Update the multisite documentations to reflect the progress in D

As some changes in OpenStack projects like KeyStone PKI token
deprecation, L2GW moved away from Neutron stadium, Tricircle
shrinked scope and became OpenStack big-tent project, and
Kingbird has made great progress in feature development
after the initial requirements discussion. Documents need to
update to reflect these recent changes.

python-kingbirdclient was introduced recently, so the usage
guide is updated to use python-kingbirdclient. The new feature
key pair synchronization is also included in the usage guide.

Change-Id: Iad9fbd441d191defa5e8793633a626ab5a24f217
Signed-off-by: joehuang <joehuang@huawei.com>

1 files changed, 365 insertions, 0 deletions

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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Multisite identity service management
+=====================================
+
+Goal
+----
+
+A user should, using a single authentication point be able to manage virtual
+resources spread over multiple OpenStack regions.
+
+Token Format
+------------
+
+There are 3 types of token format supported by OpenStack KeyStone
+
+  * **FERNET**
+  * **UUID**
+  * **PKI/PKIZ**
+
+It's very important to understand these token format before we begin the
+mutltisite identity service management. Please refer to the OpenStack
+official site for the identity management.
+http://docs.openstack.org/admin-guide-cloud/identity_management.html
+
+Please note that PKI/PKIZ token format has been deprecated.
+
+Key consideration in multisite scenario
+---------------------------------------
+
+A user is provided with a single authentication URL to the Identity (Keystone)
+service. Using that URL, the user authenticates with Keystone by
+requesting a token typically using username/password credentials. Keystone
+server validates the credentials, possibly with an external LDAP/AD server and
+returns a token to the user. The user sends a request to a service in a
+selected region including the token. Now the service in the region, say Nova
+needs to validate the token. The service uses its configured keystone endpoint
+and service credentials to request token validation from Keystone. After the
+token is validated by KeyStone, the user is authorized to use the service.
+
+The key considerations for token validation in multisite scenario are:
+  * Site level failure: impact on authN and authZ shoulde be as minimal as
+    possible
+  * Scalable: as more and more sites added, no bottleneck in token validation
+  * Amount of inter region traffic: should be kept as little as possible
+
+Hence, Keystone token validation should preferably be done in the same
+region as the service itself.
+
+The challenge to distribute KeyStone service into each region is the KeyStone
+backend. Different token format has different data persisted in the backend.
+
+* Fernet: Tokens are non persistent cryptographic based tokens and validated
+  online by the Keystone service. Fernet tokens are more lightweight
+  than PKI tokens and have a fixed size. Fernet tokens require Keystone
+  deployed in a distributed manner, again to avoid inter region traffic. The
+  data synchronization cost for the Keystone backend is smaller due to the non-
+  persisted token.
+
+* UUID: UUID tokens have a fixed size. Tokens are persistently stored and
+  create a lot of database traffic, the persistence of token is for the revoke
+  purpose. UUID tokens are validated online by Keystone, call to service will
+  request keystone for token validation. Keystone can become a
+  bottleneck in a large system. Due to this, UUID token type is not suitable
+  for use in multi region clouds, no matter the Keystone database
+  replicates or not.
+
+Cryptographic tokens bring new (compared to UUID tokens) issues/use-cases
+like key rotation, certificate revocation. Key management is out of scope for
+this use case.
+
+Database deployment as the backend for KeyStone service
+------------------------------------------------------
+
+Database replication:
+  - Master/slave asynchronous: supported by the database server itself
+    (mysql/mariadb etc), works over WAN, it's more scalable. But only master will
+    provide write functionality, domain/project/role provisioning.
+  - Multi master synchronous: Galera(others like percona), not so scalable,
+    for multi-master writing, and need more parameter tunning for WAN latency.It
+    can provide the capability for limited multi-sites multi-write
+    function for distributed KeyStone service.
+  - Symmetrical/asymmetrical: data replicated to all regions or a subset,
+    in the latter case it means some regions needs to access Keystone in another
+    region.
+
+Database server sharing:
+In an OpenStack controller, normally many databases from different
+services are provided from the same database server instance. For HA reasons,
+the database server is usually synchronously replicated to a few other nodes
+(controllers) to form a cluster. Note that _all_ database are replicated in
+this case, for example when Galera sync repl is used.
+
+Only the Keystone database can be replicated to other sites. Replicating
+databases for other services will cause those services to get of out sync and
+malfunction.
+
+Since only the Keystone database is to be replicated sync. or async. to another
+region/site, it's better to deploy Keystone database into its own
+database server with extra networking requirement, cluster or replication
+configuration. How to support this by installer is out of scope.
+
+The database server can be shared when async master/slave replication is
+used, if global transaction identifiers GTID is enabled.
+
+Deployment options
+------------------
+
+**Distributed KeyStone service with Fernet token**
+
+Fernet token is a very new format, and just introduced recently,the biggest
+gain for this token format is :1) lightweight, size is small to be carried in
+the API request, not like PKI token( as the sites increased, the endpoint-list
