The document discusses different methods for installing Drupal globally to serve websites around the world. It explains that network latency makes sites seem sluggish over 300ms and recommends serving each continent locally. For anonymous traffic, it recommends using a CDN or local Varnish caches. For sites with user logins and writes, it describes replicating writes from a master database to slaves or using a MySQL multi-master replication ring with GTIDs to allow local writes and synchronization. Application level syndication is also an option but not for full site replication.

1. Installing Drupal globally
Kalle Varisvirta
Technology Director
Exove
@kvirta

2. Prerequisites?
Moderate knowledge of Drupal and its architecture
Moderate understanding of PHP, MySQL, Varnish and
hosting of this software

3. What you’ll learn
in this session?
Why do you need to serve the whole world with a
single Drupal installation?
How can it be done?
What are the pros and cons of each method?

4. Why distribute?
Isn’t the internet already,
like, global?

5. HTTP GET

6. Traveling around
the world
takes time

7. 200 OK
...but the data has
to come back, too

8. Scandinavia - Japan
350 - 400 ms
US - India
250 - 300 ms
UK - Australia
300 - 350 ms
Network latencyICMP round-trip

9. Why is latency bad?
ICMP (ping) round-trip isn’t the whole truth
Over 300 milliseconds of network latency will make
your lightning-fast website seem sluggish
All continents your site is in business with should be
served with a local server

10. Anonymous traffic onto a Drupal
site?
Easy.

11. Anonymous traffic
Use a CDN to cache your site
No CDN? Install a local Varnish on all continents, use
GeoDNS for directing traffic to the local copy
Don’t replicate data if you’re just focusing on
anonymous. Totally not worth it.

12. Master
CDN
edge
CDN
edge
CDN
edge
CDN
edge
Writes to master
One master with CDN

13. Does everybody do it?
host www.heraldsun.com.au
www.heraldsun.com.au is an alias for
fw.heraldsun.com.au.edgesuite.net.
fw.heraldsun.com.au.edgesuite.net is an
alias for a1501.g.akamai.net.
a1501.g.akamai.net has address
184.85.223.139
a1501.g.akamai.net has address

14. Drupal-driven community site with
a lot of write traffic?
You’re in for some configuration,
installation and tuning.

15. It’s always about the
MySQL

16. Syndicating Drupal /
write traffic
Two options:
Write to master, replicate to local
Write to local, synchronize the world

17. Write to master,
replicate to local
PHP can read-write split MySQL traffic
Not problem-free on Drupal, needing a tiny hack to
core
Files can be synced with rsync, as long as writing only
happens towards the master

18. Master
Slave
Slave
Writes to master
One master, replicated
slaves, read/write split on
database level

19. Write to master,
replicate to local
Cons
Writes take quite a while, so posting comments
might seem very slow
Surprisingly many things in Drupal write to the
database
Due to replication lag, the sites might be slightly out
of date every once in a while

20. Write traffic
Two options:
Write to master, replicate to local
Write to local, synchronize the world

21. Write to local,
synchronize the world
Writing to local and synchronizing the world has been
very hard to accomplish
Master-master replications have been usually third-
party systems, like Galera
In MySQL 5.6 there’s a new possibility, MySQL GTID-
based replication ring with multiple masters

22. Write to local,
synchronize the world
GTIDs are Global Transaction Identifiers and with them,
we can create a multi-master replication ring topology
In replication ring topology, all MySQL nodes work as
slaves to the previous nodes, adding local writes to the
transaction log stream, thus being master for the next
node
With GTIDs in place, multiple masters have their own
ids in the transaction log and the transaction items
won’t collide

23. Write to local,
synchronize the world
Replication ring allows fast writes to local and fast read
from local
For Drupal, this is invisible
Only change needed is to make MySQL ignore
collisions in the cache table

24. Master
Master
Master
Multi-master MySQL ring
topology (GTID)

25. Write to local,
synchronize the world
Files can be synced with file syncing filesystems, like
GlusterFS
We’ve found Unison to be most robust and giving the
least overhead to the filesystem
Unison is just a piece of software syncing filesystems
on disk - not a filesystem itself

26. But, hey.
I only have couple
of things to syndicate.

27. Application level
syndication
Distribute content via Drupal’s own syndication
methods
Works for some content, but not nearly everything
All sites are separate and have to be configured
separately
Works for, say, country sites wanting to show the
corporate news, ie. partial content

28. Application level
syndication
Feeds can be used to both feed and import
Services can be also used, but requires either
queuing or both servers up at all times
HTTP connections over the world can be
surprisingly unreliable

29. Recap

30. Recap
Distribute if you serve the world
There are no tricks to fool the speed of light

31. Recap
For anonymous, use a CDN
For logged in users, choose the right solution for the
task
For a lot of writes, you need to write locally and
synchronize the world
If you do that, MySQL GTID multi-master ring
topology works

32. Recap
Application level integration between the Drupals can
be done
Just don’t try to syndicate everything
Make sure you don’t try to syndicate too much at a
time
Feeds works, Services works

33. Thank you!

34. Questions?
Thank you!