perf(storage-s3): stream files and abort s3 request from static handler (#13430)

### What?

Stream S3 object directly to response instead of creating a Buffer in
memory and wire up an abort controller to stop streaming if user aborts
download

### Why?

To avoid excessive memory usage and to abort s3 download if user has
aborted the request anyway.

### How?

In node environment the AWS S3 always returns a Readable. The
streamToBuffer method always required this, but the any type hided that
this was actually needed. Now there is an explicit type check, but this
should never trigger in a node server environment.

Wire up and abort controller to the request so that we tell the S3
object to also stop streaming further if the user aborts.

Fixes #10286
Maybe also helps on other issues with s3 and resource usage

packages/storage-s3/src/staticHandler.ts

@@ -27,34 +27,34 @@ interface Args {
   signedDownloads?: SignedDownloadsConfig
 }
 
-// Type guard for NodeJS.Readable streams
-const isNodeReadableStream = (body: unknown): body is Readable => {
+const isNodeReadableStream = (body: AWS.GetObjectOutput['Body']): body is Readable => {
   return (
     typeof body === 'object' &&
     body !== null &&
     'pipe' in body &&
-    typeof (body as any).pipe === 'function' &&
+    typeof body.pipe === 'function' &&
     'destroy' in body &&
-    typeof (body as any).destroy === 'function'
+    typeof body.destroy === 'function'
   )
 }
 
-const destroyStream = (object: AWS.GetObjectOutput | undefined) => {
+const abortRequestAndDestroyStream = ({
+  abortController,
+  object,
+}: {
+  abortController: AbortController
+  object?: AWS.GetObjectOutput
+}) => {
+  try {
+    abortController.abort()
+  } catch {
+    /* noop */
+  }
   if (object?.Body && isNodeReadableStream(object.Body)) {
     object.Body.destroy()
   }
 }
 
-// Convert a stream into a promise that resolves with a Buffer
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
-const streamToBuffer = async (readableStream: any) => {
-  const chunks = []
-  for await (const chunk of readableStream) {
-    chunks.push(typeof chunk === 'string' ? Buffer.from(chunk) : chunk)
-  }
-  return Buffer.concat(chunks)
-}
-
 export const getHandler = ({
   bucket,
   collection,
@@ -63,6 +63,15 @@ export const getHandler = ({
 }: Args): StaticHandler => {
   return async (req, { headers: incomingHeaders, params: { clientUploadContext, filename } }) => {
     let object: AWS.GetObjectOutput | undefined = undefined
+    let streamed = false
+
+    const abortController = new AbortController()
+    if (req.signal) {
+      req.signal.addEventListener('abort', () => {
+        abortRequestAndDestroyStream({ abortController, object })
+      })
+    }
+
     try {
       const prefix = await getFilePrefix({ clientUploadContext, collection, filename, req })
 
@@ -89,10 +98,13 @@ export const getHandler = ({
         }
       }
 
-      object = await getStorageClient().getObject({
-        Bucket: bucket,
-        Key: key,
-      })
+      object = await getStorageClient().getObject(
+        {
+          Bucket: bucket,
+          Key: key,
+        },
+        { abortSignal: abortController.signal },
+      )
 
       if (!object.Body) {
         return new Response(null, { status: 404, statusText: 'Not Found' })
@@ -130,25 +142,26 @@ export const getHandler = ({
         })
       }
 
-      // On error, manually destroy stream to close socket
-      if (object.Body && isNodeReadableStream(object.Body)) {
-        const stream = object.Body
-        stream.on('error', (err) => {
-          req.payload.logger.error({
-            err,
-            key,
-            msg: 'Error streaming S3 object, destroying stream',
-          })
-          stream.destroy()
+      if (!isNodeReadableStream(object.Body)) {
+        req.payload.logger.error({
+          key,
+          msg: 'S3 object body is not a readable stream',
         })
+        return new Response('Internal Server Error', { status: 500 })
       }
 
-      const bodyBuffer = await streamToBuffer(object.Body)
-
-      return new Response(bodyBuffer, {
-        headers,
-        status: 200,
+      const stream = object.Body
+      stream.on('error', (err) => {
+        req.payload.logger.error({
+          err,
+          key,
+          msg: 'Error while streaming S3 object (aborting)',
+        })
+        abortRequestAndDestroyStream({ abortController, object })
       })
+
+      streamed = true
+      return new Response(stream, { headers, status: 200 })
     } catch (err) {
       if (err instanceof AWS.NoSuchKey) {
         return new Response(null, { status: 404, statusText: 'Not Found' })
@@ -156,7 +169,9 @@ export const getHandler = ({
       req.payload.logger.error(err)
       return new Response('Internal Server Error', { status: 500 })
     } finally {
-      destroyStream(object)
+      if (!streamed) {
+        abortRequestAndDestroyStream({ abortController, object })
+      }
     }
   }
 }