Progress Track

Microservices

Day 1

Config Client | Config Client | Config Client
           \1        |2         /3
               +-------------+
               |Config Server|
               +-------------+

Day 2

• Fetching values from application properties to a class variables.

  @ConfigurationProperties("{name}")

• Centralized Configuration of Microservice server

  Dependency : Spring-Cloud-Config-Server

• Adding git to config server application.

  • higher priority

Day 3

• Server Configurations :

  spring.cloud.config.server.git.uri=file:///{Current directory Path}
  port : server.port={port}

• Clients Configurations :

  Dependency : spring-cloud-starter-config
  props : spring.config.import=optional:configserver:http://localhost:8888

• Multiple Profiles in app.props (activate a profile):

  spring.profiles.active={name}
  spring.cloud.config.profile={name}

Day 4

• Currency Exchange Service (Microservice Example) :
  

  • link : http://localhost:8000/currency-exchange/from/USD/to/INR

  • Fetch environment values from a class

    import org.springframework.core.env.Environment

  • Run multiple Instance of java app on different ports

    add vm options in run config : [-Dserver.port={port}]

• Currency Conversion Service (connect with exchange service) :
  

  • link : http://localhost:8100/currency-conversion/from/USD/to/INR/quantity/10

  • Get REst Data from different microservice via URI :

    RestTemplate rt = new RestTemplate().{methods};

  • OpenFeign Rest Client for service invocation (Optimize Rest Template) :

    dependency : spring-cloud-starter-openfeign
    Main class : @EnableFeignClients
    Proxy Interface : @FeignClient(name={spring.app.name}, url={url})

    • link : http://localhost:8100/currency-conversion-feign/from/USD/to/INR/quantity/10

Day 5

• Eureka Naming server (Registry for microservices name):

  Dependency : spring-cloud-starter-netflix-eureka-client
  Main class : @EnableEurekaServer

  • Disable self discovery of server

    eureka.client.register-with-eureka=false
    eureka.client.fetch-registry=false

  • link : http://localhost:8761

• Eureka Clients (service discovery) :

  eureka.client.service-url.defaultZone=http://localhost:8761/eureka

Day 6

• Load Balancing on client side (feign)

  • remove url in @FeignClient(url=?) for auto load balancing.

• Api Gateway Discovery Locator (authentication, authorization, logging, rate limiting)

  Dependency : spring-cloud-starter-gateway
  props : spring.cloud.gateway.discovery.locator.enabled=true

• Links (Initial) :

  • http://localhost:8765/CURRENCY-EXCHANGE/currency-exchange/from/USD/to/INR
  • http://localhost:8765/CURRENCY-CONVERSION/currency-conversion/from/USD/to/INR/quantity/10
  • http://localhost:8765/CURRENCY-CONVERSION/currency-conversion-feign/from/EUR/to/INR/quantity/10

• Fixing uppercase letters in links :

  props : spring.cloud.gateway.discovery.locator.lower-case-service-id=true

  • New Links (lowercase) :
    • http://localhost:8765/currency-exchange/currency-exchange/from/USD/to/INR
    • http://localhost:8765/currency-conversion/currency-conversion/from/USD/to/INR/quantity/10
    • http://localhost:8765/currency-conversion/currency-conversion-feign/from/EUR/to/INR/quantity/10

• Routes with Spring Cloud Gateway

1. Define a @Configuration Class
2. Define a @Bean of return type RouteLocator with parameters (RouteLocatorBuilder builder)
3. Define routes :

  return builder.routes()
                .route(p -> p
                        .path("/get")
                //GatewayFilterSpec filters
                        .filters(f -> f
                                .addRequestHeader("{MyHeader}", "{MyURI}")
                                .addRequestParameter("{MyParam}", "{MyValue}"))
                        .uri("http://httpbin.org/get"))
                //predicate
                .route(p -> p
                        .path("/{path}/**")
                        .uri("lb://{path}"))
                //for rewriting paths
                .route(p -> p
                        .path("/currency-conversion-new/**")
                        .filters(f -> f.rewritePath("currency-conversion-new/(?<segment>.*)", "/currency-conversion-feign/${segment}"))
                        .uri("lb://currency-conversion"))
                .build(); 

• links :
  • http://httpbin.org/get
  • http://localhost:8765/currency-exchange/from/USD/to/INR
  • http://localhost:8765/currency-conversion/from/USD/to/INR/quantity/10
  • http://localhost:8765/currency-conversion-feign/from/EUR/to/INR/quantity/10
  • http://localhost:8765/currency-conversion-new/from/AUD/to/INR/quantity/110

Day 7

• Spring Cloud Gateway Logging Filter

  class : implements gateway.filter.GlobalFilter implement method : Mono filter(ServerWebExchange exchange, GatewayFilterChain chain)

• Circuit Breaker from Resilience4j

  Dependency : resilience4j-spring-boot2
  Dependency : spring-boot-starter-aop

  • @Retry(name = "{name}") on api method
    • fallback : @Retry(fallbackMethod={implemented Method name with accepting Exception param})
  • some properties :

    resilience4j.retry.instances.{api-name}.max-attempts=5
    resilience4j.retry.instances.{api-name}.wait-duration=2s
    resilience4j.retry.instances.{api-name}.enable-exponential-backoff=true
    

• Breaking Circuit for failing microservices (closed -> open <-> half_open -> closed):

  @CircuitBreaker(name = "default", fallbackMethod = "fallbackRestTemplate")
  props : resilience4j.circuitbreaker.instances.{name}.{property}={value}

• Rate Limiting

  @RateLimiter(name = {name})
  props : resilience4j.ratelimiter.instances.{name}.{property}={value}

• Allowing Concurrent requeusts

  @BulkHead(name={name})

Microservices with Docker

Day 8

• Docker commands

  Tailing logs : logs {id} -f
  Search Image : search {imageName}
  Stopping container : pause / unpause, stop, kill
  AutoRestart Container : run --restart=always
  Events : events
  Running process : top
  container details : stats
  cpu quota : run --cpu-quota={1-100000}
  memory : run -m {memSize}{m/g}
  docker daemon : system df
  

• Distributed Tracing

  Tracing / Debugging

  • Run zipkin on port 9411

• OpenTelemetry

  • Dependencies :

    Micrometer : micrometer-observation
    OpenTelemetry : micrometer-tracing-bridge-otel
    Zipkin : opentelemetry-exporter-zipkin
    

  • Properties :

    management.tracing.sampling.probability={,1.0}
    logging.pattern.level=%5p [${spring.application.name:},%X{traceId:-},%X{spanId:-}]

  • zipkin link : http://localhost:9411

  • Enable Tracing in feign api calls :

    Dependency : feign-micrometer

  • Integrate micrometer with RestTemplate :

    @Configuration(proxyBeanMethods = false)
    class RestTemplateConfiguration {
      //create RestTemplate using RestTemplateBuilder
      @Bean
      RestTemplate restTemplate(RestTemplateBuilder builder) {
          return builder.build();
      }
    }

Day 9

• Creating container image from pom.xml

      <configuration>
          <image>
              <name>{imageName}</name>
          </image>
          <pullPolicy>IF_NOT_PRESENT</pullPolicy>
          //fixes {:} issue
          <docker>
              <host>//./pipe/dockerDesktopLinuxEngine</host>
          </docker>
      </configuration>

  - run image: docker run -p 8000:8000 devraman/ms-currency-exchange-service:0.0.1-SNAPSHOT

## Day 10