Improve error handling when executing pg_dump command

Author: MaikelH

backup.go

@@ -192,7 +192,8 @@ func (b *PostgresBackup) doPostgresBackup() (string, error) {
 		}
 	}(gzipWriter)
 
-	cmd.Stdout = gzipWriter
+	var stdout bytes.Buffer
+	cmd.Stdout = &stdout
 	var stderr bytes.Buffer
 	cmd.Stderr = &stderr
 
@@ -203,7 +204,7 @@ func (b *PostgresBackup) doPostgresBackup() (string, error) {
 	if err = cmd.Run(); err != nil {
 		// Remove partial file on failure
 		_ = os.Remove(outfile)
-		slog.Error("Failed to execute pg_dump with compression", "error", err, "output", stderr)
+		slog.Error("Failed to execute pg_dump", "error", err, "stderr", stderr.String(), "stdout", stdout.String())
 		err = fmt.Errorf("pg_dump failed %w", err)
 		return "", err
 	}
@@ -216,6 +217,12 @@ func newPostgresBackup(cfg *config.Config) (*PostgresBackup, error) {
 		tempDir: "/tmp",
 	}
 
+	// Check that the temp directory exists
+	_, err := os.Stat(pb.tempDir)
+	if err != nil {
+		return nil, fmt.Errorf("failed to access temp directory: %w", err)
+	}
+
 	// Initialize S3 client if S3 is configured
 	if cfg.S3.Bucket != "" {
 		s3Cfg := storage.S3Config{

test/compose.yaml

@@ -0,0 +1,35 @@
+services:
+  backup:
+    build:
+      context: ../
+    links:
+      - db
+    depends_on:
+      - db
+    environment:
+      POSTGRES_HOST: "db"
+      POSTGRES_DATABASE: "postgres"
+      POSTGRES_USER: "postgres"
+      POSTGRES_PASSWORD: "testpass"
+      POSTGRES_EXTRA_OPTS: '-Z1 --schema=public --blobs'
+      SCHEDULE: "@daily"
+      RUN_AT_STARTUP: "true"
+      S3_REGION: ""
+      S3_ACCESS_KEY_ID: "example"
+      S3_SECRET_ACCESS_KEY: "example"
+      S3_BUCKET: "test-bucket"
+      S3_PREFIX: "backup"
+      S3_ENDPOINT: "fsn1.your-objectstorage.com"
+  db:
+    container_name: db
+    image: postgres:17
+    environment:
+      POSTGRES_PASSWORD: testpass
+      POSTGRES_USER: postgres
+    ports:
+      - "6000:5432"
+    restart: unless-stopped
+    healthcheck:
+      test: [ "CMD-SHELL", "pg_isready -h localhost -U $$POSTGRES_USER" ]
+      interval: 2s
+      start_period: 30s