+will grows  and the token size is too long to carry in the API request) 2) no
+token persistence, this also make the DB not changed too much and with light
+weight data size (just project, Role, domain, endpoint etc). The drawback for
+the Fernet token is that token has to be validated by KeyStone for each API
+request.
+
+This makes that the DB of KeyStone can work as a cluster in multisite (for
+example, using MySQL galera cluster). That means install KeyStone API server in
+each site, but share the same the backend DB cluster.Because the DB cluster
+will synchronize data in real time to multisite, all KeyStone server can see
+the same data.
+
+Because each site with KeyStone installed, and all data kept same,
+therefore all token validation could be done locally in the same site.
+
+The challenge for this solution is how many sites the DB cluster can
+support. Question is aksed to MySQL galera developers, their answer is that no
+number/distance/network latency limitation in the code. But in the practice,
+they have seen a case to use MySQL cluster in 5 data centers, each data centers
+with 3 nodes.
+
+This solution will be very good for limited sites which the DB cluster can
+cover very well.
+
+**Distributed KeyStone service with Fernet token + Async replication (star-mode)**
+
+One master KeyStone cluster with Fernet token in one or two sites(for site
+level high availability purpose), other sites will be installed with at least
+2 slave nodes where the node is configured with DB async replication from the
+master cluster members. The async. replication data source is better to be
+from different member of the master cluster, if there are two sites for the
+KeyStone cluster, it'll be better that source members for async. replication
+are located in different site.
+
+Only the master cluster nodes are allowed to write,  other slave nodes
+waiting for replication from the master cluster member( very little delay).
+
+Pros:
+  * Deploy database cluster in the master sites is to provide more master
+    nodes, in order to provide more slaves could be done with async. replication
+    in parallel. Two sites for the master cluster is to provide higher
+    reliability (site level) for writing request, but reduce the maintaince
+    challenge at the same time by limiting the cluster spreading over too many
+    sites.
+  * Multi-slaves in other sites is because of the slave has no knowledge of
+    other slaves, so easy to manage multi-slaves in one site than a cluster, and
+    multi-slaves work independently but provide multi-instance redundancy(like a
+    cluster, but independent).
+
+Cons:
+  * Need to be aware of the chanllenge of key distribution and rotation
+    for Fernet token.
+
+Multisite VNF Geo site disaster recovery
+========================================
+
+Goal
+----
+
+A VNF (telecom application) should, be able to restore in another site for
+catastrophic failures happened.
+
+Key consideration in multisite scenario
+---------------------------------------
+
+Geo site disaster recovery is to deal with more catastrophic failures
+(flood, earthquake, propagating software fault), and that loss of calls, or
+even temporary loss of service, is acceptable. It is also seems more common
+to accept/expect manual / administrator intervene into drive the process, not
+least because you don’t want to trigger the transfer by mistake.
+
+In terms of coordination/replication or backup/restore between geographic
+sites, discussion often (but not always) seems to focus on limited application
+level data/config replication, as opposed to replication backup/restore between
+of cloud infrastructure between different sites.
+
+And finally, the lack of a requirement to do fast media transfer (without
+resignalling) generally removes the need for special networking behavior, with
+slower DNS-style redirection being acceptable.
+
+Here is more concerns about cloud infrastructure level capability to
+support VNF geo site disaster recovery
+
+Option1, Consistency application backup
+---------------------------------------
+
+The disater recovery process will work like this:
+
+1) DR(Geo site disaster recovery )software get the volumes for each VM
+   in the VNF from Nova
+2) DR software call Nova quiesce API to quarantee quiecing VMs in desired order
+3) DR software takes snapshots of these volumes in Cinder (NOTE: Because
+   storage often provides fast snapshot, so the duration between quiece and
+   unquiece is a short interval)
+4) DR software call Nova unquiece API to unquiece VMs of the VNF in reverse order
+5) DR software create volumes from the snapshots just taken in Cinder
+6) DR software create backup (incremental) for these volumes to remote
+   backup storage ( swift or ceph, or.. ) in Cinder
+7) If this site failed,
+  1) DR software restore these backup volumes in remote Cinder in the backup site.
+  2) DR software boot VMs from bootable volumes from the remote Cinder in
+     the backup site and attach the regarding data volumes.
+
+Note: Quiesce/Unquiesce spec was approved in Mitaka, but code not get merged in
+time, https://blueprints.launchpad.net/nova/+spec/expose-quiesce-unquiesce-api
+The spec was rejected in Newton when it was reproposed:
+https://review.openstack.org/#/c/295595/. So this option will not work any more.
+
+Option2, Vitrual Machine Snapshot
+---------------------------------
+1) DR software create VM snapshot in Nova
+2) Nova quiece the VM internally
+   (NOTE: The upper level application or DR software should take care of
+   avoiding infra level outage induced VNF outage)
+3) Nova create image in Glance
+4) Nova create a snapshot of the VM, including volumes
+5) If the VM is volume backed VM, then create volume snapshot in Cinder
+5) No image uploaded to glance, but add the snapshot in the meta data of the
+   image in Glance
+6) DR software to get the snapshot information from the Glance
+7) DR software create volumes from these snapshots
