KDE PIM/Akonadi: Difference between revisions

Revision as of 09:43, 17 January 2010

Akonadi TODO

The following list contains the things which need to be done for Akonadi.

Note: The person noted in the "Contact" column is not necessarily the one implementing that feature, but the one who can tell you what to do and how to help, i.e. you can also contribute to those tasks ;-)

There is also a more detailed page about bugs and missing features of things that are currently ported here.

Core

KDE 4.1 / Akonadi 1.0

Urgent tasks that need to be finished for the KDE 4.1 release (May 19th):

Status	Item	Description	Contact
DONE	Item streaming in ItemSync/ResourceBase	As discussed in Osnabrueck	<Tom/Volker>
DONE	Payload serialization format versioning	see below [email protected]	<Tobias>
DONE	API for additional item parts	As discussed in Osnabruck	<Volker/Tobias>
DONE	Infrastructure for showing additional dialogs from agents/resources	As discussed in Osnabrueck	<Tom>
DONE	Allow to limit ItemFetchJob to current cache content	Prevents search index feeder agents from downloading all remote data	Volker <[email protected]>
DONE	Fix API for item/collection modifications	See Osnabrueck meeting notes for details	Volker <[email protected]>
DONE	Plugin Versioning	For serializer plugins, also check using Qt plugin stuff instead of the libkdepim plugin framework	Tobias <[email protected]>
DONE	Tray app	small app to control the server and have a something that can report errors	Toma <[email protected]>
DONE	Backup support	Dump & Restore database contents, also useful when upgrading to a newer database version	<[email protected]>
DONE	Akonadi Artwork	Icon for the tray app	Toma <[email protected]>

KDE 4.2 / Akonadi 1.1

That's the stuff we want to have in 4.2, very roughly ordered by priority. Releases are scheduled for early January 2009.

Status	Item	Description	Contact
DONE	Server error reporting	Helpful error message when the server cannot be started or if there is some other problem communicating with it.	Volker <[email protected]>
DONE	KResource migration tool	For KABC and KCal resources, setting up Akonadi <-> KResource bridges where needed	<Volker>
DONE	KResource bridges	Basically finished, needs more testing	<Kevin>
DONE	Distribution Lists	Serializer Plugin and resource support	<Tobias,Kevin>
DONE	Complete iCal resource	error handling, robustness, legacy formats, file montitoring	<Volker>
DONE	Complete vCard resource	same as iCal + binary legacy format	<Bertjan>
DONE	Item size	Needed by Mailody	<[email protected]>
DONE	LINK/UNLINK commands	Managing item references in virtual collections	Volker <[email protected]>
DONE	Akonadi Testrunner	Running tests in a self contained Akonadi setup	Igor <[email protected]>
DONE	Remote file support for iCal/vCard resources	Replaces net/remote KRes resources	<Bertjan>
DONE	Solid integration	Switch online/offline state in ResourceBase automatically	<Bertjan>

KDE 4.3 / Akonadi 1.2

Stuff that went into KDE 4.3 and Akonadi server 1.2.

Status	Item	Description	Contact
DONE	Fix unit tests	Make unittests work without destroying the production database	<Igor/Volker>
DONE	Filesystem Backend	Store content data in files instead of the database, transfer filehandles instead of data to the client	<Andras>
DONE	IMAP resource		<Kevin>
DONE	Kolab proxy resource		<Andras>
DONE	RID based operations	Item/collection retrieval and modification based on remote identifiers	<Volker>
DONE	Microblog Support	Type library, serializer plugin, identi.ca/twitter resources	<Tom>
DONE	ResourceBase::collectionsRetrievalDone is missing	I'm working around by calling collectionsRetrievedIncremental() with empty collection lists	<Volker>

KDE 4.4 / Akonadi 1.3

The following is being worked on for KDE 4.4 and Akonadi server 1.3.

Status	Item	Description	Contact
DONE	Port KAddressBook	Replace with KContactManager	<Tobias>
DONE	Resource testing framework	Automated, shareable tests for resources	<Igor/Volker>
IN PROGRESS	Review change notifications	See the various discussions about shortcomings in that area	<Volker,Steve>
DONE	Collection statistics for sub-trees	Provide a CollectionStatus object covering the full sub-tree in the model, allowing accumulated unread counts etc.	<Kevin>
DONE	Favorite Folder Model	see current KMail	<Kevin>
DONE	Batch jobs for modifying/deleting collections/items	it would be great to have jobs which perform operations on several entities in one go	<Volker>
DONE	Collection streaming support in ResourceBase/CollectionSync	Similar to what is available for items already	<Volker>
DONE	MBox resource		<Bertjan>

Scheduled for KDE 4.5 / Akonadi 1.4

Stuff that is planned for inclusion in 4.5, partly already available in the akonadi-ports branch.

