Expectations are changing

» real-time (latency of 1 second, not 1 day)

» users are always connected

» mission-critical use cases

» consistent experience more important than peak performance

We used to write programs...

» for single servers and VMs

» for single cores

» that expect local communications (call stack)

» that expect small data snapshots (data fits into memory)

Now we write programs...

» that must exploit clusters

» that must exploit multi-core CPUs (even on cell phones!)

» that must work across async boundaries (threads, networks)

» that must process streams (i.e, data without limits)

A recap of heritage systems

heritage applications

» Single points of failure

» Difficult to scale (shared mutable state, etc)

» Different non-functional requirements (reads, writes, compute) & optimized for none!

» Long, risky release cycles

What is SOA?

Elements of SOA

» Inter-operable services

» Formal contracts (e.g, WSDL)

» Multiple protocols (e.g, SOAP, RPC, REST, CORBA, etc)

» Location transparency

» ESB

SOA framework

» Problems arise when we attempt to contradict the spirit of SOA

» Central control + location transparency

» Rigid specifications + flexibility

» Transactions + distribution

» Etc

The bad parts of SOA

“Architecture is hard enough without adding unnecessary complexity.”Ross Mason, CTO, MuleSoft

ESBStateless:

messaging, message exchange patterns (sync req/resp, async p2p messaging, pub/sub, streams), routing, service orchestration (service aggregation), security (encryption and signing), monitoring, protocol conversion, legacy adapters, payload transformation, schema validation, governance (the ability to apply business rules uniformly), service catalog

ESBStateful:

process choreography (BPM), complex event processing (CEP), reliable delivery, transaction management, split and merge (conflating, windowing, ordering)

heritage systems

» Productivity depends on working within the system context

» ESB and other heritage systems infrastructure creates difficult productivity barriers for developers

BPM

» business activity flows

» modeling, automation, execution, control, measurement, optimization

» enterprise scope

» spanning systems, employees, customers, partners

"Jack of all trades, master of none, often times better than the master of one."

Give up control to gain flexibility.Embrace new patterns to achieve balance.

How does microservice architecture (MSA) help?

Microservices

» Ubiquitous language

» Well defined models & boundaries

» Single responsibility

» Independently deployable, scalable, resilient

» Communicate via async messaging

» Own their data

» Don't expose a public API

Cloud ready infrastructure

We need to build applications...

» that exploit clusters

» that exploit multi-core CPUs

» that work across async boundaries

» that process streams

Physical infrastructure

» Nodes across multiple DCs are considered part of the same system

» Physical infrastructure abstracted away from system world view

Cluster infrastructure

» Nodes can join or leave the cluster

» Services are rebalanced across the cluster

» Node failure doesn't equal system failure

Service infrastructure

» View the world through services

» Service replicas provide elasticity and resilience

» Support multiple versions of a service, etc

Rethinking SOA with MSA

API Gateway» Some ESB functionality is

moved into API gateways

» routing, service aggregation, security (encryption and signing), protocol conversion, legacy adapters, payload transformation, service catalog

Microservices» Microservices become the

core communication abstraction within a system

» async p2p, pub/sub

» streams (split and merge (conflating, windowing, ordering), complex event processing (CEP))

Modeling» process choreography (BPM)

becomes DDD (domain driven design)

» single canonical model becomes many canonical models

» ubiquitous language

» well defined interfaces

Transactions» transaction management (2PC) becomes the saga

pattern

Both service-level and infrastructure» security (encryption and signing)

» monitoring

Summary» Microservice architecture

(MSA) is not a new concept

» MSA is the evolution of SOA for a modern world (expectations, hardware, size)