Developing Enterprise Applications for the Cloud, from Monolith to Microservices
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The document provides an overview of microservices architecture, highlighting its definition, benefits, and challenges compared to monolithic architectures. It discusses the importance of organizing around business capabilities, decentralized governance, and developing and deploying microservices effectively, including service discovery and configuration management. Additionally, it outlines strategies for migrating to microservices, emphasizing the need for independent service responsibilities and the use of various communication protocols.
Developing Enterprise Applications for the Cloud, from Monolith to Microservices
- 1. © 2015 IBM Corporation Developing Enterprise Applications for the Cloud, from Monolith to Microservices David Currie Jack Cai
- 2. Agenda • What are microservices? • Developing and deploying microservices • Migrating to a microservices architecture 1
- 4. 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
- 5. 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
- 6. 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
- 7. 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
- 8. 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
- 9. 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
- 10. 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
- 12. 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
- 13. 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
- 14. 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
- 15. 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
- 16. 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
- 17. 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
- 18. 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
- 19. 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
- 20. 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
- 21. 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
- 23. 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!
- 24. 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
- 25. Summary • What are microservices? • Developing and deploying microservices • Migrating to a microservices architecture 24
- 26. Questions? 25
- 27. Thank You Your Feedback is Important! Access the InterConnect 2015 Conference CONNECT Attendee Portal to complete your session surveys from your smartphone, laptop or conference kiosk.
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