This tutorial implements an autocomplete API powered by serverless Redis. See
the demo and
API endpoint
and
the source code.
We will keep country names in a Redis Sorted set. In Redis sorted set, elements
with the same score are sorted lexicographically. So in our case, all country
names will have the same score, 0. We keep all prefixes of country and use ZRANK
to find the terms to suggest. See
this blog post
for the details of the algorithm.
Step 1: Project Setup
I will use Serverless framework for this tutorial. You can also use AWS
SAM
If you do not have it already install serverless framework via:
npm install -g serverless
In any folder run serverless
as below:
>> serverless
Serverless: No project detected. Do you want to create a new one? Yes
Serverless: What do you want to make? AWS Node.js
Serverless: What do you want to call this project? test-upstash
Project successfully created in 'test-upstash' folder.
You can monitor, troubleshoot, and test your new service with a free Serverless account.
Serverless: Would you like to enable this? No
You can run the “serverless” command again if you change your mind later.
Inside the project folder create a node project with the command:
Then install the redis client with:
Step 2: API Implementation
Edit handler.js file as below. See
the blog post
for the details of the algorithm.
var Redis = require("ioredis");
if (typeof client === "undefined") {
var client = new Redis(process.env.REDIS_URL);
}
const headers = {
"Access-Control-Allow-Origin": "*",
"Access-Control-Allow-Credentials": true,
};
module.exports.query = async (event, context, callback) => {
if (!event.queryStringParameters || !event.queryStringParameters.term) {
return {
statusCode: 400,
headers: headers,
body: JSON.stringify({
message: "Invalid parameters. Term needed as query param.",
}),
};
}
let term = event.queryStringParameters.term.toUpperCase();
let res = [];
let rank = await client.zrank("terms", term);
if (rank != null) {
let temp = await client.zrange("terms", rank, rank + 100);
for (const el of temp) {
if (!el.startsWith(term)) {
break;
}
if (el.endsWith("*")) {
res.push(el.substring(0, el.length - 1));
}
}
}
return {
statusCode: 200,
headers: headers,
body: JSON.stringify({
message: "Query:" + event.queryStringParameters.term,
result: res,
}),
};
};
Step 3: Create database on Upstash
If you do not have one, create a database following this
guide. Copy the Redis URL by clicking Redis Connect
button inside database page. Copy the URL for ioredis as we use ioredis in our
application. Create .env file and paste your Redis URL:
This example uses ioredis, you can copy the connection string from the
Node tab in the console.
Step 4: Initialize Database
We will initialize the database with country names. Copy and run initdb.js
script from
here.
We simply put the country names and all their prefixes to the sorted set.
require('dotenv').config()
var Redis = require("ioredis");
var countries = [
{"name": "Afghanistan", "code": "AF"},
{"name": "Åland Islands", "code": "AX"},
{"name": "Albania", "code": "AL"},
{"name": "Algeria", "code": "DZ"},
...
]
var client = new Redis(process.env.REDIS_URL);
for (const country of countries) {
let term = country.name.toUpperCase();
let terms = [];
for (let i = 1; i < term.length; i++) {
terms.push(0);
terms.push(term.substring(0, i));
}
terms.push(0);
terms.push(term + "*");
(async () => {
await client.zadd("terms", ...terms)
})();
}
Step 5: Deploy Your Function
Edit serverless.yml
as below and replace your Redis URL:
service: auto-complete-api
useDotenv: true
frameworkVersion: "2"
provider:
name: aws
runtime: nodejs14.x
lambdaHashingVersion: 20201221
environment:
REDIS_URL: REPLACE_YOUR_REDIS_URL
functions:
query:
handler: handler.query
events:
- httpApi:
path: /query
method: get
cors: true
In the project folder run:
Now you can run your function with:
serverless invoke -f query -d '{ "queryStringParameters": {"term":"ca"}}'
It should give the following output:
{
"statusCode": 200,
"headers": {
"Access-Control-Allow-Origin": "*",
"Access-Control-Allow-Credentials": true
},
"body": "{\"message\":\"Query:ca\",\"result\":[\"CAMBODIA\",\"CAMEROON\",\"CANADA\",\"CAPE VERDE\",\"CAYMAN ISLANDS\"]}"
}
You can also test your function using AWS console. In your AWS Lambda section,
click on your function. Scroll down to the code sections and click on the Test
button on the top right. Use { "queryStringParameters": {"term":"ar"}}
as your
event data.
Step 6: Run Your Function Locally
In your project folder run:
serverless invoke local -f query -d '{ "queryStringParameters": {"term":"ca"}}'
It should give the following output:
{
"statusCode": 200,
"headers": {
"Access-Control-Allow-Origin": "*",
"Access-Control-Allow-Credentials": true
},
"body": "{\"message\":\"Query:ca\",\"result\":[\"CAMBODIA\",\"CAMEROON\",\"CANADA\",\"CAPE VERDE\",\"CAYMAN ISLANDS\"]}"
}