From 68b31a09b4012dd33d9cbe24d45057ef6822aeea Mon Sep 17 00:00:00 2001
From: Jack Robison <jackrobison@lbry.io>
Date: Mon, 2 Apr 2018 15:11:27 -0400
Subject: [PATCH] add daemon Component and ComponentManager classes

---
 lbrynet/daemon/Component.py        | 57 ++++++++++++++++++
 lbrynet/daemon/ComponentManager.py | 93 ++++++++++++++++++++++++++++++
 lbrynet/daemon/auth/server.py      |  2 +
 3 files changed, 152 insertions(+)
 create mode 100644 lbrynet/daemon/Component.py
 create mode 100644 lbrynet/daemon/ComponentManager.py

diff --git a/lbrynet/daemon/Component.py b/lbrynet/daemon/Component.py
new file mode 100644
index 000000000..2b6ac0582
--- /dev/null
+++ b/lbrynet/daemon/Component.py
@@ -0,0 +1,57 @@
+import logging
+from twisted.internet import defer
+from ComponentManager import ComponentManager
+
+log = logging.getLogger(__name__)
+
+
+class ComponentType(type):
+    def __new__(mcs, name, bases, newattrs):
+        klass = type.__new__(mcs, name, bases, newattrs)
+        if name != "Component":
+            ComponentManager.components.add(klass)
+        return klass
+
+
+class Component(object):
+    """
+    lbrynet-daemon component helper
+
+    Inheriting classes will be automatically registered with the ComponentManager and must implement setup and stop
+    methods
+    """
+
+    __metaclass__ = ComponentType
+    depends_on = []
+    component_name = None
+    running = False
+
+    @classmethod
+    def setup(cls):
+        raise NotImplementedError()  # override
+
+    @classmethod
+    def stop(cls):
+        raise NotImplementedError()  # override
+
+    @classmethod
+    @defer.inlineCallbacks
+    def _setup(cls):
+        try:
+            result = yield defer.maybeDeferred(cls.setup)
+            cls.running = True
+            defer.returnValue(result)
+        except Exception as err:
+            log.exception("Error setting up %s", cls.component_name or cls.__name__)
+            raise err
+
+    @classmethod
+    @defer.inlineCallbacks
+    def _stop(cls):
+        try:
+            result = yield defer.maybeDeferred(cls.stop)
+            cls.running = False
+            defer.returnValue(result)
+        except Exception as err:
+            log.exception("Error stopping %s", cls.__name__)
+            raise err
diff --git a/lbrynet/daemon/ComponentManager.py b/lbrynet/daemon/ComponentManager.py
new file mode 100644
index 000000000..8b645c014
--- /dev/null
+++ b/lbrynet/daemon/ComponentManager.py
@@ -0,0 +1,93 @@
+import logging
+from twisted.internet import defer
+
+log = logging.getLogger(__name__)
+
+
+class ComponentManager(object):
+    components = set()
+
+    @classmethod
+    def sort_components(cls, reverse=False):
+        """
+        Sort components by requirements
+        """
+        steps = []
+        staged = set()
+        components = set(cls.components)
+
+        # components with no requirements
+        step = []
+        for component in set(components):
+            if not component.depends_on:
+                step.append(component)
+                staged.add(component.component_name)
+                components.remove(component)
+
+        if step:
+            steps.append(step)
+
+        while components:
+            step = []
+            to_stage = set()
+            for component in set(components):
+                reqs_met = 0
+                for needed in component.depends_on:
+                    if needed in staged:
+                        reqs_met += 1
+                if reqs_met == len(component.depends_on):
+                    step.append(component)
+                    to_stage.add(component.component_name)
+                    components.remove(component)
+            if step:
+                staged.update(to_stage)
+                steps.append(step)
+            elif components:
+                raise SyntaxError("components cannot be started: %s" % components)
+        if reverse:
+            steps.reverse()
+        return steps
+
+    @classmethod
+    @defer.inlineCallbacks
+    def setup(cls):
+        """
+        Start Components in sequence sorted by requirements
+
+        :return: (defer.Deferred)
+        """
+        stages = cls.sort_components()
+        for stage in stages:
+            yield defer.DeferredList([component._setup() for component in stage])
+
+    @classmethod
+    @defer.inlineCallbacks
+    def stop(cls):
+        """
+        Stop Components in reversed startup order
+
+        :return: (defer.Deferred)
+        """
+        stages = cls.sort_components(reverse=True)
+        for stage in stages:
+            yield defer.DeferredList([component._stop() for component in stage])
+
+    @classmethod
+    def all_components_running(cls, *component_names):
+        """
+        :return: (bool) True if all specified components are running
+        """
+        c = {component.component_name: component for component in cls.components}
+        for component in component_names:
+            if component not in c:
+                raise NameError("%s is not a known Component" % component)
+            if not c[component].running:
+                return False
+        return True
+
+    @classmethod
+    def get_component(cls, component_name):
+        for component in cls.components:
+            if component.component_name == component_name:
+                return component
+        raise NameError(component_name)
diff --git a/lbrynet/daemon/auth/server.py b/lbrynet/daemon/auth/server.py
index a0d365a35..009df762a 100644
--- a/lbrynet/daemon/auth/server.py
+++ b/lbrynet/daemon/auth/server.py
@@ -17,6 +17,7 @@ from lbrynet.core.Error import InvalidAuthenticationToken
 from lbrynet.core import utils
 from lbrynet.daemon.auth.util import APIKey, get_auth_message
 from lbrynet.daemon.auth.client import LBRY_SECRET
+from lbrynet.daemon.Component import ComponentManager
 from lbrynet.undecorated import undecorated
 
 log = logging.getLogger(__name__)
@@ -132,6 +133,7 @@ class JSONRPCServerType(type):
 
 class AuthorizedBase(object):
     __metaclass__ = JSONRPCServerType
+    component_manager = ComponentManager
 
     @staticmethod
     def deprecated(new_command=None):