[Pulp-list] Pulp 3 waiting tasks

[Bin Li (BLOOMBERG/ 120 PARK)]

We have been seeing many waiting tasks.  They seem to be stuck forever. 
e.g.
pulpp-ob-581 /home/bli4/pulp3-script # ./get /pulp/api/v3/tasks/14b76b27-9f34-4297-88ed-5ec13cbe5e50/
HTTP/1.1 200 OK
Allow: GET, PATCH, DELETE, HEAD, OPTIONS
Connection: keep-alive
Content-Length: 323
Content-Type: application/json
Date: Fri, 03 Apr 2020 12:56:02 GMT
Server: nginx/1.16.1
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

{
    "created_resources": [], 
    "error": null, 
    "finished_at": null, 
    "name": "pulpcore.app.tasks.base.general_update", 
    "progress_reports": [], 
    "pulp_created": "2020-04-02T13:00:14.881212Z", 
    "pulp_href": "/pulp/api/v3/tasks/14b76b27-9f34-4297-88ed-5ec13cbe5e50/", 
    "reserved_resources_record": [], 
    "started_at": null, 
    "state": "waiting", 
    "worker": null
}

What could be the reason for these stuck waiting tasks? How should we troubleshot the issue? 
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