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Copy pathedge_lambda_1.js
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61 lines (55 loc) · 2.08 KB
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'use strict';
exports.handler = (event, context, callback) => {
const request = event.Records[0].cf.request;
const headers = request.headers;
if (request.uri !== '/experiment-pixel.jpg') {
// do not process if this is not an A-B test request
callback(null, request);
return;
}
const cookieExperimentA = 'X-Experiment-Name=A';
const cookieExperimentB = 'X-Experiment-Name=B';
const pathExperimentA = '/experiment-group/control-pixel.jpg';
const pathExperimentB = '/experiment-group/treatment-pixel.jpg';
/*
* Lambda at the Edge headers are array objects.
*
* Client may send multiple Cookie headers, i.e.:
* > GET /viewerRes/test HTTP/1.1
* > User-Agent: curl/7.18.1 (x86_64-unknown-linux-gnu) libcurl/7.18.1 OpenSSL/1.0.1u zlib/1.2.3
* > Cookie: First=1; Second=2
* > Cookie: ClientCode=abc
* > Host: example.com
*
* You can access the first Cookie header at headers["cookie"][0].value
* and the second at headers["cookie"][1].value.
*
* Header values are not parsed. In the example above,
* headers["cookie"][0].value is equal to "First=1; Second=2"
*/
let experimentUri;
if (headers.cookie) {
for (let i = 0; i < headers.cookie.length; i++) {
if (headers.cookie[i].value.indexOf(cookieExperimentA) >= 0) {
console.log('Experiment A cookie found');
experimentUri = pathExperimentA;
break;
} else if (headers.cookie[i].value.indexOf(cookieExperimentB) >= 0) {
console.log('Experiment B cookie found');
experimentUri = pathExperimentB;
break;
}
}
}
if (!experimentUri) {
console.log('Experiment cookie has not been found. Throwing dice...');
if (Math.random() < 0.75) {
experimentUri = pathExperimentA;
} else {
experimentUri = pathExperimentB;
}
}
request.uri = experimentUri;
console.log(`Request uri set to "${request.uri}"`);
callback(null, request);
};