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Reading notes for Building Distributed Applications with the Gin Framework: p251-p271

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Learning Day 14 of Building Distributed Applications with the Gin Framework, p251-p271 Summary, 21 total pages.

I. Technical summary

& Docker Compose

version: "3.9" 

services:
  api:
    image: api
    environment:
      - MONGO_URI=mongodb://admin:password@mongodb:27017/test?authSource=admin&readPreference=primary&ssl=false
      - MONGO_DATABASE=demo
      - REDIS_URI=redis:6379
    networks:
      - api_network
    external_links:
      - mongodb
      - redis
    scale: 5

  dashboard:
    image: dashboard
    networks:
      - api_network

  redis:
    image: redis
    networks:
      - api_network
    ports:
      - 6379:6379

  mongodb:
    image: mongo:4.4.3
    networks:
      - api_network
    ports:
      - 27017:27017
    environment:
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=password

  nginx:
    image: nginx
    ports:
      - 80:80
    volumes:
      - $PWD/:/etc/nginx/
    depends_on:
      - api
      - dashboard
    networks:
      - api_network
  
  reddit-trending:
    image: web
    environment:
      - MONGO_URI=mongodb://admin:password@mongodb:27017/test?authSource=admin&readPreference=primary&ssl=false
      - MONGO_DATABASE=demo2
    networks:
      - api_network

networks:
  api_network:

Here are some additional ones that are not explained in the book:

(1)version

The version field is deprecated in the new version of Docker Compose. For example, the code above:

version: "3.9"

It can be deleted.

(2)external_links

If the same networks are set for each service, then external_links can be removed in newer versions of Docker Compose. For example the code above:

external_links:
      - mongodb
      - redis

It can be deleted.

Robin's algorithm

The Round Robin algorithm is the default algorithm for Nginx, and is described in the official Nginx documentation (/nginx/admin-guide/load-balancer/http-load-balancer/) is:

Round Robin – Requests are distributed evenly across the servers, with server weights taken into consideration. This method is used by default (there is no directive for enabling it)。

& Traefik

Nginx and Traefik are similar software used for load balancing. The default load balancing algorithm is Round Robin, and the book uses Docker for deployment.

II. English summary

p251, The configuration specifies the environment variables and network topology that

the worker requires.

(1)topology: topos(“place”) + -logy("study")。c/u. study or places, structure of places，topology of a network (elec.)。

III. Other

On the 14th day of reading the book, I am halfway through the book. The book is written in a very easy-to-understand manner, and after counting the daily "English summaries", I realized that I have only encountered 22 vocabulary words, but the reading speed (20 pages/day) is still very slow. At this point, English is no longer an obstacle, the obstacle is the understanding and application of concepts. As an example, the author set up WORKDIR in the Dockerfile:

WORKDIR /go/src//api

From the literal meaning alone we are not difficult to understand, it is difficult to understand: (1) WORKDIR value set why good? Here spit, the author set to / go / src / / api, the actual development I think not many people will use such a name as the project directory name. (2) When to use WORKDIR and when not to use WORKDIR?(3) Where to write WORKDIR?

So how to better understand the concepts here? Here are some of my approaches: (1) Participate in real projects. This is the most direct and fastest way, but also the most difficult. Because what one can do in practice is often a small part of the work, so the limitations are very large. If you can, it is best to get involved in some open source projects. (2) Read more. Often understanding is not "one step at a time", but "slowly", you read this book can not understand, and then read a book may understand.

IV. References

1. Programming

(1) Mohamed Labouardy，《Building Distributed Applications in Gin》：/subject/35610349

2. English

(1) Etymology Dictionary：

(2) Cambridge Dictionary：

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