opensciencegrid/atlas-xcache repository overview

⁠ATLAS XCache

Image source available here: https://github.com/opensciencegrid/docker-xcache/tree/master/atlas-xcache⁠

XCache provides a caching service for data federations that serve one or more Virtual Organizations (VOs) based on the XRootD⁠ software. This image, based on the OSG XCache image⁠, implements XCache for the ATLAS⁠ data federation.

This document covers how to configure and start an ATLAS XCache container.

⁠Configuration

Before starting the container, write the following configuration on your docker host:

1. Write a file containing the following required environment variables and values for your XCache:

   • XC_ROOTDIR: The directory containing files to export from the cache
   • XC_SITENAME: The server name used for monitoring and reporting
   • XC_SPACE_HIGH_WM: High watermark for disk usage; when usage goes above the high watermark, the cache deletes until it hits the low watermark
   • XC_SPACE_LOW_WM: Low watermark for disk usage; when usage goes above the high watermark, the cache deletes until it hits the low watermark
   • XC_PORT: TCP port that XCache listens on
   • XC_RAMSIZE: Amount of memory to use for blocks in flight
   • XC_BLOCKSIZE: The size of the blocks in the cache
   • XC_PREFETCH: Number of blocks to prefetch from a file at once

2. Write cache-disks.config with paths to disks that you will mount within the container.

⁠Disabling OSG monitoring (optional)

By default, XCache reports to the OSG so that OSG staff can monitor the health of data federations. If you would like to report monitoring information to another destination, you can disable the OSG monitoring by setting the following in your environment variable configuration:

DISABLE_OSG_MONITORING = true

⁠Running a Container

To run the container, use docker run with the following options, replacing the text within angle brackets with your own values:

$ docker run --env-file=<PATH TO ENV FILE> \
             --volume <PATH TO HOST CERT>:/etc/grid-security/hostcert.pem \
             --volume <PATH TO HOST KEY>:/etc/grid-security/hostkey.pem \
             --volume <PATH TO DISK CONFIG>:/etc/xrootd/cache-disks.config \
             --volume <HOST PATH TO CACHE DISK 1>:<CONTAINER MOUNT POINT 1> \
             ...
             --volume <HOST PATH TO CACHE DISK N>:<CONTAINER MOUNT POINT N> \
             --publish <HOST PORT>:<XC_PORT> \
             --hostname <XCACHE HOSTNAME> \
             opensciencegrid/atlas-xcache:development