Bad Request API resultDownloadUrl: Cannot get presigned download url

Information

• Qiskit IBMQ Provider version: 0.17.0 (Python)

• API URL or version: https://api.quantum-computing.ibm.com/api/Network/ibm-q/Groups/open/Projects/main/Jobs/<job number>/resultDownloadUrl

• Python version: 3.6

• Operating system: Ubuntu Linux

What is the current behavior?

qiskit.providers.ibmq.job.exceptions.IBMQJobApiError: "Unable to retrieve result for job <job number>: '400 Client Error: Bad Request for url: https://api.quantum-computing.ibm.com/api/Network/ibm-q/Groups/open/Projects/main/Jobs/<job number>/resultDownloadUrl. Cannot get presigned download url., Error code: 3202

Steps to reproduce the problem

The issue only occurs when running on a real device (not a simulator). Code has worked fine in the past (prior to version 0.17.0 being released). Running code from here:

IBMQ.load_account()
provider = IBMQ.get_provider(hub='ibm-q')
small_devices = provider.backends(filters=lambda x: x.configuration().n_qubits == 5 and not x.configuration().simulator)
least_busy_device = least_busy(small_devices)
job_sim = execute(self._quantum_game.circ, least_busy_device, shots=n_times)
res_sim = job_sim.result()
counts = res_sim.get_counts(self._quantum_game.circ)

The error occurs after execute() and before .result()

What is the expected behavior?

Circuit to execute fully and results of run become available.

Suggested solutions

[jyu00]

This is now fixed. Thanks @desireevl for reporting it!

[jyu00]

This problem is due to erroneous response sent by the server through the websocket connection, which is used by job.result() to wait for the job to finish. As a temporary workaround, you can manually poll for the job status, bypassing websocket:

import time
from qiskit.providers.jobstatus import JOB_FINAL_STATES

while job.status() not in JOB_FINAL_STATES:
    time.sleep(5)
result = job.result()

“Temporary” is highlighted because using job.status() to poll is generally not recommended as it could cause the server to deny your request due to excessive requests.