Something that often comes up from various people new to using the vSphere API is how to get information very quickly about all the VirtualMachines in the inventory. There is a sample that comes with pyvmomi called getallvms.py which is an obvious place to start to get this info. When its run on an inventory that only has 30 VirtualMachines it seems pretty fast. It only takes about .5 seconds to complete. Try it on a larger inventory like something with 500+ VirtualMachines and it really starts to slow down going from .5 seconds all the way up to over 6 seconds. This number just keeps growing the larger the inventory gets. Once the inventory reaches over 1000 VirtualMachines it can take over 10 seconds for this info to be returned. In other words this solution just doesnt scale, but its often the only way new comers know. The good news is that VMware provides other ways to get this info. The bad news is that its not an obvious solution, and its kind of complicated to use, but thats what I am here for 🙂
Where I work we have over 45,000 vSphere powered Virtual Machines, and its my job as a Sr. Developer there to make sure our code is stream lined, efficient, and scales the way we do. This is why I use property collectors when I need to work with objects from the vSphere inventory. To help new users I provided a sample I call vminfo_quick which as its name implies get info about a VirtualMachine, quickly. To test this lets run the getallvms.py from above on a vCenter with 576 VirtualMachines and time it.
time python getallvms.py -s 10.12.254.119 -u 'firstname.lastname@example.org' -p password
Almost 6 1/2 seconds. Thats not too bad right? Now lets run the vminfo_quick sample I provided against that same vCenter and see how it does. I included a counter and a timer in this sample so we dont have to run time.
python vminfo_quick.py -s 10.12.254.119 -u 'email@example.com' -p password
Found 576 VirtualMachines.
Completion time: 0.368282 seconds.
As you can see using a property collector vastly improves performance. I have tested this on an inventory with 1500 VirtualMachines and it still finishes in just under 1 second. I plan to cover details around what the property collector is and how it works in future posts. Stay tuned!