CA-199656: Fix race in registering sessions with alternate databases #2595
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Signed-off-by: John Else <john.else@citrix.com>
Instead of exposing the master_database ref directly, expose a setter and document it as for testing purposes only. Signed-off-by: John Else <john.else@citrix.com>
Signed-off-by: John Else <john.else@citrix.com>
This has very similar arguments to login_no_password, but is not exposed in the Xapi_session interface. Signed-off-by: John Else <john.else@citrix.com>
For DR, xapi creates special read-only sessions which are registered with alternate databases. These sessions can be used to query the contents of these databases. The external session revalidation function checks whether sessions are registered in this way and, if they are registered, it will not destroy them. However, there is a race window during the period when one of these sessions has been created but has not yet been registered with a database. To fix this, we create the session while holding the registration mutex, so any concurrent revalidation checks will wait until the registration of the session is complete. The registration logic is moved down to login_no_password_common, as the registration mutex needs to be released before the final API call. n.b. the API call used at the end of login_no_password_common has changed from session.get_uuid to pool.get_all. The purpose of this API call is simply to get the pool master to update the last_active time on the session, so most API calls could be used here. session.get_uuid no longer works, because the session is already registered with the alternate database. pool.get_all is chosen as it is currently guaranteed to return only a small amount of data. Signed-off-by: John Else <john.else@citrix.com>
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All looks good to me! |
jonludlam
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Feb 24, 2016
CA-199656: Fix race in registering sessions with alternate databases
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