Microservices vs monolithic

Microservices - Comparing with monolithic architecture
The good, the Bad and the Ugly
Xuan-Loi Vu
Vega’s Tech Department
98 Hoang Quoc Viet
Hanoi, 06 - 01 - 2017
loivx@vega.com.vn (Tech Department) Microservices Comparing With Monolithic Hanoi, 06 - 01 - 2017 1 / 24

Introduction
Table of Contents
1 Introduction
Monolithic architecture
Microservices architecture
2 Microservices in action
1 Bounded Context
2 Service discovery and Orchestration (coordination)
3 Latency and failure from dependencies
4 Availability
5 Security
6 Database
Event-Sourcing
CQRS
Distributed transaction

Introduction
Monolithic and Microservices

Introduction Monolithic architecture
Characteristics:
one code base
usually one programming language
rarely, one application with more than two databases
deploy one WAR ﬁle (or directory hierarchy)
scale application by running multiple copies using load balancer
· · ·

Introduction Microservices architecture
Characteristics:
multiple code bases
full-stack or polygot
component’s database is independent
easy of deployment and scaling
· · ·

Pros and Cos
pros
Decentralize application so that easier maintain
Re-used component
Deployability - agility to roll out new versions
Reliability - fault affects that microservice alone and its consumers
(bulkhead)
Availability - rolling out a new version of a microservice requires little
downtime
Scalability - can be scaled independently using pools, clusters, grids
Modifiability - more flexibility to use new frameworks, libraries,
datasources, and other resources
Management - application management effort
Design autonomy - team has freedom to employ different
technologies, frameworks, and patterns

Pros and Cos - No silver bullet
cos
Determine “Bounded Context”
Deployability - more complex with many jobs, scripts, transfer areas,
and config files
Performance - communicate over the network, whereas services within
the monolith may benefit from local calls
Availability - belongs to dynamic discovery
Modifiability - database inconsistency, transaction, . . .
Testability - harder to setup and run
Management - application operation effort increases because there are
more runtime components, log files, and point-to-point interactions to
oversee
Security

Microservices in action
Table of Contents
1 Introduction
2 Microservices in action
1 Bounded Context
2 Service discovery and Orchestration (coordination)
3 Latency and failure from dependencies
4 Availability
5 Security
6 Database
Event-Sourcing
CQRS

Microservices in action Overcome disadvantages
Overcome disadvantages
Determine “Bounded Context”
Deployability, testability and management - service discovery and
coordinator
Performance - latency and failure from dependencies
Availability - cluster or HA for dynamic discovery servers
Security between components
Database (most diﬃcult and most important) - event source, CQRS,
long-lived transaction

Microservices in action 1 Bounded Context
Determine Bounded Context
How do we do?

Microservices in action 2 Service discovery and Orchestration (coordination)
Service discovery and Orchestration (coordination)
Service discovery is the automatic detection of devices and services oﬀered
by these devices on a computer network.
Orchestration is the automated arrangement, coordination, and
management of computer systems, middleware, and services
Supported and usually used tools:
Apache ZooKeeper
Consul IO by HashiCorp

Microservices in action 3 Latency and failure from dependencies
Latency and failure from dependencies
Review Netﬂix Histrix:
Give protection from and control over latency and failure from
dependencies accessed (typically over the network) via third-party
client libraries.
Stop cascading failures in a complex distributed system.
Fail fast and rapidly recover
Fallback and gracefully degrade when possible
Enable near real-time monitoring, alerting, and operational control

Microservices in action 3 Latency and failure from dependencies
Review Netﬂix Histrix - Circuit breaker

Microservices in action 4 Availability
Availability
Deploy cluster of Apache ZooKeeper or Consul:
ZooKeeper cluster
Consul cluster

Microservices in action 5 Security
Security
Usually using authentication and authorization servers:
Kerberos
Your own JWT system

Microservices in action 6 Database
Database - the most important and most diﬃcult
Review three approaches:
Event-Sourcing
CQRS

Event-Sourcing
Characteristics:
all changes to application state are stored as a sequence of events
all events are immutable
use the events log to reconstruct past states
enable Reactive pattern
Supported tools: Apache Kafka, Akka actor, . . .
More detail: Event-Sourcing Pattern

Command-Query Responsibility Segregation (CQRS)
Characteristics:
separate the read and write by using commands and queries
performing modifications and querying data separately
command and query parts could live in different services, or on
different hardware, and could make use of radically different types of
data store
often used in conjunction with the Event-Sourcing pattern
More detail: CQRS Pattern

Two-phase commit protocol
Long-lived transaction (SAGAS)

Two-phase commit protocol

Long-lived transaction (SAGAS)
Characteristics from Wikipedia:
a transaction that spans multiple database transactions. Transaction
T can be viewed as a collection of sub-transactions T1, T2, . . ., Tn
a sequence of database transactions grouped to achieve a single
atomic result
support backward and forward recovery. When a failure interrupts,
there are two choices: compensate for the executed transactions
(backward recovery), or execute the missing transactions (forward
recovery)

Conclusion
Should we prefer microservices over monolithic?
“Microservices architecture shows a lot of advantages”
However, it is not a silver bullet.

References
References
Microservice Architecture
Reactive Microservices Architecture
Pros and Cos
Event-Sourcing
Event-Sourcing CQRS stream processing with Apache Kafka
Akka Persistence
Two-Phase commit protocol
Long-lived transaction - SAGAS

Questions and answers
Questions and answers
Thank you for your attention!!!

Microservices vs monolithic

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