fix: check for empty WAL archive during WAL archiving (#458)

In the in-tree barman-cloud implementation, the check for an empty WAL
archive is performed both immediately after the restore process and when the
first WAL file is archived.

Previously, the plugin-based implementation only performed this check after
restore, skipping it during archiving of the first WAL. This patch restores
parity with the in-tree behavior by ensuring the check is also performed
during WAL archiving.

Closes: #457

Signed-off-by: Leonardo Cecchi <leonardo.cecchi@enterprisedb.com>

internal/cnpgi/common/check.go

@@ -0,0 +1,34 @@
+package common
+
+import (
+	"context"
+
+	"github.com/cloudnative-pg/barman-cloud/pkg/archiver"
+	cnpgv1 "github.com/cloudnative-pg/cloudnative-pg/api/v1"
+	"github.com/cloudnative-pg/machinery/pkg/log"
+)
+
+// CheckBackupDestination checks if the backup destination is suitable
+// to archive WALs
+func CheckBackupDestination(
+	ctx context.Context,
+	barmanConfiguration *cnpgv1.BarmanObjectStoreConfiguration,
+	barmanArchiver *archiver.WALArchiver,
+	serverName string,
+) error {
+	contextLogger := log.FromContext(ctx)
+	contextLogger.Info(
+		"Checking backup destination with barman-cloud-wal-archive",
+		"serverName", serverName)
+
+	// Get WAL archive options
+	checkWalOptions, err := barmanArchiver.BarmanCloudCheckWalArchiveOptions(
+		ctx, barmanConfiguration, serverName)
+	if err != nil {
+		log.Error(err, "while getting barman-cloud-wal-archive options")
+		return err
+	}
+
+	// Check if we're ok to archive in the desired destination
+	return barmanArchiver.CheckWalArchiveDestination(ctx, checkWalOptions)
+}

internal/cnpgi/common/wal.go

@@ -13,7 +13,9 @@ import (
 	barmanCredentials "github.com/cloudnative-pg/barman-cloud/pkg/credentials"
 	barmanRestorer "github.com/cloudnative-pg/barman-cloud/pkg/restorer"
 	cnpgv1 "github.com/cloudnative-pg/cloudnative-pg/api/v1"
+	"github.com/cloudnative-pg/cloudnative-pg/pkg/utils"
 	"github.com/cloudnative-pg/cnpg-i/pkg/wal"
+	"github.com/cloudnative-pg/machinery/pkg/fileutils"
 	walUtils "github.com/cloudnative-pg/machinery/pkg/fileutils/wals"
 	"github.com/cloudnative-pg/machinery/pkg/log"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
@@ -125,18 +127,36 @@ func (w WALServiceImplementation) Archive(
 		return nil, err
 	}
 
+	emptyWalArchiveFile := path.Join(w.PGDataPath, metadata.CheckEmptyWalArchiveFile)
 	arch, err := archiver.New(
 		ctx,
 		envArchive,
 		w.SpoolDirectory,
 		w.PGDataPath,
-		path.Join(w.PGDataPath, metadata.CheckEmptyWalArchiveFile),
+		emptyWalArchiveFile,
 	)
 	if err != nil {
 		return nil, err
 	}
 
-	// Step 2: check if this WAL file has not been already archived
+	// Step 2: Check if the archive location is safe to perform archiving
+	checkFileExisting, err := fileutils.FileExists(emptyWalArchiveFile)
+	if err != nil {
+		return nil, fmt.Errorf("while checking for empty wal archive check file %q: %w", emptyWalArchiveFile, err)
+	}
+
+	if utils.IsEmptyWalArchiveCheckEnabled(&configuration.Cluster.ObjectMeta) && checkFileExisting {
+		if err := CheckBackupDestination(
+			ctx,
+			&objectStore.Spec.Configuration,
+			arch,
+			configuration.ServerName,
+		); err != nil {
+			return nil, err
+		}
+	}
+
+	// Step 3: check if this WAL file has not been already archived
 	var isDeletedFromSpool bool
 	isDeletedFromSpool, err = arch.DeleteFromSpool(baseWalName)
 	if err != nil {
@@ -151,7 +171,7 @@ func (w WALServiceImplementation) Archive(
 		return nil, nil
 	}
 
-	// Step 3: gather the WAL files names to archive
+	// Step 4: gather the WAL files names to archive
 	options, err := arch.BarmanCloudWalArchiveOptions(ctx, &objectStore.Spec.Configuration, configuration.ServerName)
 	if err != nil {
 		return nil, err

internal/cnpgi/restore/restore.go

@@ -266,17 +266,9 @@ func (impl *JobHookImpl) checkBackupDestination(
 		}
 	}
 
-	// Get WAL archive options
-	checkWalOptions, err := walArchiver.BarmanCloudCheckWalArchiveOptions(
-		ctx, barmanConfiguration, serverName)
-	if err != nil {
-		log.Error(err, "while getting barman-cloud-wal-archive options")
-		return err
-	}
-
 	// Check if we're ok to archive in the desired destination
 	if utils.IsEmptyWalArchiveCheckEnabled(&cluster.ObjectMeta) {
-		return walArchiver.CheckWalArchiveDestination(ctx, checkWalOptions)
+		return common.CheckBackupDestination(ctx, barmanConfiguration, walArchiver, serverName)
 	}
 
 	return nil