Re: [Tracker] Tracker in RTOS

[Philip Van Hoof <spam pvanhoof be>]

On Tue, 2010-05-11 at 12:06 -0700, Remo Remo wrote:
> Hi,
>
> i have been going through web to find out whether i can integrate
> tracker for indexing & searching for emails,multimedia,sms,contacts in
> an Real-Time Operating System or low-memory embedded environment.

As long as you don't make tracker-store and tracker-miner-fs processes
that are ran as SCHED_IDLE (or the schedule priority for RT tasks, if
that's different on your system), else they might force the processes
for which you are using an RT operating system to be scheduled at a
lower priority than tracker-store and tracker-miner-fs (and that doesn't
sound very good to me, as that way you basically loose the certainties
for which you chose an RT operating system).

For very low latency & fast response times we are investigating direct-
access to our SQLite database. This will require implementing a custom
page cache implementation for SQLite which we haven't finished yet. I'm
mentioning this because once that direct-access mode is available, you
can let your queries be executed by processes with RT priority (without
having to involve tracker-store's process).

Right now, however, when you do a synchronous query to tracker-store
from a RT process, I think you'll automatically yield (as your process
will end up waiting on a unix socket in libdbus, and that's afaik a
yield already). So no problem here. But ...

When using asynchronous queries you might have to let the RT prioritized
process yield itself manually. Check out sched_yield().

Else I think you can deadlock yourself.

> I am not getting why tracker is using sqlite if it's managing its own
> RDF-based in-memory data-store.

Because Tracker isn't managing its own RDF-based in-memory data-store..

Tracker's store is using SQLite for storing the RDF triples (and doesn't
have any in-memory data-stores). Tracker also has a persistent journal,
but this journal is only used for backup/restore and journal replay. Not
for accessing the data during operation.

We have no plans to implement our own RDF-based in-memory data-store.

> should i be able to define my own metadata for particular format &
> from where i can retrieve metadata to process/stored it in list in
> another application.

I don't know what you mean. Can you give your exact use-case?

Cheers,

Philip

-- 


Philip Van Hoof
freelance software developer
Codeminded BVBA - http://codeminded.be