trivadis techevent 2016 introduction to lagom - another microservice-based framework by thomas graf

BASLE BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENEVA

HAMBURG COPENHAGEN LAUSANNE MUNICH STUTTGART VIENNA ZURICH

Introduction to Lagomanother microservice-based framework

Thomas GrafConsultant

Agenda

Introduction to Lagom2 9/23/2016

1. What is Lagom?

Overview

Running in Produktion

2. Lagom Framework

Features

Under the hood / Future Roadmap

Lagom design philosophy / Lagom core concepts

3. Lagom API

Anatomy of a Lagom project

ServiceCall explained

4. Demo


What is Lagom?

Overview


Lightbend, formerly Typesafe

Open Source / most part in Scala

Swedish word [lah-gome]

– enough, sufficient, adequate, just right just the right amount

Running in Production


sbt-native packager is used to produce zip, MSI, RPM, Docker

Lightbend ConductR* (container orchestration tool)

– Free during development

Lightbend Reactive Platform

– Split Brain Resolver (for Akka cluster)

– Lightbend Monitoring

– Requires a Lightbend subscription

ConductR* / Reactive Plattform


source: http://thenewstack.io/lightbends-lagom-offers-microservice-framework-java-developers/

Service Locator / Gateway


Service Locator

– discovers services and allows to communicate

Service Gateway

– Querying different services

– No direct access to endpoint

– Acts as a proxy; services have a different port

Result: running on the same port and assigned constantly

Idea: ConductR* is scalable because of Service Gateway

Similar products like ConductR*


Cloud Foundry

Kubernetes / Vert.x

…


Lagom Framework

Features


Lagom is a framework for creating microservice-based systems. It offers four main

features:

Service API

Persistence API

Development environment

Production environment

(introduction well documented)

Principles


Each service owns its data

Only the service has direct access to the DB

Its advocated to use Event Sourcing (ES) and CQRS

– Out of the box / optimized

– Highly opinionated on that subject

ES / CQRS


Event Sourcing (ES)

– Capture all state’s changes as events

Command Query Responsibility Segregation (CQRS)

– separate models for write and read

Idea: substitute for transactions in distributed systems

1 2 3 n…

Benefits of ES / CQRS


Allows you to time travel

Audit log

Future business opportunities

No need for ORM

No database migration script, ever

Performance & Scalability

Testability & Debuggability

Under the hood


Current version 1.0.0

– Java API, but no Scala API yet

sbt build tool (developer) / Activator 1.3.10

Play 2.5

Akka 2.4 (clustering, streams, persistence)

Cassandra (default data store)

Jackson (JSON serialization)

Guice (Dependency Injection)

Architectural concepts: immutability, circuit breakers, Event Sourcing (ES) /

CQRS (Command Query Responsibility Segregation)

Future Roadmap


Maven support

Support for other cluster orchestration tools

– new project / module for Kubernetes

Swagger integration

– Which also removes binary coupling!

Support for writing integration tests

Message broker integration

Scala API

Lagom design philosophy


Asynchronous by default, both IO and communication

Reactive Microservice Architecture, report by Jonas Bonér

Distributed persistence

High productivity

Lagom core concepts


Tools and APIs

Good architecture

Microservices concepts and best practice


Lagom API

Anatomy of a Lagom project


sbt build

Scala 2.11 and JDK8

Each service definition is split into two sbt projects:

– API

– Implementation

ServiceCall explained


ServiceCall can be invoked when consuming a service:

– Request: type of incoming request message (e.g. String)

– Response: type of outgoing response message (e.g. String)

JSON is the default serialization format for request/response messages

There are two kinds of request/response messages:

– Strict

– Streamed

interface ServiceCall<Request, Response> {CompletionStage<Response> invoke(Request request);

}

Strict Messages


ServiceCall<FriendId, NotUsed> addFriend(String userId);

@Overridedefault Descriptor descriptor() {return named("friendservice").withCalls(

pathCall("/api/users/:userId/friends", this::addFriend),).withAutoAcl(true);

}

Strict messages are fully buffered into memory

– e.g. create a user after transaction information are not needed anymore

Streamed Messages


A streamed message is of type Source (an Akka streams API)

– e.g. chat stream message and forget; cached on client side

It allows asynchronous streaming and handling of messages

Lagom will select transport protocol (currently WebSockets)

ServiceCall<NotUsed, Source<Chirp, ?>> getLiveActivityStream(String userId);

@Overridedefault Descriptor descriptor() {

return named("activityservice").withCalls(pathCall("/api/activity/:userId/live", this::getLiveActivityStream)

).withAutoAcl(true);}

Event Sourcing: Write Side


Create your own Command and Event classes

– Command: system has to do, may trigger an event

– Event: system has done (past), is stored

Subclass PersistentEntity

– Define Command and Event handlers

– Can be accessed from anywhere in the cluster

Event Sourcing: Read Side


Tightly integrated with Cassandra

Create the query tables:

– Subclass CassandraReadSideProcessor

– Consumers events produced by the PersistentEntity and updates tables in

Cassandra optimized for queries

Retrieving data: Cassandra Query Language

– e.g., SELECT id, title FROM postsummary


Demo

Chirper


Friend: handels users and relation among them.

Chirp: allows to create and retrieve

chrips (i.e., messages).

ActivityStream: allows to retrieve

history or live chrips of a user

Frontend: Play + Javascript UI


Lagom: http://www.lagomframework.com/

Lagom Git: https://github.com/lagom/lagom

Lagom Chriper: https://github.com/lagom/activator-lagom-java-chirper

Report by Jonas Bonér, free book, Reactive Service Architecture:

http://www.oreilly.com/programming/free/reactive-microservices-architecture.html

http://www.lagomframework.com/

https://github.com/lagom/lagom

https://github.com/lagom/activator-lagom-java-chirper

http://www.oreilly.com/programming/free/reactive-microservices-architecture.html

Thomas Graf

Consultant

Tel. +41 58 459 53 38

[email protected]

9/23/2016 Introduction to Lagom28

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trivadis techevent 2016 introduction to lagom - another microservice-based framework by thomas graf

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