Get me a network From boot to woot!
Matt Riedemann Armando Migliaccio Huawei SUSE N-O-P Nova PTL M-N-O Neutron PTL
Agenda • Rationale • Proposed solution • Community effort • Testing • Future work • Demo • Q&A
Rationale
Rationale
Rationale ● Cloud user wants a VM connected to the Internet ○ Neutron requires an intimate knowledge about networking ○ Must create a private logical network (for isolation) ■ Create a subnet (for IP address management) ○ Must create a router (to get external connectivity) ■ Uplink the router to a well known external network ■ Downlink the router on the previously created subnet
Rationale ● Cloud user wants a VM connected to the Internet ○ Neutron requires an intimate knowledge about networking ○ Must create a private logical network (for isolation) ■ Create a subnet (for IP address management) ○ Must create a router (to get external connectivity) ■ Uplink the router to a well known external network ■ Downlink the router on the previously created subnet
Proposed solution • What if these steps were fully automated?
Proposed solution • What if these steps were fully automated? • That is what get-me-a-network does • The operator performs a one-time setup • The user will get the network provisioned on the boot of the first VM
Proposed solution • What if these steps were fully automated? • That is what get-me-a-network does • The operator performs a one-time setup • The user will get the network provisioned on the boot of the first VM
Proposed solution On server create • • Nova and Neutron work together to figure out what to do • If the user has no network, one will be provisioned and the VM will be given external connectivity • Any other boot request will piggyback on the first and the network is reused • NOTE: VMs are not given floating IP automatically
Community effort: timeline • Liberty • May 2015 - Design discussion at Vancouver summit • July 2015 - Neutron spec merges • Aug 2015 - Neutron implementation starts (but stalls) • Mitaka • January 2016 - Neutron implementation resumes (Neutron cores at Nova mid-cycle) • March 2016 - Neutron Feature completes • Newton • May 2016 - Nova spec merges • Aug 2016 - Nova feature completes • Sep 2016 - Integration testing completes
Community effort: timeline • Some initial pushback • Consensus and blueprint specification • http://specs.openstack.org/openstack/neutron-specs/specs/mitaka/get-me-a-network.html • The building blocks • Subnet pools to provide automatic IPAM • Default external networks
Community effort: Neutron • The workflow • During the initial cloud setup, the operator: • creates default subnet pool(s) (ie. the IP space(s) to allocate subnets from) • creates a default external network (ie. the route to the Internet) • During the boot phase, Neutron (atomically): • Fetches an IP space from the default pool • Creates a network, subnet(s), router and uplink • Returns the UUID of the allocated network to Nova
Community effort: Nova • Blueprint specification • https://specs.openstack.org/openstack/nova-specs/specs/newton/implemented/get-me-a-net work.html • Considerations • Handling “none” for explicit no network allocation • Mixed-level computes • What the request format should look like (usual networks dict vs enums) • The REST API is explicit, but the CLI provides a sane default (auto) • Nova runs the “dry-run” check in Neutron to make sure everything is setup • The “dry-run” option was not part of the original Neutron implementation • Nova does not retry; Neutron auto-allocated-topology is idempotent
Community effort: Nova The workflow • • POST /servers with microversion >= 2.37 and networks=”auto” in the body • nova-api checks if all nova-compute services are new enough to handle this • nova-api validates that if no network is already available to the project, one can be automatically allocated • nova-compute: if a network is available to the project, use it, otherwise if asked to auto-allocate a network, attempt that by calling Neutron • If this succeeds, a port is created on the new network • If this fails, the server build is aborted (no retries), a fault is recorded and the instance is put into ERROR state
Testing • Test cases to expose concurrency and locking issues • Multiple users to compete on subnet pool access • Multiple requests coming from same user performing ‘first boot’ • e.g. nova boot --flavor m1.small --image centos73 --nic auto --min-count 3 • This stresses the idempotency of the auto-allocated-topology extension in Neutron
Future work • Get Floating IP automatically allocated • Initially ruled out • To avoid consuming precious “IPv4” • To allow IPv6-only environments seamlessly • Control external gateway modes • Enabling/Disabling SNAT • Provision any kind of topology • Provider networks (vlan) vs logical networks (vxlan)
Q&A
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