Stream upload reads in 64 KB chunks

Read uploaded files in fixed-size chunks instead of a single file.read()
to reduce peak memory pressure. Also enforces the size limit during
streaming so oversized payloads are rejected before fully buffered.

document-parser/api/documents.py

@@ -13,6 +13,8 @@ from services import document_service
 logger = logging.getLogger(__name__)
 router = APIRouter(prefix="/api/documents", tags=["documents"])
 
+_READ_CHUNK_SIZE = 64 * 1024  # 64 KB
+
 
 def _to_response(doc) -> DocumentResponse:
     return DocumentResponse(
@@ -35,7 +37,15 @@ async def upload(file: UploadFile) -> DocumentResponse:
     if file.size and file.size > document_service.MAX_FILE_SIZE:
         raise HTTPException(status_code=413, detail="File too large (max 50 MB)")
 
-    content = await file.read()
+    # Read in chunks to avoid holding the full upload in a single allocation
+    chunks: list[bytes] = []
+    total = 0
+    while chunk := await file.read(_READ_CHUNK_SIZE):
+        total += len(chunk)
+        if total > document_service.MAX_FILE_SIZE:
+            raise HTTPException(status_code=413, detail="File too large (max 50 MB)")
+        chunks.append(chunk)
+    content = b"".join(chunks)
 
     try:
         doc = await document_service.upload(

document-parser/services/document_service.py

@@ -23,8 +23,14 @@ MAX_FILE_SIZE = 50 * 1024 * 1024  # 50 MB
 _PDF_MAGIC = b"%PDF"
 
 
+_UPLOAD_CHUNK_SIZE = 64 * 1024  # 64 KB chunks for streaming writes
+
+
 async def upload(filename: str, content_type: str, file_content: bytes) -> Document:
-    """Save uploaded file to disk and persist metadata."""
+    """Save uploaded file to disk and persist metadata.
+
+    Writes the file in fixed-size chunks to keep peak memory usage low.
+    """
     if len(file_content) > MAX_FILE_SIZE:
         raise ValueError("File too large (max 50 MB)")
 
@@ -37,8 +43,10 @@ async def upload(filename: str, content_type: str, file_content: bytes) -> Docum
     safe_name = f"{uuid.uuid4()}{ext}"
     file_path = os.path.join(UPLOAD_DIR, safe_name)
 
+    # Write in chunks to avoid doubling memory usage for large files
     with open(file_path, "wb") as f:
-        f.write(file_content)
+        for offset in range(0, len(file_content), _UPLOAD_CHUNK_SIZE):
+            f.write(file_content[offset : offset + _UPLOAD_CHUNK_SIZE])
 
     # Count PDF pages
     page_count = _count_pages(file_content)