Service/mirrors

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Introduction

A content delivery network or Content Delivery Network (CDN) is a system of computers containing copies of data, placed at various points in a network so as to maximize bandwidth for access to the data from clients throughout the network. A client accesses a copy of the data near to the client, as opposed to all clients accessing the same central server, thereby causing a bottleneck near that server.

Goals

• Reduce bandwidth at primary download server.
• Improve quality of service for users.
• Move content closer to users, thus reducing latency.

Architecture

The Sugar Labs Content Delivery Network uses MirrorBrain as a redirector. The redirector, which lives in a Sugar Labs data center, keeps track of which files are available on which mirror. When a user requests a file, the redirector points the user to the correct mirror and automatically starts the file download.

Mirrors

The current list of available mirrors is available at http://mirrors.sugarlabs.org/

Setting up a new mirror

For mirror administrators

All you need is a web server with enough bandwidth to serve the files. To set up a new mirror, the site administrator needs to:

• Set up rsync job to synchronize a copy of the files on http://download.sugarlabs.org onto their local system. For example copy it into /rsync/download.suarlabs.org/:

 rsync -avzh rsync://download.sugarlabs.org/pub /rsync/download.sugarlabs.org

• You can schedule it daily or more frequently, but please don't sync more often than once per hour. For example, use cron to re-sync every 2 hours (on linux):

 echo "0 */2 * * * rsync -avzh rsync://download.sugarlabs.org/pub /rsync/download.sugarlabs.org" > asloSyncCronJob.txt
 crontab asloSyncCronJob.txt

• Publish the files via HTTP and -- if possible -- rsync. Rsync allows for efficient mirror monitoring (scanning). FTP is less efficient, but still preferred over an HTTP-only mirror.
• Alert the Sugar Labs System Administrators that they would like their mirror into rotation, including the following information in the request:
  • Name and URL of the mirror operator (e.g. organization)
  • Name and email address of the administrative contact
  • ISO 3166-1 alpha-2 country code of the server location
  • HTTP base URL of the files on the mirror (typically http://mirrors.example.org/sugarlabs/)
  • rsync base URL of the files on the mirror (typically rsync://mirrors.example.org/sugarlabs/)

Please contact sysadmin AT sugarlabs DOT org if you are interested in hosting a mirror.

For Sugar Labs sysadmins

To add a new mirror to the MirrorBrain redirector:

• Choose a name for the mirror, usually the host name.
• Register the mirror with MirrorBrain:

sudo -u mirrorbrain mb new <mirror name> --operator-name <operator name> \
 --operator-url <operator URL> -a <admin name> -e <admin email> \
 -c <country code> -H <base HTTP URL> -R <base rsync URL> -F <base FTP URL>

• Scan and enable the mirror:

sudo -u mirrorbrain mb scan -e <mirror name>