feat: move running the actual dump command to the db container

save.go

@@ -2,44 +2,71 @@ package main
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"io"
 	"os"
-	"os/exec"
+
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/client"
+	"github.com/docker/docker/pkg/stdcopy"
 )
 
-func runAndSaveCommand(filename, command string, args ...string) error {
-	c := exec.Command(command, args...)
-
-	//fmt.Printf("Running %s\n\n", c.String())
-
+func runAndSaveCommandInContainer(filename string, c *client.Client, container *types.ContainerJSON, command string, args ...string) error {
 	f, err := os.Create(filename)
 	if err != nil {
 		return err
 	}
 	defer f.Close()
 
-	stdout, err := c.StdoutPipe()
+	ctx := context.Background()
+
+	config := types.ExecConfig{
+		AttachStderr: true,
+		AttachStdout: true,
+		Cmd:          append([]string{command}, args...),
+	}
+
+	r, err := c.ContainerExecCreate(ctx, container.ID, config)
 	if err != nil {
 		return err
 	}
 
-	var stderr bytes.Buffer
-	c.Stderr = &stderr
-
-	err = c.Start()
+	resp, err := c.ContainerExecAttach(ctx, r.ID, types.ExecStartCheck{})
 	if err != nil {
 		return err
 	}
+	defer resp.Close()
 
-	_, err = io.Copy(f, stdout)
+	// read the output
+	var outBuf, errBuf bytes.Buffer
+	outputDone := make(chan error)
+
+	go func() {
+		// StdCopy demultiplexes the stream into two buffers
+		_, err = stdcopy.StdCopy(&outBuf, &errBuf, resp.Reader)
+		outputDone <- err
+	}()
+
+	select {
+	case err := <-outputDone:
+		if err != nil {
+			return err
+		}
+		break
+
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+
+	_, err = c.ContainerExecInspect(ctx, r.ID)
 	if err != nil {
+		fmt.Printf(errBuf.String())
 		return err
 	}
 
-	err = c.Wait()
+	_, err = io.Copy(f, &outBuf)
 	if err != nil {
-		fmt.Printf(stderr.String())
 		return err
 	}