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Added documentation to the nova.virt interface.

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This commit is contained in:
Ewan Mellor
2010-08-13 11:51:33 +01:00
parent b4b399b998
commit ea2805d372
3 changed files with 137 additions and 21 deletions
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nova/virt/connection.py
+9
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@@ -27,6 +27,15 @@ FLAGS = flags.FLAGS
def get_connection(read_only=False):
"""Returns an object representing the connection to a virtualization
platform. This could be nova.virt.fake.FakeConnection in test mode,
a connection to KVM or QEMU via libvirt, or a connection to XenServer
or Xen Cloud Platform via XenAPI.
Any object returned here must conform to the interface documented by
FakeConnection.
"""
# TODO(termie): maybe lazy load after initial check for permissions
# TODO(termie): check whether we can be disconnected
t = FLAGS.connection_type
nova/virt/fake.py
+128 -1
View File
@@ -19,6 +19,7 @@
"""
A fake (in-memory) hypervisor+api. Allows nova testing w/o a hypervisor.
This module also documents the semantics of real hypervisor connections.
"""
import logging
@@ -32,6 +33,38 @@ def get_connection(_):
class FakeConnection(object):
"""
The interface to this class talks in terms of 'instances' (Amazon EC2 and
internal Nova terminology), by which we mean 'running virtual machine'
(XenAPI terminology) or domain (Xen or libvirt terminology).
An instance has an ID, which is the identifier chosen by Nova to represent
the instance further up the stack. This is unfortunately also called a
'name' elsewhere. As far as this layer is concerned, 'instance ID' and
'instance name' are synonyms.
Note that the instance ID or name is not human-readable or
customer-controlled -- it's an internal ID chosen by Nova. At the
nova.virt layer, instances do not have human-readable names at all -- such
things are only known higher up the stack.
Most virtualization platforms will also have their own identity schemes,
to uniquely identify a VM or domain. These IDs must stay internal to the
platform-specific layer, and never escape the connection interface. The
platform-specific layer is responsible for keeping track of which instance
ID maps to which platform-specific ID, and vice versa.
In contrast, the list_disks and list_interfaces calls may return
platform-specific IDs. These identify a specific virtual disk or specific
virtual network interface, and these IDs are opaque to the rest of Nova.
Some methods here take an instance of nova.compute.service.Instance. This
is the datastructure used by nova.compute to store details regarding an
instance, and pass them into this layer. This layer is responsible for
translating that generic datastructure into terms that are specific to the
virtualization platform.
"""
def __init__(self):
self.instances = {}
@@ -42,20 +75,59 @@ class FakeConnection(object):
return cls._instance
def list_instances(self):
"""
Return the names of all the instances known to the virtualization
layer, as a list.
"""
return self.instances.keys()
def spawn(self, instance):
"""
Create a new instance/VM/domain on the virtualization platform.
The given parameter is an instance of nova.compute.service.Instance.
This function should use the data there to guide the creation of
the new instance.
Once this function successfully completes, the instance should be
running (power_state.RUNNING).
If this function fails, any partial instance should be completely
cleaned up, and the virtualization platform should be in the state
that it was before this call began.
"""
fake_instance = FakeInstance()
self.instances[instance.name] = fake_instance
fake_instance._state = power_state.RUNNING
def reboot(self, instance):
"""
Reboot the specified instance.
The given parameter is an instance of nova.compute.service.Instance,
and so the instance is being specified as instance.name.
"""
pass
def destroy(self, instance):
"""
Destroy (shutdown and delete) the specified instance.
The given parameter is an instance of nova.compute.service.Instance,
and so the instance is being specified as instance.name.
"""
del self.instances[instance.name]
def get_info(self, instance_id):
"""
Get a block of information about the given instance. This is returned
as a dictionary containing 'state': The power_state of the instance,
'max_mem': The maximum memory for the instance, in KiB, 'mem': The
current memory the instance has, in KiB, 'num_cpu': The current number
of virtual CPUs the instance has, 'cpu_time': The total CPU time used
by the instance, in nanoseconds.