Status	Item	Description	Contact
IN PROGRESS	Port KOrganizer	Port from KResource to Akonadi	<Frank/Sebastian>
IN PROGRESS	Account creation wizard	as discussed in Berlin, see below	<Volker,Laurent>
IN PROGRESS	KMail port	KMail using Akonadi	<everyone>
IN PROGRESS	Remote Search	Delegating searches to resources, see below	<Volker>

Post KDE 4.5 /Akonadi 1.4

This stuff is currently not considered for 4.5 due to lack of resources. Of course it will be added nevertheless if someone implements it. The list is completely unsorted.

Status	Item	Description	Contact
TO DO	Error reporting	Akonadi::Job basically has only one error code: Unknown	<Tobias>
IN PROGRESS	Port KNotes	File resource, serializer plugin, KNotes application, Kontact plugin	[mailto: <>]
TO DO	Batch job to retrieve a set of items from Akonadi	Those items don't belong to the same collection, rather they are located in different collections	[mailto: <>]
TO DO	CollectionFetchJob/ItemFetchJob should be able to retrieve entities by flags/mimetype	This is problematic with change notifications, as they have to know about the filtering with the \Seen flag as well. This type of filtering would be possible with full Nepomuk interface though. We don't want yet another query language here. The plan is to fix the nepomuk agent and use that as semi-public interface for now.	[mailto: <>]
TO DO	Nepomuk integration	Generic Item tag/rate/comment, etc.	<Tom>
TO DO	Sync collection tree after creating setting up a resource	see AgentInstanceCreateJob	[mailto: <>]
TO DO	Support standard commands for QUndo framework		[mailto: <>]
TO DO	Conflict detection in resources	See Osnabrueck meeting notes for details	[mailto: <>]
IN PROGRESS	Action framework	see below	Volker <[email protected]>
IN PROGRESS	Fix API docs	The libakonadi move as well as the huge API changes following it broke lots of the docs technical and content-wise, see below	<Tobias>
IN PROGRESS	Migration	Data and settings from pre-Akonadi times, see below	[mailto: <>]
IN PROGRESS	Extended notifications	Item change notification do not yet include their source collections (real and virtual)	[mailto: <>]
TO DO	Alternative for Akonadi::ResourceBase	Not using the scheduler to avoid the serialization of operations, see RSS resource. (This will get very complicated. Maybe use a proxy ResourceBase for this, which is thread-pooled?)	[mailto: <>]

Supported Types

Overview on the current state of support for various types:

Type	Serializer	Multipart Support	Models	Views	Resources	Notes
Email	yes	partial	MessageModel, MessageCollectionModel, threading proxy model	?	maildir, IMAP	threading agent
News	yes (1)	partial (1)	(1)	(1)	NNTP
Contact	yes	no	ContactModel	-	vCard, facebook, KRes
Events	yes	no	EventModel	-	iCal, KRes
Notes	no	no	-	-	-	not started yet
Feeds	yes	no	Feeds, Items	?	OPML	GSoC in playground/pim
Bookmarks	yes	no	-	-	local bookmarks, del.icio.us

(1) see Email

Mail specific extensions

Status	Item	Description	Contact
TO DO	Share mail flag code	Standard actions, standard flag enum/constants, Nepomuk interaction	[mailto: <>]

Event/Todo/Journal specific extensions

Status	Item	Description	Contact
TO DO	Todo proxy model	See KOrganizers To-Do view	<Bruno?>
IN PROGRESS	Subtype identification	See discussion on kde-pim mailinglist	<Kevin?>
TO DO	Agenda view	KOrganizer agenda view based on Akonadi	<Bruno?>
TO DO	Month view	KOrganizer month view based on Akonadi	<Bruno?>
TO DO	Timeline view	KOrganizer timeline view based on Akonadi	[mailto: <>]

