MongoDC 2012: How MongoDB Powers Doodle or Die

Mongo or Die!
How MongoDB powers Doodle or Die

Aaron Silverman
(@Zugwalt)

Doodle or Die

@DoodleOrDie

Telephone
Phrase I'd like some beer!

Phrase I'd like some deer



Doodle or Die

Doodle

Phrase Shining Apple

Doodle

Phrase Eat your fruit or DIE!

Started very, very small

4 Cores
128MB RAM
Node Server

MongoDB Server

Got serious about our servers

Small - 2GB

8 Cores MongoDB Server
256MB RAM
Node Server

Called in some Reinforcements

Large - 5GB

12 Cores MongoDB Server
1GB RAM
Node Server

In the last 30 Days:

• 2,500,000 page views

• 100,000 uniques

• 35,000 active player accounts

• 2,000,000 new doodles and descriptions

Data Information
Mongo DB • Player Info
• Chain Info (minus
3.5 GB data size
doodles)
0.5 GB index size • Group Info
~10 queries/sec • Game State
• Logs
Amazon
170 GB data size • Doodles!
• Static Content
8 GB in/month • Compressed
200 GB out/month Database Backups

MongoDB - $65 / month

Daily backups to S3: $16/mo

Total Cost To Host: $197/month
MongoDB $65
Amazon S3 $70
Node $62
Total $197

PAAS Provides Easy Upgrade Path

Custom _id
Partially random string generated using
ShortId node module
ObjectId
ObjectId("4fd02d5d78315a502d15cdde")
ObjectId("4fd02d5a78315a502d15cddd")
ObjectId("4fd02d5878315a502d15cddc")

ShortId
"8rOIwh2VD"
"1qyY61Lu1"
"5GQnbx-1"

• Shorter, less cumbersome in code /
queries
db.players.findOne({_id: ‘58mwYlTKV’});

db.chains.update({_id: ‘58mwYlTKV’},
{$set: activePlayer_id: ‘88ueYaL6V’});

• Randomness will be better for sharding
and makes it harder to cheat
http://doodleordie.com/c/5ONtvvSGH

<span class="doodle" data-jsonp="http://doodles.s3.amazonaws.com/d2/Eh8-
Po2R5/1Em5kj3LY.js">

Question Oriented Subdocuments

What chain is this player working on right now?

What are this player’s stats?

Which players are not eligible to be assigned this chain?

Goal is for most “Questions” to be able to
be answered in one query from one sub
document

db.players.findOne({_id: ‘58mwYlTKV’},
{‘game.recentSkips’: 1});

Related “Questions” will share common
ancestors

db.players.findOne({_id: ‘58mwYlTKV’},
{game: 1});

Indexes are designed to make answering
questions easy!

What chain is this player working on right now?
db.players.ensureIndex({‘game.activeChain_id’: 1});

What chains are recently awaiting a new doodle?

db.chains.ensureIndex({inUse: -1,
activeState: 1
lastModified" : -1});

players

Primary chains

groups

sessions
Support
log

players
game Often

chainHistory

stats Query
Frequency
account
login
Rarely
info

players
game • activeState
• activeChain_id
chainHistory • activeStepIndex
• recentSkips
stats
account

Answerslogin question:
“What is this player working on right now?”
info
db.players.findOne({_id: ‘58mwYlTKV’}, {game: 1});

players Chain1
game • datePlayed
• dateViewed
chainHistory

stats
account ChainN

login
Answers the question:
“What has the player worked on?”
info
db.players.findOne({_id: ‘58mwYlTKV’}, {chainHistory: 1});

players • totalSteps
game • drawSteps
• phraseSteps
chainHistory • numSkips
• numLikes
stats
account
login
Answers the question:
“What has the player worked on?”
info
db.players.findOne({_id: ‘58mwYlTKV’}, {stats: 1});

chains
• activePlayer_id
• activeState
• numSteps
• lastModified
steps
ineligiblePlayer_ids
chains are searched (not as many questions)
db.chains.findOne({inUse: false,
activeState : player.game.activeState,
ineligiblePlayer_ids: {$ne: player._id},
lastModified: { $gte: timeRange}});

chains [player_id1
player_id2,
• activePlayer_id player_id3
• activeState …
• numSteps player_idN]
• lastModified

*

Note: $addToSet and $pull work great in
steps
maintaining this array

chains [

• activePlayer_id Step1
• activeState • player_id
• numSteps • state
• lastModified • date
content
*
StepN
steps
]

Description Step Content:
• phrase

Doodle Step Content:
• url (points to S3)
• time
• numStrokes
• numDistinctColors

players queried for users who are associated
with the authenticated twitter account

db.players.find({‘login.twitter.uid’: ‘XXXXXXX’},
{game: 1, chainHistory: 1});

chain history used to load
thumbnails, complete active and previous
chain loaded

db.chains.find({_id: {$in: [player.game.activeChain_id,
player.game.lastChain_id]}});

Chains collection searched and updated for
unclaimed eligible chain to be given to player

db.chains.update({inUse: false,
activeState : player.game.activeState,
ineligiblePlayer_ids: {$ne: player._id},
lastModified: { $gte: timeRange}},
{$set: {inUse: true,
activePlayer_id: player._id,
$addToSet:
{ineligiblePlayer_ids: player._id}});

db.chains.find({activePlayer_id: player._id});

Content saved to chain

db.chains.update({_id: chain._id,
activePlayer_id: player._id}},
{$inc: {numSteps: 1},
$set: inUse: false,
lastModified: datePlayed}
$unset: {activePlayer_id: 1},
$push: {steps: {
player_id: player._id,
state: chain.activeState,
content: content,
date: datePlayed}}});

