© 2015 IBM Corporation

Developing Enterprise Applications for the Cloud,from Monolith to MicroservicesDavid Currie

Jack Cai

Agenda

• What are microservices?

• Developing and deploying microservices

• Migrating to a microservices architecture

1

What are Microservices?

2

Microservices Defined

• Application architected as a suite of small services, each

running in its own process, and communicating with lightweight

mechanisms e.g. REST/HTTP

• Services built around business capabilities

• Each service independently deployable via automation

• Minimal centralised governance

• May be written in different languages

• May use different data storage technologies

3

Contrast with a Monolithic Architecture

Monolithic Microservice

Architecture Built as a single logical executable (typically

the server-side part of a three tier client-

server-database architecture)

Built as a suite of small services, each running

separately and communicating with lightweight

mechanisms

Modularity Based on language features Based on business capabilities

Agility Changes to the system involve building and

deploying a new version of the entire

application

Changes can be applied to each service

independently

Scaling Entire application scaled horizontally behind

a load-balancer

Each service scaled independently when needed

Implementation Typically written in one language Each service implemented in the language that

best fits the need

Maintainability Large code base intimidating to new

developers

Smaller code base easier to manage

Transaction ACID BASE

4

Componentization via Services

• Component is a unit of software that is independently

replaceable and upgradeable

• Libraries are components that are linked in to a program and

called used in-memory function calls

• Services are out-of-process components who communication,

for example, via web service requests or RPC

• Unlike libraries, services can be independently redeployed

• Using a service results in an explicit published interface

• Remote calls are more expense leading to coarser-grained APIs

• A service may consist of multiple processes e.g. the application

process, cache, and associated database

5

Organized around Business Capabilities

• Monolithic project teams are often aligned around technology

layers meaning even simple changes involve multiple teams

Any organization that designs a system (defined broadly) will

produce a design whose structure is a copy of the organization's

communication structure – Melvyn Conway, 1967

• Organize services around business capabilities results in cross-

functional teams

• Typically those teams are small (Amazon “Two pizza team”) but

don’t get hung up on the ‘micro’

• Strong tie-in to DevOps: each team is responsible for the entire

lifecycle of its service

6

Smart Endpoints and Dumb Pipes

• Historically there has been an emphasis on putting intelligence

(e.g. routing, transformation and even choreography) in to the

communications channel e.g. Enterprise Service Bus

• Microservices communicate directly using simple protocols such

as REST/HTTP and AMQP

• Significant differentiator from what we traditionally think of in a

SOA architecture

• Try to avoid versioning by making services and clients tolerant

to changes

• API Gateway (used to consolidate multiple client calls)

somewhat contrary to this

7

Decentralization

• Decentralized governance

• Monoliths tend to standardise on a single technology platform

whereas it may be appropriate to use different tools (e.g.

languages or databases) for different parts of an application

• With microservices, ‘standardisation’ is through sharing of

common code/tools

• Decentralized data management

• Each service owns its own data model and data

• Coordination between services must be transaction-less (use

eventual consistency and compensation)

8

Microservice Challenges

• Greater operational complexity – more moving parts

• Devs need significant ops skills

• Service interfaces and versioning

• Duplication of effort across service implementations

• Additional complexity of creating a distributed system – network

latency, fault tolerance, serialization, …

• Designing decoupled non-transactional systems is hard

• Avoiding latency overhead of large numbers of small service

invocations

• Locating service instances

• Maintaining availability and consistency with partitioned data

• End-to-end testing

9

Developing and Deploying Microservices

10

Reducing Operational Complexity

• Platform-as-a-Service exists to remove the complexity of

deploying applications – the PaaS provider also handles the

complexity of managing and monitoring the infrastructure

• Cloud Foundry provides a consistent deployment mechanism

regardless of programming language

• Buildpacks ensure that applications are kept up-to-date with

new versions of the runtime and libraries

• Routing and load balancing handled by Cloud Foundry router

• Service dependencies are resolved at deployment time

• Repeatable deployment through IBM DevOps Services or CLI,

Maven/Gradle/Travis/Jenkins plugins (you can even run Jenkins

on Cloud Foundry!)

