Add threadgroup to manage timers and greenthreads.

Part of blueprint service-infrastructure

Change-Id: I40593b6ad13d99d9e63c8c04154a0dac5aced02e
Signed-off-by: Angus Salkeld <asalkeld@redhat.com>

2 files changed, 141 insertions, 7 deletions

diff --git a/openstack/common/service.py b/openstack/common/service.py
index b464aea..01c38a4 100644
--- a/openstack/common/service.py
+++ b/openstack/common/service.py
@@ -30,6 +30,7 @@ import eventlet
 import greenlet
 
 from openstack.common import log as logging
+from openstack.common import threadgroup
 from openstack.common.gettextutils import _
 
 
@@ -290,24 +291,39 @@ class ProcessLauncher(object):
 class Service(object):
     """Service object for binaries running on hosts.
 
-    A service takes a manager."""
+    A service takes a manager and periodically runs tasks on the manager."""
 
-    def __init__(self, host, manager, *args, **kwargs):
+    def __init__(self, host, manager,
+                 periodic_interval=None,
+                 periodic_fuzzy_delay=None):
         self.host = host
         self.manager = manager
-        self.running = False
+        self.periodic_interval = periodic_interval
+        self.periodic_fuzzy_delay = periodic_fuzzy_delay
+        self.tg = threadgroup.ThreadGroup('service')
+        self.periodic_args = []
+        self.periodic_kwargs = {}
 
     def start(self):
-        self.running = True
         if self.manager:
             self.manager.init_host()
 
+        if self.periodic_interval and self.manager:
+            if self.periodic_fuzzy_delay:
+                initial_delay = random.randint(0, self.periodic_fuzzy_delay)
+            else:
+                initial_delay = 0
+            self.tg.add_timer(self.periodic_interval,
+                              self.manager.run_periodic_tasks,
+                              initial_delay,
+                              *self.periodic_args,
+                              **self.periodic_kwargs)
+
     def stop(self):
-        self.running = False
+        self.tg.stop()
 
     def wait(self):
-        while self.running:
-            time.sleep(.1)
+        self.tg.wait()
 
 
 def launch(service, workers=None):
diff --git a/openstack/common/threadgroup.py b/openstack/common/threadgroup.py
new file mode 100644
index 0000000..a9dfa5e
--- /dev/null
+++ b/openstack/common/threadgroup.py
@@ -0,0 +1,118 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2012 Red Hat, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+import os
+import sys
+
+from eventlet import event
+from eventlet import greenthread
+from eventlet import greenpool
+
+from openstack.common import loopingcall
+from openstack.common.gettextutils import _
+from openstack.common import log as logging
+
+
+LOG = logging.getLogger(__name__)
+
+
+def _thread_done(gt, *args, **kwargs):
+    args[0].thread_done(args[1])
+
+
+class Thread(object):
+    """
+    Wrapper around a greenthread, that holds a reference to
+    the ThreadGroup. The Thread will notify the ThreadGroup
+    when it has done so it can be removed from the threads
+    list.
+    """
+    def __init__(self, name, thread, group):
+        self.name = name
+        self.thread = thread
+        self.thread.link(_thread_done, group, self)
+
+    def stop(self):
+        self.thread.cancel()
+
+    def wait(self):
+        return self.thread.wait()
+
+
+class ThreadGroup():
+    """
+    The point of this class is to:
+    - keep track of timers and greenthreads (making it easier to stop them
+      when need be).
+    - provide an easy API to add timers.
+    """
+    def __init__(self, name, thread_pool_size=10):
+        self.name = name
+        self.pool = greenpool.GreenPool(thread_pool_size)
+        self.threads = []
+        self.timers = []
+
+    def add_timer(self, interval, callback, initial_delay=None,
+                  *args, **kwargs):
+        pulse = loopingcall.LoopingCall(callback, *args, **kwargs)
+        pulse.start(interval=interval,
+                    initial_delay=initial_delay)
+        self.timers.append(pulse)
+
+    def add_thread(self, callback, *args, **kwargs):
+        gt = self.pool.spawn(callback, *args, **kwargs)
+        th = Thread(callback.__name__, gt, self)
+        self.threads.append(th)
+
+    def thread_done(self, thread):
+        try:
+            thread.wait()
+        except Exception as ex:
+            LOG.exception(ex)
+        finally:
+            self.threads.remove(thread)
+
+    def stop(self):
+        current = greenthread.getcurrent()
+        for x in self.threads:
+            if x is current:
+                # don't kill the current thread.
+                continue
+            try:
+                x.stop()
+            except Exception as ex:
+                LOG.exception(ex)
+
+        for x in self.timers:
+            try:
+                x.stop()
+            except Exception as ex:
+                LOG.exception(ex)
+        self.timers = []
+
+    def wait(self):
+        for x in self.timers:
+            try:
+                x.wait()
+            except Exception as ex:
+                LOG.exception(ex)
+        current = greenthread.getcurrent()
+        for x in self.threads:
+            if x is current:
+                continue
+            try:
+                x.wait()
+            except Exception as ex:
+                LOG.exception(ex)