Forem: Lawson

Monolithic vs Microservice

Lawson — Tue, 21 Mar 2023 15:18:03 +0000

Microservice

Monolithic Architecture

A monolithic design refers to software that is built and deployed as a signle unit, called a monolith. A monolith usually consists of a user interface, a server-side application and a database.

The concept behind monolithic software is that different parts of a system are closely tied together, such as in a monolith, this system is called to exhibit tigh coupling.

This architecture has a number of benefits:

Simple to test and deploy
Easy scaling by running multiple copies behind a load balancer.
Perfomant and low latency. Requests are served from a signle unit which means the request path contains few network hops and components.

Monolithic Hell

Overwhelmingly Complex

Applications are software systems that tend to grow over time, accumulating more and more functionality. As a result, they often become huge and difficult to comprehend, even for experienced developers. This can make fixing bugs and implementing new features a daunting task that requires a significant amount of time and effort.

Larger apps take longer to start up.

Larger apps, with more complex features and functionalities, require more time to start up. This can be due to a variety of factors, such as larger amounts of data to load, more complex algorithms to run, or more resources required to manage the larger app. If we have to regularly restart the application server, it causes a large part of the day to be spent waiting around, and productivity suffers. In addition, it is important to consider the impact of such downtime on clients and customers who may be relying on the application for critical business functions. Extended downtime may result in lost revenue, missed deadlines, and a negative impact on the company's reputation. Therefore, it is essential to implement measures to minimize the frequency and duration of server outages, such as regular maintenance and updates, load balancing, and failover systems.

Reliability

When a software application is composed of multiple modules running within the same process, it is important to consider the impact of bugs within these modules. One such bug that can have significant consequences is a memory leak. If a memory leak is present in any of the modules, it can gradually consume more and more memory, eventually causing the entire process to crash.

Extremely difficult to adopt new frameworks and languages.

Microservice

A microservice is a software development technique that structures an application as a collection of small, independent services that work together to accomplish a larger goal.

A service typically implements a set of distinct features or functionality, such as order management, customer management, etc. Each microservice is a mini-application that has
its own hexagonal architecture consisting of business logic along with various adapters.

Some microservices would expose an API that’s consumed by other microservices or by the application’s clients. Other microservices might implement a web UI. At runtime, each instance is often a cloud virtual machine (VM) or a Docker container.

Benefits and drawbacks

Benefits

It tackles the problem of complexity.

It decomposes what would otherwise be a monstrous monolithic application into a set of services.
While the total amount of functionality is unchanged, the application has been broken up into manageable services.
Individual services are much faster to develop and much easier to understand and maintain.

Independence

The developers are free to choose whatever technologies make sense.
When writing a new service, they have a option of using technology. Moreover, since services are relatively small. it becomes more feasible to rewrite the old service using current technology.
At runtime, each service is often a cloud virtual machine (VM) or a Docker container.
the Microservices Architecture pattern enables each service to be scaled independently.

Easy to deploy

Developers never need to coordinate the deployment of changes that are local to their service
These kinds of changes can be deployed as soon as they have been tested.

Drawbacks

One drawback is the name itself.

The term microservice places excessive emphasis on service size. In fact, there are some developers who advocate for building extremely fine-grained 10-100 LOC services. While small services are preferable, it’s important to remember that small services are a means to an end, and not the primary goal. The goal of microservices is to sufficiently decompose the application in order to facilitate agile application development and deployment.

A microservices application is a distributed system.

Developers need to choose and implement an inter-process communication mechanism based on either messaging or RPC. Moreover, they must also write code to handle partial failure, since the destination of a request might be slow or unavailable. While none of this is rocket science, it’s much more complex than in a monolithic application, where modules invoke one another via
language-level method/procedure calls.

The partitioned database architecture.

Business transactions that update multiple business entities are fairly common. These kinds of transactions are trivial to implement in a monolithic application because there is a single
database. In a microservices-based application, however, you need to update multiple databases owned by different services. Using distributed transactions is usually not an option, and not only because of the CAP theorem.

Implementing changes that span multiple services.

For example, let’s imagine that you are implementing a story that requires changes to services A, B, and C, where A depends upon B and B depends upon C. In a monolithic application you could simply change the corresponding modules, integrate the changes, and deploy them in one go. In contrast, in a Microservices Architecture pattern you need to carefully plan and coordinate the rollout of changes to each of the services. For example, you would need to update service C, followed by service B, and then finally service A. Fortunately, most changes typically impact only
one service; multi-service changes that require coordination are relatively rare.

Why are the results like this?

