What is it?

XCache is a service that provides caching of data accessed using xrootd protocol. It sits in between client and an upstream xrootd servers and can cache/prefetch full files or only blocks already requested. To use it to cache file that is at root://origin.org:1094/my_file.txt simply prepend name of the caching server: root://caching_server.org:1094//root://origin.org:1094/my_file.txt
When deployed using kubernetes all relevant parameters are configured throught the container environment variables.


Mandatory variables

Variable Meaning
XC_SITE ATLAS specific. Used in registering cache in AGIS and in all monitoring. Has to correspond to ATLAS sitename.

Optional settings

Implemented Option Variable Default Meaning
No Rucio N2N XC_RUCIO_N2N True This is ATLAS specific thing. To avoid multiple cache copies of the same file (obtained from different sources) it will strip source specific part of the path.
Yes Monitoring XC_REPORT_COLLECTOR http://uct2-collectd.mwt2.org:8080 This is xrootd internal monitoring info. Actual service status is monitored through the kubernetes infrastructure.
Yes Port XC_PORT 1094
No Subfile caching SUBFC True
Yes Prefetching XC_PREFETCH 0
Yes Block size XC_BLOCKSIZE 1M
Yes Disk usage high watermark XC_SPACE_HIGH_WM 95%
Yes Disk usage low watermark XC_SPACE_LOW_WM 80%
Yes RAM size XC_RAMSIZE half of the free RAM At least 1g. Units are ...

To Do

  • Add subfile caching option
  • Test
  • Create core collecting pod.
  • Add summary stream monitoring