+9) DR software create  backup (incremental) for these volumes to backup storage
+   ( swift or ceph, or.. ) in Cinder
+10) If this site failed,
+  1) DR software restore these backup volumes to Cinder in the backup site.
+  2) DR software boot vm from bootable volume from Cinder in the backup site
+     and attach the data volumes.
+
+This option only provides single VM level consistency disaster recovery.
+
+This feature is already available in current OPNFV release.
+
+Option3, Consistency volume replication
+---------------------------------------
+1) DR software creates datastore (Block/Cinder, Object/Swift, App Custom
+   storage) with replication enabled at the relevant scope, for use to
+   selectively backup/replicate desire data to GR backup site
+2) DR software get the reference of storage in the remote site storage
+3) If primary site failed,
+  1) DR software managing recovery in backup site gets references to relevant
+     storage and passes to new software instances
+  2) Software attaches (or has attached) replicated storage, in the case of
+     volumes promoting to writable.
+
+Pros:
+  * Replication will be done in the storage level automatically, no need to
+    create backup regularly, for example, daily.
+  * Application selection of limited amount of data to replicate reduces
+    risk of replicating failed state and generates less overhear.
+  * Type of replication and model (active/backup, active/active, etc) can
+    be tailored to application needs
+
+Cons:
+  * Applications need to be designed with support in mind, including both
+    selection of data to be replicated and consideration of consistency
+  * "Standard" support in Openstack for Disaster Recovery currently fairly
+    limited, though active work in this area.
+
+Note: Volume replication v2.1 support project level replication.
+
+
+VNF high availability across VIM
+================================
+
+Goal
+----
+
+A VNF (telecom application) should, be able to realize high availability
+deloyment across OpenStack instances.
+
+Key consideration in multisite scenario
+---------------------------------------
+
+Most of telecom applications have already been designed as
+Active-Standby/Active-Active/N-Way to achieve high availability
+(99.999%, corresponds to 5.26 minutes of unplanned downtime in a year),
+typically state replication or heart beat between
+Active-Active/Active-Active/N-Way (directly or via replicated database
+services, or via private designed message format) are required.
+
+We have to accept the currently limited availability ( 99.99%) of a
+given OpenStack instance, and intend to provide the availability of the
+telecom application by spreading its function across multiple OpenStack
+instances.To help with this, many people appear willing to provide multiple
+“independent” OpenStack instances in a single geographic site, with special
+networking (L2/L3) between clouds in that physical site.
+
+The telecom application often has different networking plane for different
+purpose:
+
+1) external network plane: using for communication with other telecom
+   application.
+
+2) components inter-communication plane: one VNF often consisted of several
+   components, this plane is designed for components inter-communication with
+   each other
+
+3) backup plane: this plane is used for the heart beat or state replication
+   between the component's active/standby or active/active or N-way cluster.
+
+4) management plane: this plane is mainly for the management purpose, like
+   configuration
+
+Generally these planes are separated with each other. And for legacy telecom
+application, each internal plane will have its fixed or flexble IP addressing
+plan.
+
+There are some interesting/hard requirements on the networking (L2/L3)
+between OpenStack instances, at lease the backup plane across different
+OpenStack instances:
+
+To make the VNF can work with HA mode across different OpenStack instances in
+one site (but not limited to), need to support at lease the backup plane across
+different OpenStack instances:
+
+1) L2 networking across OpenStack instance for heartbeat or state replication.
+Overlay L2 networking or shared L2 provider networks can work as the backup
+plance for heartbeat or state replication. Overlay L2 network is preferred,
+the reason is:
+
+   a. Support legacy compatibility: Some telecom app with built-in internal L2
+      network, for easy to move these app to VNF, it would be better to provide
+      L2 network.
+   b. Isolated L2 network will simplify the security management between
+      different network planes.
+   c. Easy to support IP/mac floating across OpenStack.
+   d. Support IP overlapping: multiple VNFs may have overlaping IP address for
+      cross OpenStack instance networking.
+
+Therefore, over L2 networking across Neutron feature is required in OpenStack.
+
+2) L3 networking across OpenStack instance for heartbeat or state replication.
+For L3 networking, we can leverage the floating IP provided in current
+Neutron, or use VPN or BGPVPN(networking-bgpvpn) to setup the connection.
+
+L3 networking to support the VNF HA will consume more resources and need to
+take more security factors into consideration, this make the networking
+more complex. And L3 networking is also not possible to provide IP floating
+across OpenStack instances.
+
+3) The IP address used for VNF to connect with other VNFs should be able to be
+floating cross OpenStack instance. For example, if the master failed, the IP
+address should be used in the standby which is running in another OpenStack
+instance. There are some method like VRRP/GARP etc can help the movement of the
+external IP, so no new feature will be added to OpenStack.
+
+Several projects are addressing the networking requirements, deployment should
+consider the factors mentioned above.
+  * Tricircle: https://github.com/openstack/tricircle/
+  * Networking-BGPVPN: https://github.com/openstack/networking-bgpvpn/
+  * VPNaaS: https://github.com/openstack/neutron-vpnaas