"""
i = self.instances[instance_id]
return {'state': i._state,
'max_mem': 0,
@@ -64,15 +136,70 @@ class FakeConnection(object):
'cpu_time': 0}
def list_disks(self, instance_id):
"""
Return the IDs of all the virtual disks attached to the specified
instance, as a list. These IDs are opaque to the caller (they are
only useful for giving back to this layer as a parameter to
disk_stats). These IDs only need to be unique for a given instance.
Note that this function takes an instance ID, not a
compute.service.Instance, so that it can be called by compute.monitor.
"""
return ['A_DISK']
def list_interfaces(self, instance_id):
"""
Return the IDs of all the virtual network interfaces attached to the
specified instance, as a list. These IDs are opaque to the caller
(they are only useful for giving back to this layer as a parameter to
interface_stats). These IDs only need to be unique for a given
instance.
Note that this function takes an instance ID, not a
compute.service.Instance, so that it can be called by compute.monitor.
"""
return ['A_VIF']
def block_stats(self, instance_id, disk_id):
"""
Return performance counters associated with the given disk_id on the
given instance_id. These are returned as [rd_req, rd_bytes, wr_req,
wr_bytes, errs], where rd indicates read, wr indicates write, req is
the total number of I/O requests made, bytes is the total number of
bytes transferred, and errs is the number of requests held up due to a
full pipeline.
All counters are long integers.
This method is optional. On some platforms (e.g. XenAPI) performance
statistics can be retrieved directly in aggregate form, without Nova
having to do the aggregation. On those platforms, this method is
unused.
Note that this function takes an instance ID, not a
compute.service.Instance, so that it can be called by compute.monitor.
"""
return [0L, 0L, 0L, 0L, null]
def interface_stats(self, instance_id, iface_id):
"""
Return performance counters associated with the given iface_id on the
given instance_id. These are returned as [rx_bytes, rx_packets,
rx_errs, rx_drop, tx_bytes, tx_packets, tx_errs, tx_drop], where rx
indicates receive, tx indicates transmit, bytes and packets indicate
the total number of bytes or packets transferred, and errs and dropped
is the total number of packets failed / dropped.
All counters are long integers.
This method is optional. On some platforms (e.g. XenAPI) performance
statistics can be retrieved directly in aggregate form, without Nova
having to do the aggregation. On those platforms, this method is
unused.
Note that this function takes an instance ID, not a
compute.service.Instance, so that it can be called by compute.monitor.
"""
return [0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L]
nova/virt/libvirt_conn.py
-20
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@@ -261,12 +261,6 @@ class LibvirtConnection(object):
def get_disks(self, instance_id):
"""
Note that this function takes an instance ID, not an Instance, so
that it can be called by monitor.
Returns a list of all block devices for this domain.
"""
domain = self._conn.lookupByName(instance_id)
# TODO(devcamcar): Replace libxml2 with etree.
xml = domain.XMLDesc(0)
@@ -304,12 +298,6 @@ class LibvirtConnection(object):
def get_interfaces(self, instance_id):
"""
Note that this function takes an instance ID, not an Instance, so
that it can be called by monitor.
Returns a list of all network interfaces for this instance.
"""
domain = self._conn.lookupByName(instance_id)
# TODO(devcamcar): Replace libxml2 with etree.
xml = domain.XMLDesc(0)
@@ -347,18 +335,10 @@ class LibvirtConnection(object):
def block_stats(self, instance_id, disk):
"""
Note that this function takes an instance ID, not an Instance, so
that it can be called by monitor.
"""
domain = self._conn.lookupByName(instance_id)
return domain.blockStats(disk)
def interface_stats(self, instance_id, interface):
"""
Note that this function takes an instance ID, not an Instance, so
that it can be called by monitor.
"""
domain = self._conn.lookupByName(instance_id)
return domain.interfaceStats(interface)