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| 1 | +import { |
| 2 | + DynamoDBClient, |
| 3 | + QueryCommand, |
| 4 | + QueryCommandInput, |
| 5 | +} from "@aws-sdk/client-dynamodb"; |
| 6 | +import type { |
| 7 | + CloudFrontRequestEvent, |
| 8 | + CloudFrontRequestResult, |
| 9 | +} from "aws-lambda"; |
| 10 | + |
| 11 | +const DEFAULT_AWS_REGION = "us-east-2"; |
| 12 | +const AVAILABLE_REPLICAS = ["us-west-2"]; |
| 13 | +const DYNAMODB_TABLE = "infra-core-api-linkry"; |
| 14 | +const FALLBACK_URL = process.env.FALLBACK_URL || "https://acm.illinois.edu/404"; |
| 15 | +const DEFAULT_URL = process.env.DEFAULT_URL || "https://www.acm.illinois.edu"; |
| 16 | +const CACHE_TTL = "30"; // seconds to hold response in PoP |
| 17 | + |
| 18 | +/** |
| 19 | + * Determine which DynamoDB replica to use based on Lambda execution region |
| 20 | + */ |
| 21 | +function selectReplica(lambdaRegion: string): string { |
| 22 | + // First check if Lambda is running in a replica region |
| 23 | + if (AVAILABLE_REPLICAS.includes(lambdaRegion)) { |
| 24 | + return lambdaRegion; |
| 25 | + } |
| 26 | + |
| 27 | + // Otherwise, find nearest replica by region prefix matching |
| 28 | + const regionPrefix = lambdaRegion.split("-").slice(0, 2).join("-"); |
| 29 | + if (regionPrefix === "us") { |
| 30 | + return DEFAULT_AWS_REGION; |
| 31 | + } |
| 32 | + |
| 33 | + for (const replica of AVAILABLE_REPLICAS) { |
| 34 | + if (replica.startsWith(regionPrefix)) { |
| 35 | + return replica; |
| 36 | + } |
| 37 | + } |
| 38 | + |
| 39 | + return DEFAULT_AWS_REGION; |
| 40 | +} |
| 41 | + |
| 42 | +const currentRegion = process.env.AWS_REGION || DEFAULT_AWS_REGION; |
| 43 | +const targetRegion = selectReplica(currentRegion); |
| 44 | +const dynamodb = new DynamoDBClient({ region: targetRegion }); |
| 45 | + |
| 46 | +console.log(`Lambda in ${currentRegion}, routing DynamoDB to ${targetRegion}`); |
| 47 | + |
| 48 | +export const handler = async ( |
| 49 | + event: CloudFrontRequestEvent, |
| 50 | +): Promise<CloudFrontRequestResult> => { |
| 51 | + const request = event.Records[0].cf.request; |
| 52 | + const path = request.uri.replace(/^\/+/, ""); |
| 53 | + |
| 54 | + console.log(`Processing path: ${path}`); |
| 55 | + |
| 56 | + if (!path) { |
| 57 | + return { |
| 58 | + status: "301", |
| 59 | + statusDescription: "Moved Permanently", |
| 60 | + headers: { |
| 61 | + location: [{ key: "Location", value: DEFAULT_URL }], |
| 62 | + "cache-control": [ |
| 63 | + { key: "Cache-Control", value: `public, max-age=${CACHE_TTL}` }, |
| 64 | + ], |
| 65 | + }, |
| 66 | + }; |
| 67 | + } |
| 68 | + |
| 69 | + // Query DynamoDB for records with PK=path and SK starting with "OWNER#" |
| 70 | + try { |
| 71 | + const queryParams: QueryCommandInput = { |
| 72 | + TableName: DYNAMODB_TABLE, |
| 73 | + KeyConditionExpression: |
| 74 | + "slug = :slug AND begins_with(access, :owner_prefix)", |
| 75 | + ExpressionAttributeValues: { |
| 76 | + ":slug": { S: path }, |
| 77 | + ":owner_prefix": { S: "OWNER#" }, |
| 78 | + }, |
| 79 | + ProjectionExpression: "redirect", |
| 80 | + Limit: 1, // We only need one result |
| 81 | + }; |
| 82 | + |
| 83 | + const response = await dynamodb.send(new QueryCommand(queryParams)); |
| 84 | + |
| 85 | + if (response.Items && response.Items.length > 0) { |
| 86 | + const item = response.Items[0]; |
| 87 | + |
| 88 | + // Extract the redirect URL from the item |
| 89 | + const redirectUrl = item.redirect?.S; |
| 90 | + |
| 91 | + if (redirectUrl) { |
| 92 | + console.log(`Found redirect: ${path} -> ${redirectUrl}`); |
| 93 | + return { |
| 94 | + status: "302", |
| 95 | + statusDescription: "Found", |
| 96 | + headers: { |
| 97 | + location: [{ key: "Location", value: redirectUrl }], |
| 98 | + "cache-control": [ |
| 99 | + { key: "Cache-Control", value: `public, max-age=${CACHE_TTL}` }, |
| 100 | + ], |
| 101 | + }, |
| 102 | + }; |
| 103 | + } |
| 104 | + console.log(`Item found but no redirect attribute for path: ${path}`); |
| 105 | + } else { |
| 106 | + console.log(`No items found for path: ${path}`); |
| 107 | + } |
| 108 | + } catch (error) { |
| 109 | + if (error instanceof Error) { |
| 110 | + console.error( |
| 111 | + `DynamoDB query failed for ${path} in region ${targetRegion}:`, |
| 112 | + error.message, |
| 113 | + ); |
| 114 | + } else { |
| 115 | + console.error(`Unexpected error:`, error); |
| 116 | + } |
| 117 | + } |
| 118 | + |
| 119 | + // Not found - redirect to fallback |
| 120 | + return { |
| 121 | + status: "307", |
| 122 | + statusDescription: "Temporary Redirect", |
| 123 | + headers: { |
| 124 | + location: [{ key: "Location", value: FALLBACK_URL }], |
| 125 | + "cache-control": [ |
| 126 | + { key: "Cache-Control", value: `public, max-age=${CACHE_TTL}` }, |
| 127 | + ], |
| 128 | + }, |
| 129 | + }; |
| 130 | +}; |
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