🐛 Fix race condition in file download

src/cdn/funcs/saveResponse.ts

@@ -15,9 +15,11 @@ export default function saveResponse(
   //Remember file size
   const headerLength = Number(response.headers['content-length']);
 
+  const writeStream = fs.createWriteStream(filePath);
+
   //If we receive a part of the response, write it to disk
-  let previousChunk: Promise<void> = new Promise((innerResolve) => { innerResolve(); });
   let totalLength = 0;
+  const chunkPromises: Array<Promise<void>> = [];
   response.on('data', (chunk: Buffer) => {
     totalLength += chunk.length;
 
@@ -26,18 +28,12 @@ export default function saveResponse(
       return reject(`Expected length ${headerLength} but received at least ${totalLength}.`);
     }
 
-    //If previous chunk was not yet written to disk, wait until it finished to avoid a race condition
-    previousChunk.then(() => {
-      previousChunk = new Promise((innerResolve, innerReject) => {
     //Write chunk to disk
-        fs.appendFile(filePath, chunk, { encoding: 'binary' }, (error) => {
+    chunkPromises.push(new Promise((writeResolve) => {
-          if (error) {
+      writeStream.write(chunk, () => {
-            return reject(`Could not write to disk: [${error.code}] ${error.name}: ${error.message}.`);
+        writeResolve();
-          }
-          innerResolve();
-        });
-      });
       });
+    }));
   });
 
   //If we finished reading response, check for correctness, then return it
@@ -50,7 +46,7 @@ export default function saveResponse(
     //wait until everything is written to disk, then return file name
     //TODO: need to automatically delete file once it is no longer used
     //TODO: need to provide methods to seek through file
-    previousChunk.then(() => {
+    Promise.all(chunkPromises).then(() => {
       resolve(filePath);
     });
   });

src/ssn/extractFileStream.ts

@@ -24,6 +24,7 @@ export default function extractFileStream(file: ISsnFileEntry, inputStream: stre
   //pipe into decompression
   const decompressTransform = zlib.createInflateRaw();
   decompressTransform.on('error', (error) => {
+    //TODO: need to throw error sync, not async
     throw new Error(`Error during decompression: ${error.message}`);
   });
   curStream = curStream.pipe(decompressTransform);

src/ssn/getPatch.ts

@@ -32,6 +32,7 @@ export default async function getPatch(product: Product, from: number, to: numbe
   //Then we need to wait for disks to finish download before we can extract individual files
   //TODO: we can optimize this to already extract some files as soon as their relevant parts are downloaded
   const diskFilenames = await Promise.all(diskFiles);
+  console.debug(diskFilenames);
   //const dvArray = bufferArray.map((buffer) => new DataView(buffer));
 
   //TODO: Verify that downloaded files match the hash in `solidpkg.pieces`