add the use of context in the distributed database example

Author: steevehook

mutexes/distributed-db/app/app.go

@@ -1,6 +1,7 @@
 package app
 
 import (
+	"context"
 	"flag"
 	"fmt"
 	"log"
@@ -37,26 +38,35 @@ func New() (*App, error) {
 	}
 	w := workers.NewGossip(svc)
 	a := &App{
-		Server: srv,
-		Worker: w,
+		Server:  srv,
+		Worker:  w,
 	}
 
 	return a, nil
 }
 
 type App struct {
-	Server *http.Server
-	Worker workers.Gossip
+	Server  *http.Server
+	Worker  workers.Gossip
 }
 
-func (a App) Start() error {
-	go a.Worker.Start()
+func (a App) Start(ctx context.Context) error {
+	go a.Worker.Start(ctx)
 
 	log.Println("server started on address", a.Server.Addr)
 	err := a.Server.ListenAndServe()
-	if err != nil {
+	if err != nil && err != http.ErrServerClosed {
 		return err
 	}
 
 	return nil
 }
+
+func (a App) Stop(ctx context.Context) error {
+	log.Println("shutting down the http server")
+	err := a.Server.Shutdown(ctx)
+	if err != nil && err != context.Canceled {
+		return fmt.Errorf("could not stop the http server: %w", err)
+	}
+	return nil
+}

mutexes/distributed-db/main.go

@@ -1,19 +1,38 @@
 package main
 
 import (
-	"log"
-
+	"context"
 	"distributed-db/app"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
 )
 
 func main() {
+	ctx, cancel := context.WithCancel(context.Background())
+	//defer cancel()
+	signals := make(chan os.Signal, 1)
+	signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)
+
 	a, err := app.New()
 	if err != nil {
 		log.Fatalf("could not create the app: %v", err)
 	}
 
-	err = a.Start()
-	if err != nil {
-		log.Fatalf("could not start the app: %v", err)
+	go func() {
+		err = a.Start(ctx)
+		if err != nil {
+			log.Fatalf("could not start the app: %v", err)
+		}
+	}()
+
+	select {
+	case <-signals:
+		cancel()
+		err = a.Stop(ctx)
+		if err != nil {
+			log.Fatalf("could not stop the app: %v", err)
+		}
 	}
 }

mutexes/distributed-db/repositories/cache.go

@@ -34,19 +34,7 @@ func (c *Cache) Set(key, value string) models.CacheItem {
 	return item
 }
 
-func (c *Cache) Get(key string) *models.CacheItem {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
-
-	item, ok := c.data[key]
-	if !ok {
-		return nil
-	}
-
-	return &item
-}
-
-func (c *Cache) GetMany(keys []string) []models.CacheItem {
+func (c *Cache) Get(keys []string) []models.CacheItem {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 

mutexes/distributed-db/services/cache.go

@@ -9,8 +9,7 @@ import (
 )
 
 type CacheRepository interface {
-	Get(key string) *models.CacheItem
-	GetMany(keys []string) []models.CacheItem
+	Get(keys []string) []models.CacheItem
 	Set(key, value string) models.CacheItem
 }
 
@@ -57,7 +56,7 @@ func (svc CacheSvc) Get(keys []string) []models.CacheItem {
 	cacheItems := make([]models.CacheItem, 0)
 	for node, sums := range nodeToSums {
 		if node == svc.tokens.Nodes.CurrentNode {
-			items := svc.cacheRepo.GetMany(sums)
+			items := svc.cacheRepo.Get(sums)
 			for _, item := range items {
 				item.Node = node
 				cacheItems = append(cacheItems, item)

mutexes/distributed-db/workers/gossip.go

@@ -1,6 +1,7 @@
 package workers
 
 import (
+	"context"
 	"log"
 	"time"
 )
@@ -21,10 +22,16 @@ type Gossip struct {
 	svc gossiper
 }
 
-func (g *Gossip) Start() {
+func (g *Gossip) Start(ctx context.Context) {
 	log.Println("worker started successfully")
+
 	for {
-		g.svc.Gossip()
-		time.Sleep(gossipPeriod)
+		select {
+		case <-ctx.Done():
+			log.Println("stopping the gossip worker")
+			return
+		case <-time.NewTicker(gossipPeriod).C:
+			g.svc.Gossip()
+		}
 	}
 }