Platform Team/Server Kit/sugar-client

Summary

A program to run on Sugar clients side to interact with Sugar Server Kit based school server. It implements the Client API for usage, e.g. in Sugar Shell, and the sugar-client utility to get access to the same API from the console.

Functionality

The high level functionality is described by DBus API sugar-client provides. These DBus services will be accessible right after installing sugar-client package, e.g., to reuse them in Sugar Shell code. To call the same functionality from the command line, use sugar-client utility.

Registration on a school server

That's the first operation that should be processed to let the rest of sugar-client functionality working properly. The key configuration option here, is api-url that points to sugar-server's API. If api-url was not explicitly specified, the default one, http://schoolserver:8000, will be used. If api-url was explicitly specified, it will be kept for later usage.

The result of registration will be:

• Setting the /desktop/sugar/collaboration/jabber_server GConf key with Jabber server url to support Sugar collaboration;
• School server reply will be formed as a regular sugar-client.conf configuration file and placed to user's profile directory. This configuration will be reused for all other sugar-client functionality.

If auto-register configuration option is set, sugar-client will try to make auto-registration on a server on Sugar startup. Auto-registration will happen if client is not registered at all or registration is outdated (school server asked clients to process re-registration).

To process registration, either call DBus API or use sugar-client utility:

sugar-client register [<api-url>]

Auto Journal restore

The affected usecase:

• a XO processed several auto backups (the regular practice in the field),
• and was reflashed,
• XO was not restored manually before the first auto backup,
• the first auto backup will cleanup backuped Journal on the server (Journal after reflashing is empty),
• any later restore using UI will restore empty Journal (though, it is possible to restore Journal for particular date using CLI tools).

Since disabling auto backups will be considered as a regression, sugar-client needs to provide a way to auto restore Journal after reflashing.

The implementation will be:

• auto-register option needs to be more than 0,
• backup-timeout needs to be more than 0,
• auto-restore needs to be True,
• Journal should be empty,
• right after registering newly reflashed XO, sugar-client will start restoring the Journal.

Usage statistics

Summary:

• Implementation is based on sugar-stats library.
• Client behaviour is entirely controlled by stats server.

To activate stats client activity, background operations need to be activated. The procedures are:

• sugar-client requests server for stats parameters in stats-timeout period, in particular:
  • should stats gathering process start or stop,
  • client side storage parameters;
• if server needs stats, client start gathering process;
• during the server interaction, client sends already collected stats.

To start stats activity, client side should have the following configuration:

• stats-url, HTTP(S) url to the stats server,
• stats-timeout, how frequent (in seconds) client should connect to stats server to upload new information and correct current behaviour.

The stats gathering process might be initiated manually by the command:

sugar-client -d monitor [OPTIONS]

It is important to use secure connection with server, specify server's certificate via stats-ca-certs parameter.

Stats configuration

Stats related configuration is being stored in sugar-client.conf configuration file in [stats] section:

[stats]
rras = ["RRA:AVERAGE:0.5:1:4320", "RRA:AVERAGE:0.5:5:2016"]
step = 60
enabled = true

Background operations

Sugar-client might process background operations. To make it possible, add

sugar-client session

command line call to, e.g., ~/.sugar/debug file, to let it run on Sugar Shell startup. It is important to let sugar-client know about environment variables like DISPLAY and DBUS_SESSION_BUS_ADDRESS. This command will start, if it was not started before, DBus service on session bus.

Background operations are:

• Process auto-registration.
  If auto-register option is 1, sugar-client will process auto-registration for never registered clients. If auto-register option is more than 1, sugar-client will check if auto-registration is needed on every start.
• Process regular Journal backup.
  If backup-timeout option is more than 0, sugar-client will try to backup the Journal periodically in backup-timeout seconds.
• Process automatic Journal restore
  if auto-restore is True.
• Process regular unattended packages update.
  If update-timeout option is more than 0, sugar-client will try to call update process periodically in update-timeout seconds;
• Process stats monitoring.
  If stats-url is set.

In all cases, periodical operations will be triggered only once within the same timeout period, even after Sugar session restart.

Background operations will be processed from DBus service. While working, such DBus service will log into ~/.sugar/current-profile/logs/sugar-client.log file.

Backwards compatibility

Sugar Shell code

The sugar-client initiative is intended to replace several client side tools to collect all server interaction functionality in the same place and provide it via DBus API. To support already existed tools, sugar-client provides the same name programs that forward the processing to sugar-client utility:

• dextrose-updater
  utility from Dextrose-2 to process native packages updates.
• journal-backup
  Journal backup from Dextrose-2.
• journal-restore
  Journal restore from Dextrose-2.
• ds-backup.sh and ds-backup.py
  Journal backup from OLPC XS distribution.

Treating UUIDs

While interacting with a sugar-server, sugar-client is different, in case of treating UUIDs while registration, with Sugar Shell code. The UUID value will be a hash of SSH public key (how it is being used for JIDs in Sugar Shell). After registration, UUID value will be kept in ~/.sugar/profile/sugar-client.conf file as a sugar-client's uuid configuration option.

OLPC XS

In addition to Sugar Server Kit based solutions, sugar-client will interoperate with OLPC XS school servers.

TODO

Distribution

The sugar-client distribution contains:

• sugar-client-service utility
  the main program that implements entirely functionality as DBus services for Client API;
• sugar-client utility
  to call DBus API from the console;
• .service files
  to run sugar-client-service for each exported DBus interface;
• backwards compatibility command wrappers.

Configuration

The configuration occurs based on several sources (sorted by applied order):

• /etc/sugar-client.conf
  system-wide configuration file,
• ~/.config/sugar-client/config
  user-wide configuration file,
• ~/.sugar/current-profile/sugar-client.conf
  configuration got after registration on a server,

Configuration files contain option names equal to command-line arguments. To get the current configuration, call:

sugar-client-service config

Troubleshooting

In special cases, it is possible to execute sugar-client operations directly, instead of calling DBus service. For that reason, -d command-line argument needs to be passed:

sugar-client -d update

Getting involved

• Report on bugs.
• Read the HACKING file to know how to contribute with code.

Resources

• Sources.
• Current stable binary packages.
• Development binary packages.