+					continue
+				}
 				log.Fatalf("Failed to read event: %v", err)
 			}
+
 			ts := time.Unix(int64(evt.Header.Timestamp), 0).Format(time.RFC3339)
 			log.Printf("Event received: %s %s, %d\n", evt.Header.Type.String(), ts, evt.Header.NextOffset)
 
@@ -47,6 +69,8 @@ func main() {
 				}
 			}
 		}
+		cancel()
+	}
 }
 
 func validate(cond bool, msg string) {
@@ -56,3 +80,27 @@ func validate(cond bool, msg string) {
 		os.Exit(2)
 	}
 }
+
+func handleShutdown() <-chan struct{} {
+	sig := make(chan os.Signal, 1)
+	done := make(chan struct{})
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		<-sig
+		log.Println("Shutdown requested")
+		close(done)
+	}()
+	return done
+}
+
+func isTimeout(err error) bool {
+	if err == nil {
+		return false
+	}
+	err = errors.Cause(err)
+	if err == context.DeadlineExceeded || err == context.Canceled {
+		return true
+	}
+	ne, ok := err.(*net.OpError)
+	return ok && ne.Timeout()
+}

reader/enhanced_reader.go

@@ -59,8 +59,8 @@ func (r *EnhancedReader) WhitelistTables(database string, tables ...string) erro
 }
 
 // ReadEvent reads next event from the binary log.
-func (r *EnhancedReader) ReadEvent() (*Event, error) {
-	evt, err := r.reader.ReadEvent()
+func (r *EnhancedReader) ReadEvent(ctx context.Context) (*Event, error) {
+	evt, err := r.reader.ReadEvent(ctx)
 	if err != nil {
 		return nil, err
 	}
@@ -78,30 +78,8 @@ func (r *EnhancedReader) ReadEvent() (*Event, error) {
 // NextRowsEvent returns the next rows event for a whitelisted table. It blocks
 // until next event is received or context is cancelled.
 func (r *EnhancedReader) NextRowsEvent(ctx context.Context) (*EnhancedRowsEvent, error) {
-	evtch := make(chan *EnhancedRowsEvent)
-	errch := make(chan error)
-	go func() {
-		evt, err := r.nextRowsEvent()
-		if err != nil {
-			errch <- err
-		} else {
-			evtch <- evt
-		}
-	}()
-
-	select {
-	case evt := <-evtch:
-		return evt, nil
-	case err := <-errch:
-		return nil, err
-	case <-ctx.Done():
-		return nil, nil
-	}
-}
-
-func (r *EnhancedReader) nextRowsEvent() (*EnhancedRowsEvent, error) {
 	for {
-		evt, err := r.reader.ReadEvent()
+		evt, err := r.reader.ReadEvent(ctx)
 		if err != nil {
 			return nil, err
 		}

reader/reader.go

@@ -1,6 +1,8 @@
 package reader
 
 import (
+	"context"
+
 	"github.com/juju/errors"
 	"github.com/localhots/bocadillo/binlog"
 	"github.com/localhots/bocadillo/reader/slave"
@@ -61,8 +63,8 @@ func New(dsn string, sc slave.Config) (*Reader, error) {
 }
 
 // ReadEvent reads next event from the binary log.
-func (r *Reader) ReadEvent() (*Event, error) {
-	connBuff, err := r.conn.ReadPacket()
+func (r *Reader) ReadEvent(ctx context.Context) (*Event, error) {
+	connBuff, err := r.conn.ReadPacket(ctx)
 	if err != nil {
 		return nil, errors.Annotate(err, "read next event")
 	}

reader/slave/slave_conn.go

@@ -1,6 +1,7 @@
 package slave
 
 import (
+	"context"
 	"database/sql/driver"
 	"fmt"
 	"io"
@@ -65,8 +66,8 @@ func Connect(dsn string, conf Config) (*Conn, error) {
 
 // ReadPacket reads next packet from the server and processes the first status
 // byte.
-func (c *Conn) ReadPacket() ([]byte, error) {
-	data, err := c.conn.ReadPacket()
+func (c *Conn) ReadPacket(ctx context.Context) ([]byte, error) {
+	data, err := c.conn.ReadPacket(ctx)
 	if err != nil {
 		return nil, err
 	}