Resources, Agents and others

Status	Item	Description	Contact
DONE	KResource Akonadi bridge	for applications using KCal or KABC	Kevin <[email protected]>
DONE	Akonadi KResource bridge	for data accessed through KCal or KABC resources	Kevin <[email protected]>
TO DO	Expire Agent		[mailto: <>]
DONE	MBOX Resource		<Bertjan>
DONE	Extend IMAP Resource		<Kevin/Andras>
IN PROGRESS	POP3 Resource		<Thomas>
IN PROGRESS	RSS Resource	in akonadi-ports branch (Details)	<Dmitry/Frank>
IN PROGRESS	Filter Agent		<Szymon>
TO DO	Search		[mailto: <>]
TO DO	History resource		[mailto: <>]
IN PROGRESS	Filter Rule GUI	Used by filters and searches	<Szymon>

Resource status overview (this should list all resources existing in KDE3 or already under development for Akonadi):

Resource	Retrieve Collections	Retrieve Items	Change Collections	Change Items	Configuration	Notes
iCal	yes (4)	yes (1) (2)	no	yes	yes	remote file support, file watching with conflict handling
vCard	yes (4)	yes (1) (2)	no	yes	yes	remote file support, file watching with conflict handling
maildir	yes (1) (4)	yes (1) (2)	?	?	yes
mbox	no	no	no	no	no	not started yet, code exists in KMail
IMAP	yes (1) (4)?	yes (1) (2)	no	no	no	code exists in kio_imap4 and Mailody, support for extensions: quota, ACL, annotations missing, what about Kolab and Scalix?
NNTP	yes (4)	yes (2)	n/a	n/a	yes	Needs support for local collection names and collection hierarchy
Local Bookmarks	?	?	?	?	(3)	Code in akonadi/resources
OpenChange	?	?	?	?	?	Code in akonadi/resources
Facebook	?	?	?	?	?	Code in playground/pim
del.icio.us	?	?	?	yes	no	Code in playground/pim
KABC	yes(6)	yes	no	yes	yes
KCal	yes(6)	yes	yes(7)	yes	yes

only full sync supported currently, need optimization
does not yet honor cache policy
still relies on QSettings for configuration and/or doesn't provide configuration over D-Bus
does not yet provide correct access control settings
only adding new items, not changing existing ones
availability of child collections depend on whether the KResource plugin has subresources
child collections can be added or removed if the KCal plugin can have subresources

KResource Migration Status

Everything without migration support is implicitly converted to use the compat bridge currently.

KABC migration status

KResource	Feature equivalent agent	Migration support	Notes
directory			vCard dir in development
file	vCard file	4.2	binary format no longer supported, migrated to compat bridge instead
groupdav
groupwise
kolab
ldapkio
net	vCard file	TODO
scalix
slox
xmlrpc

KCal Migration Status

KResource	Feature equivalent agent	Migration support	Notes
blog
bugzilla
groupdav
groupwise
kabc (birthday)	birthdays	4.3
kolab
localdir
local	iCal file	4.2
remote	iCal file	TODO	remote supports different URLs for upload and download, the iCal file agent doesn't, is this needed at all?
featureplan			probably obsolete since we don't use the XML featureplan anymore
scalix
slox
xmlrpc

Akonadi Braindump

Ideas/notes etc. on various open issues in Akonadi.

Akonadi Standard Actions

Idea: Have something like KStandardAction for Akonadi that not only includes the representation of the action but also its state management and the actual operations. Like libakonadi that should be splitted into a generic, type-independent part and be extensible for type-specific actions. This will enable code sharing among many applications and guarantee consistent actions everywhere.

State management: watch selection models of a collection and/or item model.

Use KXMLGUI for context menus in standard views to allow easy extensibility with custom actions.

Generic actions:

new collection [done]
new virtual collection
delete collection [done for single selection]
copy collection [done]
cut collection
paste collection [done]
synchronize collection [done for single selection]
synchronize resource
synchronize everything
show collection properties dialog [done]
delete item(s) [done]
copy item(s) [done]
cut item(s)
paste item(s) [done]
paste native data
tag item(s)
comment item
rate item(s)
configure resource
add resource? (would need a type parameter, etc.)
delete resource
manage local subscriptions [done]
move to submenu
copy to submenu

The list is definitely long enough to make this worthwhile.

