2023-05-25 Meeting Notes

Date

May 25, 2023

Participants

@James Walder
@Thomas, Jyothish (STFC,RAL,SC)
@Alexander Rogovskiy
@Ian Johnson
Lancaster: Gerard, Matt, Steven

Apologies:
@Alison Packer , @Alastair Dewhurst

Goals

List of Epics
New tickets
Consider new functionality / items
Detailed discussion of important topics
Site report activity

Discussion topics

Current status of Echo Gateways / WNs testing

Recent sandbox’s for review / deployments:

Item	Presenter	Notes

Item	Presenter	Notes
Vector Read updates to Echo		https://stfc.atlassian.net/wiki/spaces/GRIDPP/pages/188153912 Post-mortem to be held today
Next steps for WN deployment		Move to 5.5.4-2 (core) + 5.5.4-3 (xroot-ceph-buffered): GitHub - stfc/xrootd at v5.5.4patched Release 5.5.4-3 non striper reads in buffered IO · stfc/xrootd-ceph Status: lcg2268 running with that config. n_connections from xrdceph file close metrics show similar numbers compared to other nodes in 5.3.3-2 without readv lcg2268 (with change) lcg2267 (without changes) No failures of lhcb jobs were observed on the test WN so far.
EBUSY in readV requests		https://stfc.atlassian.net/browse/XRD-64
Discussion on merging bufferedIO into master. Also to discuss pushing changes to “upstream” (xrootd/xroot-ceph”		Buffered io merge into master by Jo-stfc · Pull Request #44 · stfc/xrootd-ceph Needs testing for ‘correctness’ Also some discussion ongoing on xrootd “issues” on the xrootd-ceph sub-module: Remove xrootd-ceph git submodule and bring the code back to the main repository by amadio · Pull Request #2008 · xrootd/xrootd
SEGV investigations with -S multi-stream flags		@Ian Johnson Preparing script for ‘git-bisect run <script>’ to run, automating the search of a range of commits. This should identify the commit that introduced the unexpected corrective action that now allows multiple streams in XrdCeph without the SEGV. Guilherme commented in segfault from XrdXrootdProtocol::do_OffloadIO · Issue #1821 · xrootd/xrootd about reading release notes for a clue; I tried and didn’t find anything relevant.
CMSD status		https://stfc.atlassian.net/browse/XRD-41 @Thomas, Jyothish (STFC,RAL,SC) identified that xrdcp via the redirector using root protocol requires two “/” in the LFN to work correctly. Although this is the nominally correct path construction for xroot-based paths; existing transfers work with just a single-/ and may break from some corner-case person/VO. Assuming we want a solution which maintains backwards compatibility, we may need to explicitly add: `all.export / # already existing line # add in the lines all.export cms all.export store #special cms 'namespace' # and for other pools` What’s the impact? Do we need “/” export now. Should we consider the authdb file logic too ? To understand exactly how the export / authdb / “// \| /" finally interact ?
Transfers of 0-byte files		https://stfc.atlassian.net/browse/XRD-62Q: Could close? Observed Dune transfer failures using 0-byte files/ @Thomas, Jyothish (STFC,RAL,SC) identified FTS not supporting 0-byte transfers, hence the cause of the reported failures. @Ian Johnson noted that the “classic” RADOS striper implementation doesn’t appear to create an object until data is written to it; is there a use case which might call for the creation of 0-byte files?