This document provides an overview of microservices for developers experienced with monolithic applications. It discusses how microservices address modern app needs like continuous delivery and variable scaling. Key aspects covered include determining service boundaries, designing APIs, managing distributed data, and setting up platforms to support microservices. The goal is to help monolith developers understand what to expect when working on microservices projects.

1. Enterprise Developers Guild
9/26/2017
Microservices
Primer for
Monolithic Devs

2. 1
2
3
4
5
Agenda
Microservices Overview
Service and API Boundaries
Designing for Distributed Data
Managing Microservices
Demo with Azure Service Fabric
GOAL: Understand what to expect on Microservices projects

3. Impact of Modern Apps
 Users expect more features without downtime
 Developers have to figure out a solution

4. Monolith vs. Microservices

5. Monolithic SOA Microservices
Evolution of Architectures
GoF Patterns, SOLID, Hexagonal, Testable

6. Use Cases – App Features
 SaaS product
 Availability critical
 Variable I/O & Scale
 Variant feature changes

7. Use Cases – Business Features
 Remain competitive – QTM
 Evolving business model
 Acquisition-based model

8. When to start with monoliths
(Realistically – Most of the time)
 Unknown growth/adoption
 Boundaries not well-defined
 No DevOps culture

9. MSDN
Determining
Service
Boundaries

10. DDD: Bounded Context
“Bounding contexts gives team
members a clear and shared
understanding of what has to
be consistent and what can
develop independently.”
- Eric Evans, Domain-Driven Design, 2003

11. Bounded Context Example
Course
Subject
Student
Class Schedule
Faculty
Advisor

12. Bounded Context Example
Course
Subject
Student
Class ScheduleCourse ID Faculty
Member
Advisor ID
(Faculty Member)
Add/Edit courses
Add/Edit students,
Set semester class schedule
Add/Edit
faculty members

13. The Microservices Version

14. Entities & Processes
Services boundaries tend to be separated by nouns & verbs
Student
Service
Course
Service
NOUNS (Entity CRUD)
Batch
Enrollment
Search
Prospects
VERBS (Business Process)

15. Optional Monolithic Start
 Bounded Contexts
 Variable Scaling
 Change Frequency
 Business Process
Start large and break down based on:

16. EXAMPLE: EF Bounded Context
// Typical EF setup with all data models in single DB context
public class SchoolDbContext : DbContext, ISchoolDbContext
{
public DbSet<Student> Students { get; set; }
public DbSet<Course> Courses { get; set; }
public DbSet<Subject> Subjects { get; set; }
public DbSet<Faculty> Faculty { get; set; }
public DbSet<FacultyMember> FacultyMembers { get; set; }
}

17. EXAMPLE: EF Bounded Context
// Contexts grouped by entities w/ related, specific operations
public class StudentDbContext : DbContext
{
public DbSet<Student> Students { get; set; }
public DbSet<ClassSchedule> ClassSchedules { get; set; }
}
public class CourseDbContext : DbContext { }
public class FacultyDbContext : DbContext { }

18. MSDN
Managing
APIs

19. API Death Stars

20. API Gateway

21. Follow good REST principles
 Resource hierarchies
 HTTP methods & status codes
GET /students/123/schedule/2017 | 200
POST /students/123/schedule | 201
PUT ...
PATCH ...
DELETE ...

22. Versioning
URI
/v1/students/123
Query String
/students/123?v=1.0
Accept Header
/students/123
Accept: x.student-api.v1+json

23. MSDN
Managing
Distributed
Data

24. Monolith Queries
SELECT -- Syllabus and advisor info
FROM StudentSyllabus ss
INNER JOIN Syllabus s ON ss.SyllabusId = s.Id
INNER JOIN Course c ON s.CourseId = c.Id
INNER JOIN Advisor a ON ss.AdvisorId = a.Id
INNER JOIN [User] u ON a.UserId = u.Id
WHERE ss.[Year] = @currentYear
AND ss.StudentId = @studentId
AND ss.IsActive = 1

25. Querying Distributed Databases

26. Cross-Service Queries

27. Cross-Service Queries
fetch('/api/v1/students/12345/schedule/2017')
.then((response) => response.json())
.then(function(student) {
// Call the other services to get “join” data
var advisorApi = '/api/v1/faculty/members/' + student.advisorId;
var courseApis = [];
student.courses.forEach(function(course) {
courseApis.push('/api/v1/courses/' + course.id);
}, this);
// Create promises, merge results, data binding, etc.
});

28. Materialized Views

29. Materialized Views
fetch('/api/v1/students/12345/syllabus/2017')
.then((response) => response.json())
.then(function(student) {
// Call the other services to get “join” data
var advisorApi = '/api/v1/faculty/members/' + student.advisorId;
var courseApis = [];
student.courses.forEach(function(course) {
courseApis.push('/api/v1/courses/' + course.id);
}, this);
// Create promises, merge results, data binding, etc.
});
// Trade-off is more backend code for event publishing
fetch('/api/v1/students/12345/schedule/2017’).then(...)

30. Monolith Commands
using (IDbContext db = _dbFactory.GetContext())
{
Syllabus syllabusDataModel = db.Syllabus.Single(s =>
s.Id == syllabusDomainModel.Id);
Mapper.MapChanges(
syllabusDataModel, syllabusDomainModel);
// Built-in transactions for related tables
db.SaveChanges();
}

31. Eventually Consistent Services

32. Event Sourcing

33. Managing
Microservices

34. Team DevOps
Repos Builds Releases

35. Unit Testing
Internal Logic
• In-memory only
• Mock/fake dependencies

36. Unit Testing
Owned Dependencies
• Provisioning/Teardown
• Longer duration

37. Unit Testing
Non-Owned Dependencies
• Contracts
• Consumer vs. Provider

38. Platform Checklist
 Frameworks
 Logging
 Monitoring
 Auto Scaling
 Service Discovery
 Instant Rollback
 Auto Versioning
 Failure Resistance
 Self-Service Provisioning
 Rapid Deployment
To run microservices, you need:

39. Platforms
PaaS CaaS IaaS
 Azure Service Fabric
 Pivotal Cloud Foundry
 Cloud w/ Frameworks:
 Netflix OSS
 Mantl
 Amazon ECS
 Azure Container
Services
 Google Container
Engine
 VMs

40. Tools/Frameworks/Libraries
Event Stores
 Eventuate
 Cosmos DB Change Feed
 eventstore.org
Service Discovery
 Service Fabric Naming Service
 Consul
 Netflix Eureka
API Gateway
 Azure/AWS API Management
 Mulesoft
 Google Apigee
Event Messaging
 Azure/AWS queue services
 Apache Kafka
 RabbitMQ

41. More Info
Questions? lfaulkner@cardinalsolutions.com
Design patterns and technical approaches:
http://microservices.io/
https://docs.microsoft.com/en-us/azure/architecture/ (Cloud Patterns PDF)
https://martinfowler.com/articles/microservices.html
How they did it:
http://searchmicroservices.techtarget.com/ (RSS)
https://medium.com/netflix-techblog
https://blogs.msdn.microsoft.com/bharry/ (How the VSTS team does it)