  The OSG-operated Open Science Pool is an HTCondor-based virtual cluster that
aggregates resources from compute clusters provided by several organizations.
Most of the resources are not owned by OSG, so demand-based dynamic
provisioning is important for maximizing usage without incurring excessive
waste. OSG has long relied on GlideinWMS for most of its resource provisioning
needs but is limited to resources that provide a Grid-compliant Compute
Entrypoint. To work around this limitation, the OSG Software Team has developed
a glidein container that resource providers could use to directly contribute to
the OSPool. The problem of that approach is that it is not demand-driven,
relegating it to backfill scenarios only. To address this limitation, a
demand-driven direct provisioner of Kubernetes resources has been developed and
successfully used on the NRP. The setup still relies on the OSG-maintained
backfill container image but automates the provisioning matchmaking and
successive requests. That provisioner has also been extended to support
Lancium, a green computing cloud provider with a Kubernetes-like proprietary
interface. The provisioner logic has been intentionally kept very simple,
making this extension a low-cost project. Both NRP and Lancium resources have
been provisioned exclusively using this mechanism for many months.
