Making the global state reference a defined part of the node makes
some parts of the block device processing easier and removes the need
for other global values.
The state is passed to PluginNodeBase.__init__() and expected to be
passed into all nodes as they are created. NodeBase.__init__() is
updated with the new paramater 'state'.
The parameter is removed from the create() call as nodes can simply
reference it at any point as "self.state".
This is similar to 1cdc8b20373c5d582ea928cfd7334469ff36dbce, except it
is based on I68840594a34af28d41d9522addcfd830bd203b97 which loads the
node-list from pickled state for later cmd_* calls. Thus we only
build the state *once*, at cmd_create() time as we build the node
list.
Change-Id: I468dbf5134947629f125504513703d6f2cdace59
Currently the later cmd_* calls -- umount, cleanup, delete -- all
recreate the node graph by parsing the config file using
create_graph()
There is some need, however, to have a sense of global state when
building the node list. The problem is, this is a one time operation
-- we do not want to rebuild that state for these later calls (see the
"loaded" checks in proposed
Ic3b805f9258128d5233b21ff25579c03487c7fcc).
An insight here seems to be that these cmd_* calls do not actually
want to re-parse the configuration file and rebuild the node list;
they just want to walk the node list in reverse with the state as
provided after cmd_create().
So, rather than re-creating the node list, we might as well just
pickle it, save it to disk along side the state dictionary dump and
reload it for cmd_*.
After this, I think we can safely have PluginBase.__init__() be passed
the state. We will now know that this will only be called once,
during initial creation.
Change-Id: I68840594a34af28d41d9522addcfd830bd203b97
A couple of things going on, but I think it makes sense to do them
atomically.
The NodeBase.create() argument "results" is the global state
dictionary that will be saved to "state.json", and re-loaded in later
phases and passed to them as the argument "state". So for
consistency, call this argument "state" (this fits with the change out
to start building the state dictionary earlier in the
PluginBase.__init__() calls).
Since the "state" is a pretty important part of how everything works,
move it into a separate object. This is treated as essentially a
singleton. It bundles it nicely together for some added
documentation [1].
We move instantiation of this object out of the generic
BlockDevice.__init__() call and into the actual cmd_* drivers. This
is because there's two distinct instantiation operations -- creating a
new state (during cmd_create) and loading an existing state (other
cmd_*). This is also safer -- since we know the cmd_* arguments are
looking for an existing state.json, we will fail if it somehow goes
missing.
To more fully unit test this, some testing plugins and new
entry-points are added. These add known state values which we check
for. These should be a good basis for further tests.
[1] as noted, we could probably do some fun things in the future like
make this implement a dictionary and have some saftey features like
r/o keys.
Change-Id: I90eb711b3e9b1ce139eb34bdf3cde641fd06828f
