Troubleshooting 401 Errors Uploading AAB via Python Client

We understand the frustration that comes with encountering a 401 Unauthorized error during a critical build upload process, especially when dealing with large Android App Bundles (AAB) approaching 10GB in size. The Google Play Developer API is robust, but the resumable upload process requires precise handling of authentication tokens and HTTP status codes. When a resumable upload fails with a 401 error specifically at the final chunk, it almost always points to an issue with the OAuth 2.0 access token lifecycle or the underlying HTTP connection management.

In this comprehensive guide, we will dissect the technical reasons behind this specific failure scenario and provide a definitive solution. We will cover the nuances of the google-auth library, the specific behavior of the httplib2 transport layer, and how to correctly implement a resilient uploader for large AAB files using the Python client libraries.

Understanding the Root Cause of the 401 Error

The error message Request is missing required authentication credential indicates that the HTTP request sent to androidpublisher.googleapis.com did not contain a valid Authorization header. While the initial chunks of the upload succeeded, the final chunk—often where the server finalizes the bundle processing—failed authentication.

There are three primary reasons this occurs in a resumable upload scenario:

Token Expiration During Long Uploads: A 10GB upload split into chunks takes time. If the OAuth 2.0 access token expires while the upload is still in progress (but before the final chunk is sent), the AuthorizedHttp wrapper may fail to refresh the token seamlessly on the final request.
Incorrect HTTP Redirect Handling: The Google Cloud Storage backend, which handles the uploads, uses the HTTP 308 Permanent Redirect status code to indicate that the client should continue sending data to a different URI. The standard httplib2 library follows redirects automatically, but for resumable uploads, we must manually handle the 308 status to maintain the session state.
Connection Timeouts and Keep-Alive: When using httplib2 with a custom timeout, the underlying connection might be severed by the server or network middleware after a long idle period between chunks, causing the authentication context to be lost.

Diagnosing the Authentication Setup

Before modifying the code, we must verify the authentication credentials. The snippet provided uses a Service Account JSON key. While this is the standard method for server-to-server interactions, the permissions must be configured correctly.

Service Account Permissions

We ensure the Service Account has the necessary permissions in the Google Cloud Console:

Navigate to IAM & Admin > Service Accounts.
Select the service account used for the upload.
Click Keys and verify the JSON key is valid.
Crucially, navigate to the Google Play Console > Setup > API Access.
Grant the Service Account the “Release Manager” or “Release Viewer” role for the specific app. Without this, the API will authenticate the user but reject the request with a 403 or 401 depending on the endpoint.

Scopes Verification

The scope https://www.googleapis.com/auth/androidpublisher is correct and sufficient for uploading bundles. However, we must ensure no other scopes are interfering.

Refining the Python Code for Resumable Uploads

The core issue in the provided snippet likely lies in how httplib2 handles the final chunk and token refreshing. We need to switch to a more modern transport adapter or strictly control the AuthorizedHttp instance.

1. Switching from `httplib2` to `requests` (Recommended)

The google-auth library works natively with the requests library, which is generally more reliable for handling large file streams and complex redirect logic than httplib2. The google_auth_httplib2 wrapper is known to have edge cases with long-running uploads.

We recommend refactoring the HTTP transport layer to use google_auth_requests.

Updated Import Statements:

import google.auth
from google.auth.transport.requests import AuthorizedSession
from google.oauth2 import service_account
from googleapiclient.discovery import build
from googleapiclient.http import MediaFileUpload
import requests

2. Implementing the Correct Transport Layer

Instead of wrapping httplib2, we create an AuthorizedSession that handles token refreshing automatically for every request.

def build_authenticated_service(credentials_path):
    # Define the scopes required for the Google Play Developer API
    SCOPES = ['https://www.googleapis.com/auth/androidpublisher']
    
    # Load credentials from the JSON key file
    credentials = service_account.Credentials.from_service_account_file(
        credentials_path, scopes=SCOPES
    )
    
    # Create an AuthorizedSession using the google-auth-requests adapter
    # This session automatically handles OAuth2 token refreshing
    authed_session = AuthorizedSession(credentials)
    
    # Build the service object with the custom HTTP session
    # Note: We pass the authed_session as the 'http' parameter
    service = build('androidpublisher', 'v3', http=authed_session)
    
    return service

3. Handling the Resumable Upload Logic

The MediaFileUpload class handles the chunking logic. However, the request.next_chunk() method relies on the underlying HTTP transport. When using the requests transport, we rely on the built-in retry mechanisms provided by the client library.

