Refactor S3MultipartUploadStream to optimize buffer handling and improve upload efficiency (#494)

- Replaced Buffer.concat with chunk accumulation to reduce time complexity during writes.
- Introduced bufferedBytes to track total size of accumulated chunks.
- Updated upload logic to handle parts more efficiently, minimizing memory overhead.
- Enhanced logging in upload function to include selected encoder format for better traceability.

(cherry picked from commit ce8bba2f18d807d4872b168e451e4501b1acb824)

lib/record/s3-multipart-upload-stream.js

@@ -15,7 +15,9 @@ class S3MultipartUploadStream extends Writable {
     this.uploadId = null;
     this.partNumber = 1;
     this.multipartETags = [];
-    this.buffer = Buffer.alloc(0);
+    // accumulate incoming chunks to avoid O(n^2) Buffer.concat on every write
+    this.chunks = [];
+    this.bufferedBytes = 0;
     this.minPartSize = 5 * 1024 * 1024; // 5 MB
     this.s3 = new S3Client(opts.bucketCredential);
     this.metadata = opts.metadata;
@@ -31,13 +33,13 @@ class S3MultipartUploadStream extends Writable {
     return response.UploadId;
   }
 
-  async _uploadBuffer() {
+  async _uploadPart(bodyBuffer) {
     const uploadPartCommand = new UploadPartCommand({
       Bucket: this.bucketName,
       Key: this.objectKey,
       PartNumber: this.partNumber,
       UploadId: this.uploadId,
-      Body: this.buffer,
+      Body: bodyBuffer,
     });
 
     const uploadPartResponse = await this.s3.send(uploadPartCommand);
@@ -54,11 +56,16 @@ class S3MultipartUploadStream extends Writable {
         this.uploadId = await this._initMultipartUpload();
       }
 
-      this.buffer = Buffer.concat([this.buffer, chunk]);
+      // accumulate without concatenating on every write
+      this.chunks.push(chunk);
+      this.bufferedBytes += chunk.length;
 
-      if (this.buffer.length >= this.minPartSize) {
+      if (this.bufferedBytes >= this.minPartSize) {
-        await this._uploadBuffer();
+        const partBuffer = Buffer.concat(this.chunks, this.bufferedBytes);
-        this.buffer = Buffer.alloc(0);
+        // reset accumulators before awaiting upload to allow GC
+        this.chunks = [];
+        this.bufferedBytes = 0;
+        await this._uploadPart(partBuffer);
       }
 
       callback(null);
@@ -69,8 +76,11 @@ class S3MultipartUploadStream extends Writable {
 
   async _finalize(err) {
     try {
-      if (this.buffer.length > 0) {
+      if (this.bufferedBytes > 0) {
-        await this._uploadBuffer();
+        const finalBuffer = Buffer.concat(this.chunks, this.bufferedBytes);
+        this.chunks = [];
+        this.bufferedBytes = 0;
+        await this._uploadPart(finalBuffer);
       }
 
       const completeMultipartUploadCommand = new CompleteMultipartUploadCommand({

lib/record/upload.js

@@ -51,8 +51,10 @@ async function upload(logger, socket) {
 
           /**encoder */
           let encoder;
+          let recordFormat;
           if (account[0].record_format === 'wav') {
             encoder = new wav.Writer({ channels: 2, sampleRate, bitDepth: 16 });
+            recordFormat = 'wav';
           } else {
             // default is mp3
             encoder = new PCMToMP3Encoder({
@@ -60,7 +62,9 @@ async function upload(logger, socket) {
               sampleRate: sampleRate,
               bitrate: 128
             }, logger);
+            recordFormat = 'mp3';
           }
+          logger.info({ record_format: recordFormat, channels: 2, sampleRate }, 'record upload: selected encoder');
 
           /* start streaming data */
           pipeline(