[Expired for neutron because there has been no activity for 60 days.]
** Changed in: neutron
Status: Incomplete => Expired
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https://bugs.launchpad.net/bugs/1426427
Title:
Improve tunnel_sync server side rpc to handle race conditions
Status in neutron:
Expired
Bug description:
We have a concern that we may have race conditions with the following
code snippet:
if host:
host_endpoint = driver.obj.get_endpoint_by_host(host)
ip_endpoint = driver.obj.get_endpoint_by_ip(tunnel_ip)
if (ip_endpoint and ip_endpoint.host is None
and host_endpoint is None):
driver.obj.delete_endpoint(ip_endpoint.ip_address)
elif (ip_endpoint and ip_endpoint.host != host):
msg = (_("Tunnel IP %(ip)s in use with host %(host)s"),
{'ip': ip_endpoint.ip_address,
'host': ip_endpoint.host})
raise exc.InvalidInput(error_message=msg)
elif (host_endpoint and host_endpoint.ip_address !=
tunnel_ip):
# Notify all other listening agents to delete stale
tunnels
self._notifier.tunnel_delete(rpc_context,
host_endpoint.ip_address, tunnel_type)
driver.obj.delete_endpoint(host_endpoint.ip_address)
Consider two threads (A and B), where for
Thread A we have following use case:
if Host is passed from an agent and it is not found in DB but the passed
tunnel_ip is found, delete the endpoint from DB and add the endpoint with
(tunnel_ip, host), it's an upgrade case.
whereas for Thread B we have following use case:
if passed host and tunnel_ip are not found in the DB, it is a new endpoint.
Both threads will do the following in the end:
tunnel = driver.obj.add_endpoint(tunnel_ip, host)
tunnels = driver.obj.get_endpoints()
entry = {'tunnels': tunnels}
# Notify all other listening agents
self._notifier.tunnel_update(rpc_context, tunnel.ip_address,
tunnel_type)
# Return the list of tunnels IP's to the agent
return entry
Since, Thread A first deletes the endpoints and adds it, we may have chances
where Thread B doesn't get that endpoint in get_endpoints call during race
condition.
One way to overcome this problem would be instead of doing
delete_endpoint we could introduce update_endpoint method in
type_drivers.
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