Evolving StoRM WebDAV: Delegation of file transfers to NGINX and support for SciTags

After the deprecation of the open-source Globus Toolkit used for GridFTP transfers, the WLCG community has shifted its focus to the HTTP protocol. The WebDAV protocol extends HTTP to create, move, copy and delete resources on web servers. StoRM WebDAV provides data storage access and management through the WebDAV protocol over a POSIX file system. Mainly designed to be used by the WLCG community, StoRM WebDAV supports authentication through X.509 certificates, VOMS proxies and JSON Web Tokens (JWT). Moreover, Third-Party Copies (an extension of the WebDAV COPY verb to support copies between data centers) are supported.
With the aim of improving data transfer performance, this contribution describes the changes made to StoRM WebDAV in order to delegate file transfers to the external reverse proxy NGINX, decoupling them from the internal Java implementation. To simplify even more the StoRM WebDAV codebase, also the validation of VOMS proxies and JWTs is delegated to NGINX, augmented with specific modules developed by us. Even with this solution, authorization is still enforced by StoRM WebDAV.
Following the effort of the WLCG community to have better metrics about data flows, this contribution also describes the work done in order to support SciTags, an initiative promoting identification of the science domains and their high-level activities at the network level.