Microservices Primer for Monolithic Devs

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

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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

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

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

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

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

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

MSDN
Determining
Service
Boundaries

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

Bounded Context Example
Course
Subject
Student
Class Schedule
Faculty
Advisor

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

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)

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

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; }
}

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 { }

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

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

MSDN
Managing
Distributed
Data

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

Querying Distributed Databases

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.
});

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(...)

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();
}

Eventually Consistent Services

Team DevOps
Repos Builds Releases

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

Unit Testing
Owned Dependencies
• Provisioning/Teardown
• Longer duration

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

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:

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

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

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)

Microservices Primer for Monolithic Devs

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