Coding Resiliently with Akka

Coding
in

Resiliently
Akka
Scala
with

Derek Wyatt
Twitter: @derekwyatt
Email: derek@derekwyatt.org
Tuesday, 4 February, 14

’s Resiliency?
What


’s Resiliency?
What
W

Tolerance against faults


’s Resiliency?
What
W


W

Grace in the face of insane success


’s Resiliency?
What
W


W


W

Slowing down instead of shutting down


’s Resiliency?
What
W


W


W

Slowing down instead of shutting down
Resiliency is about reacting to the crap that happens
because life is, basically a problem


C
Cloud Resiliency
C


C
Cloud Resiliency
C
Queues
C

Virtual Machines
C

C
Clustered Databases

Zookeeper
C

Load
C Balancers

C
Cloud Resiliency
C

g to
Queues s. Virtual Machines
oin
C
mg
C
I’
ol
t to
m.
rea
G
the
use
C you Databases
Clustered
me
su
s
aZookeeper
C
Load
C Balancers


How Akka Helps


How Akka Helps
5 Akka is a toolki for asynchrony
Resilient systems are asynchronous systems


How Akka Helps

5 Akka is buil using queues
Queues add resilient points of communication


How Akka Helps


5 Akka divorces threads from work
Improper use of threads kills resiliency


How Akka Helps



5 Akka’s Actors incorporate faul tolerance
A crash is just standard operating procedure


How Akka Helps




5 Akka Clusters
Clustering? Come on... Resilient

How Akka Helps

!
re
o
m
’s
re
e
th
d
n






A



5 Akka Clusters

Clustering? Come on... Resilient

Why We Don’t Code Resiliently


Why.k.a Don’t backResiliently
We Call Code Hell
a
1) REST request comes in
2) Validate user identity
3) Get profile from DB
4) Grab a few pics
5) Get recent Twitter activity
6) Return REST response


We Call Code Hell
a
Do i
t
and
4) Grab a few pics


asyn
chro
nous
don’
ly
t bl
ock

We Call Code Hell
a
Do i
t
and
4) Grab a few pics

asyn
chro
nous
don’
ly
t bl
ock

Welcome to Callback
Hell

ack Hell
Callb


ack Hell
Callb
public void restHandler(RESTRequest req) {
idService.validate(req.userInfo,
new Callback(ValidateResult result) {
if (result.isValid) {
db.getProfile(req.userId,
new Callback(UserProfile profile) {
picServer.get(profile.pic1, new Callback(Pic p1) {
twitterServer.getRecentActivity(req.userInfo, new Callback(TwitterActivity activity) {
req.sendResponse(pic1, pic2, pic3, pic4, pic5, activity)
})
})
})
})
})
})
}

})


})

ack Hell
Callb
public void restHandler(RESTRequest req) {

☉ We didn’t handle timeouts
idService.validate(req.userInfo,
new Callback(ValidateResult result) {
if (result.isValid) {
We didn’t handle
☉db.getProfile(req.userId, errors
new Callback(UserProfile profile) {
☉ We actually didn’t make it thread

☉


We did throw up a little though...

twitterServer.getRecentActivity(req.userInfo, new Callback(TwitterActivity activity) {
req.sendResponse(pic1, pic2, pic3, pic4, pic5, activity)
})
})
})
})
})
})
}

})


})

safe

synchrony
nctional A
Fu


synchrony
nctional A
Fu

implicit val timeout = Timeout(30.seconds)
def restHandler(req: RESTRequest): Future[RESTResponse] = {
val resp = for {
validity <- idService.validate(req.userInfo)
if validity.isValid
profile <- db.getProfile(req.userId)
pic1 <- picServer.get(profile.pic1)
activity <- twitterServer.getRecentActivity(req.userInfo)
} yield SuccessfulResponse(pic1, pic2, pic3, pic4, pic5, activity)
resp.recover { e => FailedResponse(e) }
}


synchrony
nctional A
Fu

implicit val timeout = Timeout(30.seconds)
def restHandler(req: RESTRequest): Future[RESTResponse] = {
val resp = for {
validity <- idService.validate(req.userInfo)
if validity.isValid
profile <- db.getProfile(req.userId)
activity <- twitterServer.getRecentActivity(req.userInfo)
} yield SuccessfulResponse(pic1, pic2, pic3, pic4, pic5, activity)
resp.recover { e => FailedResponse(e) }
}

☉
☉
☉

We handle timeouts (!!)

☉

We got to keep our lunch down


We handle errors (!!)

It’s immutable and thread safe (!!)

