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GridFTP and GSI Migration

6 December 2019

Introduction

The GridFTP protocol (for data transfer) and GSI (as an Authentication and Authorization Infrastructure, AAI) were selected for the OSG ecosystem nearly 15 years ago. In both cases, approaches are becoming increasingly niche; as they have not become widely adopted - indeed, as the communities dramatically shrink while the Internet ecosystem grows - the support costs are increasingly directly shouldered by the OSG.

For example, we currently use the GridFTP and GSI implementations in the Grid Community Toolkit (GCT). While the OSG contributes to the GCT (a fork of the abandoned Globus Toolkit) to sustain operations, the long-term plan is to migrate our community off these approaches. The end of the Globus Toolkit is a stark reminder of how niche the current ecosystem is: even the original reference implementation was abandoned.

Thus, OSG has the opportunity and motivation to evolve toward a data transfer protocol and security techniques that better fit our needs and allow us to connect to more vibrant software communities. For the data transfer, we are proposing HTTP; for the AAI, we are proposing the use of bearer tokens, HTTPS, and OAuth2.

The production-oriented nature of the OSG — and the embedding of OSG-LHC in the WLCG community — means that careful coordination, communication, and planning are needed whenever we migrate away from production services. OSG has executed several such technology transitions before and managing the full software lifecycle is part of our value to stakeholders. This document proposes affected services, replacement technologies, and rough timelines for a transition.

Overall Timeline

Date Milestone or Deliverable Completed
Aug 2019 Beginning of OSG 3.5 release series (last release series depending on GCT)
Aug 2019 Including HTCondor 8.9.2 in the ‘upcoming’ repository (first HTCondor version with SciTokens support).
Oct 2019 OSG no longer carries OSG-specific patches for the GCT. All patches are upstreamed or retired.
Jan 2020 "GSI free" site demo. Show, at proof-of-concept / prototype level, all components without use of GCT.
July 2020 All GCT-free components are in OSG-Upcoming.
Jan 2021 OSG series 3.6, without GCT dependencies, is released.
Jan 2022 End of support for OSG 3.5.

Frequently Asked Questions

How does SciTokens interoperate with other token technologies in the WLCG?

The scitokens-cpp library used by OSG can transparently use both WLCG JSON Web Tokens (JWTs) and SciTokens.

Will a US-LHC migration from GridFTP to XRootD require the same migration for WLCG?

No but we have been working to ensure that we coordinate our activities through the WLCG DOMA group.

What role does LCMAPS play with SciTokens?

LCMAPS only works with GSI. The model for SciTokens is sufficiently more simple for sites that the full complexity of LCMAPS is not needed.

What does a SciTokens transition for GlideinWMS mean for European sites?

The only piece that involves European sites is the factory to CE relationship: given HTCondor-CE 4.0 already supports SciTokens, we have begun to engage with the ARC-CE team.

What are the T1s going to do? No SRM? How does tape work with XRootD and HTTPS?

Note that CTA, which CERN is planning to transition to this year, only has XRootD support.

We don't think there's a clear HTTPS picture here (or a clear dCache picture for SRM-free) so there will need to be coordination with other groups (e.g. the QoS working group).

Can WLCG-FTS handle both SciTokens and x509 certificates at the same time?

Yes.

Can PhEDEx handle SciTokens?

Yes.