XCache
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.
Links
Configuration
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