Lawson — Tue, 27 Dec 2022 07:49:46 +0000

const defaultEmployee = {
  tasks: []
}

const employees = []

const NUMEBR_OF_EMPLOYEE = 5
const INDEX_CEO = 0

for (let index = 0; index <= NUMEBR_OF_EMPLOYEE; index++) {
  const employee = {
    ...defaultEmployee,
    role: index
  }

  if (employee.role === INDEX_CEO) {
    employee.tasks.push({ salary: 10.000 })
  } else {
    employee.tasks.push({ salary: 1.0 })
  }

  employees.push(employee)
  console.log(defaultEmployee)
}

console.log(employees)

Result:

Using Absolute Paths in React Native

Lawson — Wed, 15 Jun 2022 14:30:04 +0000

Expectation

// Hmmm
import {add} from '../../../../../../../utils';

// Awesome!
import {add} from 'utils';

How ?

Step 1: Install babel-plugin-module-resolver

npm install --save-dev babel-plugin-module-resolver
// or
yarn add --dev babel-plugin-module-resolver

Step 2: Add the following code to babel.config.js file.

module.exports = {
  presets: ['module:metro-react-native-babel-preset'],
  plugins: [
    [
      require.resolve('babel-plugin-module-resolver'),
      {
        root: ["./src"],
      }
    ],
  ]
};

Step 3: Create file jsconfig.json

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "*": ["src/*"],
    }
  }
}

React Style Guide

Lawson — Thu, 29 Apr 2021 08:54:01 +0000

React Style Guide (2021)

src: the original post: https://github.com/airbnb/javascript/tree/master/react

I wanted to create this post to mark back what's important when someone is just starting out with React. Therefore, I would like to receive comments from everyone.

Basic Rules

Only include one React component per file.
Always use JSX syntax.

Naming

List itemExtensions: Use .jsx extension for React components. eslint: react/jsx-filename-extension
Filename: Use PascalCase for filenames. E.g., ReservationCard.jsx.
Reference Naming: Use PascalCase for React components and camelCase for their instances.

// bad
import reservationCard from './ReservationCard';

// good
import ReservationCard from './ReservationCard';

// bad
const ReservationItem = <ReservationCard />;

// good
const reservationItem = <ReservationCard />;

Component Naming: Use the filename as the component name. For example, ReservationCard.jsx should have a reference name of ReservationCard. However, for root components of a directory, use index.jsx as the filename and use the directory name as the component name:

// bad
import Footer from './Footer/Footer';

// bad
import Footer from './Footer/index';

// good
import Footer from './Footer';

Higher-order Component Naming: Use a composite of the higher-order component’s name and the passed-in component’s name as the displayName on the generated component. For example, the higher-order component withFoo(), when passed a component Bar should produce a component with a displayName of withFoo(Bar).

Why? A component’s displayName may be used by developer tools or in error messages, and having a value that clearly expresses this relationship helps people understand what is happening.

// bad
export default function withFoo(WrappedComponent) {
  return function WithFoo(props) {
    return <WrappedComponent {...props} foo />;
  }
}

// good
export default function withFoo(WrappedComponent) {
  function WithFoo(props) {
    return <WrappedComponent {...props} foo />;
  }

  const wrappedComponentName = WrappedComponent.displayName
    || WrappedComponent.name
    || 'Component';

  WithFoo.displayName = `withFoo(${wrappedComponentName})`;
  return WithFoo;
}

Declaration

Do not use displayName for naming components. Instead, name the component by reference.

// bad
export default React.createClass({
  displayName: 'ReservationCard',
  // stuff goes here
});

// good
export default function ReservationCard(props) {
    return ()
}

Alignment

Follow these alignment styles for JSX syntax. eslint: react/jsx-closing-bracket-location react/jsx-closing-tag-location

// bad
<Foo superLongParam="bar"
     anotherSuperLongParam="baz" />

// good
<Foo
  superLongParam="bar"
  anotherSuperLongParam="baz"
/>

// if props fit in one line then keep it on the same line
<Foo bar="bar" />

// children get indented normally
<Foo
  superLongParam="bar"
  anotherSuperLongParam="baz"
>
  <Quux />
</Foo>

// bad
{showButton &&
  <Button />
}

// bad
{
  showButton &&
    <Button />
}

// good
{showButton && (
  <Button />
)}

// good
{showButton && <Button />}

// good
{someReallyLongConditional
  && anotherLongConditional
  && (
    <Foo
      superLongParam="bar"
      anotherSuperLongParam="baz"
    />
  )
}

// good
{someConditional ? (
  <Foo />
) : (
  <Foo
    superLongParam="bar"
    anotherSuperLongParam="baz"
  />
)}

Props

Always use camelCase for prop names, or PascalCase if the prop value is a React component.

// bad
<Foo
  UserName="hello"
  phone_number={12345678}
/>

// good
<Foo
  userName="hello"
  phoneNumber={12345678}
  Component={SomeComponent}
/>

Omit the value of the prop when it is explicitly true. eslint: react/jsx-boolean-value

// bad
<Foo
  hidden={true}
/>

// good
<Foo
  hidden
/>

// very good
<Foo hidden />

Avoid using an array index as key prop, prefer a stable ID. eslint: react/no-array-index-key

Why? Not using a stable ID is an anti-pattern because it can negatively impact performance and cause issues with component state.

We don’t recommend using indexes for keys if the order of items may change.

