Add --ignore-missing-chunks option to forget

5 files changed, 24 insertions, 11 deletions

diff --git a/obnamlib/delegator.py b/obnamlib/delegator.py
index f0c6038a..5065a62d 100644
--- a/obnamlib/delegator.py
+++ b/obnamlib/delegator.py
@@ -198,10 +198,10 @@ class RepositoryDelegator(obnamlib.RepositoryInterface):
         client = self._lookup_client_by_generation(generation_id)
         return client.set_generation_key(generation_id.gen_number, key, value)
 
-    def remove_generation(self, generation_id):
+    def remove_generation(self, generation_id, ignore_missing_chunks=False):
         self._require_got_client_lock(generation_id.client_name)
         client = self._lookup_client_by_generation(generation_id)
-        return client.remove_generation(generation_id.gen_number)
+        return client.remove_generation(generation_id.gen_number, ignore_missing_chunks)
 
     def get_generation_chunk_ids(self, generation_id):
         client = self._lookup_client_by_generation(generation_id)
diff --git a/obnamlib/fmt_6/repo_fmt_6.py b/obnamlib/fmt_6/repo_fmt_6.py
index 31ae8779..3cc54426 100644
--- a/obnamlib/fmt_6/repo_fmt_6.py
+++ b/obnamlib/fmt_6/repo_fmt_6.py
@@ -340,7 +340,7 @@ class RepositoryFormat6(obnamlib.RepositoryInterface):
         self._raw_unlock_client(client_name)
 
     def _remove_chunks_from_removed_generations(
-            self, client_name, remove_gen_nos):
+            self, client_name, remove_gen_nos, ignore_missing_chunks=False):
 
         def find_chunkids_in_gens(gen_nos):
             chunkids = set()
@@ -358,7 +358,7 @@ class RepositoryFormat6(obnamlib.RepositoryInterface):
                     keep.append(gen_number)
             return keep
 
-        def remove_chunks(chunk_ids):  # pragma: no cover
+        def remove_chunks(chunk_ids, ignore_missing_chunks=False):  # pragma: no cover
             for chunk_id in chunk_ids:
                 try:
                     checksum = self._chunklist.get_checksum(chunk_id)
@@ -368,14 +368,16 @@ class RepositoryFormat6(obnamlib.RepositoryInterface):
                     self._remove_chunk(chunk_id)
                 else:
                     self.remove_chunk_from_indexes(chunk_id, client_name)
-                    if not self._chunksums.chunk_is_used(checksum, chunk_id):
+                    # We can skip removal if the chunk doesn't exist
+                    skip_removal = ignore_missing_chunks and not self.has_chunk(chunk_id)
+                    if not skip_removal and not self._chunksums.chunk_is_used(checksum, chunk_id):
                         self._remove_chunk(chunk_id)
 
         keep_gen_nos = find_gens_to_keep()
         keep_chunkids = find_chunkids_in_gens(keep_gen_nos)
         maybe_remove_chunkids = find_chunkids_in_gens(remove_gen_nos)
         remove_chunkids = maybe_remove_chunkids.difference(keep_chunkids)
-        remove_chunks(remove_chunkids)
+        remove_chunks(remove_chunkids, ignore_missing_chunks)
 
     def get_allowed_client_keys(self):
         return []
@@ -547,7 +549,7 @@ class RepositoryFormat6(obnamlib.RepositoryInterface):
         client_name, gen_number = self._unpack_gen_id(gen_id)
         return str(gen_number)
 
-    def remove_generation(self, gen_id):
+    def remove_generation(self, gen_id, ignore_missing_chunks=False):
         tracing.trace('gen_id=%s' % repr(gen_id))
         client_name, gen_number = self._unpack_gen_id(gen_id)
         self._require_client_lock(client_name)
@@ -561,7 +563,8 @@ class RepositoryFormat6(obnamlib.RepositoryInterface):
         self._forget_open_client_info_cached_generation(
             open_client_info, gen_id)
 
-        self._remove_chunks_from_removed_generations(client_name, [gen_number])
+        self._remove_chunks_from_removed_generations(client_name, [gen_number],
+                ignore_missing_chunks)
         open_client_info.client.start_changes(create_tree=False)
         open_client_info.client.remove_generation(gen_number)
 
diff --git a/obnamlib/fmt_ga/client.py b/obnamlib/fmt_ga/client.py
index 65422855..ecd3b21a 100644
--- a/obnamlib/fmt_ga/client.py
+++ b/obnamlib/fmt_ga/client.py
@@ -174,7 +174,7 @@ class GAClient(object):
         else:
             return str(1)
 
-    def remove_generation(self, gen_number):
+    def remove_generation(self, gen_number, ignore_missing_chunks=False):
         self._load_data()
         remaining = []
         removed = False
diff --git a/obnamlib/plugins/forget_plugin.py b/obnamlib/plugins/forget_plugin.py
index 860cd116..c12c36a4 100644
--- a/obnamlib/plugins/forget_plugin.py
+++ b/obnamlib/plugins/forget_plugin.py
@@ -24,6 +24,8 @@ class ForgetPlugin(obnamlib.ObnamPlugin):
     '''Forget generations.'''
 
     def enable(self):
+        forget_group = obnamlib.option_group['forget'] = 'Forgetting generations (forget)'
+
         self.app.add_subcommand(
             'forget', self.forget, arg_synopsis='[GENERATION]...')
         self.app.settings.string(
@@ -31,6 +33,11 @@ class ForgetPlugin(obnamlib.ObnamPlugin):
             'policy for what generations to keep '
             'when forgetting')
 
+        self.app.settings.boolean(
+            ['ignore-missing-chunks'],
+            'ignore missing chunks when forgetting generations',
+            group=forget_group)
+
     def forget(self, args):
         '''Forget (remove) specified backup generations.'''
         self.app.settings.require('repository')
@@ -130,4 +137,4 @@ class ForgetPlugin(obnamlib.ObnamPlugin):
                 'Pretending to remove generation %s' %
                 self.repo.make_generation_spec(genid))
         else:
-            self.repo.remove_generation(genid)
+            self.repo.remove_generation(genid, self.app.settings['ignore-missing-chunks'])
diff --git a/obnamlib/repo_interface.py b/obnamlib/repo_interface.py
index f16d6925..50832290 100644
--- a/obnamlib/repo_interface.py
+++ b/obnamlib/repo_interface.py
@@ -572,11 +572,14 @@ class RepositoryInterface(object):
         '''Set a key/value pair for a given generation.'''
         raise NotImplementedError()
 
-    def remove_generation(self, generation_id):
+    def remove_generation(self, generation_id, ignore_missing_chunks=False):
         '''Remove an existing generation.
 
         The removed generation may be the currently unfinished one.
 
+        When removing chunks, don't try to remove those that are missing
+        if ignore_missing_chunks is set to True.
+
         '''
         raise NotImplementedError()