The Circuit Breaker


The Circuit Breaker
⦿

For the times when you gotta fail the whale


The Circuit Breaker
⦿

Calls Failing
Fast

Su
cc
ess

p
Tri

r
ake
Bre

Open

eset

Closed
Trip

Reset Bre


Atte
mpt R

aker

Brea

ker

Half
Open

The Circuit Breaker
⦿

Calls Failing
Fast

Su
cc
ess

p
Tri

r
ake
Bre

Open

eset

Closed
Trip

Reset Bre


Atte
mpt R

aker

Brea

ker

Half
Open

DB

The Circuit Breaker
⦿

Calls Failing
Fast

Su
cc
ess

p
Tri

r
ake
Bre

Open

eset

Closed
Trip

Reset Bre


Atte
mpt R

pen
it O
ircu
C

aker

Brea

ker

Half
Open

Circu
it Clo
sed

DB

ad Balancing
Lo
Actors are untyped endpoints
You can easily swap one for another
Actors have dispatchers
How messages are dispatched is configurable
You can only communicate through messages
You can route them however you like
Messages can carry the state data
Actors then become completely stateless and
Resilient

Scaling Up


Scaling Up
⦿ It’s all about dispatchers and untyped endpoints


Scaling Up
⦿ It’s all about dispatchers and untyped endpoints

ActorRef

Client

Actor

ActorRef

Balancing
Dispatcher

Actor

ActorRef

•
•


Actor

Normally the
message from the
client would go to
the middle Actor,
but the Balancing
Dispatcher lets
the last one “steal”
it because it can
handle it faster.

Scaling Out


Scaling Out
☉Routers are another way for messages to reach Actors


Scaling Out
A router igures ou which Actor
☉to send to based on rules


Scaling Out
DB
Actor


Router

DB
Actor

DB Cluster
Machine 2

DB
Actor

Client

DB Cluster
Machine 1

DB Cluster
Machine 3

Scaling Out
Client


Router

DB Cluster
Machine 1

DB
Actor

DB Cluster
Machine 2

DB
Actor

This router can
ute consistently
ro
based on sender

DB
Actor

DB Cluster
Machine 3

Scaling Out
This router can
ute consistently
ro
based on sender

Client

☉

Router

Routers can also resize the
number o Actors dynamically


DB
Actor

DB Cluster
Machine 1

DB
Actor

DB Cluster
Machine 2

DB
Actor

DB Cluster
Machine 3

Clustering


Clustering
Akka can spawn and communicate with Actors
⦿
on remote nodes


Clustering
⦿
on remote nodes

oring!
B


Clustering
⦿
on remote nodes
(OK, that’s really cool, but...)

oring!
B


Clustering
⦿
on remote nodes

oring!
B

⦿ You can cluster your Actors as well


Clustering
⦿
on remote nodes

oring!
B


Akka takes care of letting you know when
⦿
nodes come and go


Clustering
⦿
on remote nodes

oring!
B


Akka takes care of letting you know when
⦿
nodes come and go
Clustering provides a ton of possibilities to
⦿
design for resiliency

nce - Event Sourcing
Persiste


Persiste
⨂ Akka provides the ability to persist incoming messages


Persiste
⨂ This helps for fault tolerance... DUH


Persiste
⨂ It also provides the ability to move stateful Actors


Persiste
⨂ It also provides the ability to move stateful Actors
⨂ Or provide tools for “Crash-Only” software

sh!
ra
C Actor

Message

Actor
Event 1
Event 2
Event 3


Good to go!

Being Resilient


Being Resilient
☉Akka provides the foundation for resilien programming and design
⨳ Queues, Dispatchers, Async, Messages, realistic guarantees


Being Resilient

☉

Then you ge...

Message Oriented
Flexibility

⨳ Routers
⨳
⨳ Persistence
⨳ Clustering
⨳ Resiliency Patterns
⨳ Remote Deployment


Being Resilient

☉

Then you ge...

Message Oriented
Flexibility

⨳ Routers
⨳
⨳ Persistence
⨳ Clustering

☉

Existing cloud components are vial for resiliency


Being Resilient

☉

Then you ge...

Message Oriented
Flexibility

⨳ Routers
⨳
⨳ Persistence
⨳ Clustering

☉
Akka picks up where those components leave of
☉
Existing cloud components are vial for resiliency


Go write some Code

Get Scala

http://scala-lang.org
http://github.com/scala/scala

Get Akka
http://akka.io
http://github.com/akka/akka


Derek Wyatt
Twitter: @derekwyatt
Email: derek@derekwyatt.org

Coding Resiliently with Akka

Recomendados

Recomendados

Más contenido relacionado

Último

Último (20)

Destacado

Destacado (20)

Coding Resiliently with Akka