Here is the corrected upload workflow:

def upload_aab(service, package_name, aab_file_path, edit_id):
    # Define chunk size (e.g., 10MB). 
    # For a 10GB file, 10MB chunks are manageable.
    CHUNK_SIZE = 10 * 1024 * 1024 
    
    # Initialize the media uploader
    # resumable=True is critical for large files
    bundle = MediaFileUpload(
        aab_file_path,
        mimetype='application/octet-stream',
        chunksize=CHUNK_SIZE,
        resumable=True
    )

    # Prepare the upload request
    request = service.edits().bundles().upload(
        editId=edit_id,
        packageName=package_name,
        media_body=bundle
    )

    # Execute the resumable upload
    # The googleapiclient handles the loop internally, but we can wrap it for custom retry logic
    response = None
    while response is None:
        try:
            status, response = request.next_chunk()
            if status:
                print(f"Uploaded {int(status.progress() * 100)}%")
        except HttpError as e:
            # Specifically handling 401 here, though the transport should handle refresh
            if e.resp.status == 401:
                print("Encountered 401: Token expired or invalid. Retrying...")
                # If using the requests transport, this might indicate a session issue.
                # Force a refresh of credentials if manually managing them.
                # However, with AuthorizedSession, this usually indicates a network interruption.
                raise
            else:
                print(f"An error occurred: {e}")
                raise

    print("Upload complete!")
    return response

Deep Dive: Why `httplib2` Causes 401 on Final Chunk

In the original code snippet, there was a specific line: http.redirect_codes = http.redirect_codes - {308}

This line removes 308 from the list of automatic redirect codes. This is technically correct for resumable uploads because the client must read the Location header from the 308 response and send the next chunk to that new URL. However, httplib2 is an older library.

The failure mechanism works like this:

Chunk N-1 Sent: The client sends a chunk.
Server Responds 308: The server says “OK, send next chunk to https://storage.googleapis.com/.../upload_id=XYZ”.
Client Sends Final Chunk: The client sends the final chunk to the new URL.
Token Expiry: If the token expires during the processing of the final chunk (which involves the server saving the file and updating the Play Console record), the AuthorizedHttp wrapper attempts to refresh the token.
The Glitch: In httplib2, if the connection context is tied to the specific storage URL (which is temporary), the token refresh request might be sent to the wrong endpoint or without the correct headers, resulting in the 401 error.

By switching to google_auth_requests.AuthorizedSession, we bypass this context-specific issue. The AuthorizedSession attaches the Authorization header to every request dynamically, ensuring that even if a redirect occurs, the authentication is re-applied correctly.

Handling Token Expiration Manually

Although the AuthorizedSession handles refreshing, sometimes the timing of the final chunk request is critical. If the upload takes longer than the token’s lifetime (typically 1 hour), we need to ensure the credentials are valid before the final chunk is dispatched.

We can implement a wrapper that checks the token expiry before the final step.

from google.auth.transport.requests import Request

def ensure_valid_credentials(credentials):
    """
    Checks if the credentials are expired and refreshes them if necessary.
    """
    if credentials.expired and credentials.refresh_token:
        print("Refreshing access token...")
        credentials.refresh(Request())
    return credentials

However, if you are using the AuthorizedSession, this happens automatically. The 401 error you are seeing suggests that the refresh might be failing or the token is invalid (e.g., revoked or scoped incorrectly).

Alternative: Using `google-api-python-client` MediaIoBaseUpload

For extremely large files (10GB), using MediaFileUpload is standard, but we can also use MediaIoBaseUpload if we want more control over the file stream. This is often more stable for large AABs.

