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Support for Open vSwitch
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.. contents:: :depth: 3
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This is a design document detailing the implementation of support for
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Open vSwitch in the Ganeti tool chain.
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Current state and shortcomings
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==============================
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At the moment Ganeti's support for Open vSwitch is very basic and
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limited to connecting instances to an existing vSwitch.
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The shortcomings of this approach are:
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1. The full functionality (VLANs, QoS and trunking) of Open vSwitch is not used.
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2. Open vSwitch cannot be managed centrally.
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Proposed changes
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----------------
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1. Implement functions into gnt-cluster and gnt-node to manage Open vSwitch through Ganeti.
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   It should be possible to create, modify and delete vSwitches. The resulting configuration
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   shall automatically be done on all members of the node group, if possible. Connecting Ethernet 
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   devices to vSwitches should be managed through this interface as well.
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2. Implement VLAN-capabilities: Instances shall have additional information for every NIC: VLAN-ID
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   and port type. These are used to determine their type of connection to Open vSwitch. This will
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   require modifying the methods for instance creation and modification
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3. Implement NIC bonding: Functions to bond NICs for performance improvement, load-balancing and
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   failover should be added. It is preferable to have a configuration option to determine the
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   type of the trunk, as there are different types of trunks (LACP dynamic and static, different
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   failover and load-balancing mechanisms)
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4. Set QoS level on per instance basis: Instances shall have an additional information: maximum
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   bandwidth and maximum burst. This helps to balance the bandwidth needs between the VMs and to
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   ensure fair sharing of the bandwidth.
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Automatic configuration of OpenvSwitches
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++++++++++++++++++++++++++++++++++++++++
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Ideally, the OpenvSwitch configuration should be done automatically.
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This needs to be done on node level, since each node can be individual and a setting on cluster / node group
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level would be too global is thus not wanted. 
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The task that each node needs to do is:
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  ``ovs-vsctl addbr <switchname>`` with <switchname> defaulting to constants.DEFAULT_OVS
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  ``ovs-vsctl add-port <switchname> <ethernet device>`` optional: connection to the outside
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This will give us 2 parameters, that are needed for the OpenvSwitch Setup:
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  switchname: Which will default to constants.DEFAULT_OVS when not given
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  ethernet device: Which will default to None when not given, might be more than one (NIC bonding)
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These parameters should be set at node level for individuality, _but_ can have defined defaults on cluster
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and node group level, which can be inherited and thus allow a cluster or node group wide configuration.
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If a node is setup without parameters, it should use the settings from the parent node group or cluster. If none
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are given there, defaults should be used.
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As a first step, this will be implemented for using 1 ethernet device only. Functions for nic bonding will be added
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later on.
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Configuration changes for VLANs
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+++++++++++++++++++++++++++++++
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nicparams shall be extended by a value "vlan" that will store the VLAN information for each NIC.
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This parameter will only be used if nicparams[constants.NIC_MODE] == constants.NIC_MODE_OVS,
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since it doesn't make sense in other modes.
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Each VLAN the NIC belongs to shall be stored in this single value. The format of storing this information
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is the same as the one which is used in Xen 4.3, since Xen 4.3 comes with functionality to support
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OpenvSwitch.
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This parameter will, at first, only be implemented for Xen and will have no effects on other hypervisors.
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Support for KVM will be added in the future.
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Example:
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switch1 will connect the VM to the default VLAN of the switch1.
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switch1.3 means that the VM is connected to an access port of VLAN 3.
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switch1.2:10:20 means that the VM is connected to a hybrid port on switch1, carrying VLANs 2 untagged and 
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VLANs 10 and 20 tagged.
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switch1:44:55 means that the VM is connected to a trunk port on switch1, carrying VLANS 44 and 55
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This configuration string is split at the dot or colon respectively and stored in nicparams[constants.NIC_LINK] 
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and nicparams[constants.NIC_VLAN] respectively. Dot or colon are stored as well in nicparams[constants.NIC_VLAN].
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For Xen hypervisors, this information can be concatenated again and stored in the vif config as
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the bridge parameter and will be fully compatible with vif-openvswitch as of Xen 4.3.
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Users of older Xen versions should be able to grab vif-openvswitch from the Xen repo and use it
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(tested in 4.2).
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gnt-instance modify shall be able to add or remove single VLANs from the vlan string without users needing
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to specify the complete new string.
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NIC bonding
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+++++++++++
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To be done
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Configuration changes for QoS
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+++++++++++++++++++++++++++++
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Instances shall be extended with configuration options for
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- maximum bandwidth
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- maximum burst rate
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New configuration objects need to be created for the Open vSwitch configuration.
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All these configuration changes need to be made available on the whole node group.
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.. vim: set textwidth=72 :
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