Check for existence of required XRootD plugins before use

[Copilot]

Missing Pelican-specific XRootD plugins (libXrdHttpPelican, libXrdS3, libXrdClPelican) cause XRootD startup failures or runtime errors with cryptic messages. Detection happens too late to provide actionable guidance.

Changes

New xrootd/plugin_check.go:

• Plugin existence validation in ConfigXrootd() before config file generation
• Search paths: standard lib directories + XRD_PLUGINPATH/LD_LIBRARY_PATH/DYLD_LIBRARY_PATH
• Handles XRootD's automatic version suffixing (libXrdHttpPelican-5.so for v5.x)
• Conditional checks based on configuration:
  • libXrdHttpPelican.so: when Server.DropPrivileges enabled (cache/origin)
  • libXrdS3.so: when Origin.StorageType is "s3"
  • libXrdClPelican.so: all caches (pelican:// URL support)

Error message format:

Required XRootD plugin(s) not found: libXrdHttpPelican.so, libXrdClPelican.so
Please install the missing plugin(s) in one of the following directories:
  /usr/lib
  /usr/lib64
  /usr/local/lib
Or set the XRD_PLUGINPATH, LD_LIBRARY_PATH, or DYLD_LIBRARY_PATH environment variable.
Note: XRootD may add a version suffix to plugin names (e.g., libXrdHttpPelican-5.so)

Platform support: Linux (.so), macOS (.dylib), with environment variable precedence.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• cilogon.org
  • Triggering command: /tmp/go-build3516977188/b001/xrootd.test /tmp/go-build3516977188/b001/xrootd.test -test.testlogfile=/tmp/go-build3516977188/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true nIaJ7UXlI e_pubkey.go ux-amd64/pkg/tool/linux_amd64/vet -p github.com/press--norc mpile ux-amd64/pkg/tool/linux_amd64/vet -W olang.org/grpc@v1.67.3/encoding/-errorsas fg 0.1-go1.25.0.linux-amd64/pkg/tool/linux_amd64/vet . theus/prometheus--64 mpile 0.1-go1.25.0.lin/tmp/ccVgu5b3.o (dns block)
  • Triggering command: /tmp/go-build3252025759/b001/xrootd.test /tmp/go-build3252025759/b001/xrootd.test -test.testlogfile=/tmp/go-build3252025759/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true -test.run=TestHttpOriginConfig fg 0.1-go1.25.0.linux-amd64/pkg/tool/linux_amd64/vet ists theus/prometheus--64 m 0.1-go1.25.0.lin/tmp/ccVgu5b3.o -o 36021/b779/_pkg_.a m 0.1-go1.25.0.linux-amd64/pkg/tool/linux_amd64/vet _crypt.go g/grpc/credentia--64 mpile 0.1-go1.25.0.lin/tmp/cc6DDlAE.o (dns block)
• topology.opensciencegrid.org
  • Triggering command: /tmp/go-build134467915/b001/xrootd.test /tmp/go-build134467915/b001/xrootd.test -test.testlogfile=/tmp/go-build134467915/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true .a -trimpath ux-amd64/pkg/tool/linux_amd64/vet -p rat-go/jwx/v2/jw-V=full mpile ux-amd64/pkg/tool/linux_amd64/vet -w 5qlY-QRxK fg 0.1-go1.25.0.linux-amd64/pkg/tool/linux_amd64/vet -c /azure-sdk-for-g--64 mpile 0.1-go1.25.0.lin/tmp/ccxPwJdI.o (dns block)
  • Triggering command: /tmp/go-build3516977188/b001/xrootd.test /tmp/go-build3516977188/b001/xrootd.test -test.testlogfile=/tmp/go-build3516977188/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true nIaJ7UXlI e_pubkey.go ux-amd64/pkg/tool/linux_amd64/vet -p github.com/press--norc mpile ux-amd64/pkg/tool/linux_amd64/vet -W olang.org/grpc@v1.67.3/encoding/-errorsas fg 0.1-go1.25.0.linux-amd64/pkg/tool/linux_amd64/vet . theus/prometheus--64 mpile 0.1-go1.25.0.lin/tmp/ccVgu5b3.o (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Check for existence of required plugins</issue_title>
<issue_description>@jhiemstrawisc noticed that if Pelican-specific XRootD plugins are not in the environment, this is not noticed they're used. In some cases (libXrdHttpPelican, libXrdOssS3), this may cause XRootD to fail startup with difficult-to-understand error messages. In other cases (libXrdClPelican), XRootD starts fine and the missing plugin isn't noticed until objects are downloaded.

In the cache configuration code, check for their existence and give a clearer error message.

Note that XRootD automatically adds the major version to the plugin name. So, libXrdHttpPelican.so in the config file will be libXrdHttpPelican-5.so on disk.

Search the dynamic loader paths for the appropriate plugin names according to the rules for the platform. This may include /etc/ld.so.conf and friends on Linux and multiple environment variables.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Check for existence of required plugins #3025

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[turetske]

@bbockelm This seems to share/duplicate the xrootd version work I did. Maybe see about getting copilot to take that into account? Specifically #3092

[bbockelm]

@jhiemstrawisc - I think this one is ready for re-review!