Amazon DynamoDBとAWS Lambdaを使ってナンバリング(採番)する。Node.js

numbering.js

"use strict";

var AWS = require('aws-sdk');
var documentClient = new AWS.DynamoDB.DocumentClient();

function asyncPutDb(hashKey) {

 return new Promise(function(resolve, reject) {
  var params = {
   TableName: process.env.DYNAMODB_TABLENAME,
   Item: {
    keyid: hashKey,
    countindex: 1
   }
  };

  documentClient.put(params, function(err, data) {
   if (err) {
    reject("asyncPutDb");
   }
   else {
    resolve(1);
   }
  });
 });
}

function asyncUpdateDb(hashKey) {

 return new Promise(function(resolve, reject) {
  var params = {
   TableName: process.env.DYNAMODB_TABLENAME,
   Key: {
    "keyid": hashKey
   },
   UpdateExpression: "set countindex = countindex + :addvalue",
   ExpressionAttributeValues: {
    ":addvalue": 1
   },
   ReturnValues: 'UPDATED_NEW'
  };

  documentClient.update(params, function(err, data) {
   if (err) {
    resolve(-2);
   }
   else {
    resolve(data.Attributes.countindex);
   }
  });
 });
}

function setResultJson(hashKey, countindex) {
 return {
  keyid: hashKey,
  countindex: countindex
 };
}

exports.handler = (event, context, callback) => {

 var response = {
  statusCode: 200,
  headers: { "Access-Control-Allow-Origin": "*" },
  body: {
   keyid: event.pathParameters.keyid,
   countindex: -1
  }
 };

 console.log("keyid:", event.pathParameters.keyid);

 asyncUpdateDb(event.pathParameters.keyid)
  .then(function(resultUpdate) {
   if (resultUpdate > 0) {
    console.log("resultUpdate:", resultUpdate);
    response.body = JSON.stringify(setResultJson(event.pathParameters.keyid, resultUpdate));
    callback(null, response);
   }
   else {
    asyncPutDb(event.pathParameters.keyid, response)
     .then(function(resultPut) {
      console.log("resultPut:", resultPut);
      response.body = JSON.stringify(setResultJson(event.pathParameters.keyid, resultPut));
      callback(null, response);
     })
     .catch(function(err) {
      console.log("put error:", err);
      callback(null, JSON.stringify(err));
     });
   }
  });
};