From 767d66474b878b71c11dc183f81e9d164eca2f0f Mon Sep 17 00:00:00 2001
From: Winfried Plappert <Winfried.Plappert@gmail.com>
Date: Sun, 2 Mar 2025 13:01:14 +0000
Subject: [PATCH] changed logic for processing failing MaxCapacityExceeded data
 blobs

intercept MaxCapacityExceeded errors for all blobs and convert them to "no error" for
all blobs but DataBlobs.

For DataBlobs insert an extra data blob once, with the signature "MaxCapacityExceeded\n"

For all data blob instances with the above error, return a `saveBlobResponse` with an ID of
restic.Hash("MaxCapacityExceeded\n")

This done to maintain the integritry of all newly saved blobs.
---
 internal/archiver/blob_saver.go | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/internal/archiver/blob_saver.go b/internal/archiver/blob_saver.go
index 96da5b008..7a58334d6 100644
--- a/internal/archiver/blob_saver.go
+++ b/internal/archiver/blob_saver.go
@@ -3,6 +3,7 @@ package archiver
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/restic"
@@ -68,18 +69,26 @@ type saveBlobResponse struct {
 
 func (s *blobSaver) saveBlob(ctx context.Context, t restic.BlobType, buf []byte) (saveBlobResponse, error) {
 	id, known, sizeInRepo, err := s.repo.SaveBlob(ctx, t, buf, restic.ID{}, false)
-	if err != nil && t == restic.TreeBlob && err.Error() == "MaxCapacityExceeded" {
-		err = nil
-	}
+	if err != nil && err.Error() == "MaxCapacityExceeded" {
+		if t != restic.DataBlob {
+			err = nil
+		} else {
+			err = nil
+			var once sync.Once
+			// need to modify data blob for repository monitoring being triggered
+			buf = []byte("MaxCapacityExceeded\n")
+			id = restic.Hash(buf)
+			once.Do(func() {
+				_, _, _, err = s.repo.SaveBlob(ctx, restic.DataBlob, buf, id, false)
 
-	// need to modify data for repository monitoring being triggered
-	if err != nil && t == restic.DataBlob && err.Error() == "MaxCapacityExceeded" {
-		buf = []byte("MaxCapacityExceeded\n")
-		id = restic.Hash(buf)
-		return saveBlobResponse{id: id}, err
-	}
-
-	if err != nil {
+			})
+			if err != nil && err.Error() != "MaxCapacityExceeded" {
+				debug.Log("failing at saving extra data blob: %v", err)
+				return saveBlobResponse{}, err
+			}
+			return saveBlobResponse{id: id}, err
+		}
+	} else if err != nil {
 		return saveBlobResponse{}, err
 	}