Merge pull request #1470 from hercules-ci/locking-usability

Locking usability improvements

nixops/args.py

@@ -352,6 +352,12 @@
 subparser.add_argument(
  "args", metavar="SSH_ARGS", nargs=REMAINDER, help="SSH flags and/or command",
 )
+subparser.add_argument(
+ "--now",
+ dest="now",
+ action="store_true",
+ help="do not acquire a lock before fetching the state",
+)
 
 subparser = add_subparser(
  subparsers, "ssh-for-each", help="execute a command on each machine via SSH"
@@ -443,14 +449,12 @@
  "--freeze",
  dest="freeze_fs",
  action="store_true",
- default=False,
  help="freeze filesystems for non-root filesystems that support this (e.g. xfs)",
 )
 subparser.add_argument(
  "--force",
  dest="force",
  action="store_true",
- default=False,
  help="start new backup even if previous is still running",
 )
 subparser.add_argument(
@@ -478,17 +482,12 @@
  help="do not perform backup actions on the specified machines",
 )
 subparser.add_argument(
- "--wait",
- dest="wait",
- action="store_true",
- default=False,
- help="wait until backup is finished",
+ "--wait", dest="wait", action="store_true", help="wait until backup is finished",
 )
 subparser.add_argument(
  "--latest",
  dest="latest",
  action="store_true",
- default=False,
  help="show status of latest backup only",
 )
 
@@ -498,7 +497,6 @@
 subparser.add_argument(
  "--keep-physical",
  dest="keep_physical",
- default=False,
  action="store_true",
  help="do not remove the physical backups, only remove backups from nixops state",
 )
@@ -518,7 +516,6 @@
 subparser.add_argument(
  "--keep-physical",
  dest="keep_physical",
- default=False,
  action="store_true",
  help="do not remove the physical backups, only remove backups from nixops state",
 )

nixops/locks/__init__.py

@@ -2,10 +2,35 @@
 from typing_extensions import Protocol
 
 
+"""
+Interface to a lock driver.
+
+An implementation should inherit from LockDriver in order to for a plugin to be
+able to integrate it.
+"""
+
+
+# This separation was introduced to hide the LockOptions details from the
+# LockInterface type. It only matters for construction and clients don't have
+# to know about it.
+class LockInterface(Protocol):
+ # lock: acquire a lock.
+ # Note: no arguments will be passed over kwargs. Making it part of
+ # the type definition allows adding new arguments later.
+ def lock(self, description: str, exclusive: bool, **kwargs) -> None:
+ raise NotImplementedError
+
+ # unlock: release the lock.
+ # Note: no arguments will be passed over kwargs. Making it part of
+ # the type definition allows adding new arguments later.
+ def unlock(self, **kwargs) -> None:
+ raise NotImplementedError
+
+
 LockOptions = TypeVar("LockOptions")
 
 
-class LockDriver(Protocol[LockOptions]):
+class LockDriver(LockInterface, Protocol[LockOptions]):
  # Hack: Make T a mypy invariant. According to PEP-0544, a
  # Protocol[T] whose T is only used in function arguments and
  # returns is "de-facto covariant".
@@ -26,15 +51,3 @@ def options(**kwargs) -> LockOptions:
 
  def __init__(self, args: LockOptions) -> None:
  raise NotImplementedError
-
- # lock: acquire a lock.
- # Note: no arguments will be passed over kwargs. Making it part of
- # the type definition allows adding new arguments later.
- def lock(self, **kwargs) -> None:
- raise NotImplementedError
-
- # unlock: release the lock.
- # Note: no arguments will be passed over kwargs. Making it part of
- # the type definition allows adding new arguments later.
- def unlock(self, **kwargs) -> None:
- raise NotImplementedError

nixops/locks/noop.py

@@ -19,5 +19,5 @@ def __init__(self, args: NoopLockOptions) -> None:
  def unlock(self, **_kwargs) -> None:
  pass
 
- def lock(self, **_kwargs) -> None:
+ def lock(self, description, exclusive, **_kwargs) -> None:
  pass