Spring & Guice DI

Spring

The way to use @Autowired and register beans:

@Component	simple bean
@Controller	servlet control ben
@Repository	DAO classes
@Configuration	general bean
XML file	define bean from xml

Also use @Bean to register a bean on method level.

@ComponentScan to detects and instantiates annotated components automatically

Guice

@Inject instead of @Autowired

@Provides instead of @Bean

Governator plugin instead of @ComponentScan

Guice Injection Styles

LOCATION	INJECTION ORDER	MOTIVATION	COMMENT
Constructor	First	Class immutability1 Mandatory dependencies	Only one allowed with @Inject.
Field	Second	Quick prototyping Code that doesn’t need testing	Injection order is random.
Setter	Third	Dealing with legacy classes Optional dependencies2	Injection

More info:

https://www.baeldung.com/guice-spring-dependency-injection
https://www.amazon.com/Google-Guice-Lightweight-Dependency-Firstpress/dp/1590599977

Kafka, Spark, and Elasticsearch (architecture comparison)

	Kafka	Spark	Elasticsearch
Horizontal Scale	Topic/Partition	RDD/Partition	Index/Shard (default 5 primary shards per index)
Resource/cluster manager	Zookeeper	YARN, Mesos, or standalone	Master Node
Cluster node	Broker	Worker	Node
Execution unit	Partition Leader	Executor	Lucene Index
Core		RDD	Inverted index
Applications	Producer/Consumer	Driver	Search
Replication	Follower (ISR)		Replica shard

Kafka:

http://cloudurable.com/blog/kafka-architecture/index.html

Spark:

https://www.dezyre.com/article/apache-spark-architecture-explained-in-detail/338

https://www.edureka.co/blog/spark-architecture/

Elasticsearch:

https://buildingvts.com/elasticsearch-architectural-overview-a35d3910e515

http://solutionhacker.com/elasticsearch-architecture-overview/

Microservices

12 factor app pattern

Four-tier application architecture

Two key attributes of microservice architecture:

1.     Loosely coupled:  means that you can update the services independently; updating one service doesn’t require changing any other services.

2.     bounded context: A microservice with correctly bounded context is self‑contained for the purposes of software development. You can understand and update the microservice’s code without knowing anything about the internals of its peers, because the microservices and its peers interact strictly through APIs and so don’t share data structures, database schemata, or other internal representations of objects.

Best practices for designing a microservices architecture:

1.     Create a separate data store for each microservice.

2.     Keep code at a similar level of maturity: if you need to add or rewrite some of the code in a deployed microservice that is working well, create a new microservice for the new or changed code.  Then deploy and test the new one.  Then merge/combine them.

3.     Do a separate build for each microservice.

4.     Deploy in containers.

5.     Treat servers as stateless.

More info: https://www.nginx.com/blog/microservices-at-netflix-architectural-best-practices/

API Gateway

·       Ngnix

·       Netflix Zuul 1

·       Spring Cloud Gateway

·       Linkerd

Their performance comparison:

https://engineering.opsgenie.com/comparing-api-gateway-performances-nginx-vs-zuul-vs-spring-cloud-gateway-vs-linkerd-b2cc59c65369

OpenAPI

OpenAPI Specification (formerly known as Swagger spec) is the industry standard for defining REST APIs.

Sample:

    swagger: "2.0"
    info:
      title: "Airport Codes"
      description: "Get the name of an airport from its three-letter IATA code."
      version: "1.0.0"
    # This field will be replaced by the deploy_api.sh script.
    host: "YOUR-PROJECT-ID.appspot.com"
    schemes:
      - "https"
    paths:
      "/airportName":
        get:
          description: "Get the airport name for a given IATA code."
          operationId: "airportName"
          parameters:
            -
              name: iataCode
              in: query
              required: true
              type: string
          responses:
            200:
              description: "Success."
              schema:
                type: string
            400:
              description: "The IATA code is invalid or missing."

API spec edit APICURIO:

https://www.apicur.io/

hapi-swagger:

https://github.com/glennjones/hapi-swagger