Collection Model / Collection View

Ideas/missing features/bugs of the collection model/view:

Enable/disable status columns
Show status after the name (see KMail)
~~Size column~~
Save/restore layout
~~Custom collection icons (see KMail, also needed for resource defined special folders (eg. Inbox)~~
Status tooltips (see KMail in 3.5.9) [still missing quota info]
Quick search
~~Favorite folder view as proxy model on top of the normal collection model (FlatCollectionProxyModel might be helpful for there)~~
Accumulated statistics (unread, total, size)
Fix dnd: move/copy/cancel menu always shows up and never has any effect

Compatibility

Notes on how to keep long-term protocol, source and binary compatibility.

~~Detect server version in Akonadi::Session, might be useful in case of protocol extensions/changes~~
What about database server version updates?
~~Versioning or any other kind of serialization format meta data, we'll need that in case of changes in serialization formats (see eg. Robert's compression patch where this is needed)~~
~~We currently use 32 bit ids, probably hard to change later on, is that enough?~~
~~Plugin versioning~~

Resource API issues

Notes/ideas/complaints about the Akonadi::ResourceBase API:

Extremely error prone:
- Scheduler dead-locks when a requested operation is not correctly announced as finished, esp. a problem in error cases.
- Using the result methods multiple times or when not requested asserts
~~Item streaming is missing, requiring all data to be in memory at once~~
Non-incremental updates need to know the results of ItemSync to not have to provide all data, even for already existing/unchanged items.

API / BC issues

Smaller stuff that should be fixed before the ABI freeze and is not yet listed above:

Cleanup the D-Bus format used by NotificationMessage
No mentioning of "IMAP" in the public API, we are not using IMAP
Naming and installed location of libraries, headers and executables (see discussion on kde-pim ML)
~~Payload part labels are QStrings, attribute types are QByteArray~~

Deployment issues

Multiple access: Should multiple Akonadi instances' mysqlds access a single set of data files the mysql will likely corrupt the data. This can happen in any NFS+YP installation where users can log onto any machine and access shared homes. MySQL relies on filesystem locking to prevent multiple access. MySQL multiple instance docu.
InnoDB tables should not be used on NFS.
NFS speed: MySQL documentation recommends against locating its data files on network shares.
AppArmor: Distros' AppArmor profiles prevent MySQL from writing outside its defined data directory (usually /var/lib/mysql). This is a problem at least with *buntu and openSUSE. These will need to be adapted. It is possible to daisy-chain profiles so that MySQL started by Akonadi receives a different profile to MySQL running standalone. An empty profile has all rights. Another possibility is to adapt the general MySQL profile so it can write to ${XDG_DATA_HOME}/akonadi(usually ${HOME/}.local/share/akonadi). Both support for profile chaining and ${HOME} may depend on the version of AppArmor installed. What about SELinux?
Backup: MySQL data files should not be backed up without telling the mysqld process, otherwise a corrupt backup will be made. LOCK TABLES and FLUSH TABLES at the least. A dump can be made or mysqlhotbackup may be used in some circumstances. We should consider sysadmins' backup techniques when planning/promoting Akonadi, as a simple rsync cronjob with running Akonadi will not work. MySQL backup advice.

Account Creation Wizard

Notes on the resource configuration wizard discussion.

WizardBase class
Wizard discovery via .desktop files
A wizard can configure multiple resources (eg. IMAP + LDAP for Kolab) and non-resources (mailtransport)
Optionally hide resources completely covered by wizards in the Add Account dialog
List wizards in the Add Account dialog
Store Account -> Resources information to offer deletion of depending resources

PostgreSQL Support

Has been merged for Akonadi server 1.3. We still need a volunteer for continuous testing and maintenance though.

Documentation

Avoid examples using KJob::exec() due to its problematic side-effects.
Examples in the ItemCreateJob docs (and maybe others) operate on items in the root collection which does not work at all
Resurrect the server API docs
Content of http://api.kde.org/4.x-api/kdepim-apidocs/akonadi/html/index.html should probably be moved to server or client lib docs

Migration of pre-Akonadi data and settings

KCal/KABC
- switch KRes resources to Akonadi KRes compat resources, use KRes Akonadi compat resource, basically injecting Akonadi inbetween
- Replace Akonadi KRes compat resources with their ported equivalent
- Application side does not need migration code, "only" port to Akonadi
KMail
- Should migrate to one resource per account + one for previous local folders
- Problem: local folders are mixed mbox/maildir
  - Dedicated KMail compat resource?
  - Convert everything to maildir first?
- Flags are stored in proprietary binary format
KNode
- Migrate every account to NNTP resource
- Local flags should be preserved, stored in proprietary binary format
- Local subscription state should be preserved (where is that stored?)
- Local folders using MBOX format + proprietary binary index
Akregator

Search & Virtual Collections

Got their own page by now:

KMail Breakdown Plan

The current plan is to put some parts of KMail into a stand-alone library, independent of KMail. This increases code reuse (for example, the message composer could be shared with Mailody) and makes the code a lot easier to maintain and to port to Akonadi.

