[mirror discuss] Re: mirrorbrain for sugar labs

Peter ask me to continue a private thread on this mailing list.  Also
CCing Matthew Zeier from mozilla infrastructure.  I was looking for
Mozilla's solution and he pointed me in the direction of mirrorbrain.

On Thu, Sep 24, 2009 at 5:25 PM, Peter Pöml <poeml_at_cmdline.net> wrote:
> Hi David!
>
> thank you for writing. Interesting to learn about Sugar. It sounds exciting!
>
> Would you mind me resending my reply with the MirrorBrain mailing list
> Cc'ed, and continue discussion there? I think it would be great material for
> the list and could provide insight to others. It's also great to see some
> activity there :-) (If not, no problem at all.)

done

> On 24.09.2009, at 22:33, David Farning wrote:
>>
>> I am looking at using mirrorbrain as the CDN for wki.sugarlabs.org .
>> We are still pretty small we generally have 200G per day but peak at
>> 32000G per day during releases.
>
> That's not nothing ;) I'd say it is an amount where a carefully set up
> infrastructure with mirrors makes sense. Also, it sounds like there would be
> a lot of users that one wants to keep happy, and who would benefit from
> every improvement. And from looking

We are currently running our infrastructure from the FSF's colocation
facility.  So I include keeping our generous host happy pretty high on
the list.

>> On normal day the majority of our traffic comes from
>> activities.sugarlabs.org . a.sl.o is based off of mozilla's amo so
>> anything we do here help them.
>
> I see, http://activities.sugarlabs.org/ is very similar as
> https://addons.mozilla.org/, and it offers download links to lots of .xo
> files, and redirects to
> http://download.sugarlabs.org/sources/activities/ from where the files are
> downloaded.
> For now, I only note the redirection to d.sl.o, and no further redirection
> from there.
>
> I also see other downloads, like
> http://wiki.sugarlabs.org/go/Sugar_on_a_Stick which links to some mirrors.
>
>> We have a small collection of mirrors that help us during releases.
>> But, the user must manually chose between mirrors. Agggg.
>
> Okay, so from what I would guess at this stage is that d.sl.o could redirect
> to the mirrors, instead of delivering the .xo files all by itself; correct?
> That would be exactly where MirrorBrain is could step in.


Yes, the two main pieces are the sugar on a stick images and the .xo files.

>> My questions are:
>> 1. Is it worth it to use mirrorbrain at this stage?  Particularly
>> around releases.
>
> Yes, definitely, the only thing to keep in mind is that deploying it costs
> time, but I would think that it is worth the effort. If you have very few
> mirrors, it can be the life-saver for the releases -- and if you gradually
> get more mirrors, it will improve the service quality for the end users
> because they can usually be routed to a better mirror.

Yes,  this is particularly important because many of our large
deployments are in remote regions.  Something like 80% of our .xo
traffic is from Uruguay.

> The effort in deployment is mainly in building and installing the software
> and its different components. This is certainly doable and I'm happy to help
> with it. If you run, say, purely on a CentOS5 based shop with aged Apache
> and complicated deployment procedures, it can be difficult, but d.sl.o
> rather seems to run Apache/2.2.11 on Ubuntu, which means that Apache is new
> enough, and everything else will be available as well I guess. I would
> actually like to build MirrorBrain packages on Ubuntu, and that might be a
> reason to do that maybe?

Everything except the build farm is Ubuntu.  Ubuntu packages would be
nice.  But I am willing to build from scratch.

>> 2. How will mirror brain interact will a.sl.o(AMO)?  Will new
>> activites just be served from that primary node until mirrorbrain runs
>> a scan to verify the the new activite has been rsynced to a mirror
>> node.
>
> MirrorBrain needs the file tree locally and can work off it as a normal
> Apache. If it doesn't know a mirror for a file, Apache will just deliver it
> as normal; if a mirror is known, Apache will redirect to it. Therefore,
> publishing new files is just a matter of putting them into the file tree.
> Later, mirrors will catch up, and as soon as they are scanned, Apache will
> know about the presence on the mirrors and redirect to them.

Ok great, so then we can modify the rsync so that only popular files
are mirrored.  a.sl.o keeps every version of an activity in the main
tree for historical purposes.  But there is no reason to keep copies
on the mirrors.

> If large amounts of content are published at once, it can be useful (or even
> needed) to first publish them only for the mirrors, by putting them into a
> stage area that they can access, and later update Apache's file tree, when
> they are distributed enough. Another regime (useful if the file tree is
> large and gets frequent, small updates) could be to push-sync files as soon
> they come in, and directly scan after each push.

Ok, we can figure that out.  It would be cool if a.sl.o could trigger
the push when ever a new activity is added.

> Maybe there is even an existing release infrastructure that one could
> integrate with.

We are not that fancy yet.

>> 3. How does mirrorbrain work with mysql? Do the admin framework and
>> tool set work with mysql yet?
>
> At the beginning of this year, I abandoned MySQL support in all the tools,
> but the core (the mod_mirrorbrain Apache module) will work. The tools to
> maintain the mirror database won't work, and while this could probably be
> fixed, I can say that when the list of mirrors is not long, and one is
> proficient in the mysql commandline, it is certainly possible to maintain
> the mirror data manually with the mysql client. I did so for a long time in
> fact, before I finally started to write some tools.
>
> I would recommend to use PostgreSQL because that will result in a setup that
> is clean and as documented, and also the database will be self-contained and
> low-maintenance enough that it would matter much to anyone which database is
> used underneath.
>
> However, mod_mirrorbrain will happily use MySQL as file database. I am
> *quite* sure that the scanner script also still works with MySQL, but I
> can't promise, as I haven't tested it since I did the switch to PostgreSQL.
>
> I decided to switch to PostgreSQL because Apache's DBD framework cannot use
> two different databases in one vhost yet, and I needed a special datatype in
> PostgreSQL to implement mod_asn (which you won't need with only few mirrors;
> don't bother to install it). I was aware that it might put off some people
> that are more familiar with MySQL, but I can speak very positively about
> PostgreSQL, it is a great piece of software and it was a pleasurable
> experience to me to get acquainted with it. I am happy to help with that;
> it's not difficult, just a little different.

Using postgresSQL is not a blocker.  So we can worry about that later.

> It would of course be an option to re-implement MySQL support and PostgreSQL
> at the same time, but my time has been to scarce so far to even consider
> this, as there are other things that would seem more important, as e.g. the
> lack of a web interface, that I would like to tackle.
>
>
> Does this help further?

So, I guess my next steps are:
1. set up a opensuse VM and install mirrorbrain to see how it is
suppose to work.
2. Set up a ubuntu VM matching the sugar labs infrastructure and
install mirrorbrain.

I'll try to do that this weekend.  I am sure I will have questions

david
> Peter
>

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