This document discusses Lagom, a microservices framework for building reactive, distributed systems on the JVM. Lagom promotes building loosely coupled services with explicit boundaries and focuses on asynchronous communication. It provides tools for event sourcing, CQRS, and clustering services for scalability. The document outlines Lagom's approach and provides resources for learning more.

1. @myfear
Taking the friction out of microservice
frameworks with Lagom
Markus Eisele
@myfear
http://blog.eisele.net
http://www.lightbend.com

2. @myfear

3. @myfear
real-time
consistent
experience
always
connected
business
critical
server
snapshot
core localcores distributed
clustersstreams
?

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http://www.internetlivestats.com/internet-users/
J2EE
Spring
RoR
Akka
Reactive Manifesto
Microservices

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“We used the right
tools to build the
wrong things.”

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Rather than acting on data at rest, modern
software increasingly operates on data in near
real-time.

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Asynchronous, non-blocking, real-time,
highly-available, loosely coupled, scalable,
fault-tolerant, concurrent, reactive, event-
driven, push instead of pull, distributed,
low-latency, high throughput…...

8. @myfear

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“Microservices”
is a lousy term

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“All this hype about microservices
makes me sad. And not about the
concept, but about the name. As I
wrote before, “micro” in
“microservices” means absolutely
nothing. What is worse, it confuses
everybody. Again and again I see
people focusing on “micro” and
falling into nanoservices trap.”
Eugene Kalenkovich

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Lagom (pronounced [ˈlɑ̀ːɡɔm]) is a
Swedish word meaning
"just the right amount".
The Lexin Swedish-English dictionary
defines lagom as "enough, sufficient,
adequate, just right".
https://en.wikipedia.org/wiki/Lagom

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another one?

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“We need to build systems
for flexibility and resiliency, not
just efficiency and robustness.

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Not really: Lagom is opinionated!
• Use context bounds as boundaries for services!
(Domain Driven Design)
• The event log is the book of record!
(Event Sourcing)
• Separate the read and write sides!
(CQRS)
• Microservices, too, need to be elastic and resilient!
(Reactive)
• Developer experience matters!
(The Lagom development setup)
• Takes you all the way to production!

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Lagom
Persistence
Event
Sourcing
CQRS
implements leads to
Persistence to CQRS

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Read
Side
Write
Side
Service
Interfaces
User views
data in the
UI
User makes a
change in the
UI
commandquery
response
Update
data store
changes
CQRS at a glance

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• We implementour aggregateroots as
Persistent Entities
• Persistent Entities will receive commands
• Triggered by a command, Persistent
Entities will change their state
• Example: Add a friend, remove a friend
Lagom-Services and Persistent Entities

19. @myfear
• Lagom allows you to
scale out by forming a
cluster of nodes
• Nodes can be added and
removed dynamically
• Lagom allows you to
scale out by distributing
your Persistent Entities in
the cluster
Lagom Cluster

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Event Sourcing - storing deltas
• Every state change is materialized in an
Event
• All events are stored in an Event Log
• Current state is constructed by replaying
all events
• No object-relational impedancemismatch
• Bullet-proof auditing and historical tracing
• Support future ways of looking at data
• Performance and scalability
• Testability

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Read Side is derived from Event-Log
• Events forwarded to read side to
build different representations
• ElasticSearch
• SQL, de-normalized
• Stream Processor / Analytics
• BI
• OLAP
• …

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Event Sourcing with Lagom Persistence revisited
• Keep all data in memory!
• Store all state changes as events
• Replay all events of an actor to recreate it
• Strong consistency for Actor (aggregate)
and Journal
• Eventual Consistency for Read Side

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Lagom-Services are Reactive
• Asynchronous I/O
• Asynchronous communication as first class
• WebSocket support
• Reactive Streams support
• Distributed by default
• Built-on Akka Clustering, Sharding,
Persistence

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Developer Support
• Run all microservices at once
• Embedded Cassandra DB
• Intra-service communicationvia service
locator
• Hot reloading

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Java API Scala API
Client Libraries
Protocols
Programming Model
Kafka Cassandra
JDBC
Service Locator
Service Gateway
Security
Play
JMS
REST
TCP/UDP
File IO
Akka Streams
Akka Persistence
SOAP
Play
SOAP
Akka Actors Camel
Spark
Streaming
Lagom
RP
Integra-tion
Developer UI /
REPL
Akka Cluster
Play JPA / Slick
FTP
SMTP
Integration Technologies

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• Reactive Microservices Framework for the JVM
• Focused on right sized services
• Asynchronous I/O and communication as first class
priorities
• Highly productive developmentenvironment
• Takes you all the way to production
Recap.

27. @myfear
Next Steps! Download and try Lagom!
Project Site:
http://www.lightbend.com/lagom
GitHub Repo:
https://github.com/lagom
Documentation:
http://www.lagomframework.com/documentation/1.0.x/Home.html
Example:
https://github.com/typesafehub/activator-lagom-java

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Written for architects and developers that must quickly gain
a fundamental understanding of microservice-based
architectures, this free O’Reilly report explores the journey
from SOA to microservices, discusses approaches to
dismantling your monolith, and reviews the key tenets of a
Reactive microservice:
• Isolate all the Things
• Act Autonomously
• Do One Thing, and Do It Well
• Own Your State, Exclusively
• Embrace Asynchronous Message-Passing
• Stay Mobile, but Addressable
• Collaborate as Systems to Solve Problems
http://bit.ly/ReactiveMicroservice

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The detailed example in this report is based on Lagom, a
new framework that helps you follow the requirements for
building distributed, reactive systems.
• Get an overview of the Reactive Programming model and
basic requirements for developing reactive
microservices
• Learn how to create base services, expose endpoints,
and then connect them with a simple, web-based user
interface
• Understand how to deal with persistence, state, and
clients
• Use integration technologies to start a successful
migration away from legacy systems
http://bit.ly/DevelopReactiveMicroservice

30. @myfear
http://bit.ly/SustainableEnterprise
• Understand the challenges of starting a greenfield
development vs tearing apart an existing brownfield
application into services
• Examine your business domain to see if microservices would
be a good fit
• Explore best practices for automation, high availability, data
separation, and performance
• Align your development teams around business capabilities
and responsibilities
• Inspect design patterns such as aggregator, proxy, pipeline, or
shared resources to model service interactions

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