Introduction to AVSC

AVSC, short for Apache Avro Schema Compiler, is an essential tool for working with Avro schema in data serialization and deserialization processes. This comprehensive guide aims to provide you with an introductory overview of AVSC, along with detailed explanations of its APIs.

Getting Started with AVSC

To begin using AVSC, you need to install the library. Use the command below:

npm install avsc

Creating and Parsing Schemas

AVSC allows you to create and parse Avro schemas easily. Here’s an example:

const avro = require('avsc');

const type = avro.Type.forSchema({
  type: 'record',
  name: 'User',
  fields: [
    { name: 'name', type: 'string' },
    { name: 'age', type: 'int' }
  ]
});

const buf = type.toBuffer({ name: 'John', age: 30 }); // Encodes a User record
const user = type.fromBuffer(buf); // Decodes a User record

console.log(user); // { name: 'John', age: 30 }

Serializing and Deserializing Data

With AVSC, you can easily serialize and deserialize data as shown below:

// Serialization
const userSchema = {
  type: 'record',
  name: 'User',
  fields: [
    { name: 'username', type: 'string' },
    { name: 'email', type: 'string' }
  ]
};

const UserType = avro.Type.forSchema(userSchema);
const userData = { username: 'jane_doe', email: 'jane@example.com' };

const serializedBuffer = UserType.toBuffer(userData);
console.log(serializedBuffer);

// Deserialization
const deserializedData = UserType.fromBuffer(serializedBuffer);
console.log(deserializedData); // { username: 'jane_doe', email: 'jane@example.com' }

Working with Complex Types

AVSC supports complex types such as unions, enums, and arrays. Here’s an example of using these types:

const complexType = avro.Type.forSchema({
  type: 'record',
  name: 'Entity',
  fields: [
    { name: 'id', type: 'int' },
    { name: 'tags', type: { type: 'array', items: 'string' } },
    { name: 'status', type: { type: 'enum', name: 'Status', symbols: ['ACTIVE', 'INACTIVE'] } }
  ]
});

const entityBuffer = complexType.toBuffer({ id: 1, tags: ['tag1', 'tag2'], status: 'ACTIVE' });
const entity = complexType.fromBuffer(entityBuffer);

console.log(entity); // { id: 1, tags: ['tag1', 'tag2'], status: 'ACTIVE' }

Application Example with AVSC

Let’s create a simple application that uses AVSC to serialize and deserialize user data:

const express = require('express');
const avro = require('avsc');

const app = express();
app.use(express.json());

const userType = avro.Type.forSchema({
  type: 'record',
  name: 'User',
  fields: [
    { name: 'username', type: 'string' },
    { name: 'email', type: 'string' }
  ]
});

app.post('/user', (req, res) => {
  const buffer = userType.toBuffer(req.body);
  res.send(buffer);
});

app.get('/user/:buf', (req, res) => {
  const buffer = Buffer.from(req.params.buf, 'base64');
  const user = userType.fromBuffer(buffer);
  res.json(user);
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

In this example, we set up an Express server with two endpoints. One endpoint serializes user data to binary format, and the other deserializes the binary data back to JSON format.

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