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@nicusX
Created February 19, 2018 16:13
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Lambda@Edge A/B testing - Origin Request
'use strict';
const sourceCoookie = 'X-Source';
const sourceMain = 'main';
const sourceExperiment = 'experiment';
const experimentBucketName = 'my-experiment.s3.amazonaws.com';
const experimentBucketRegion = 'eu-west-1';
// Origin Request handler
exports.handler = (event, context, callback) => {
const request = event.Records[0].cf.request;
const headers = request.headers;
const source = decideSource(headers);
// If Source is Experiment, change Origin and Host header
if ( source === sourceExperiment ) {
console.log('Setting Origin to experiment bucket');
// Specify Origin
request.origin = {
s3: {
authMethod: 'origin-access-identity',
domainName: experimentBucketName,
path: '',
region: experimentBucketRegion
}
};
// Also set Host header to prevent “The request signature we calculated does not match the signature you provided” error
headers['host'] = [{key: 'host', value: experimentBucketName }];
}
// No need to change anything if Source was Main or undefined
callback(null, request);
};
// Decide source based on source cookie.
const decideSource = function(headers) {
const sourceMainCookie = `${sourceCoookie}=${sourceMain}`;
const sourceExperimenCookie = `${sourceCoookie}=${sourceExperiment}`;
// Remember a single cookie header entry may contains multiple cookies
if (headers.cookie) {
// ...ugly but simple enough for now
for (let i = 0; i < headers.cookie.length; i++) {
if (headers.cookie[i].value.indexOf(sourceExperimenCookie) >= 0) {
console.log('Experiment Source cookie found');
return sourceExperiment;
}
if (headers.cookie[i].value.indexOf(sourceMainCookie) >= 0) {
console.log('Main Source cookie found');
return sourceMain;
}
}
}
console.log('No Source cookie found (Origin undecided)');
}
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