  // bad
  {todos.map((todo, index) =>
    <Todo
      {...todo}
      key={index}
    />
  )}

  // good
  {todos.map(todo => (
    <Todo
      {...todo}
      key={todo.id}
    />
  ))}

Always define explicit defaultProps for all non-required props.

Why? propTypes are a form of documentation, and providing defaultProps means the reader of your code doesn’t have to assume as much. In addition, it can mean that your code can omit certain type checks.

  // bad
  function SFC({ foo, bar, children }) {
    return <div>{foo}{bar}{children}</div>;
  }
  SFC.propTypes = {
    foo: PropTypes.number.isRequired,
    bar: PropTypes.string,
    children: PropTypes.node,
  };

  // good
  function SFC({ foo, bar, children }) {
    return <div>{foo}{bar}{children}</div>;
  }
  SFC.propTypes = {
    foo: PropTypes.number.isRequired,
    bar: PropTypes.string,
    children: PropTypes.node,
  };
  SFC.defaultProps = {
    bar: '',
    children: null,
  };

Use spread props sparingly. > Why? Otherwise you’re more likely to pass unnecessary props down to components. And for React v15.6.1 and older, you could pass invalid HTML attributes to the DOM.

Exceptions:

HOCs that proxy down props and hoist propTypes

  function HOC(WrappedComponent) {
    return class Proxy extends React.Component {
      Proxy.propTypes = {
        text: PropTypes.string,
        isLoading: PropTypes.bool
      };

      render() {
        return <WrappedComponent {...this.props} />
      }
    }
  }

Spreading objects with known, explicit props. This can be particularly useful when testing React components with Mocha’s beforeEach construct.

  export default function Foo {
    const props = {
      text: '',
      isPublished: false
    }

    return (<div {...props} />);
  }

Notes for use:
Filter out unnecessary props when possible. Also, use prop-types-exact to help prevent bugs.

  // bad
  render() {
    const { irrelevantProp, ...relevantProps } = this.props;
    return <WrappedComponent {...this.props} />
  }

  // good
  render() {
    const { irrelevantProp, ...relevantProps } = this.props;
    return <WrappedComponent {...relevantProps} />
  }

Refs

Always use ref callbacks. eslint: react/no-string-refs

// bad
<Foo
  ref="myRef"
/>

// good
<Foo
  ref={(ref) => { this.myRef = ref; }}
/>

Parentheses

Wrap JSX tags in parentheses when they span more than one line. eslint: react/jsx-wrap-multilines

// bad
render() {
  return <MyComponent variant="long body" foo="bar">
           <MyChild />
         </MyComponent>;
}

// good
render() {
  return (
    <MyComponent variant="long body" foo="bar">
      <MyChild />
    </MyComponent>
  );
}

// good, when single line
render() {
  const body = <div>hello</div>;
  return <MyComponent>{body}</MyComponent>;
}

Methods

Use arrow functions to close over local variables. It is handy when you need to pass additional data to an event handler. Although, make sure they do not massively hurt performance, in particular when passed to custom components that might be PureComponents, because they will trigger a possibly needless rerender every time.

function ItemList(props) {
  return (
    <ul>
      {props.items.map((item, index) => (
        <Item
          key={item.key}
          onClick={(event) => { doSomethingWith(event, item.name, index); }}
        />
      ))}
    </ul>
  );
}

Bind event handlers for the render method in the constructor. eslint: react/jsx-no-bind

Why? A bind call in the render path creates a brand new function on every single render. Do not use arrow functions in class fields, because it makes them challenging to test and debug, and can negatively impact performance, and because conceptually, class fields are for data, not logic.

// bad
class extends React.Component {
  onClickDiv() {
    // do stuff
  }

  render() {
    return <div onClick={this.onClickDiv.bind(this)} />;
  }
}

// very bad
class extends React.Component {
  onClickDiv = () => {
    // do stuff
  }

  render() {
    return <div onClick={this.onClickDiv} />
  }
}

// good
class extends React.Component {
  constructor(props) {
    super(props);

    this.onClickDiv = this.onClickDiv.bind(this);
  }

  onClickDiv() {
    // do stuff
  }

  render() {
    return <div onClick={this.onClickDiv} />;
  }
}

Do not use underscore prefix for internal methods of a React component.

Why? Underscore prefixes are sometimes used as a convention in other languages to denote privacy. But, unlike those languages, there is no native support for privacy in JavaScript, everything is public. Regardless of your intentions, adding underscore prefixes to your properties does not actually make them private, and any property (underscore-prefixed or not) should be treated as being public. See issues #1024, and #490 for a more in-depth discussion.
```
// bad
React.createClass({
  _onClickSubmit() {
    // do stuff
  },

  // other stuff
});

// good
class extends React.Component {
  onClickSubmit() {
    // do stuff
  }

  // other stuff
}
```

Be sure to return a value in your render methods. eslint: react/require-render-return

// bad
render() {
  (<div />);
}

// good
render() {
  return (<div />);
}