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Implement flush locking for nodes

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Implements a locking mechanism to prevent clobbering of node
flushes. When a flush begins, a global cluster lock is placed
which is freed once the flush completes. While the lock is in place,
other flush events queue waiting for the lock to free before
proceeding.

Modifies the CLI output flow when the `--wait` option is specified.
First, if a lock exists when running the command, the message is
tweaked to indicate this, and the client will wait first for the
lock to free, and then for the flush as normal. Second, the wait
depends on the active lock rather than the domain_status for
consistency purposes.

Closes #32
This commit is contained in:
Joshua Boniface
2019-05-10 23:52:24 -04:00
parent 045ad131af
commit c19902d952
3 changed files with 34 additions and 7 deletions
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23
client-common/node.py
View File

@ -134,24 +134,33 @@ def flush_node(zk_conn, node, wait):
if not common.verifyNode(zk_conn, node):
return False, 'ERROR: No node named "{}" is present in the cluster.'.format(node)
retmsg = 'Flushing hypervisor {} of running VMs.'.format(node)
if zkhandler.readdata(zk_conn, '/locks/flush_lock') == 'True':
retmsg = 'Flushing hypervisor {} of running VMs. A flush lock currently exists; flush will continue once the lock is freed.'.format(node)
lock_wait = True
else:
retmsg = 'Flushing hypervisor {} of running VMs.'.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 flush.')
# Add the new domain to Zookeeper
zkhandler.writedata(zk_conn, {
'/nodes/{}/domainstate'.format(node): 'flush'
})
if wait == True:
while True:
# Wait cannot be triggered from the API
if wait:
time.sleep(1)
while zkhandler.readdata(zk_conn, '/locks/flush_lock') == 'True':
time.sleep(1)
node_state = zkhandler.readdata(zk_conn, '/nodes/{}/domainstate'.format(node))
if node_state == "flushed":
break
return True, retmsg