feat(containers): long running background task

Author: cyclimse

containers/long-running-task-go/Dockerfile

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+FROM golang:1.23-alpine3.21 AS builder
+
+WORKDIR /app
+
+COPY go.* ./
+RUN go mod download
+
+COPY . ./
+
+RUN go build -o server ./cmd/server
+
+FROM alpine:3.21
+
+COPY --from=builder /app/server /app/server
+
+CMD ["/app/server"]

containers/long-running-task-go/README.md

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+# Long Running Task
+
+This example showcases running a long background task in a container during the 15m retention period.
+
+## Deploying
+
+This example can be deployed using the Scaleway CLI:
+
+```bash
+scw container deploy region=pl-waw
+```

containers/long-running-task-go/cmd/server/main.go

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+package main
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"net/http"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+var (
+	signalChan = make(chan os.Signal, 1)
+	wg         sync.WaitGroup
+
+	disableGracefulShutdown = os.Getenv("DISABLE_GRACEFUL_SHUTDOWN") != ""
+
+	longRunningJobDuration        = os.Getenv("LONG_RUNNING_JOB_DURATION")
+	parsedLongRunningJobDuration  time.Duration
+	defaultLongRunningJobDuration = 14 * time.Minute
+)
+
+func main() {
+	slog.SetDefault(slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+		AddSource: true,
+	})))
+
+	if longRunningJobDuration != "" {
+		var err error
+
+		parsedLongRunningJobDuration, err = time.ParseDuration(longRunningJobDuration)
+		if err != nil {
+			slog.Error("failed to parse LONG_RUNNING_JOB_DURATION", "error", err)
+			os.Exit(1)
+		}
+
+		slog.Info("LONG_RUNNING_JOB_DURATION set", "duration", parsedLongRunningJobDuration)
+	} else {
+		parsedLongRunningJobDuration = defaultLongRunningJobDuration
+		slog.Info("LONG_RUNNING_JOB_DURATION not set, using default", "duration", parsedLongRunningJobDuration)
+	}
+
+	srv := &http.Server{
+		Addr:    ":8080",
+		Handler: http.HandlerFunc(handler),
+	}
+
+	// Handle SIGTERM.
+	if !disableGracefulShutdown {
+		signal.Notify(signalChan, syscall.SIGTERM)
+	}
+
+	// Start HTTP server.
+	if disableGracefulShutdown {
+		slog.Info("server started")
+
+		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			slog.Error("server failed to start", "error", err)
+			os.Exit(1)
+		}
+	} else {
+		go func() {
+			slog.Info("server started")
+
+			if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+				slog.Error("server failed to start", "error", err)
+				os.Exit(1)
+			}
+		}()
+
+		sig := <-signalChan
+		slog.Info("received signal", "signal", sig)
+
+		// This should not take a lot of time because the handler is non-blocking.
+		if err := srv.Shutdown(context.Background()); err != nil {
+			slog.Error("server failed to shutdown", "error", err)
+		}
+
+		// This is where we wait for the long running tasks to finish.
+		wg.Wait()
+	}
+}
+
+func handler(w http.ResponseWriter, _ *http.Request) {
+	wg.Add(1)
+
+	taskID := uuid.NewString()
+	go longBackgroundTask(taskID, parsedLongRunningJobDuration)
+
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write([]byte("Started long background task: " + taskID))
+}
+
+func longBackgroundTask(taskID string, duration time.Duration) {
+	defer wg.Done()
+
+	slog.Info("long background task started", "taskID", taskID, "duration", duration)
+
+	sleepTime := 1 * time.Second
+	numIterations := int(duration / sleepTime)
+
+	for i := range numIterations {
+		slog.Info("long background task running...",
+			"iteration", i,
+			"total", numIterations,
+			"taskID", taskID)
+
+		time.Sleep(sleepTime)
+	}
+
+	slog.Info("long background task finished", "taskID", taskID)
+}

containers/long-running-task-go/go.mod

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+module github.com/scaleway/serverless-examples/containers/long-running-task-go
+
+go 1.23
+
+toolchain go1.23.4
+
+require github.com/google/uuid v1.6.0

containers/long-running-task-go/go.sum

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+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=