Status	Item	Description	Contact
TO DO	Bodypart formatters		[mailto: <>]
IN PROGRESS	Reader Window		<Andris>
IN PROGRESS	Composer: Message Composer		<Constantin>
IN PROGRESS	Composer: GUI Window		<Constantin>
DONE	Queue Manager for mailtransport		<Constantin>
TO DO	Templates: Core		[mailto: <>]
TO DO	Templates: GUI		[mailto: <>]
TO DO	Port KMCommands		[mailto: <>]
TO DO	Port away from KMMessage and KMFolder* everywhere it is left	An idea might be: wrap KMMsgBase/KMMessage inside a reference counted Message class. Insulate everything else from it by wrapper functions. KMFolder should be easier...	[mailto: <>]
TO DO	Migration application for index and other config		[mailto: <>]
TO DO	Port MDNs		[mailto: <>]

The Road to World Domination

Sort of related so the stuff above but with a scope for all of KDE PIM and beyond.

Status	Item	Description	Contact
TO DO	Share identity config GUI parts	eg. the signature configuration widget	[mailto: <>]
DONE	Mailtransport Agent	Global shared outbox, central mail sending instance	<Constantin>
TO DO	Recently sent to support in mailtransport	related to above, based on Akonadi/Nepomuk	[mailto: <>]
IN PROGRESS	Composer engine	Shared stuff for KMail/KNode/Mailody: Crypto, editor, editor actions, attachment model, message assembly, etc.	<Constantin>

Akonadi FAQ

This FAQ primarily deals with technical and design questions, if you have questions about using Akonadi (such as "I get error X when starting Akonadi"), please refer to userbase.kde.org/Akonadi.

Where do I find the Akonadi config files?

~/.config/akonadi/

Where does Akonadi store my data?

Akonadi merely acts as a cache for your data, the actual content stays where it has always been, .ics/.vcf/MBOX files, local maildirs, IMAP- and groupware servers. There is only a limited amount of data stored exclusively in Akonadi:

Data not supported by the corresponding backends, such as email flags in case of maildir/mbox. This is comparable to KMail's binary index files stored alongside these files in pre-Akonadi times.
Internal meta-data used by application or resources, such as information about the last synchronization with a backend or translated folder names.
Data that has been changed while the corresponding backend has been offline and has not yet been uploaded.

Where can I find the Akonadi database?

~/.local/share/akonadi/

Where can I find the source code?

There are three different parts of source code:

The Akonadi server, which is KDE-independent. Currently, the code can be found at kdesupport/akonadi. The server code will likely move to the freedesktop.org project in the future, the move has already been requested.
The Akonadi KDE client libraries are in kdepimlibs/akonadi.
Various agents, resources, the Akonadi console and much other misc stuff is in kdepim/akonadi

Where can I find documentation?

The documentation is mainly in the code itself, in the form of doxygen comments. You can find the generated documentation on [api.kde.org api.kde.org], for example:

General documentation, including a design overview, is here

Note that some links in the above documentation which point to the server or the KDE client libraries are currently broken, use the links below to access that documentation.

Documentation for the KDE Akonadi client library is here
Documentation about the server is here

Which DBMS does Akonadi use?

So far only MySQL. There is some work on PostgreSQL support going on though. Basically, every database that is supported by QtSQL can be used, requiring minimal changes in the code at most. However, not all of them provide the features needed by Akonadi (see next two questions).

Why not use sqlite?

We tried. Really. It can't handle the concurrent access very well, in the best case this means very slow operations, but we've also seen deadlocks and failing transactions. Once that's fixed in sqlite, adjusting Akonadi to use it again instead of MySQL is no problem.

Why not use MySQL/Embedded?

We tried that as well, there are two reasons for not using it: No support for the InnoDB engine (which we need for transaction support) and poor availability (only OpenSUSE provided usable packages, needed a patched QSQL driver).

