OMERO sessions¶
OMERO sessions simplifies the handling of login sessions for OMERO.blitz.
In short:
- Sessions are a replacement for the standard JavaEE security infrastructure.
- Sessions unify the Blitz and RMI session handling, making working with Java RMI more like Blitz (since the JavaEE interaction is essentially “conversationless”).
- Sessions provide the ability (especially in Blitz) to quit a session and rejoin it later as long as it has not timed out, possibly useful for moving from one machine to another.
- Sessions provide the ability to share the same space. Two users/clients attached to the same session would experience the same life-cycle.
- Sessions provide a scratch space to which any data can be written for and by job/script executions.
- Sessions act as a global cache (in memory or on disk) to speed up various server tasks, including login. With further extensions like http://terracotta.org/, sessions could serve as a “distributed” cache.
- Sessions prevent sending passwords in plain text or any other form. After that, all session interactions take place via a shared secret key.
Design¶
All services other than ISession, assume that a user is logging in with a username equal to session uuid. Whereas previously one logged in with:
ome.system.Principal p = new ome.system.Principal("josh","user","User");
behind the scenes, now the “josh” value is replaced by the UUID of a ome.model.meta.Session instance.
The session is acquired by a call to:
ome.api.ISession.createSession(Principal princpal, String credentials);
and carries information related to the current user’s session.
Session session;
session.getUuid(); // Unique identifier; functions as a temporary password. DO NOT SHARE IT.
session.getTimeToIdle(); // Number of milliseconds which the user can idle without session timeout
session.getTimeToLive(); // Total number of milliseconds for which the session can live
session.getStarted(); // Start of session
session.getClosed(); // if != null, then session is closed
These properties cannot be modified.
Other properties are for use by clients:
session.getMessage(); // General purpose message statement
session.getAgent(); // Can be used to specify which program the user is using
session.getDefaultEventType(); // Default event type (the third argument "User" to Principal above)
session.getDefaultPermissions(); // String representation of umask (e.g. "rw----")
After changing a property on the session returned by createSession() it is possible to save them to the server via:
ome.api.ISession.updateSession(Session);
Finally, when finished, to conserve resources it is possible to destroy the session via:
ome.api.ISession.closeSession(Session);
Existing sessions¶
In OMERO.blitz, it is possible to reacquire the session if it is still active, by passing the previous session UUID as your password (User principal is ignored).
client = omero.client()
servicefactory = client.createSession()
iadmin = servicefactory.getAdminService()
olduuid = iadmin.getEventContext().sessionUuid
// lose connection
client = omero.client()
servicefactory = client.createSession(omero.sys.Principal(), olduuid)
// now reattached
See also
