fix: detect silent wget failures in container DownloadFile

DownloadFile discarded wget's exit code, so failed downloads (e.g.
unreachable host) produced no error. The caller then tried to restore
a missing or empty .bak file, yielding a confusing 'volume is empty'
message from SQL Server.

Add ExecInspect to runCmdInContainer to capture the exit code. Check
wget's exit code in DownloadFile and panic with stderr context on
failure.

Also adds mkdir -p for idempotent directory creation.

Fixes #566

Author: dlevy-msft-sql

internal/container/controller.go

@@ -250,23 +250,27 @@ func (c Controller) DownloadFile(id string, src string, destFolder string) {
 		panic("Must pass in non-empty destFolder")
 	}
 
-	cmd := []string{"mkdir", destFolder}
+	cmd := []string{"mkdir", "-p", destFolder}
 	c.runCmdInContainer(id, cmd)
 
 	_, file := filepath.Split(src)
-
-	// Wget the .bak file from the http src, and place it in /var/opt/sql/backup
-	cmd = []string{
-		"wget",
-		"-O",
-		destFolder + "/" + file, // not using filepath.Join here, this is in the *nix container. always /
-		src,
+	if file == "" {
+		panic("src URL has no filename: " + src)
+	}
+	dest := destFolder + "/" + file // not using filepath.Join here, this is in the *nix container. always /
+
+	cmd = []string{"wget", "-O", dest, src}
+	_, stderr, exitCode := c.runCmdInContainer(id, cmd)
+	if exitCode != 0 {
+		msg := "download failed: " + src
+		if len(stderr) > 0 {
+			msg += "\nwget output: " + string(stderr)
+		}
+		panic(msg)
 	}
-
-	c.runCmdInContainer(id, cmd)
 }
 
-func (c Controller) runCmdInContainer(id string, cmd []string) ([]byte, []byte) {
+func (c Controller) runCmdInContainer(id string, cmd []string) ([]byte, []byte, int) {
 	trace("Running command in container: " + strings.Join(cmd, " "))
 
 	response, err := c.cli.ExecCreate(
@@ -308,7 +312,14 @@ func (c Controller) runCmdInContainer(id string, cmd []string) ([]byte, []byte)
 	trace("Stdout: " + string(stdout))
 	trace("Stderr: " + string(stderr))
 
-	return stdout, stderr
+	inspect, err := c.cli.ExecInspect(
+		context.Background(),
+		response.ID,
+		client.ExecInspectOptions{},
+	)
+	checkErr(err)
+
+	return stdout, stderr, inspect.ExitCode
 }
 
 // ContainerRunning returns true if the container with the given ID is running.

internal/container/controller_test.go

@@ -5,10 +5,11 @@ package container
 
 import (
 	"fmt"
-	"github.com/stretchr/testify/assert"
 	"net/http"
 	"net/http/httptest"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestController_ListTags(t *testing.T) {
@@ -54,7 +55,7 @@ func TestController_EnsureImage(t *testing.T) {
 	}))
 	defer ts.Close()
 
-	c.DownloadFile(id, ts.URL, "test.txt")
+	c.DownloadFile(id, ts.URL+"/test.bak", "/tmp")
 
 	err = c.ContainerStop(id)
 	checkErr(err)
@@ -187,3 +188,10 @@ func TestController_DownloadFileNeg3(t *testing.T) {
 		c.DownloadFile("not_blank", "not_blank", "")
 	})
 }
+
+func TestController_DownloadFileNoFilename(t *testing.T) {
+	c := NewController()
+	assert.Panics(t, func() {
+		c.DownloadFile("not_blank", "http://host:9999/", "/tmp")
+	})
+}