<SNIP>
This is mail was getting way too long.
About the clear all verb.
No.
Just loop, find the connections YOU OWN and clean them. Even though you don't
want to support multiple clients to VDSM API doesn't mean the engine shouldn't
behave like a proper citizen.
It's the same reason why VDSM tries and not mess system resources it didn't
initiate.
------------------------
As I see it the only point of conflict is the so called non-peristed
connections.
I will call them transient connections from now on.
There are 2 user cases being discussed
1. Wait until a connection is made, if it fails don't retry and automatically
unmanage.
2. If the called of the API forgets or fails to unmanage a connection.
Your suggestion as I understand it:
Transient connections are:
- Connection that VDSM will only try to connect to once and will not
reconnect to in case of disconnect.
My problem with this definition that it does not specify the "end of life" of
the connection.
Meaning it solves only use case 1. If all is well, and it usually is, VDSM will
not invoke a disconnect.
So the caller would have to call unmanage if the connection succeeded at the
end of the flow.
Now, if you are already calling unmanage if connection succeeded you can just
call it anyway.
instead of doing: (with your suggestion)
----------------
manage
wait until succeeds or lastError has value
try:
do stuff
finally:
unmanage
do: (with the canonical flow)
---
manage
try:
wait until succeeds or lastError has value
do stuff
finally:
unmanage
This is simpler to do than having another connection type.
Now that we got that out of the way lets talk about the 2nd use case.
API client died in the middle of the operation and unmanage was never called.
Your suggested definition means that unless there was a problem with the
connection VDSM will still have this connection active. The engine will have to
clean it anyway.
The problem is, VDSM has no way of knowing that a client died, forgot or is
thinking really hard and will continue on in about 2 minutes.
Connections that live until they die is a hard to define and work with
lifecycle. Solving this problem is theoretically simple.
Have clients hold some sort of session token and force the client to update it
at a specified interval. You could bind resources (like domains, VMs,
connections) to that session token so when it expires VDSM auto cleans the
resources.
This kind of mechanism is out of the scope of this API change. Further more I
think that this mechanism should sit in the engine since the session might
actually contain resources from multiple hosts and resources that are not
managed by VDSM.
In GUI flows specifically the user might do actions that don't even touch the
engine and forcing it to refresh the engine token is simpler then having it
refresh the VDSM token.
I understand that engine currently has no way of tracking a user session. This,
as I said, is also true in the case of VDSM. We can start and argue about which
project should implement the session semantics. But as I see it it's not
relevant to the connection management API.
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