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dockerdocker-network

How to avoid race condition during docker overlay network creation?

I have two machines HostA and HostB with consul and docker daemon properly configured so that I can use docker network create -d overlay sharednet

I have a TestScript.sh to check if a network exists and if not create the network. And this script is available on both HostA and HostB. I also have a MasterScript.sh only on A, which basically just invoke TestScript.sh on each machine. After I run my MasterScript.sh, I see a surprising result, two network with the same name got created!!! This is arguably a docker daemon synchronization issue.

[HostA]# docker network ls
NETWORK ID          NAME                 DRIVER
ad492bba9efa        sharednet            overlay
ba53d4e7b739        sharednet            overlay

[HostB]# docker network ls
NETWORK ID          NAME                 DRIVER
ad492bba9efa        sharednet            overlay
ba53d4e7b739        sharednet            overlay

The expected behavior is that when I created a network testnw on HostA, then on HostB I should see something like this

[HostB]# docker network ls
68994f95cd67        testnw               overlay
[HostB]# docker network create -d overlay testnw
Error response from daemon: network with name testnw already exists

Due to some restrictions I cannot modify the MasterScript.sh, but I can modify my TestScript.sh. So the question is, is it possible for me to resolve this race condition under this restriction?

Solution

  • This issue had been reported to Docker Github, and is currently being tracked under https://github.com/docker/docker/issues/20648