Ganeti Web Manager caches objects for performance reasons.

Why are things cached?

Ganeti is a bottleneck when accessing data. In tests, over 97% of time taken to render a normal page in Ganeti Web Manager is spent waiting for Ganeti to respond to queries. Thus, Ganeti Web Manager caches some of Ganeti’s data.

Manual Updates

Sometimes it is necessary to refresh objects manually. To do this, navigate to the detail page for the cluster of the object that needs to be refreshed, and click the “Refresh” button. This will refresh the cluster and all of its objects.

Cached Cluster Objects

Some database-bound objects cache Ganeti data automatically. The functionality for this caching is encapsulated in the CachedClusterObject class. Any models which inherit from this class will gain this functionality.

Bypassing the Cache

The cache cannot currently be bypassed reasonably. CachedClusterObject uses __init__() to do part of its work. An unreasonable, albeit working, technique is to abuse the ORM:

values = VirtualMachine.objects.get(id=id)
vm = VirtualMachine()
for k, v in values.items():
    setattr(vm, k, v)

RAPI Cache

RAPI clients are cached in memory, and a hash of cluster information is stored in order to locate them quickly. The entire scheme is no longer necessary since RAPI clients are no longer expensive to allocate, and will be removed soon.

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