Improved error handling/reporting.

Closes #12.

CHANGES

@@ -8,6 +8,7 @@ Version 0.9
 
 (feature release, released on X)
 
+- Improved error handling / reporting. (#12)
 - Use fcntl() instead of flock() when locking repository/cache. (#15)
 - Let ssh figure out port/user if not specified so we don't override .ssh/config (#9)
 

attic/archive.py

@@ -10,7 +10,7 @@
 from io import BytesIO
 from attic import xattr
 from attic.chunker import chunkify
-from attic.helpers import uid2user, user2uid, gid2group, group2gid, \
+from attic.helpers import Error, uid2user, user2uid, gid2group, group2gid, \
     Statistics, decode_dict, st_mtime_ns, make_path_safe
 
 ITEMS_BUFFER = 1024 * 1024
@@ -72,11 +72,11 @@ def peek(self):
 
 class Archive(object):
 
-    class DoesNotExist(Exception):
-        pass
+    class DoesNotExist(Error):
+        """Archive {} does not exist"""
 
-    class AlreadyExists(Exception):
-        pass
+    class AlreadyExists(Error):
+        """Archive {} already exists"""
 
     def __init__(self, repository, key, manifest, name, cache=None, create=False,
                  checkpoint_interval=300, numeric_owner=False):

attic/archiver.py

@@ -11,7 +11,7 @@
 from attic.repository import Repository
 from attic.cache import Cache
 from attic.key import key_creator
-from attic.helpers import location_validator, format_time, \
+from attic.helpers import Error, location_validator, format_time, \
     format_file_mode, ExcludePattern, exclude_path, adjust_patterns, to_localtime, \
     get_cache_dir, get_keys_dir, format_timedelta, prune_split, Manifest, Location, remove_surrogates
 from attic.remote import RepositoryServer, RemoteRepository, ConnectionClosed
@@ -477,24 +477,9 @@ def main():
     archiver = Archiver()
     try:
         exit_code = archiver.run(sys.argv[1:])
-    except Repository.DoesNotExist:
-        archiver.print_error('Error: Repository not found')
-        exit_code = 1
-    except Repository.AlreadyExists:
-        archiver.print_error('Error: Repository already exists')
-        exit_code = 1
-    except Archive.AlreadyExists as e:
-        archiver.print_error('Error: Archive "%s" already exists', e)
-        exit_code = 1
-    except Archive.DoesNotExist as e:
-        archiver.print_error('Error: Archive "%s" does not exist', e)
-        exit_code = 1
-    except Cache.RepositoryReplay:
-        archiver.print_error('Cache is newer than repository, refusing to continue')
-        exit_code = 1
-    except ConnectionClosed:
-        archiver.print_error('Connection closed by remote host')
-        exit_code = 1
+    except Error as e:
+        archiver.print_error(e.get_message())
+        exit_code = e.exit_code
     except KeyboardInterrupt:
         archiver.print_error('Error: Keyboard interrupt')
         exit_code = 1

attic/cache.py

@@ -5,7 +5,7 @@
 from binascii import hexlify
 import shutil
 
-from .helpers import get_cache_dir, decode_dict, st_mtime_ns, unhexlify, UpgradableLock
+from .helpers import Error, get_cache_dir, decode_dict, st_mtime_ns, unhexlify, UpgradableLock
 from .hashindex import ChunkIndex
 
 
@@ -13,9 +13,8 @@ class Cache(object):
     """Client Side cache
     """
 
-    class RepositoryReplay(Exception):
-        """
-        """
+    class RepositoryReplay(Error):
+        """Cache is newer than repository, refusing to continue"""
 
     def __init__(self, repository, key, manifest):
         self.timestamp = None

attic/helpers.py

@@ -14,9 +14,22 @@
 import fcntl
 
 
+class Error(Exception):
+    """Error base class"""
+
+    exit_code = 1
+
+    def get_message(self):
+        return 'Error: ' + type(self).__doc__.format(*self.args)
+
+
 class UpgradableLock:
 
+    class LockUpgradeFailed(Error):
+        """Failed to acquire write lock on {}"""
+
     def __init__(self, path, exclusive=False):
+        self.path = path
         try:
             self.fd = open(path, 'r+')
         except IOError:
@@ -28,7 +41,10 @@ def __init__(self, path, exclusive=False):
         self.is_exclusive = exclusive
 
     def upgrade(self):
-        fcntl.lockf(self.fd, fcntl.LOCK_EX)
+        try:
+            fcntl.lockf(self.fd, fcntl.LOCK_EX)
+        except OSError as e:
+            raise self.LockUpgradeFailed(self.path)
         self.is_exclusive = True
 
     def release(self):

attic/remote.py

@@ -4,17 +4,16 @@
 import select
 from subprocess import Popen, PIPE
 import sys
-import getpass
 
+from .helpers import Error
 from .repository import Repository
 from .lrucache import LRUCache
 
 BUFSIZE = 10 * 1024 * 1024
 
 
-class ConnectionClosed(Exception):
-    """Connection closed by remote host
-    """
+class ConnectionClosed(Error):
+    """Connection closed by remote host"""
 
 
 class RepositoryServer(object):

attic/repository.py

@@ -7,7 +7,7 @@
 from zlib import crc32
 
 from .hashindex import NSIndex
-from .helpers import IntegrityError, read_msgpack, write_msgpack, unhexlify, UpgradableLock
+from .helpers import Error, IntegrityError, read_msgpack, write_msgpack, unhexlify, UpgradableLock
 from .lrucache import LRUCache
 
 MAX_OBJECT_SIZE = 20 * 1024 * 1024
@@ -30,11 +30,15 @@ class Repository(object):
     DEFAULT_MAX_SEGMENT_SIZE = 5 * 1024 * 1024
     DEFAULT_SEGMENTS_PER_DIR = 10000
 
-    class DoesNotExist(KeyError):
-        """Requested key does not exist"""
+    class DoesNotExist(Error):
+        """Repository {} does not exist"""
+
+    class AlreadyExists(Error):
+        """Repository {} already exists"""
+
+    class InvalidRepository(Error):
+        """{} is not a valid repository"""
 
-    class AlreadyExists(KeyError):
-        """Requested key does not exist"""
 
     def __init__(self, path, create=False):
         self.io = None
@@ -70,11 +74,11 @@ def open(self, path):
         self.path = path
         if not os.path.isdir(path):
             raise self.DoesNotExist(path)
-        self.lock = UpgradableLock(os.path.join(path, 'config'))
         self.config = RawConfigParser()
         self.config.read(os.path.join(self.path, 'config'))
-        if self.config.getint('repository', 'version') != 1:
-            raise Exception('%s Does not look like an Attic repository')
+        if not 'repository' in self.config.sections() or self.config.getint('repository', 'version') != 1:
+            raise self.InvalidRepository(path)
+        self.lock = UpgradableLock(os.path.join(path, 'config'))
         self.max_segment_size = self.config.getint('repository', 'max_segment_size')
         self.segments_per_dir = self.config.getint('repository', 'segments_per_dir')
         self.id = unhexlify(self.config.get('repository', 'id').strip())

attic/testsuite/helpers.py

@@ -84,5 +84,5 @@ def test_read_only_lock_file(self):
         file = tempfile.NamedTemporaryFile()
         os.chmod(file.name, 0o444)
         lock = UpgradableLock(file.name)
-        self.assert_raises(OSError, lock.upgrade)
+        self.assert_raises(UpgradableLock.LockUpgradeFailed, lock.upgrade)
         lock.release()