Stream files to the ModelScan API endpoint rather than hold entire files in memory

backend/src/clients/modelScan.ts

@@ -1,4 +1,5 @@
 import fetch, { Response } from 'node-fetch'
+import { Readable } from 'stream'
 
 import config from '../utils/config.js'
 import { BadReq, InternalError } from '../utils/error.js'
@@ -65,13 +66,21 @@ export async function getModelScanInfo() {
   return (await res.json()) as ModelScanInfoResponse
 }
 
-export async function scanFile(file: Blob, file_name: string) {
+export async function scanStream(stream: Readable, file_name: string, file_size: number) {
   const url = `${config.avScanning.modelscan.protocol}://${config.avScanning.modelscan.host}:${config.avScanning.modelscan.port}`
   let res: Response
 
   try {
     const formData = new FormData()
-    formData.append('in_file', file, file_name)
+    formData.append(
+      'in_file',
+      {
+        [Symbol.toStringTag]: 'File',
+        size: file_size,
+        stream: () => stream,
+      },
+      file_name,
+    )
 
     res = await fetch(`${url}/scan/file`, {
       method: 'POST',

backend/src/connectors/fileScanning/modelScan.ts

@@ -1,7 +1,6 @@
-import { Response } from 'node-fetch'
 import { Readable } from 'stream'
 
-import { getModelScanInfo, scanFile } from '../../clients/modelScan.js'
+import { getModelScanInfo, scanStream } from '../../clients/modelScan.js'
 import { getObjectStream } from '../../clients/s3.js'
 import { FileInterfaceDoc, ScanState } from '../../models/File.js'
 import log from '../../services/log.js'
@@ -39,9 +38,7 @@ export class ModelScanFileScanningConnector extends BaseFileScanningConnector {
 
     const s3Stream = (await getObjectStream(file.bucket, file.path)).Body as Readable
     try {
-      // TODO: see if it's possible to directly send the Readable stream rather than a blob
-      const fileBlob = await new Response(s3Stream).blob()
-      const scanResults = await scanFile(fileBlob, file.name)
+      const scanResults = await scanStream(s3Stream, file.name, file.size)
 
       const issues = scanResults.summary.total_issues
       const isInfected = issues > 0

backend/test/clients/__snapshots__/modelScan.spec.ts.snap

@@ -14,7 +14,7 @@ exports[`clients > modelScan > getModelScanInfo > success 1`] = `
 ]
 `;
 
-exports[`clients > modelScan > scanFile > success 1`] = `
+exports[`clients > modelScan > scanStream > success 1`] = `
 [
   [
     "undefined://undefined:undefined/scan/file",
@@ -23,10 +23,17 @@ exports[`clients > modelScan > scanFile > success 1`] = `
         Symbol(state): [
           {
             "name": "in_file",
-            "value": File {
-              Symbol(kHandle): Blob {},
-              Symbol(kLength): 0,
-              Symbol(kType): "application/x-hdf5",
+            "value": FileLike {
+              Symbol(state): {
+                "blobLike": {
+                  "size": 0,
+                  "stream": [Function],
+                  Symbol(Symbol.toStringTag): "File",
+                },
+                "lastModified": 0,
+                "name": "safe_model.h5",
+                "type": undefined,
+              },
             },
           },
         ],

backend/test/clients/modelScan.spec.ts

@@ -1,6 +1,7 @@
+import { PassThrough } from 'stream'
 import { describe, expect, test, vi } from 'vitest'
 
-import { getModelScanInfo, scanFile } from '../../src/clients/modelScan.js'
+import { getModelScanInfo, scanStream } from '../../src/clients/modelScan.js'
 
 const configMock = vi.hoisted(() => ({
   avScanning: {
@@ -59,7 +60,7 @@ describe('clients > modelScan', () => {
     expect(() => getModelScanInfo()).rejects.toThrowError(/^Unable to communicate with the ModelScan service./)
   })
 
-  test('scanFile > success', async () => {
+  test('scanStream > success', async () => {
     const expectedResponse = {
       summary: {
         total_issues: 0,
@@ -90,28 +91,32 @@ describe('clients > modelScan', () => {
       text: vi.fn(),
       json: vi.fn(() => expectedResponse),
     })
-    const response = await scanFile(new Blob([''], { type: 'application/x-hdf5' }), 'safe_model.h5')
+    // force lastModified to be 0
+    const date = new Date(1970, 0, 1, 0)
+    vi.setSystemTime(date)
+
+    const response = await scanStream(new PassThrough(), 'safe_model.h5', 0)
 
     expect(fetchMock.default).toBeCalled()
     expect(fetchMock.default.mock.calls).toMatchSnapshot()
     expect(response).toStrictEqual(expectedResponse)
   })
 
-  test('scanFile > bad response', async () => {
+  test('scanStream > bad response', async () => {
     fetchMock.default.mockResolvedValueOnce({
       ok: false,
       text: vi.fn(() => 'Unrecognised response'),
       json: vi.fn(),
     })
-    expect(() => scanFile(new Blob([''], { type: 'application/x-hdf5' }), 'safe_model.h5')).rejects.toThrowError(
+    expect(() => scanStream(new PassThrough(), 'safe_model.h5', 0)).rejects.toThrowError(
       /^Unrecognised response returned by the ModelScan service./,
     )
   })
 
-  test('scanFile > rejected', async () => {
+  test('scanStream > rejected', async () => {
     fetchMock.default.mockRejectedValueOnce('Unable to communicate with the inferencing service.')
 
-    expect(() => scanFile(new Blob([''], { type: 'application/x-hdf5' }), 'safe_model.h5')).rejects.toThrowError(
+    expect(() => scanStream(new PassThrough(), 'safe_model.h5', 0)).rejects.toThrowError(
       /^Unable to communicate with the ModelScan service./,
     )
   })