add process_utils.py (#35)

Co-authored-by: jarbasai <jarbasai@mailfence.com>

Author: JarbasAl

ovos_utils/process_utils.py

@@ -0,0 +1,143 @@
+import sys
+from collections import namedtuple
+from enum import IntEnum
+
+
+class ProcessState(IntEnum):
+    """Oredered enum to make state checks easy.
+
+    For example Alive can be determined using >= ProcessState.ALIVE,
+    which will return True if the state is READY as well as ALIVE.
+    """
+    NOT_STARTED = 0
+    STARTED = 1
+    ERROR = 2
+    STOPPING = 3
+    ALIVE = 4
+    READY = 5
+
+
+# Process state change callback mappings.
+_STATUS_CALLBACKS = [
+    'on_started',
+    'on_alive',
+    'on_ready',
+    'on_error',
+    'on_stopping',
+]
+
+# namedtuple defaults only available on 3.7 and later python versions
+if sys.version_info < (3, 7):
+    StatusCallbackMap = namedtuple('CallbackMap', _STATUS_CALLBACKS)
+    StatusCallbackMap.__new__.__defaults__ = (None,) * 5
+else:
+    StatusCallbackMap = namedtuple(
+        'CallbackMap',
+        _STATUS_CALLBACKS,
+        defaults=(None,) * len(_STATUS_CALLBACKS),
+    )
+
+
+class ProcessStatus:
+    """Process status tracker.
+
+    The class tracks process status and execute callback methods on
+    state changes as well as replies to messagebus queries of the
+    process status.
+
+    Args:
+        name (str): process name, will be used to create the messagebus
+                    messagetype "mycroft.{name}...".
+        bus (MessageBusClient): Connection to the Mycroft messagebus.
+        callback_map (StatusCallbackMap): optionally, status callbacks for the
+                                          various status changes.
+    """
+
+    def __init__(self, name, bus=None, callback_map=None, namespace="mycroft"):
+        self.name = name
+        self._namespace = namespace
+        self.callbacks = callback_map or StatusCallbackMap()
+        self.state = ProcessState.NOT_STARTED
+
+        # Messagebus connection
+        self.bus = None
+        if bus:
+            self.bind(bus)
+
+    def bind(self, bus):
+        self.bus = bus
+        self._register_handlers()
+
+    def _register_handlers(self):
+        """Register messagebus handlers for status queries."""
+        self.bus.on(f'{self._namespace}.{self.name}.is_alive', self.check_alive)
+        self.bus.on(f'{self._namespace}.{self.name}.is_ready', self.check_ready)
+
+        # The next one is for backwards compatibility
+        self.bus.on(f'mycroft.{self.name}.all_loaded', self.check_ready)
+
+    def check_alive(self, message=None):
+        """Respond to is_alive status request.
+
+        Args:
+            message: Optional message to respond to, if omitted no message
+                     is sent.
+
+        Returns:
+            bool, True if process is alive.
+        """
+        is_alive = self.state >= ProcessState.ALIVE
+
+        if message:
+            status = {'status': is_alive}
+            self.bus.emit(message.response(data=status))
+
+        return is_alive
+
+    def check_ready(self, message=None):
+        """Respond to all_loaded status request.
+
+        Args:
+            message: Optional message to respond to, if omitted no message
+                     is sent.
+
+        Returns:
+            bool, True if process is ready.
+        """
+        is_ready = self.state >= ProcessState.READY
+        if message:
+            status = {'status': is_ready}
+            self.bus.emit(message.response(data=status))
+
+        return is_ready
+
+    def set_started(self):
+        """Process is started."""
+        self.state = ProcessState.STARTED
+        if self.callbacks.on_started:
+            self.callbacks.on_started()
+
+    def set_alive(self):
+        """Basic loading is done."""
+        self.state = ProcessState.ALIVE
+        if self.callbacks.on_alive:
+            self.callbacks.on_alive()
+
+    def set_ready(self):
+        """All loading is done."""
+        self.state = ProcessState.READY
+        if self.callbacks.on_ready:
+            self.callbacks.on_ready()
+
+    def set_stopping(self):
+        """Process shutdown has started."""
+        self.state = ProcessState.STOPPING
+        if self.callbacks.on_stopping:
+            self.callbacks.on_stopping()
+
+    def set_error(self, err=''):
+        """An error has occured and the process is non-functional."""
+        # Intentionally leave is_started True
+        self.state = ProcessState.ERROR
+        if self.callbacks.on_error:
+            self.callbacks.on_error(err)