If you are still facing issues with the standard client, consider this approach which utilizes the underlying http object more directly:

import io
import os
from googleapiclient.http import MediaIoBaseUpload

# Open the file in binary mode
file_size = os.path.getsize(aab_file_path)
file_handle = open(aab_file_path, 'rb')

# Use MediaIoBaseUpload
media = MediaIoBaseUpload(
    file_handle,
    mimetype='application/octet-stream',
    chunksize=10 * 1024 * 1024,
    resumable=True
)

request = service.edits().bundles().upload(
    editId=edit_id, 
    packageName=package_name, 
    media_body=media
)

response = None
while response is None:
    try:
        status, response = request.next_chunk(num_retries=5)
        if status:
            print(f"Uploaded {int(status.progress() * 100)}%")
    except Exception as e:
        print(f"Error during upload: {e}")
        # If a 401 occurs here, it is likely a credential issue at the Google Backend
        # Ensure the service account is active in Google Play Console
        raise
finally:
    file_handle.close()

Best Practices for 10GB AAB Uploads

Uploading a 10GB AAB is not trivial. Network stability and configuration are just as important as the code.

1. Network Stability and Timeouts

The original code snippet sets timeout=ANDROID_CHUNK_TIMEOUT. While this prevents indefinite hanging, a 10GB upload on a slower connection might legitimately take longer than a standard timeout. We recommend:

Set the timeout to a high value (e.g., 600 seconds) or disable it for the upload session specifically.
Ensure your network upload speed is sufficient. A 10GB file on a 10Mbps upload link takes ~2.5 hours.

2. Chunk Size Optimization

The chunksize parameter in MediaFileUpload is critical.

Too Small (e.g., 256KB): The overhead of HTTP requests for each chunk will slow down the process significantly and increase the chance of hitting rate limits.
Too Large (e.g., 50MB+): If a network error occurs, you must restart that entire chunk.
Recommended: For a 10GB file, a chunk size between 5MB and 10MB is the sweet spot. It balances overhead with resilience.

3. Retry Logic

Network blips are inevitable. The next_chunk(num_retries=3) method is good, but for a 10GB file, we recommend a more robust retry logic that catches HttpError 401 specifically.

If a 401 occurs during the upload, it usually means the token is dead. We can force a refresh of the underlying credentials and restart the upload from the last successful chunk.

# Advanced Retry Logic
last_response = None
for attempt in range(MAX_RETRY_ATTEMPTS):
    try:
        while last_response is None:
            status, last_response = request.next_chunk(num_retries=3)
            if status:
                print(f"Progress: {status.progress() * 100:.2f}%")
        break
    except HttpError as e:
        if e.resp.status == 401:
            print("Token expired during upload. Refreshing and resuming...")
            # Force refresh credentials
            credentials.refresh(Request())
            # The MediaFileUpload object maintains the resume URL, 
            # so next_chunk() should resume from where it left off.
            # However, if the underlying 'AuthorizedHttp' session is stale, 
            # we might need to rebuild the request with new http object.
            pass
        else:
            print(f"Non-recoverable error: {e}")
            raise

Verifying the “Edit” Lifecycle

A common oversight is the lifecycle of the editId. The editId represents a transaction on the Google Play Console. If an edit expires or is committed before the upload finishes, subsequent requests will fail.

Create Edit: You must create an edit at the beginning and hold it open.
Upload Bundle: Upload the AAB to that specific edit.
Commit Edit: Only after the upload is 100% successful should you commit the edit.

Ensure that the editId used in service.edits().bundles().upload is the same one created earlier and has not timed out. Google Play edits typically expire after a short period (e.g., a few hours). If your 10GB upload takes longer than the edit’s validity, the API will reject the upload with a 401 or 404.

To mitigate this, you can extend the validity of the edit or ensure the upload is the first step after creation.

Final Summary of the Solution

To resolve the 401 error when uploading a 10GB AAB via the Python client:

Switch Transport: Move from httplib2 and google_auth_httplib2 to google_auth_requests.AuthorizedSession. This handles OAuth2 refreshing more natively and correctly manages the session headers during redirects.
Verify Credentials: Double-check the Service Account configuration in the Google Play Console. It must have “Release Manager” permissions.
Manage Edit Lifecycle: Ensure the editId is fresh and hasn’t expired during the long upload process.
Optimize Chunking: Use a chunk size of 5-10MB to balance speed and reliability.
Error Handling: Implement a catch for HttpError 401 that forces a credential refresh and relies on the resumable nature of the upload to continue.

By adhering to these protocols, we ensure a stable and authenticated connection to the Google Play Developer API, allowing even massive 10GB AAB files to upload successfully.

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