A Simple API Using AWS RDS, Lambda, and API Gateway
Let's use a host of AWS tools—RDS, Lambda, and API Gateway—to create a simple API that can scale on your cloud deployment.
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Join For FreeI wrote about a simple API with AWS DynamoDB, Lambda, and API Gateway last week. I like this approach because of the simple nature of AWS DynamoDB. One benefit of going this route is that you can even bypass Lambda, as the AWS API Gateway can work directly with AWS DynamoDB API. I’m just playing around with different configurations and pushing forward my understanding of what is possible, and this week I switched out the database with AWS RDS, which opens up the ability to use MySQL or Postgres as the backend for any API.
For this example, I’m using a simple items database, which you can build with this SQL script after you fire up an RDS instance (I’m using MySQL):
CREATE TABLE `items` (
`item_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(100) DEFAULT NULL,
PRIMARY KEY (`account_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
Next, I wanted to have the basic CRUD operations for my API. I opted to use Node.js running in Lambda for the code layer of this API, starting with the ability to get all records from the database:
var mysql = require('mysql');
exports.handler = function(event, context) {
var connection = mysql.createConnection({
host: '[rds_host]',
user: '[rds_user]',
password: '[rds_password]',
database: '[rds_database]'
});
connection.query('SELECT * FROM items', function(error, results, fields) {
context.succeed(results);
});
After that, I want to be able to insert new records:
var mysql = require('mysql');
exports.handler = function(event, context) {
var connection = mysql.createConnection({
host: '[rds_host]',
user: '[rds_user]',
password: '[rds_password]',
database: '[rds_database]'
});
sql = "INSERT INTO items(name)";
sql = sql + " VALUES('" + event.name + "')";
connection.query(sql, function(error, results, fields) {
response = {};
response['item_id'] = results.insertId;
response['name'] = event.name;
context.succeed(response);
});
}
Then, of course, be able to get a single record:
var mysql = require('mysql');
exports.handler = function(event, context) {
var connection = mysql.createConnection({
host: '[rds_host]',
user: '[rds_user]',
password: '[rds_password]',
database: '[rds_database]'
});
sql = "SELECT * FROM items WHERE item_id = " + event.item_id;
connection.query(sql, function(error, results, fields) {
context.succeed(results);
});
}
Then be able to update a single record:
var mysql = require('mysql');
exports.handler = function(event, context) {
var connection = mysql.createConnection({
host : '[rds_host]',
user : '[rds_user]',
password : '[rds_password]',
database : '[rds_database]'
});
sql = "UPDATE items SET ";
sql = sql + "name = '" + event.name + "'";
sql = sql + " WHERE item_id = " + event.item_id;
connection.query(sql, function (error, results, fields) {
response = {};
response['item_id'] = event.item_id;
response['name'] = event.name;
context.succeed(response);
});
}
And of course I want to be able to delete records:
var mysql = require('mysql');
exports.handler = function(event, context) {
var connection = mysql.createConnection({
host: '[rds_host]',
user: '[rds_user]',
password: '[rds_password]',
database: '[rds_database]'
});
sql = "DELETE FROM items WHERE item_ID = " + event.item_id;
connection.query(sql, function(error, results, fields) {
response = {};
response['deleted'] = event.item_id;
context.succeed(results);
});
}
Now that I have the business logic set up in AWS Lambda for reading, and writing data to my relational database I want an API front-end for this backend setup. I am using AWS API Gateway as the API layer, and to set up, I’m just importing an OpenAPI definition to jumpstart things:
swagger'2.0'
info
title"Item API"
description"This is a simple API"
termsOfService"https://example.com/tos/"
contact
name API Evangelist
url https //apievangelist.com
email info@apievangelist.com
license
name Need a License for Interface
url http //example.com/license/
version v1.2
host example.com
basePath /
schemes
http
produces
application/json
paths
/items
get
summary Get Items
description Returns items.
operationId getItems
responses
'200'
description Item Response
schema
type array
items
$ref"#/definitions/item"
'500'
description Error Response
schema
type array
items
$ref"#/definitions/error"
tags
Items
x-lambda-script /lambda-scripts/get_items/index.js
post
summary Add Item
description Add item.
operationId addItem
parameters
in body
name body
schema
$ref'#/definitions/item'
responses
'200'
description Item Response
schema
type array
items
$ref"#/definitions/item"
'500'
description Error Response
schema
type array
items
$ref"#/definitions/error"
tags
Items
x-lambda-script /lambda-scripts/create_item/index.js
/items//{item_id}/
get
summary Get item.
description Returns a single item
operationId getItem
parameters
in path
requiredtrue
type string
name item_id
description The item id.
responses
'200'
description Item Response
schema
type array
items
$ref"#/definitions/item"
'500'
description Error Response
schema
type array
items
$ref"#/definitions/error"
tags
Items
x-lambda-script /lambda-scripts/get_item/index.js
put
summary Update item.
description Updates an item.
operationId updateItem
parameters
in path
requiredtrue
type string
name item_id
description The item id.
in body
name body
schema
$ref'#/definitions/item'
responses
'200'
description Item Response
schema
type array
items
$ref"#/definitions/item"
'403'
description No Access Response
schema
type array
items
$ref"#/definitions/error"
'500'
description Error Response
schema
type array
items
$ref"#/definitions/error"
tags
Items
x-lambda-script /lambda-scripts/update_item/index.js
delete
summary Delete item.
description Deletes an item.
operationId deleteItem
parameters
in path
requiredtrue
type string
name item_id
description'The item id.'
responses
'200'
description Contact Response
schema
type array
items
$ref"#/definitions/item"
'403'
description No Access Response
schema
type array
items
$ref"#/definitions/error"
'500'
description Error Response
schema
type array
items
$ref"#/definitions/error"
tags
Items
x-lambda-script /lambda-scripts/delete_item/index.js
definitions
item
description The developer item.
properties
item_id
description'The id for the item.'
type string
name
description'The name of the item.'
type string
error
description'Describes an HTTP error returned'
properties
code
description'Repeat the HTTP status code'
type integer
message
description'A plain language message explaining the error'
type integer
This gives me the skeleton framework for my API, with the paths and methods I need to accomplish the basics of reading and writing data. Now, I just need to wire up each API method to its accompanying Lambda function, something API Gateway makes easy.
Now I have an API for my basic backend. There is one thing you have to do to make each method work properly with the Lambda function. You have to set up a body mapping to the item_id when passed in the path for the PUT, GET, and DELETE functions. If you don’t the item_id won’t be passed on to the Lambda function — it took me a while to get this one.
There are other things you have to do, like setting up a usage plan, turning on API key access for each API, and setting up custom domain if you want, but hopefully this simple gets the point across. I will work on other parts in future posts. Hopefully, it provides a basic example of an API using RDS, Lambda, and API Gateway, which is something I have wanted to have in my toolbox for some time.
The process has opened my eyes up wider to the serverless world, as well as playing more with Node.js — which has been on my list for some time now. It provides a pretty solid, scalable, manageable way to deploy an API using AWS. I have all the code on GitHub and will be evolving as I push it forward.
If you apply the Lambda scripts, make sure you upload individually as zipped files so that the MySQL dependencies are there, otherwise the script won’t connect to the database. It should provide a base template you can use to seed any basic data API. This is why I’ve added it to my API Evangelist toolbox, giving me a simple, forkable set of scripts I can use as a seed for any new API. I will add more scripts and templates to it over time, rounding off the functionality as I evolve in my understanding of deploying API using AWS RDS, Lambda, and API Gateway.
Published at DZone with permission of Kin Lane, DZone MVB. See the original article here.
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