Serverless Api Gateway Proxy Lambda with Axios to serve binary files (PDF)? - pdf

Question

I am using serverless and axios to "passthrough" a PDF generated by the
stampery api, which needs credentials I do not want to save client-side.
In principle I get the PDF as an arraybuffer from axios, transform the arraybuffer to an buffer, which I then use to create a base64 string, needed by API Gateway binary treatment, which can be "activated" by including the isBase64Encoded: true property in the callback response object.
The following code yields an empty PDF:
const axios = require('axios');
const stamperyClientId = 'xxx';
const stamperySecret = 'xxx';
const stampery = axios.create({
baseURL: 'https://api-prod.stampery.com',
auth: {
username: stamperyClientId,
password: stamperySecret
}
});
module.exports.hello = (event, context, callback) => {
const response = {
statusCode: 200,
headers: {
'Content-Type' : 'application/pdf',
'Content-Disposition': 'inline; filename="certificate.pdf"'
},
isBase64Encoded: true
};
stampery.get(`/stamps/5b2a612680e0190004bcccc8.pdf`, {
responseType: 'arrayBuffer',
})
.then(res => {
const buffer = Buffer.from(res.data)
const base64Str = buffer.toString('base64')
response.body = base64Str
callback(null, response);
})
};
The PDF is retrieved by: `curl https://xxx.execute-api.eu-west-1.amazonaws.com/dev/certificate -o my.pdf -H "Accept: application/pdf"
I tested the setup with fileReadSync, which turned out fine:
module.exports.hello = (event, context, callback) => {
const content = fs.readFileSync("data/sample.pdf");
const response = {
statusCode: 200,
headers: {
"Content-Type": "application/pdf",
"Content-Disposition": "inline; filename=\"sample.pdf\""
},
body: content.toString("base64"),
isBase64Encoded: true
};
return callback(null, response);
};
What am I missing? Is this the right way to transform an axios arraybufferinto a base64 string?
P.S. My serverless.yml is given by:
functions:
hello:
handler: handler.hello
events:
- http:
path: certificate.pdf
method: get
package:
include:
- data/sample.pdf
resources:
Resources:
ApiGatewayRestApi:
Type: AWS::ApiGateway::RestApi
Properties:
Name: dev-stamper
BinaryMediaTypes:
- "application/pdf" # or whichever ones you need
where I already thought of the necessary binary media types.

Answer 1

Ok... the error was a simple typo. I wrote arraybuffer in camel case arrayBuffer, so Axios returned a string instead of an arraybuffer.
Change this line:
stampery.get(`/stamps/5b2a612680e0190004bcccc8.pdf`, {
responseType: 'arrayBuffer',
})
to
stampery.get(`/stamps/5b2a612680e0190004bcccc8.pdf`, {
responseType: 'arraybuffer',
})
and everything works as a charm...