Race condition in -watch

[mhsmith]

We are using docker-gen in this dynamic DNS server: https://github.com/ncarlier/dockerfiles/tree/master/dnsmasq. This requires that the DNS configuration is updated when docker-gen is started, and whenever containers are started and stopped thereafter. Unfortunately, there is a gap between the initial update and the point where docker-gen starts watching for events, as shown in this log:

2015-02-11 18:45:42,946 INFO spawned: 'docker-gen' with pid 9
2015-02-11 18:45:43,001 INFO spawned: 'dnsmasq' with pid 10
2015/02/11 18:45:43 Generated '/etc/dnsmasq.conf' from 4 containers
2015/02/11 18:45:43 Running 'supervisorctl restart dnsmasq'
[...]
2015/02/11 18:45:45 Watching docker events

Any containers started during that 2-second window will not appear in DNS until the next docker event, which may be an indefinite period of time.

Solution: docker-gen should start watching for events before its initial update.

[jwilder]

#147 might help here.

[mitar]

How would HUP help here?

[gigablah]

It manually triggers docker-gen to do a re-scan of containers.

[jwilder]

Fixed via #156