• Cloud Foundry V3 API to allow multiple processes per app

11

Service Discovery

• Within a Cloud Foundry environment, routes and the CF

router provide all that is needed to locate a service instance

• Cloud Controller manages distribution and availability of

application instances

• Blue-green deployments supported by binding multiple

application versions to the same route

• cf cups (create user provided service) provides a convenient

mechanism to inform one microservice of the route for a

microservice on which it is dependent

• Where instances of a microservice are deployed to multiple

Cloud Foundry environments, consider using a runtime registry

e.g. Eureka or highly-available data store e.g. etcd or

Zookeeper

12

Configuration

• The same application should be deployable in to multiple

environments – don’t build configuration in to the application

• Environment variables are a simple mechanism portable across

most runtimes and cloud and non-cloud environments

• Cloud Foundry provides the ability to set environment variables

in the manifest at push time or subsequently via cf set-env

• Netflix Archaius provides a mechanism to poll a hierarchy of

configuration sources

• Property files and URLs out of the box but other configuration

sources are pluggable

13

Design for Failure

• Any service call could fail where failure could be anything from

an immediate error code to never returning – need to handle

that gracefully

• Emphasis on real-time monitoring of technical and business

metrics

• Application monitoring through Monitoring and Analytics service

or third-party service e.g. New Relic

• Gives insights which might not be uncovered in a monolithic

application

• Implement patterns from ‘Release It!’ e.g. via Netflix Hystrix

• Circuit Breaker – protect from downstream failures

• Bulkhead – limit resources that can be consumed

• Timeout

• Testing for failures: Simian Army

14

Communication Protocols

• Cloud Foundry currently only supports inbound HTTP

• Web sockets is an option in preference to long polling

• JSON may be the best fit for client facing services but consider

other options such as Apache Thrift or Google Protocol Buffers

where serialization efficiency is important

• Typically start with synchronous protocols and add

asynchronous (e.g. via MQ Light) where needed to support the

interaction style or performance goals

• Parallel invocation of downstream services may be required to

ensure responsiveness is maintained

• Consider using a reactive programming model (e.g. RxJava) or

Java 8’s CompletableFuture

15

Securing Microservices

• Cloud Foundry applications are all public facing (Application

Security Groups introduced in the CF 1.3 release relate to

outbound traffic)

• Normal rules apply e.g. basic authentication and authorisation

as a starting point

• Bluemix Single Sign On service provides a simple mechanism

to use an existing identity source or Bluemix based user registry

for SSO

16

Testing Strategies

• http://martinfowler.com/articles/microservice-testing

• Unit testing inside a microservice

• Integration testing between a microservice and its

dependencies (e.g. other services or external datastore)

• Component testing of a microservice either with or without its

dependencies

• Contract testing by consumers of a microservice

• End-to-end testing of a system of microservices

• Use the Cloud Foundry Java client library from unit tests to

communicate with the environment

• Microservices are typically very amenable to testing with

‘shadow traffic’ where requests are sent to both new and old

versions of the service

17

Twelve Factor Apps and Cloud Foundry

1. One codebase tracked in revision control, many deploys

• Cloud Foundry application is unit of deployment

2. Explicitly declare and isolate dependencies

• Cloud Foundry buildpack brings runtime dependencies

3. Store config in the environment

• Facilitated by binding to services

4. Treat backing services as attached resources

• Create and bind to service

5. Strictly separate build and run stages

• Staging to immutable container

6. Execute the app as one or more stateless processes

• Stateless containers

18

Twelve Factor Apps and Cloud Foundry

7. Export services via port binding

• HTTP port exposed by container

8. Scale out via the process model

• cf scale

9. Maximize robustness with fast startup and graceful shutdown

• Cloud Foundry can deploy/scale quickly but can your app?

10. Keep development, staging, and production as similar as

possible

• Cloud Foundry everywhere

11. Treat logs as event streams

• Loggregator

12. Run admin/management tasks as one-off processes

• Push single-shot application

19

UI

(PHP)

Catalog

Service

Ordering

(Java) Catalog

Service

Catalog

(node.js)

Micro Services Example

AndroidiOS

x3

SendGrid SQLDB Address

Validation

Cloudant

Analytics

Auto

Scaling

Single

Sign-on

MySQL

20

Migrating to a Microservices Architecture

21

Decomposing to Services

• Decomposition isn’t about services reaching a certain size or a

certain number – aim for each service to have a single

responsibility

• Services should be independently replaceable and upgradeable

• Differences in speed of change may be another reason to

separate services

• Separate databases before separating services

• Dependency analysis tools such as JDepend may assist in

finding natural boundaries

• Ensure existing transactions continue to reside within a single

service or redesign to use compensation and/or eventual

consistency

• Decide what you want the teams to look like first!

Extend the Monolith

• Build new features as microservices around an existing

monolith

• Use existing APIs or glue code for integration

• Cloud Integration service in IBM Bluemix provides a mechanism

to access existing enterprise data and systems

23

Summary

• What are microservices?

• Developing and deploying microservices

• Migrating to a microservices architecture

24

Questions?

25

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