[Crunchv2] Option to use host networking for containers
Docker bridge networking has bugs on certain kernels. Add a flag to crunch-run to instruct containers to use host networking instead of the default bridge network.
Intend to support the following use case: the entire cluster is running compute nodes which will use host networking instead of bridge networking.
Sysadmin will specify the option via command line (which can be configured in crunch-dispatch-slurm).
We will provide two options:
- Use host networking when networking is enabled, and "none" when it is disabled.
When a container is created with --net=none, the container is given an "empty" network namespace (only the loopback device is available.) If kernel bugs are associated with Docker's bridge networking, this option would use host networking for those containers that need it, while maintaining isolation for containers that don't need networking.
- Use host networking for all containers.
If kernel bugs make network namespaces totally unusable, always use --net=host, so that network namespaces are not used at all. This should sidestep the issue, at the expense of reduced isolation from the host system.
11255-docker-host-networking @ bfd73917834d89e9e8c55b6bb4e05912741fbf8a
I think the flag docs should say "for containers with networking enabled" instead of "when API: true". Even though that happens to be the only case where we enable networking right now, the flag really makes sense in terms of networking, not API access.
(from chat) (10:59:03 AM) tom: Still seems to me we might as well offer that option in a way that isn't necessarily bundled with the "lose ability to turn off networking" sacrifice... we can make two options that do separate meaningful things, and document the kernel bug workaround as "use both of these options at once and you should be OK"Specifically how about the following orthogonal options
- Use specified network mode when enabling network access (default "default")
- Enable network access for all containers regardless of what's specified in runtime constraints
- always enable networking, but use default networking mode
- use "bridge" networking mode regardless of what the docker default is (in case this can change)
- use some other docker networking mode we don't know about yet
The combination of flags needed for the old-kernel workaround should be documented at http://doc.arvados.org/install/crunch2-slurm/install-dispatch.html