Do I need a running MySQL server?

No. Akonadi starts its own local MySQL server (unless configured otherwise, see next question). All you need is having the 'mysqld' binary installed at runtime (usually found in the mysql-server package of your distribution).

Can Akonadi use a normal MySQL server running on my system?

Yes, it can. You find the corresponding settings in ~/.config/akonadi/akonadiserverrc.

I don't like a database server because of backups/running on NFS/etc.

See section "Deployment Issues" above, we are aware of that and working on it. Some of these, like backup/restore are already implemented. But please be aware that most of this issues also existed before (eg. with KMail's custom binary indexes).

Can a single Akonadi instance be used by multiple users?

No. There has to be one Akonadi server instance per user. However, it is possible to use a shared database server.

Can I access the Akonadi server on a remote machine?

No. Akonadi is not a groupware server. It's a local cache only.

What's the differences between Akonadi and EDS?

EDS is limited to contacts and calendar data, Akonadi is type-independent. Especially, Akonadi is designed to also handle high-volume data such as email. Akonadi and EDS also differ largely in their access protocol on a technical level (Corba/D-Bus vs. local socket with IMAP-like protocol/D-Bus) and also on a protocol level (type specific vs. generic).

How do I create a collection?

From the developers point of view, there is Akonadi::CollectionCreateJob for that, from the users point of view, most applications allow that, eg. Mailody or akonadiconsole.

However, there is one limitation: Top-level collections can only be created by resources, not by normal applications. The reason for that is that every object (collection or item) is supposed to have an owning resource, that is a resource that is responsible for storing and retrieving that object. There is an ongoing discussion to remove this restriction though.

So, if you want to create a collection eg. for testing purposes, add a resource first. Most Akonadi applications offer an option to do that, a module for KControl is planned as well.

How do I disable automatic migration from KDE's traditional framework?

The migration tool is controlled by standard KDE configuration file called kres-migratorrc.

Distributors or system administrators wanting to disable the automatism will probably want to that globally, e.g. by editing the installed default configuration file, or by using KDE's configuration hierachy and using a profile config between that and the user level.

The quickest way to deactivate it for one user account only is to use KDE's kwriteconfig tool to set the respective configration value with a simple copy&paste of the following command:

kwriteconfig --file kres-migratorrc --group Migration --key Enabled --type bool false

Please note that at some point KDE applications such as Kontact, KOrganizer, KMail will be using Akonadi directly, at which point migration either has to be enabled or performed manually.

As of KDE 4.4 (and its development releases and when building from SVN trunk) this already applies to KAddressBook and KMail's address book access.

How do I completely disable Akonadi startup?

Warning

If you already have applications natively using Akonadi, you of course can't disable Akonadi startup. KAddressBook (as of KDE 4.4 and its test versions), Mailody, KMail (as of KDE 4.4 and its test versions for address book related things) and KPilot are applications that are already based on Akonadi.

Other applications, like KOrganizer, are not based on Akonadi yet, at the time of writing. Instead, they use the old KResource framework for storing contacts, calendars and notes. During the KDE 4.2 beta time, these KResources were automatically migrated to Akonadi-based KResources, the so-called Akonadi compatibility resources. Therefore, applications like KOrganizer would use Akonadi indirectly through KResources, and therefore would start the Akonadi server when being started.

If Akonadi doesn't start up correctly for you, the following should help you to disable Akonadi startup and use your old KResources again.

First, disable automatic migration like described in the above FAQ entry. Then, open System Settings, go to the Advanced tab and open the KDE Resources config panel. There, you can configure which type of KResources are used for contacts, calendars and notes. If the migration to Akonadi was successful, you'll probably only see the Akonadi Compatibility Resource as an active resource, and all others disabled.

To disable Akonadi startup, enable your old resources again, then disable and delete the Akonadi compatibility resource.

What is the relation between Akonadi and OpenSync?

Akonadi and OpenSync focus on different aspects and complement each other. Akonadi provides a unified way to access PIM data for applications and a framework to implement powerful connectors to varies data sources. OpenSync focus is on syncing two sets of PIM data.

An Akonadi plugin for OpenSync is currently under development, allowing to sync PIM data available through Akonadi with any other system supported by OpenSync, especially mobile phones.

When should I use Akonadi?

