Convert Consoles To Use Objects Framework

https://blueprints.launchpad.net/nova/+spec/convert-consoles-to-objects

Make consoles to use the objects framework – the current console code does not take advantage of the framework objects, instead it provides some types (console/type.py) to handle them. These types do not provide any features to handle versioning, RPC or any kind of methods to make them useful.

Problem description

The current code does not provide any mechanism to handle versioning. Additionally, since RPC cannot handle classes derived from the Python object type, we need to handle a dict “connect_info” between RPC calls and no way is provided to share the state of the console across processes.

Another problem comes with the token, memcached is not a database and cannot guarantee that the expire time will be respected, a token can expire before that limit (eviction). By using the framework objects we can get the opportunity to store the whole state of Console object with a valid token in the database and share the state between process.

For instance bug 1425640 needs to know when an user is connected to a particular port from a number of perspectives: from the compute node, to return the next port defined and not connected; from the proxy to reject new connections on already connected port from the API to let user informed no more port are available.

We will also enhance security by only storing a hash of tokens in the database after to have returned the clean one to the users. Then when users will request to connect a console the token passed will be hashed and compared to the one stored in the database for validation.

A new option will be introduced “console_tokens_backend” which will allow operator to switch between different backends. The scope of this spec will allow 2 backends: consoleauth (using memcached) or database. The consoleauth service will be retained for legacy compatibility but in a deprecated status, supported for one release. After the period the consoleauth service can be removed.

Because the new tokens will go in the database we need to consider cells v2. The child cell database is the appropriate place for console connection info because it relates directly to instances. Currently the console connection URLs returned to the user only contain a token. This is not sufficient to determine which cell holds the console connection. This can be resolved by adding the instance uuid to the query string in the URL. This approach is backward compatible with the existing console proxies. Ultimately it is still the token that determines authority to connect to the console, but we will add verification that the instance uuid in the URL matches the instance uuid in the connection info retrieved for the token.

Use Cases

Developer can take advantage of using the framework objects when adding a new console or features.

Proposed change

• Define a new ConsoleConnection object.

• Convert drivers to generate ConsoleConnection object.

• Define schema and API to store ConsoleConnection object in child cell database.

• Update code to store ConsoleConnection with valid token in database or consoleauth dependant on the switch until consoleauth is removed.

• Add the instance uuid to the console proxy URLs to allow proxies to locate the child cell database containing the connection info.

• Update proxies to use the database or consoleauth dependant on the switch until consoleauth is removed.

• Define a periodic task to clean expired object stored in database; To balance the load and avoid blocking the database during too much time each compute nodes will be responsible to clean connection_info for guests they host.

• Fix bug 1425640

Alternatives

Continue to use memcached as a backend will make the behavior of connection information not previsible since objects can be evicted. Also in order to fix issue 1425640 and 1455252 a scan has to be done to list available ports which is difficult when using memcached without add specific code to maintain a list of stored keys.

Data model impact

A new ConsoleConnection model needs to be defined with attributes:

• instance: an instance which refer the console

• host: a string field to handle hostname

• port: an int field to handle service number

• token_hash: a string field to handle a token or null

• access_url: a string field to handle access or null

• options: a dict field to handle particular information like usetls, internal_access_path, mode…

• expires: a date time to indicate when the token expires or null

The database schema

CREATE TABLE console_connection (
     instance_uuid CHAR(36) NOT NULL,
     host VARCHAR(255) NOT NULL,
     port INT NOT NULL,
     token_hash CHAR(40),
     access_url VARCHAR(255),
     options TEXT,
     expires DATETIME,

     PRIMARY KEY (instance_uuid, host, port),
     INDEX (token, instance_uuid),
     FOREIGN KEY (instance_uuid)
       REFERENCES instances(uuid)
       ON DELETE CASCADE
);

Note

No migration are expected from serialized dicts connection info stored in memcached to the database, during the upgrade clients already connected to consoles will keep their connections until proxy will be restarted. At this step we expect to have the consoleauth service to also have been restarted.

REST API impact

None

Security impact

In the point of view of tokens we can expect a better security since currently tokens are stored in memcached which does not provide any security layer. Now only hash of tokens will be stored in the database also security policy will enhanced to be the same than other critical components stored in database.

Notifications impact

None

Other end user impact

When proxyclient will be restartred users will be disconnected from our consoles but should reconnect to it with the same token if not already expired.

Performance Impact

The database load will increase but we can expect that with a minimal impact for DBA.

Other deployer impact

The consoleauth service must be restarted before proxy services. When proxy will be restarted clients will be disconnected from consoles. consoleauth will continue to work as backend until a deprecated period of one release operator are encouraged to switch on the database backend (see option: console_tokens_backend).

If the deployer choses to use the database to store console connection information the consoleauth service will not be required.

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

PaulMurray

Other contributors:

sahid-ferdjaoui

Work Items

• Convert code to use objects framework

• Update consoleauth to take advantage of the database to handle tokens

• Fix bug 1425640

Dependencies

None

Testing

The current code is already tested by functional and unit tests since we do not provide any feature we can consider that the code will be well covered by those tests.

The new version will be tested in the gate.

Documentation Impact

None

References

None

History

Revisions

Release Name	Description
Liberty	Introduced
Newton	Re-proposed
Pike	Re-proposed
Queens	Re-proposed