Implement locking for unflush as well

References #32

client-common/node.py

@@ -169,13 +169,34 @@ def ready_node(zk_conn, node):
     if not common.verifyNode(zk_conn, node):
         return False, 'ERROR: No node named "{}" is present in the cluster.'.format(node)
 
+    if zkhandler.readdata(zk_conn, '/locks/flush_lock') == 'True':
+        retmsg = 'Restoring hypervisor {} to active service. A flush lock currently exists; unflush will continue once the lock is freed.'.format(node)
+        lock_wait = True
+    else:
         retmsg = 'Restoring hypervisor {} to active service.'.format(node)
+        lock_wait = False
+        
+    # Wait cannot be triggered from the API
+    if wait:
+        click.echo(retmsg)
+        retmsg = ""
+        if lock_wait:
+            time.sleep(1)
+            while zkhandler.readdata(zk_conn, '/locks/flush_lock') == 'True':
+                time.sleep(1)
+            click.echo('Previous flush completed. Proceeding with unflush.')
 
     # Add the new domain to Zookeeper
     zkhandler.writedata(zk_conn, {
         '/nodes/{}/domainstate'.format(node): 'unflush'
     })
 
+    # Wait cannot be triggered from the API
+    if wait:
+        time.sleep(1)
+        while zkhandler.readdata(zk_conn, '/locks/flush_lock') == 'True':
+            time.sleep(1)
+
     return True, retmsg
 
 def get_info(zk_conn, node):

node-daemon/pvcd/NodeInstance.py

@@ -364,6 +364,16 @@ class NodeInstance(object):
         })
 
     def unflush(self):
+        # Wait indefinitely for the flush_lock to be freed
+        time.sleep(0.5)
+        while zkhandler.readdata(self.zk_conn, '/locks/flush_lock') == 'True':
+            time.sleep(2)
+
+        # Acquire the flush lock
+        zkhandler.writedata(self.zk_conn, {
+            '/locks/flush_lock': 'True'
+        })
+
         self.inflush = True
         self.logger.out('Restoring node {} to active service.'.format(self.name), state='i')
         zkhandler.writedata(self.zk_conn, { '/nodes/{}/domainstate'.format(self.name): 'ready' })
@@ -386,6 +396,11 @@ class NodeInstance(object):
 
         self.inflush = False
 
+        # Release the flush lock
+        zkhandler.writedata(self.zk_conn, {
+            '/locks/flush_lock': 'False'
+        })
+
 #
 # Find a migration target
 #