Player updated and given new state

db.players.update({_id: player._id,
'game.activeChain_id': chain._id},
{$inc: {‘stats.totalSteps’: 1},
$set: {'game.activeState': nextState,
'game.lastChain_id’: chain._id},
$unset: {'game.activeChain_id': 1,
'game.activeStepIndex': 1}});

Active chain and chain history reloaded

Doodle strokes will be saved to S3
(but url to S3 and metadata saved to chain)
{"color":"#000000","size":15,"path":[307,66,308,66,308,68,308,69,308,70,308,71,308,7
2,308,73,306,76,305,79,305,81,302,83,302,84,302,85,302,86,301,87,300,89,300,90,300
,91,300,92,300,95,300,97,300,102,300,103,300,104,300,108,300,109,300,110,301,114,
303,116,304,116,305,119,305,121,307,124,309,127,310,130,310,131,313,132,314,133,
316,137,317,138,320,140,321,140,323,143,326,143,328,143,333,144,337,144,341,144,
343,144,347,143,352,143,354,141,357,140,358,140,359,139,362,138,363,138,365,137,
368,135,369,132,370,131,371,130,374,128,375,128,376,125,378,125,379,124,380,123,
381,123,382,120,385,119,386,118,388,115,391,112,394,109,394,107,394,106,397,104,
397,103,397,102,397,101,397,100,397,98,397,96,397,94,397,93,397,91,397,90,397,88,
397,87,397,86,397,83,395,80,395,79,395,77,394,74,393,72,393,70,393,67,392,65,391,6
3,389,62,388,59,386,57,383,54,383,52,381,49,379,48,378,47,376,46,375,44,374,43,372
,43,370,42,369,42,368,42,364,41,362,41,359,41,355,41,351,42,349,42,347,42,346,44,3
43,44,342,45,339,46,337,47,336,48,333,49,332,51,330,51,328,51,327,52,326,53,323,53
,322,53,321,54,320,55,317,55,316,56,314,58,309,59,306,61,306,62,305,62,304,63]}

Player’s chainHistory retrieved and
filtered/sorted on server; applicable chains
retrieved

db.players.find({‘login.urlSafe’: urlSafeUid},
{chainHistory: 1});

db.chains.find({$in: chain_idArr});

Retrieved chains ordered based on pre-
determined sorting.

Some Additional Doodle or Die Tricks

Build assumptions into queries

Alice and Bob are in an awesome group

groups:
{
_id: ‘8rOIwh2VD’,
members: [
{name: ‘Alice’, dateJoined: ‘2012-05-24’},
{name: ‘Bob’, dateJoined: ‘2012-05-25’}
]
banned: [
{name: ‘Eve’, dateBanned: ‘2012-05-25’}
]
}

Eve tries to join despite being banned!

Bugs in our code fail to detect Eve’s trickery
and the update query is run!

groups.update(
{_id: ‘8rOIwh2VD’},
{$push:
{members:
{name: ‘Eve’,
dateJoined: new Date()}
},
},
function(err) {
if (err) throw err;
callback();
});

groups:
{
_id: ‘8rOIwh2VD’,
members: [
{name: ‘Alice’, dateJoined: ‘2012-05-24’},
{name: ‘Bob’, dateJoined: ‘2012-05-25’},
{name: ‘Eve’, dateJoined: ‘2012-05-26’}
]
banned: [
{name: ‘Eve’, dateRequested: ‘2012-05-25’}
]
}

Blast! She got through! How can we help
prevent this?

Bake in our assumptions!

groups.update(
{_id: ‘8rOIwh2VD’,
‘members.name’: {$ne: ‘Eve’},
‘banned.name’: {$ne: ‘Eve’}},
{$push:
{members:
{name: ‘Eve’,
dateJoined: new Date()}
},
},
function(err, updateCount) {
if (err) throw err;
if (updateCount !== 1) throw new Error(‘bugs!’);
callback(updateCount === 1);
});

To assign a player a new chain, we only need
their _id and game information

players

game
chainHistory
stats
account
login
info

To load a player’s profile content, we just
need their history, stats, and profile info

players

game
chainHistory
stats
account
login
info

We need to assign Bob a new chain, lets
figure out what state he needs next

players.find({name: ‘Bob’});

This will fetch and send back the ENTIRE
player object!

Lets specify that we only want our “game”
subdocument
players.find({name: ‘Bob’}, {fields: [‘game’]});

Hooray! Much less to send over the series
of tubes.

Less obvious database structure

mysql> DESC players;
+----------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------+---------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| activeStateId | int(11) | YES | | NULL | |
| activeStepId | int(11) | YES | | NULL | |
+----------------+---------+------+-----+---------+-------+

Data integrity up to application

Mysql> ALTER TABLE players
ADD CONSTRAINT fk_players_chains
FOREIGN KEY (activeChainId) REFERENCES chains(id);

/* Oh no! This is going to mess things up! */

players.update({_id: ‘c58D4’},
{$set: {‘game.activeChain_id’: ‘bad_id’}});

No mature GUI query development tools

If we could start over would we still use MongoDB?

Absolutely!
• NoSQL in general is great for rapid prototyping

• Fantastic performance

• Intuitive language keeps it easy to run one-off
queries

• Excellent (and now officially supported) Node
driver

Questions?

@Zugwalt @DoodleOrDie

MongoDC 2012: How MongoDB Powers Doodle or Die

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Editor's Notes