1 files changed, 94 insertions, 0 deletions
diff --git a/src/pybind/mgr/mirroring/fs/dir_map/state_transition.py b/src/pybind/mgr/mirroring/fs/dir_map/state_transition.py
new file mode 100644
index 000000000..ef59a6a87
--- /dev/null
+++ b/src/pybind/mgr/mirroring/fs/dir_map/state_transition.py
@@ -0,0 +1,94 @@
+import logging
+from enum import Enum, unique
+from typing import Dict
+
+log = logging.getLogger(__name__)
+
+@unique
+class State(Enum):
+    UNASSOCIATED   = 0
+    INITIALIZING   = 1
+    ASSOCIATING    = 2
+    ASSOCIATED     = 3
+    SHUFFLING      = 4
+    DISASSOCIATING = 5
+
+@unique
+class ActionType(Enum):
+    NONE       = 0
+    MAP_UPDATE = 1
+    MAP_REMOVE = 2
+    ACQUIRE    = 3
+    RELEASE    = 4
+
+@unique
+class PolicyAction(Enum):
+    MAP    = 0
+    UNMAP  = 1
+    REMOVE = 2
+
+class TransitionKey:
+    def __init__(self, state, action_type):
+        self.transition_key = [state, action_type]
+
+    def __hash__(self):
+        return hash(tuple(self.transition_key))
+
+    def __eq__(self, other):
+        return self.transition_key == other.transition_key
+
+    def __neq__(self, other):
+        return not(self == other)
+
+class Transition:
+    def __init__(self, action_type, start_policy_action=None,
+                 finish_policy_action=None, final_state=None):
+        self.action_type = action_type
+        self.start_policy_action = start_policy_action
+        self.finish_policy_action = finish_policy_action
+        self.final_state = final_state
+
+    def __str__(self):
+        return "[action_type={0}, start_policy_action={1}, finish_policy_action={2}, final_state={3}".format(
+            self.action_type, self.start_policy_action, self.finish_policy_action, self.final_state)
+
+class StateTransition:
+    transition_table = {} # type: Dict[TransitionKey, Transition]
+
+    @staticmethod
+    def transit(state, action_type):
+        try:
+            return StateTransition.transition_table[TransitionKey(state, action_type)]
+        except KeyError:
+            raise Exception()
+
+    @staticmethod
+    def is_idle(state):
+        return state in (State.UNASSOCIATED, State.ASSOCIATED)
+
+StateTransition.transition_table = {
+    TransitionKey(State.INITIALIZING, ActionType.NONE) : Transition(ActionType.ACQUIRE),
+    TransitionKey(State.INITIALIZING, ActionType.ACQUIRE) : Transition(ActionType.NONE,
+                                                                       final_state=State.ASSOCIATED),
+
+    TransitionKey(State.ASSOCIATING, ActionType.NONE) : Transition(ActionType.MAP_UPDATE,
+                                                                   start_policy_action=PolicyAction.MAP),
+    TransitionKey(State.ASSOCIATING, ActionType.MAP_UPDATE) : Transition(ActionType.ACQUIRE),
+    TransitionKey(State.ASSOCIATING, ActionType.ACQUIRE) : Transition(ActionType.NONE,
+                                                                      final_state=State.ASSOCIATED),
+
+    TransitionKey(State.DISASSOCIATING, ActionType.NONE) : Transition(ActionType.RELEASE,
+                                                                      finish_policy_action=PolicyAction.UNMAP),
+    TransitionKey(State.DISASSOCIATING, ActionType.RELEASE) : Transition(ActionType.MAP_REMOVE,
+                                                                         finish_policy_action=PolicyAction.REMOVE),
+    TransitionKey(State.DISASSOCIATING, ActionType.MAP_REMOVE) : Transition(ActionType.NONE,
+                                                                            final_state=State.UNASSOCIATED),
+
+    TransitionKey(State.SHUFFLING, ActionType.NONE) : Transition(ActionType.RELEASE,
+                                                                 finish_policy_action=PolicyAction.UNMAP),
+    TransitionKey(State.SHUFFLING, ActionType.RELEASE) : Transition(ActionType.MAP_UPDATE,
+                                                                    start_policy_action=PolicyAction.MAP),
+    TransitionKey(State.SHUFFLING, ActionType.MAP_UPDATE) : Transition(ActionType.ACQUIRE),
+    TransitionKey(State.SHUFFLING, ActionType.ACQUIRE) : Transition(ActionType.NONE,
+                                                                    final_state=State.ASSOCIATED),
+    }