Ensuring cache presence before starting borg create. Fixes #7450

src/borg/cache.py

@@ -514,6 +514,15 @@ def __init__(
         self.txn_active = False
 
         self.path = cache_dir(self.repository, path)
+        if os.path.exists(self.path) and not self.check_cache_integrity():
+            logger.warning("Rebuilding cache as some cache-files have gone missing")
+            if not os.path.exists(os.path.join(self.path, "chunks")):
+                self.recreate_cache_config(delete_existing=True)  # recreating to remove integrity data stored in config
+                self.chunks = ChunkIndex()
+                self.chunks.write(os.path.join(self.path, "chunks"))
+            elif not os.path.exists(os.path.join(self.path, "config")):
+                self.recreate_cache_config()
+
         self.security_manager = SecurityManager(self.repository)
         self.cache_config = CacheConfig(self.repository, self.path, lock_wait)
 
@@ -900,6 +909,13 @@ def create_master_idx(chunk_idx):
             self.do_cache = os.path.isdir(archive_path)
             self.chunks = create_master_idx(self.chunks)
 
+    def check_cache_integrity(self):
+        cache_files = ["chunks", "config"]
+        for file in cache_files:
+            if not os.path.exists(os.path.join(self.path, file)):
+                return False
+        return True
+
     def check_cache_compatibility(self):
         my_features = Manifest.SUPPORTED_REPO_FEATURES
         if self.cache_config.ignored_features & my_features:
@@ -921,6 +937,15 @@ def wipe_cache(self):
         self.chunks = ChunkIndex()
         with SaveFile(os.path.join(self.path, files_cache_name()), binary=True):
             pass  # empty file
+        self.recreate_cache_config()
+
+    def recreate_cache_config(self, delete_existing=False):
+        if delete_existing and os.path.exists(os.path.join(self.path, "config")):
+            os.unlink(os.path.join(self.path, "config"))
+        if not os.path.exists(os.path.join(self.path, "config")):
+            self.cache_config = CacheConfig(self.repository, self.path)
+            self.cache_config.create()
+            self.cache_config.load()  # loading config here to initialize property `_config`
         self.cache_config.manifest_id = ""
         self.cache_config._config.set("cache", "manifest", "")
 

src/borg/testsuite/archiver/create_cmd.py

@@ -13,6 +13,7 @@
 
 from ... import platform
 from ...constants import *  # NOQA
+from ...helpers import get_cache_dir
 from ...manifest import Manifest
 from ...platform import is_cygwin, is_win32, is_darwin
 from ...repository import Repository
@@ -659,6 +660,30 @@ def test_file_status_cs_cache_mode(self):
         )
         self.assert_in("M input/file1", output)
 
+    @pytest.mark.allow_cache_wipe
+    def test_cache_rebuild_on_missing_cache_files(self):
+        """test if borg rebuilds cache if any of the cache files have gone missing"""
+        self.cmd(f"--repo={self.repository_location}", "rcreate", RK_ENCRYPTION)
+        self.create_regular_file("file1", size=10)
+        self.cmd(f"--repo={self.repository_location}", "create", "archive1", "input")
+        info = json.loads(self.cmd(f"--repo={self.repository_location}", "rinfo", "--json"))
+        repository = info["repository"]
+        cache_dir = os.path.join(get_cache_dir(), repository["id"])
+        config_cache_path = os.path.join(cache_dir, "config")
+        chunk_cache_path = os.path.join(cache_dir, "chunks")
+        os.unlink(config_cache_path)
+        self.create_regular_file("file2", size=10)
+        self.cmd(f"--repo={self.repository_location}", "create", "archive2", "input")
+        assert os.path.exists(config_cache_path)
+        os.unlink(chunk_cache_path)
+        self.create_regular_file("file3", size=10)
+        self.cmd(f"--repo={self.repository_location}", "create", "archive3", "input")
+        assert os.path.exists(chunk_cache_path)
+        self.create_regular_file("file4", size=10)
+        os.unlink(config_cache_path)
+        self.cmd(f"--repo={self.repository_location}", "create", "archive4", "input")
+        assert os.path.exists(config_cache_path)
+
     def test_file_status_ms_cache_mode(self):
         """test that a chmod'ed file with no content changes does not get chunked again in mtime,size cache_mode"""
         self.create_regular_file("file1", size=10)