AWS-Serverless-Express How To Get Previous Route - node.js

Question

I have an export button on my front-end that when clicked, sends a POST on our Express server to log the button click. This uses the route app.post(usagereport) . What I want to be able to do is capture the route the user was at when they clicked export. However, since the code to send the POST request is it's own route, it only ever returns that route's name when trying something like req.route.
I'm using API Gateway + Lambda + AWS-Serverless-Express.
I was thinking I could store something like req.session.previousRoute in req.session to capture the last route the user loaded and then return this to the access log code. However, I was unsure if this approach would work on Lambda or perhaps there is just a better way to handle it.
Here is my server.js (trimmed down)
// create the server and setup routes
const app = express();
const mysql = require("mysql");
// AWS-Serverless-Express https://github.com/awslabs/aws-serverless-express
const awsServerlessExpressMiddleware = require("aws-serverless-express/middleware");
app.use(awsServerlessExpressMiddleware.eventContext());
//Setup paths to database connection pools
const nawfprojectsDB = require("../lib/naWfProjectsDb.js");
const queries = require("./queries.js");
const accessLog = require("../lib/accessLog.js");
//Setup a timestamp for logging
const timestamp = new Date().toString();
// S3 Data Mitigation is needed when a data set exceeds 5 MB in size.
// This is a restriction of Lambda itself (they say 6 MB but want to ensure we dont ever hit the limit)
const s3DataMitigation = require("../lib/s3DataMitigation.js");
let environment = process.env.NODE_ENV;
app.get("/wg_data", (req, res, callback) => {
const dataSet = "wg_data";
nawfprojectsDB.query(queries.wg_data, (err, result) => {
if (err) {
console.log(err);
}
s3Data(dataSet, res, callback, result);
console.log(
timestamp,
"Returned " + result.length + " rows from " + dataSet
);
});
accessLog({ dataSet, req });
});
// Usage report everytime export button is clicked
app.post("/usagereport", (req) => {
const currentPath = dataSet;
const dataSet = "Data Exported: " + currentPath;
console.log(timestamp, "Data exported");
accessLog({ dataSet, req });
});
module.exports = app;
accessLog.js
let nawfprojectsDB = require("./naWfProjectsDb.js");
let queries = require("../routes/queries.js");
let environment = process.env.NODE_ENV;
//Insert data into access_logs table when usageLog is called
const accessLog = ({ dataSet, req }) => {
// We only want to log access when in beta, gamma, or prod. Not in development.
if (environment === "development") {
console.log("No access log as we are in dev");
} else {
// req.apiGateway comes from AWS-Serverless-Express - https://github.com/awslabs/aws-serverless-express
const user = req.apiGateway.event.requestContext.authorizer.principalId;
let sqlData = [dataSet, user, environment];
// Run the log_access query using the sqlData above
nawfprojectsDB.query(queries.log_access, sqlData, (err) => {
if (err) {
console.error("MySQL query error: " + err);
}
console.log("Access log added for: ", user, " at data set: ", dataSet);
});
}
};
module.exports = accessLog;

Answer 1

Solved my own question.
The way solved this was using express-session. I set req.session.previousRoute within each of my routes. I can then access this in my usagereport route.
const { v4: uuidv4 } = require("uuid");
const express = require("express");
const cookieParser = require("cookie-parser");
const session = require("express-session");
const randomString = uuidv4();
let sessionOptions = {
cookie: {
secret: randomString,
maxAge: 269999999999,
},
saveUninitialized: true,
resave: true,
};
// create the server and setup routes
const app = express();
// Add express-session Middleware - https://www.npmjs.com/package/express-session
app.use(cookieParser(randomString)); // Need cookieParser to properly parse our random string into the type of value expected by session
app.use(session(sessionOptions));
// AWS-Serverless-Express - https://github.com/awslabs/aws-serverless-express
const awsServerlessExpressMiddleware = require("aws-serverless-express/middleware");
app.use(awsServerlessExpressMiddleware.eventContext());
app.get("/wg_data", (req, res, callback) => {
const dataSet = "wg_data";
const action = "Accessed";
req.session.previousRoute = dataSet; // This is where we set the previousRoute in session
nawfprojectsDB.query(queries.wg_data, (err, result) => {
if (err) {
console.log(err);
}
s3Data(dataSet, res, callback, result);
console.log(
timestamp,
"Returned " + result.length + " rows from " + dataSet
);
});
accessLog({ dataSet, action, req });
});
// Usage report everytime export button is clicked
app.post("/usagereport", (req) => {
// Here we grab the previousRoute set in session to see the true place the data was exported from
const action = "Exported";
const previousRoute = req.session.previousRoute; // Now when usagereport is triggered, it knows the previous route from the session and uses that here.
const dataSet = previousRoute;
console.log(timestamp, "Data exported from ", previousRoute);
accessLog({ dataSet, action, req });
});