Schreiben Sie einen Anforderungs-URI auf der Grundlage der KeyValueStore Konfiguration für ein CloudFront Functions-Viewer-Anforderungsereignis neu

Das folgende Codebeispiel zeigt, wie eine Anforderungs-URI auf der Grundlage der KeyValueStore Konfiguration für ein CloudFront Functions-Viewer-Anforderungsereignis neu geschrieben wird.

JavaScript

JavaScript Runtime 2.0 für CloudFront Funktionen

Anmerkung

Es gibt noch mehr dazu GitHub. Das vollständige Beispiel und Informationen zur Einrichtung und Ausführung finden Sie im CloudFront Functions-Beispiel-Repository.

import cf from 'cloudfront'; 

// (Optional) Replace KVS_ID with actual KVS ID
const kvsId = "KVS_ID";
// enable stickiness by setting a cookie from origin or using another edge function
const stickinessCookieName = "appversion";
// set to true to enable console logging
const loggingEnabled = false;
   
// function rewrites the request uri based on configuration in KVS
// example config in KVS in key:value format
// "latest": {"a_weightage": .8, "a_url": "v1", "b_url": "v2"}
// given above key and value in KVS the request uri will be rewritten 
// for example http(s)://domain/latest/something/else will be rewritten as http(s)://domain/v1/something/else or http(s)://domain/v2/something/else depending on weightage
// if no configuration is found, then the request is returned as is
async function handler(event) {
    // NOTE: This example function is for a viewer request event trigger. 
    // Choose viewer request for event trigger when you associate this function with a distribution. 
    const request = event.request;
    const pathSegments = request.uri.split('/');
    const key = pathSegments[1];
    
    // if empty path segment or if there is valid stickiness cookie 
    // then skip call to KVS and let the request continue.
    if (!key || hasValidSticknessCookie(request.cookies[stickinessCookieName], key)) {
        return event.request;
    }

    try {
        // get the prefix replacement from KVS
        const replacement = await getPathPrefixByWeightage(key);
        if (!replacement) {
            return event.request;
        }
        //Replace the first path with the replacement 
        pathSegments[1] = replacement;
        log(`using prefix ${pathSegments[1]}`)
        const newUri = pathSegments.join('/');
        log(`${request.uri} -> ${newUri}`);
        request.uri = newUri;

        return request;
    } catch (err) {
        // No change to the path if the key is not found or any other error
        log(`request uri: ${request.uri}, error: ${err}`);
    }
    // no change to path - return request 
    return event.request;
}

// function to get the prefix from KVS
async function getPathPrefixByWeightage(key) {
    const kvsHandle = cf.kvs(kvsId);
    // get the weightage config from KVS
    const kvsResponse = await kvsHandle.get(key);
    const weightageConfig = JSON.parse(kvsResponse);
    // no configuration - return null    
    if (!weightageConfig || !isFinite(weightageConfig.a_weightage)) {
        return null;
    } 
    // return the url based on weightage
    // return null if no url is configured
    if (Math.random() <= weightageConfig.a_weightage) {
        return weightageConfig.a_url ? weightageConfig.a_url: null;
    } else {
        return weightageConfig.b_url ? weightageConfig.b_url : null;
    }
}

// function to check if the stickiness cookie is valid
function hasValidSticknessCookie(stickinessCookie, pathSegment) {
    // if the value exists and it matches pathSegment
    return (stickinessCookie && stickinessCookie.value === pathSegment)
}

function log(message) {
    if (loggingEnabled) {
        console.log(message);
    }
}

Eine vollständige Liste der AWS SDK-Entwicklerhandbücher und Codebeispiele finden Sie unterVerwendung CloudFront mit einem SDK AWS. Dieses Thema enthält auch Informationen zu den ersten Schritten und Details zu früheren SDK-Versionen.