[Kimchi-devel] [PATCH] [Wok 1/2] Issue #122 - Make AsyncTask stoppable.

[pvital at linux.vnet.ibm.com]

From: Paulo Vital <pvital at linux.vnet.ibm.com>

This patch gives to user a way to 'stop' a Task that is still running by setting
the Task status to "killed".

Since an AsyncTask is basic a thread running in the system and this thread can
execute a pure Python method or a background command (by using run_command()
from wok.utils), the developer must pass to AsyncTask constructor a method to be
executed by the DELETE operation, called here as 'kill_cb'. If none kill_cb is
passed, the task will not be able to stopped and an error message will be raised
to user if DELETE operation is executed. Otherwise, the kill_cb method will be
executed by kill() method (responsible to execute the DELETE operation) of
AsyncTask class and its status set to 'killed'.

Signed-off-by: Paulo Vital <pvital at linux.vnet.ibm.com>
---
 docs/API/tasks.md      |  2 ++
 src/wok/asynctask.py   | 18 +++++++++++++++++-
 src/wok/i18n.py        |  2 ++
 src/wok/model/tasks.py | 13 +++++++++++++
 4 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/docs/API/tasks.md b/docs/API/tasks.md
index e0c404f..2068f29 100644
--- a/docs/API/tasks.md
+++ b/docs/API/tasks.md
@@ -27,8 +27,10 @@ server.
         * running: The task is running
         * finished: The task has finished successfully
         * failed: The task failed
+        * killed: The task was killed by user
     * message: Human-readable details about the Task status
     * target_uri: Resource URI related to the Task
+* **DELETE**: Kill the Task, moving its status to 'killed'
 * **POST**: *See Task Actions*
 
 **Actions (POST):**
diff --git a/src/wok/asynctask.py b/src/wok/asynctask.py
index b98ad9a..ecd9029 100644
--- a/src/wok/asynctask.py
+++ b/src/wok/asynctask.py
@@ -26,6 +26,9 @@ import traceback
 import uuid
 
 
+from wok.exception import InvalidOperation
+
+
 tasks_queue = {}
 
 
@@ -41,10 +44,11 @@ def clean_old_tasks():
 
 
 class AsyncTask(object):
-    def __init__(self, target_uri, fn, opaque=None):
+    def __init__(self, target_uri, fn, opaque=None, kill_cb=None):
         self.id = str(uuid.uuid1())
         self.target_uri = target_uri
         self.fn = fn
+        self.kill_cb = kill_cb
         self.status = 'running'
         self.message = 'The request is being processing.'
         self.timestamp = time.time()
@@ -79,3 +83,15 @@ class AsyncTask(object):
         except KeyError:
             msg = "There's no task_id %s in tasks_queue. Nothing changed."
             cherrypy.log.error_log.error(msg % self.id)
+
+    def kill(self):
+        if self.kill_cb is None:
+            raise InvalidOperation('WOKASYNC0002E')
+
+        try:
+            self.kill_cb()
+            self.status = 'killed'
+            self.message = 'Task killed by user.'
+        except Exception, e:
+            self.message = e.message
+            raise InvalidOperation('WOKASYNC0004E', {'err': e.message})
diff --git a/src/wok/i18n.py b/src/wok/i18n.py
index ade2ae9..7ba7c24 100644
--- a/src/wok/i18n.py
+++ b/src/wok/i18n.py
@@ -34,7 +34,9 @@ messages = {
     "WOKAPI0009E": _("You don't have permission to perform this operation."),
 
     "WOKASYNC0001E": _("Unable to find task id: %(id)s"),
+    "WOKASYNC0002E": _("There is no callback to execute the kill task process."),
     "WOKASYNC0003E": _("Timeout of %(seconds)s seconds expired while running task '%(task)s."),
+    "WOKASYNC0004E": _("Unable to kill task due error: %(err)s"),
 
     "WOKAUTH0001E": _("Authentication failed for user '%(username)s'. [Error code: %(code)s]"),
     "WOKAUTH0002E": _("You are not authorized to access Kimchi"),
diff --git a/src/wok/model/tasks.py b/src/wok/model/tasks.py
index 6a2b4bf..8ae1ce4 100644
--- a/src/wok/model/tasks.py
+++ b/src/wok/model/tasks.py
@@ -68,3 +68,16 @@ class TaskModel(object):
 
         raise TimeoutExpired('WOKASYNC0003E', {'seconds': timeout,
                                                'task': task.target_uri})
+
+    def delete(self, id):
+        """
+        'Stops' an AsyncTask, by executing the kill callback provided by user
+        when created the task. Task's status will be changed to 'killed'.
+        """
+        try:
+            task = tasks_queue[id]
+        except KeyError:
+            raise NotFoundError("WOKASYNC0001E", {'id': id})
+
+        if task.status is 'running':
+            task.kill()
-- 
2.7.4