S3 Fix

server.js

@@ -9,8 +9,14 @@ const PORT = process.env.PORT || 3000;
 
 // Where the model files actually live. Set S3_BUCKET to index a bucket;
 // otherwise the local models/ folder is used, which is what development does.
-const S3_BUCKET = process.env.S3_BUCKET || '';
-const S3_PREFIX = normalisePrefix(process.env.S3_PREFIX || 'skins/');
+// MODEL_S3_* names match the other projects; the plain names are accepted too.
+const S3_BUCKET = process.env.MODEL_S3_BUCKET || process.env.S3_BUCKET || '';
+const S3_PREFIX = normalisePrefix(
+  process.env.MODEL_S3_KEY_PREFIX || process.env.S3_PREFIX || 'skins/'
+);
+const S3_REGION = process.env.MODEL_S3_REGION || process.env.AWS_REGION;
+const S3_ACCESS_KEY = process.env.MODEL_S3_ACCESS_KEY_ID || '';
+const S3_SECRET_KEY = process.env.MODEL_S3_SECRET_ACCESS_KEY || '';
 const MODEL_ROOT = process.env.MODEL_ROOT || path.join(__dirname, 'models');
 
 // Where the browser fetches model files from. The default keeps them on this
@@ -46,10 +52,25 @@ function buildIndex(keys, prefix) {
   return out;
 }
 
-async function listBucketKeys() {
+let s3Client = null;
+
+function getS3Client() {
+  if (s3Client) return s3Client;
   // Required lazily so local development needs no AWS dependency installed.
-  const { S3Client, ListObjectsV2Command } = require('@aws-sdk/client-s3');
-  const client = new S3Client({ region: process.env.AWS_REGION });
+  const { S3Client } = require('@aws-sdk/client-s3');
+  // Explicit credentials only when given; otherwise fall back to the default
+  // chain, which picks up an EC2 instance role or ~/.aws/credentials.
+  const credentials =
+    S3_ACCESS_KEY && S3_SECRET_KEY
+      ? { accessKeyId: S3_ACCESS_KEY, secretAccessKey: S3_SECRET_KEY }
+      : undefined;
+  s3Client = new S3Client({ region: S3_REGION, credentials });
+  return s3Client;
+}
+
+async function listBucketKeys() {
+  const { ListObjectsV2Command } = require('@aws-sdk/client-s3');
+  const client = getS3Client();
 
   const keys = [];
   let token;