[RFC] pynfs: add courteous server tests

[Calum Mackay <calum.mackay@oracle.com>]

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hi Bruce,

At Chuck's suggestion, I've added an initial PyNFS test to aid work on a 
courteous server. A simple test, along the lines you indicated, that 
locks a file, waits twice the lease period, and tries to unlock:

OK -> PASS (courteous server)
BADSESSION -> WARNING (discourteous server)


Before sending my patch, Chuck asked me to add the second test you 
suggested:

	- A second test creates a new client, acquires a file lock, and
	  waits two lease periods.  Then creates a second client, which
	  attempts to acquire the lock.  The second client should
	  succeed.



This doesn't seem to differentiate between these three cases:

1. a discourteous server, which invalidates the client 1 state, and 
frees all client 1's locks, upon lease expiry, then allows client 2 to 
lock the file. The above test spec would result in a PASS for a 
discourteous server, which doesn't seem right.

2. a broad-grained courteous server, which invalidates the client 1 
state, and frees all client 1's locks, because of conflicting access 
from client 2 (after client 1's lease expiry), who is then granted the 
lock. A PASS here would be correct.

3. a fine-grained courteous server, which persists the session, but 
revokes that particular client 1 lock, because of conflicting access 
from client 2 (after client 1's lease expiry), who is granted the lock. 
A PASS here would be correct.

Or am I misreading your suggestion?


If I've read it right, the test could differentiate between cases 2) and 
3), by having client 1 try to unlock, after client 2 successfully locks, 
where client 1 will see either BADSESSION (case 2) or SOME_STATE_REVOKED 
/ EXPIRED (case 3). But we don't need to differentiate cases 2) and 3), 
since a PASS would be correct in either case.

However that won't differentiate between cases 1) and 2), where client 1 
will see BADSESSION in each case. Yet case 1) ought to result in a 
WARNING, and case 2) in a PASS?


cheers,
calum.

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