Querying the Federation¶
Before we can reserve resources, it is useful to know what resources are available across the
federation. This tutorial will walk you through using the
Context object you created in
the previous tutorial to communicate with aggregates known to
Finding Aggregate Locations¶
geni-lib contains a set of package files which have pre-built objects representing known
aggregates that are ready for you to use, contained within the following Python modules:
geni.aggregate.exogeni geni.aggregate.instageni geni.aggregate.instageni_openflow geni.aggregate.opengeni geni.aggregate.protogeni geni.aggregate.vts
While these aggregates objects will likely cover your needs,
geni-lib may of course not be
updated as frequently as new aggregates come online. You can find a list of the current set of
aggregates on the GENI Wiki.
Getting Aggregate Information¶
Given that we have our previously created
Context object, and a wealth of aggregate objects
available to us, the GENI federation provides the ability to request two blocks of information
from each aggregate - the version information (which you may have seen briefly in a previous
tutorial), and a list of the advertised resources.
The result from
getversion, as we saw in the previous tutorial, is reasonably concise and
human readable (but also contains information about API versions and supported request formats
that you may need to extract in your tools). The list of advertised resources is acquired using
listresources call, and returns a large XML document describing the available resources,
which is relatively difficult to work with without a tool.
We will be using GENI AM API version 2 throughout this tutorial. Some API call names will be different if you elect to interact with aggregates using AM API version 3 in the future.
Lets start by getting an advertisement from a single aggregate. If you built a custom context using Python code you will need to replace the code below to load your custom context:
$ python >>> import geni.util >>> context = geni.util.loadContext() >>> import geni.aggregate.instageni as IGAM >>> ad = IGAM.Illinois.listresources(context)
Now of course we have an advertisement (assuming everything went well) stored into a Python object, which is reasonably boring!
If you get timeouts or failures, you may want to try a different InstaGENI aggregate (this one may
be particularly busy). You can get a list of (mostly) aggregate objects by using the
on the IGAM module -
We can simply print out the advertisement raw text to see what the aggregate sent us:
>>> print ad.text <rspec xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" ...... ...
As you can see, even with this relatively small rack (5 hosts) the amount of data is significant.
geni-libhas parsed this advertisement into a more functional object, we have access to data objects instead of just raw xml. For example, we can inspect the routable address space available at a site:
>>> ad.routable_addresses.available 167 >>> ad.routable_addresses.capacity 190
You may have noticed that if you just print the
routable_addressesattribute, you get nothing useful:
>>> ad.routable_addresses <geni.rspec.pgad.RoutableAddresses object at 0x1717f10>
While we are adding online documentation for
geni-libobjects, there are many objects that are undocumented. However, you can still gain some insight by using the
dir()built-in to see what attributes are available:
>>> dir(ad.routable_addresses) ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'available', 'capacity', 'configured']
In general attributes starting with underscores are not useful to us, so we can see 3 attributes of value -
configured. In most cases their meanings should be obvious, so just knowing they exist even without documentation is quite helpful.
There are also 3 iterators that are provided with
>>> for svlan in ad.shared_vlans: ... print svlan ... mesoscale-openflow exclusive-openflow-1755 exclusive-openflow-1756 exclusive-openflow-1757 ...snip...
shared_vlansjust iterates over a set of strings,
nodeobjects are much more complex and have many more attributes and nested data structures to allow you to fully inspect their state:
>>> print dir(ad.nodes) [..., 'available', 'component_id', 'component_manager_id', 'exclusive', 'hardware_types', 'images', 'interfaces', 'location', 'name', 'shared', 'sliver_types']
Particularly useful for the puposes of binding requests to certain nodes at a given site is the component_id:
>>> for node in ad.nodes: ... print node.component_id ... urn:publicid:IDN+instageni.illinois.edu+node+procurve2 urn:publicid:IDN+instageni.illinois.edu+node+pc3 urn:publicid:IDN+instageni.illinois.edu+node+pc5 urn:publicid:IDN+instageni.illinois.edu+node+interconnect-ion urn:publicid:IDN+instageni.illinois.edu+node+pc1 urn:publicid:IDN+instageni.illinois.edu+node+interconnect-campus urn:publicid:IDN+instageni.illinois.edu+node+pc2 urn:publicid:IDN+instageni.illinois.edu+node+interconnect-geni-core urn:publicid:IDN+instageni.illinois.edu+node+pc4 urn:publicid:IDN+instageni.illinois.edu+node+internet
Spend some time inspecting the other attributes of each node. You can get a specific node by using Python indexing on the
>>> node = ad.nodes >>> node.component_id 'urn:publicid:IDN+instageni.illinois.edu+node+pc3'
Iterating Over Aggregates¶
Often you will want to inspect a large number of aggregates (particularly if there are of an idential or
similar type) in order to find those that have availability in the resources that you require. The aggregate
geni-lib provide some convenience methods for assisting in this task:
>>> import geni.aggregate.instageni as IGAM >>> for am in IGAM.aggregates(): ... print am.name ... ig-cenic ig-cwru ig-clemson ig-cornell ig-ohmetrodc ig-gatech ig-gpo ig-illinois ...snip...
Using this iterator you can act on each aggregate in a given module with the same snippet of code.
Lets try getting (and saving) the
getversionoutput from each InstaGENI site:
>>> import json >>> for am in IGAM.aggregates(): ... print am.name ... verdata = am.getversion(context) ... ver_file = open("%s-version.json" % (am.name), "w+") ... json.dump(verdata, ver_file) ... ig-cenic ig-cwru ig-clemson ...snip...
This will write out a file for every aggregate (barring any exceptions) to the current directory.
verdata in the above case is a Python
dict object, so we need to pick a way to write it
(in a human readable form) to a file. In the above example we pick serializing to JSON (which is
reasonably readable), but you could also use the
pprint module to format it nicely to a file
as a nice string.
We can now combine all of the above pieces, plus some Python knowledge, into some useful scripts.
getversioncode fragment above into a standalone script, and improve it to continue to the next aggregate if any exceptions are thrown by the current aggregate (unreachable, busy, etc.).
Write a script that prints out the number of availble routable IPs for each InstaGENI aggregate.