If the cursor is too long, list_folder_continue api always encounter 504 timeout

Hi ethanfang,

The problem in your case is that you have lots of namespaces. Every single namespace gets locked by self. Since you need to lock all namespaces together, looks like the task takes too long. You need to split list processing for different namespaces to avoid such a deadlock. On other side, as you mentioned too many calls take too long to establish connections (Dropbox SDKs doesn't support multi-call on single connection). As a workaround you can perform such a request serie on you own on a single connection and so speed up the processing. I just created a simple example in Python:

#!/usr/bin/python3

from http.client import HTTPSConnection, _CS_IDLE
from urllib.parse import urlparse, urlunparse
from json import JSONDecoder, JSONEncoder

token = '<your access token here>'
paths = ['', '/path1', 'id:..', ...] # id's or paths to all your namespaces

def requestListResponse(conn, path):
  body = JSONEncoder().encode({"path": path,
                               "include_mounted_folders": False,
                               "recursive": True}).encode()
  headers = {'Host': conn.host,
             'Content-Length': len(body),
             'Connection': 'Keep-Alive',
             'Authorization': 'Bearer ' + token,
             'Content-Type': 'application/json'}
  conn._HTTPConnection__state = _CS_IDLE
  conn.request("POST", "/2/files/list_folder", body, headers)
  return conn.response_class(conn.sock, method=conn._method)

def requestListContResponse(conn, cursor):
  body = '{"cursor":"' f"{cursor}" '"}'
  headers = {'Host': conn.host,
             'Content-Length': len(body),
             'Connection': 'Keep-Alive',
             'Authorization': 'Bearer ' + token,
             'Content-Type': 'application/json'}
  conn._HTTPConnection__state = _CS_IDLE
  conn.request("POST", "/2/files/list_folder/continue", body, headers)
  return conn.response_class(conn.sock, method=conn._method)

def handleResponse(resp):
  resp.begin()
  if 200 != resp.status:
    raise RuntimeError(f"Status: {resp.status}\nHeader info:\n{resp.info()}\n"
                       f"\n{resp.read().decode()}")
  return JSONDecoder().decode(resp.read().decode())

def listFolders(paths):
  conn = HTTPSConnection("api.dropboxapi.com")
  responses = []
  for path in paths:
    responses.append(requestListResponse(conn, path))
    while len(responses) > 4:
      resp = responses.pop(0)
      result = handleResponse(resp)
      for entry in result['entries']:
        yield entry
      if result['has_more']:
        responses.append(requestListContResponse(conn, result['cursor']))
  while len(responses):
    resp = responses.pop(0)
    result = handleResponse(resp)
    for entry in result['entries']:
      yield entry
    if result['has_more']:
      responses.append(requestListContResponse(conn, result['cursor']))

for e in listFolders(paths):
  print(f"{e['.tag']}: {e['name']} with path -> {e['path_lower']}")

Hope the above demonstrates the idea clearly.