More precisely, when should you use for your application specific data instead of eg. just using a local file directly.

Akonadi is especially useful when you need one the following:

Different backends for your data, like eg. a local file and a remote server. Akonadi provides a unified interface for application developers to access your data independent of the actual backend.
Caching and change replay of remote data. Akonadi has support for that built in, giving you free offline support for any remote backend.
Desktop-wide sharing of your data. As soon as more than one application (say your main applications and a plasmoid) accesses the same data you need to deal with locking, conflict detection, change notifications, etc. - or let Akonadi do that for you.

However, if you are just looking for a simple way to store your application data without needing one of the above, using Akonadi usually means more implementation work for relatively little gain.

Akonadi needs too much space in my home directory!

An empty, unused Akonadi database needs about 100 Mb of disk space. This is due to the MySQL InnoDB log files which work similar to a journal in a modern file system. These files are constant in size and independent of the actual data stored in Akonadi. The default size is optimized for performance on average desktop hardware where the use of 100 Mb of disk space is no problem. In other cases, such as multi-user systems or embedded devices, this default might not be optimal though.

The default size can be configured, globally or per-user. The global configuration file can be found in $PREFIX/share/config/akonadi/mysql-global.conf, the per-user file is in ~/.config/akonadi/mysql-local.conf and overwrites settings of the global file. In any of these files, you can change the settings innodb_log_file_size and assign it a smaller value than the default (64M).

For this setting to take effect you need to restart Akonadi. With older Akonadi versions (<=1.1.1) you might need to manually remove the InnoDB log files from ~/.local/share/akonadi/db_data for this change to take effect. The log files do not contain data after a clean shutdown and thus can safely be removed while Akonadi is not running.

An alternative approach especially for multi-user systems might be the use of a single, global MySQL server instance.

My Akonadi resource seems to randomly hang/stop working!

A very common problem of resources based on Akonadi::ResourceBase are "unguarded exit paths" from one of the methods you have reimplemented there. See the following example:

void MyResource::retrieveItems( const Collection &collection ) {

 if ( someError )
   return;
 itemsRetrieved( myItems );

}

In case of an error you leave retrieveItems() without telling Akonadi::ResourceBase that you are done with the task. Therefore, it is assumed the requested item retrieval takes a bit longer (which is not uncommon for resources for remote backends, results typically come in in a result slot connected to a job class for example) and waits until you announce the task is finished.

The following example does it correctly:

void MyResource::itemAdded( const Akonadi::Item &item, const Akonadi::Collection &parent ) {

 if ( noNetwork ) { // transient error
   deferTask( i18n( "Offline, will retry later." ) );
 } else if ( item_not_valid ) { // permanent error 
   cancelTaks( i18n( "Got invalid crap, can't store that." ) );
 } else {
   // store the item here
   Item newItem( item );
   newItem.setRemoteId( my_new_remote_id );
   changeCommitted( newItem );
 }

}

The following methods require explicit notification that a task has been completed:

retrieveX
any method indicating changes, ie. itemAdded|Changed|Moved|Removed(), collectionAdded|Changed|Moved|Removed()
any custom task scheduled with ResourceBase::scheduleCustomTask()

Refer to the API documentation of Akonadi::ResourceBase for the various ways to do that correctly, there are a few different ways, depending on the current task:

Successful completion with convenience features, eg. changeCommitted(), itemsRetrieved() etc.
Error cases with convenience features, eg. cancelTask(), deferTask()
Only indicate completion, with everything else done manually, eg. changeProcessed(), taskDone()

To confirm a resource is affected by this problem, the "Resource Schedulers" tab of akonadiconsole is very useful (needs to be enabled in the context menu first, causes too much slowdown otherwise). It shows the state of the internal task scheduler of your resource, allowing you to spot stuck tasks.

@@ Line 657: / Line 657: @@
 * Meetings
 ** [[Projects/PIM/Akonadi/Meeting2008-11|Halloween Sprint 2008]]
-** [[Projects/PIM/Meetings/Osnabrueck_7|Osnabrueck 7]]
+** [http://community.kde.org/KDE_PIM/Meetings/Osnabrueck_7 Osnabrueck 7]
 ** [[Projects/PIM/Akonadi/Meeting2009-04|Akonadi April Sprint 2009]]
 ** [[Projects/PIM/Meetings/GCDS_2009|GCDS/aKademy 2009]]