From 12c2f5618c52e9092144d063b020841d1dd25663 Mon Sep 17 00:00:00 2001
From: Dominique Leuenberger <dimstar@opensuse.org>
Date: Mon, 9 Feb 2015 17:25:43 +0100
Subject: [PATCH] Locking: Let's get some locking mechanism so we hopefully
 step less on each others toes.

---
 osclib/stagingapi.py | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/osclib/stagingapi.py b/osclib/stagingapi.py
index e793ca9a..44dcb99f 100644
--- a/osclib/stagingapi.py
+++ b/osclib/stagingapi.py
@@ -8,12 +8,14 @@ import json
 import logging
 import urllib2
 import time
+import sys
 import re
 from xml.etree import cElementTree as ET
 
 import yaml
 
 from osc import oscerr
+from osc import conf
 from osc.core import change_review_state
 from osc.core import delete_package
 from osc.core import get_request
@@ -36,8 +38,10 @@ class StagingAPI(object):
         Initialize instance variables
         """
 
+        user = conf.config['api_host_options'][apiurl]['user']
         self.apiurl = apiurl
         self.opensuse = opensuse
+        self.grab_lock('openSUSE:Factory:Staging', user)
         self.rings = (
             'openSUSE:{}:Rings:0-Bootstrap'.format(self.opensuse),
             'openSUSE:{}:Rings:1-MinimalX'.format(self.opensuse),
@@ -46,6 +50,9 @@ class StagingAPI(object):
         self.ring_packages = self._generate_ring_packages()
         self.packages_staged = self._get_staged_requests()
 
+    def __del__(self):
+        self.release_lock('openSUSE:Factory:Staging')
+
     def makeurl(self, l, query=None):
         """
         Wrapper around osc's makeurl passing our apiurl
@@ -84,6 +91,42 @@ class StagingAPI(object):
                 return self.retried_PUT(url, data)
             raise e
 
+    def read_lock(self, project):
+        url = self.makeurl(['source', project, '_attribute', 'openSUSE:LockedBy'])
+        root = ET.parse(http_GET(url)).getroot()
+        try:
+            lockedby = root[0][0].text
+        except IndexError:
+            # There was no value specified we could parse - assume unlocked
+            lockedby = None
+        return lockedby
+
+    def set_lock(self, project, user):
+        url = self.makeurl(['source', project, '_attribute', 'openSUSE:LockedBy'])
+        try:
+            schema = "<attributes><attribute namespace='openSUSE' name='LockedBy'><value>%s</value></attribute></attributes>"
+            http_POST(url, data=schema % user)
+        except:
+           print "Failed to acquire lock - exiting"
+           sys.exit(2)
+
+    def grab_lock(self, project, user):
+        lockedby = self.read_lock(project)
+        if lockedby != None:
+            print "Staging tasks are currently executed by %s - project locked" % lockedby
+            sys.exit(9)
+        self.set_lock(project, user)
+        # wait 2s to see if the lock is now actually ours or if we were racing somebody
+        time.sleep(2)
+
+        lockedby = self.read_lock(project)
+        if  lockedby != user:
+            print "Lock was stolen by '%s' - ABORTING" % lockedby
+            sys.exit(8)
+
+    def release_lock(self, project):
+        self.set_lock(project, '')
+
     def _generate_ring_packages(self):
         """
         Generate dictionary with names of the rings