SLO middleware allows admin to change `max_manifest_segments` (default is 10000), but we do have another setting in constraints called `MAX_BUFFERED_SLO_SEGMENTS` (default is 10000) that use for a SLO DELETE request. The value is hard code, admin can't change it.
Imagine the use case, when admin increase the `max_manifest_segments` to 50000, that means users can upload SLO have > 10000 segments without any issue. But users won't able to delete it due to `MAX_BUFFERED_SLO_SEGMENTS`. And you will see the error in below,
DEBUG:requests.packages.urllib3.connectionpool:http://192.168.190.21:80 "DELETE /v1/AUTH_demo/test/test.img?multipart-manifest=delete HTTP/1.1" 200 None
DEBUG:swiftclient:REQ: curl -i http://192.168.190.21/v1/AUTH_demo/test/test.img?multipart-manifest=delete DELETE -H "X-Auth-Token: AUTH_<SKIP>"
DEBUG:swiftclient:RESP STATUS: 200 OK
DEBUG:swiftclient:RESP HEADERS: {u'Date': u'Thu, 01 Feb 2018 05:44:25 GMT', u'Transfer-Encoding': u'chunked', u'Content-Type': u'text/plain', u'X-Openstack-Request-Id': u'tx04a88f6de6804ca9aa8a9-005a72a939', u'X-Trans-Id': u'tx04a88f6de6804ca9aa8a9-005a72a939'}
DEBUG:swiftclient:RESP BODY: Number Deleted: 0
Number Not Found: 0
Response Body: Too many buffered slo segments to delete.
Response Status: 400 Bad Request
https://github.com/openstack/swift/blob/master/swift/common/middleware/slo.py#L1182-L1184
I'm inclined to set SLO's bulk-deleter's max_deletes_ per_request to a big number. Not equal to SLO's max_manifest_ segments, but something big enough that, even if your current max_manifest_ segments is less than its historic high, your users can still delete any SLO manifest that they have.