1. Kazuhiro Ogura
@goura
小椋 一宏

2. Building a Minecraft
Server for Families
(Using AutoScalingGroup)
Kazuhiro Ogura
HDE, Inc.

3. Of course you know
about Minecraft

4. http://www.gamespot.com/articles/minecraft-passes-100-million-registered-users-14-3-million-sales-on-pc/1100-6417972/

5. http://www.wired.co.uk/news/archive/2014-03/13/minecraft-cloudmaker

6. I’m playing this game
for about a year

7. …with my 7-years old son

8. Minecraft is not an MMO

9. But It’s an MO
(Massive Multiplayer Online Game)

10. P2P Play
PC
(Host)
PC
(Guest)
PC
(Guest)
PC
(Guest)

11. Not for a kid/dad who
doesn’t live in the same
timeframe

12. Dedicated Server
Server
(Host)
PC
(Guest)
PC
(Guest)
PC
(Guest)

13. minecraft_server.jar
• Free
• Distributed as a jar file (Need JRE to run)
• Official version from Mojang,
open source clone also available (Bukkit)

14. So I started like this

15. Server
(Host)
My PC
(Guest)
Kid’s PC
(Guest)
Sakura VPS
RAM: 512MB
Daytime

16. Server
(Host)
My PC
(Guest)
Kid’s PC
(Guest)
Sakura VPS
RAM: 512MB
Nighttime

17. Server
(Host)
My PC
(Guest)
Kid’s PC
(Guest)
Sakura VPS
RAM: 512MB
Weekends

18. This worked
for a while

19. Kid builds in daytime,
dad mines at night

20. Kid builds in daytime,
dad mines at night

21. On weekends we explore
scary places together
Image taken from:
http://www.fromstrangeworlds.com/designing-interactive-systems-for-storytelling/

22. But the happy times
didn’t last forever

23. Complexed structures
raise the server load

24. Example: Automated
Chicken Cooking Machine

25. Red stone circuits
http://gaming.stackexchange.com/questions/16208/what-are-some-tips-for-mastering-redstone-circuits
http://www.minecraftforum.net/topic/1226503-redstone-block-with-behavior-that-allows-parallel-wiring/

26. CPU: Not enough!
512MB: Not enough!
Annoying delay which
disturbs the playability…

27. So I first planned
buying a home server

28. THEN SUDDENLY

29. I remembered what
I’m doing at HDE

30. Use the cloud
and save money!

31. Solution:
EC2 Spot Instances!

32. m3.medium
vCPU: 2
RAM: 3.75GB

33. $0.101/h
for an on-demand
m3.medium instance

34. m3.medium for about $0.01/h
(today’s price)

35. The price varies over time

36. but spot instances are
generally very cheap!

37. My First Plan
• When I want to play,
• API bids for a spot instance
• Spot instance boots up and mounts a particular
EBS, via cloudinit script
• Instance registers itself on a DNS to make it easily
accessible from the client

38. But this is difficult
• How do I control this from outside of EC2?
• I want to casually switch the server on and off

39. Auto Scaling Group

40. Auto Scaling Group
Example: Min:1 Max:4
On low load
On high load

41. But we don’t auto
scale at all ;-)

42. We scale manually

43. Auto Scaling Group
Min:1 Max:1
Min:0 Max:0
When we are playing
minecraft
When we are not playing
minecraft
Me
Kid

44. And made a UI for kids

45. Capacity: 0
Started: No
Up: No
“Stopped”
“Start”

46. Capacity: 1
Started: No
Up: No
“Told the server
to start up.”
“Please stand
by.”

47. Capacity: 1
Started: Yes
Up: No
“The server
started.”
“Wait for
a minute.”

48. Capacity: 1
Started: Yes
Up: Yes
“It’s running.”
“Stop”

49. Python + boto + Flask
Lines: 74(excluding HTML templates)
So easy!

50. I only pay 10-30 JPY
per a week for this!

51. 社長だけど
かなりケチです

52. Other tweaks
• I’m actually using “desired capacity” feature of auto
scaling group to control the number of the instances
• Instance uses dynamic-DNS to bind it’s IP to a fixed
FQDN
• Instance watches the Minecraft directory and
terminates itself (sets capacity to 0) if there are no
activities for an hour
• Anyway the server kills itself after certain hours

53. This technique is also useful
when you have to keep a
non-critical server up

54. Happy Mining!