post.js

'use strict'

const uuid = require('uuid')
const AWS = require('aws-sdk')
const logger = require('logger')
const otel = require('@opentelemetry/api')

module.exports.handler = async (event) => {
  logger.info('The event', event)

  // Get the current active span
  const activeSpan = otel.trace.getSpan(otel.context.active())
  try {
    const body = JSON.parse(event.body)

    const post = {
      id: uuid.v4(),
      title: body.title,
      content: body.content,
      created: new Date().toISOString(),
    }
    // Add the post to the active span
    activeSpan.setAttribute('post.id', post.id)

    await writeToDb(post)
    // Add an event to the span, signaling a post was created
    activeSpan.addEvent('POST_CREATED', { 'post.id': post.id })

    return {
      statusCode: 200,
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ message: 'Post created', post }),
    }
  } catch (error) {
    logger.info('There was an error handling a request', { event, error })
    activeSpan.recordException(error)
    // Set the active span status to error
    activeSpan.setStatus({ code: otel.SpanStatusCode.ERROR })
    return {
      statusCode: 500,
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ message: 'Fatal Error' }),
    }
  }
}

async function writeToDb(post) {
  const dynamoDb = new AWS.DynamoDB.DocumentClient({
    apiVersion: '2012-08-10',
    region: process.env.REGION,
  })
  const tableName = process.env.PROJECTION_TABLE

  const params = {
    TableName: tableName,
    Item: {
      partitionKey: `post#${post.id}`,
      data: post,
      type: 'post',
    },
    ConditionExpression: 'attribute_not_exists(partitionKey)',
  }

  try {
    await dynamoDb.put(params).promise()
  } catch (err) {
    logger.error('There was an error writing to the database', { post, error })
    throw err
  }
}