feature(backups): lock and unlock at will

selfprivacy_api/backup/backuppers/restic_backupper.py

@@ -227,6 +227,24 @@ class ResticBackupper(AbstractBackupper):
                 raise ValueError("cannot init a repo: " + output)
 
     def is_initted(self) -> bool:
+        command = self.restic_command(
+            "check",
+        )
+
+        with subprocess.Popen(
+            command,
+            stdout=subprocess.PIPE,
+            shell=False,
+            stderr=subprocess.STDOUT,
+        ) as handle:
+            # communication forces to complete and for returncode to get defined
+            output = handle.communicate()[0].decode("utf-8")
+            if handle.returncode != 0:
+                return False
+            return True
+
+    def unlock(self) -> None:
+        """Remove stale locks."""
         command = self.restic_command(
             "unlock",
         )
@@ -235,10 +253,41 @@ class ResticBackupper(AbstractBackupper):
             command,
             stdout=subprocess.PIPE,
             shell=False,
+            stderr=subprocess.STDOUT,
         ) as handle:
+            # communication forces to complete and for returncode to get defined
+            output = handle.communicate()[0].decode("utf-8")
             if handle.returncode != 0:
-                return False
-            return True
+                raise ValueError("cannot unlock the backup repository: ", output)
+
+    def lock(self) -> None:
+        """
+        Introduce a stale lock.
+        Mainly for testing purposes.
+        Double lock is supposed to fail
+        """
+        command = self.restic_command(
+            "check",
+        )
+
+        # using temporary cache in /run/user/1000/restic-check-cache-817079729
+        # repository 9639c714 opened (repository version 2) successfully, password is correct
+        # created new cache in /run/user/1000/restic-check-cache-817079729
+        # create exclusive lock for repository
+        # load indexes
+        # check all packs
+        # check snapshots, trees and blobs
+        # [0:00] 100.00%  1 / 1 snapshots
+        # no errors were found
+
+        try:
+            for line in output_yielder(command):
+                if "indexes" in line:
+                    break
+                if "unable" in line:
+                    raise ValueError(line)
+        except Exception as e:
+            raise ValueError("could not lock repository") from e
 
     def restored_size(self, snapshot_id: str) -> int:
         """

selfprivacy_api/backup/util.py

@@ -1,8 +1,10 @@
 import subprocess
 from os.path import exists
+from typing import Generator
 
 
-def output_yielder(command):
+def output_yielder(command) -> Generator[str, None, None]:
+    """Note: If you break during iteration, it kills the process"""
     with subprocess.Popen(
         command,
         shell=False,
@@ -10,9 +12,15 @@ def output_yielder(command):
         stderr=subprocess.STDOUT,
         universal_newlines=True,
     ) as handle:
-        for line in iter(handle.stdout.readline, ""):
-            if "NOTICE:" not in line:
-                yield line
+        if handle is None or handle.stdout is None:
+            raise ValueError("could not run command: ", command)
+
+        try:
+            for line in iter(handle.stdout.readline, ""):
+                if "NOTICE:" not in line:
+                    yield line
+        except GeneratorExit:
+            handle.kill()
 
 
 def sync(src_path: str, dest_path: str):

tests/test_graphql/test_backup.py

@@ -758,3 +758,18 @@ def test_move_blocks_backups(backups, dummy_service, restore_strategy):
 
     with pytest.raises(ValueError):
         Backups.restore_snapshot(snap, restore_strategy)
+
+
+def test_double_lock_unlock(backups, dummy_service):
+    # notice that introducing stale locks is only safe for other tests if we erase repo in between
+    # which we do at the time of writing this test
+
+    Backups.provider().backupper.lock()
+    with pytest.raises(ValueError):
+        Backups.provider().backupper.lock()
+
+    Backups.provider().backupper.unlock()
+    Backups.provider().backupper.lock()
+
+    Backups.provider().backupper.unlock()
+    Backups.provider().backupper.unlock()