Merge "console: convert consoles code to use objects framework"
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specs/liberty/approved/convert-consoles-to-objects.rst
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specs/liberty/approved/convert-consoles-to-objects.rst
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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=========================================
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Convert Consoles To Use Objects Framework
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=========================================
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https://blueprints.launchpad.net/nova/+spec/convert-consoles-to-objects
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Make consoles to use the objects framework -- the current console code
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does not take advantage of the framework objects, instead it provides
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some types (console/type.py) to handle them. These types do not
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provide any features to handle versioning, RPC or any kind of methods
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to make them useful.
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Problem description
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===================
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The current code does not provide any mechanism to handle versioning.
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Additionally, since RPC cannot handle classes derived from the Python object
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type, we need to handle a dict "connect_info" between RPC calls and no
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way is provided to share the state of the console across processes.
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Another problem comes with the token, memcached is not a database and
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cannot guarantee that the expire time will be respected, a token can
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expire before that limit (eviction). By using the framework objects
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we can get the opportunity to store the whole state of Console object
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with a valid token in the database and share the state between
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process.
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For instance bug 1425640 needs to know when an user is connected to a
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particular port from a number of perspectives: from the compute node, to
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return the next port defined and not connected; from the proxy to
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reject new connections on already connected port from the API to
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let user informed no more port are available.
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We will also enhance security by only storing SHA-1 of tokens in the
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database after to have returned the clean one to the users. Then when
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users will request to connect a console the token passed will be
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hashed and compared to the one stored in the database for validation.
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A new option will be introduced "console_tokens_backend" wich will
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allow operator to switch between different backends. The scope of this
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spec will allow 2 backends (memcached, database) The memcached backend
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will be implemented for legacy compatibility but in a deprecated
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status, supported for one release.
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Use Cases
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----------
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Developer can take advantage of using the framework objects when
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adding a new console or features.
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Project Priority
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-----------------
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None
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Proposed change
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===============
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* Define a new ConsoleConnection object
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* Convert drivers to return ConsoleConnection
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* Remove using of the connect_info's dict
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* Define schema and API to store ConsoleConnection object in database
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* Update code to store ConsoleConnection with valid token in database
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instead of a cache.
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* Define a periodic task to clean expired object stored in database;
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To balance the load and avoid blocking the database during too much
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time each compute nodes will be responsible to clean connection_info
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for guests they host.
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* Fix bug 1425640
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Alternatives
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------------
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Continue to use memcached as a backend will make the behavior of
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connection information not previsible since objects can be
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evicted. Also in order to fix issue 1425640 and 1455252 a scan has to
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be done to list available ports which is difficult when using
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memcached without add specific code to maintain a list of stored keys.
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Data model impact
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-----------------
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A new ConsoleConnection model needs to be defined with attributes:
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- instance: an instance which refer the console
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- host: a string field to handle hostname
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- port: an int field to handle service number
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- token_hash: a string field to handle a token or null
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- access_url: a string field to handle access or null
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- options: a dict field to handle particular information like usetls,
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internal_access_path, mode...
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- expires: a date time to indicate when the token expires or null
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The database schema ::
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CREATE TABLE console_connection (
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instance_uuid CHAR(36) NOT NULL,
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host VARCHAR(255) NOT NULL,
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port INT NOT NULL,
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token_hash CHAR(40),
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access_url VARCHAR(255),
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options TEXT,
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expires DATETIME,
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PRIMARY KEY (instance_uuid, host, port),
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INDEX (token, instance_uuid),
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FOREIGN KEY (instance_uuid)
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REFERENCES instances(uuid)
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ON DELETE CASCADE
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);
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.. note::
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No migration are expected from serialized dicts connection info
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stored in memcached to the database, during the upgrade clients
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already connected to consoles will keep their connections until
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proxy will be restarted. At this step we expect to have the
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consoleauth service to also have been restarted. Users precedently
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disconnected can reuse the same token to reconnect the consoles if
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not already expired.
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REST API impact
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---------------
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None
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Security impact
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---------------
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In the point of view of tokens we can expect a better security since
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currently tokens are stored in memcached which does not provide any
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security layer. Now only hash of tokens will be stored in the database
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also security policy will enhanced to be the same than other critical
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components stored in database.
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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When proxyclient will be restartred users will be disconnected from
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our consoles but should reconnect to it with the same token if not
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already expired.
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Performance Impact
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------------------
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The database load will increase but we can expect that with a minimal
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impact for DBA.
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Other deployer impact
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---------------------
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The consoleauth service must be restarted before proxy services. When
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proxy will be restarted clients will be disconnected from consoles.
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Memcached will continue to work as backend until a deprecated period
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of one release operator are encouraged to switch on the database
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backend (see option: console_tokens_backend).
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Developer impact
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----------------
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None
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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sahid-ferdjaoui
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Work Items
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----------
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* Convert code to use objects framework
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* Update consoleauth to take advantage of the database to handle
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tokens
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* Fix bug 1425640
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Dependencies
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============
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None
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Testing
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=======
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The current code is already tested by functional and unit tests since
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we do not provide any feature we can consider that the code will be
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well covered by tests.
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Documentation Impact
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====================
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None
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References
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==========
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None
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