Comment 1 for bug 1815618

Quick summary of my findings so far:

At the time of reporting I thought this is a combination of client and server side bugs. But now I think this should be fixed purely on server side.

My original thinking was based on the fact that neutronclient can update a qos rule, while osc cannot. And my first attempt for a fix was to get osc to send the same body as neutronclient does.

But if you take a closer look at the PUT bodies sent by both clients, you may ask why neutron-server mandates the presence of the direction field in the body even when the direction field is not being updated? We only want to update min_kbps here. So the body sent by osc should be accepted by neutron-server as a valid request.

While debugging I also realized it's practically impossible to get osc (ie. openstacksdk more precisely) to send the same body as neutronclient does. The basic reason is the logic in the _update() method here:

https://github.com/openstack/openstacksdk/blob/master/openstack/proxy.py#L178

Instead of sending a single PUT, it first GETs the resource and only includes the changed fields into the PUT body. By that it does not care if '[--ingress|--egress]' was present on the command line as long as the direction field's value does not change. In the source I don't see a way to force the inclusion a field that didn't change. So with the current openstacksdk I don't think this can be fixed on the client side.

Anyway there's an easy workaround if someone is willing to fiddle with curl:

$ cat min-bw-rule-update
#! /bin/sh

# export TOKEN="$( openstack token issue -f value -c id )"
# min-bw-rule-update NEUTRON-BASE-URL POLICY-ID RULE-ID DIRECTION MIN-KBPS
# min-bw-rule-update http://127.0.0.1:9696 188a2f59-ab90-41a3-9e6f-58e641a34544 f392837a-09e2-4b5e-8c29-86670797679e egress 1001

neutron_base_url="${1:?}"
policy_id="${2:?}"
rule_id="${3:?}"
direction="${4:?}"
min_kbps="${5:?}"

cat <<EOF |
{"minimum_bandwidth_rule":
    {"direction": "$direction",
     "min_kbps": "$min_kbps"}}
EOF
curl \
    --silent \
    --insecure \
    --request PUT \
    --header "content-type: application/json" \
    --header "x-auth-token: ${TOKEN:?}" \
    --data @- \
    "${neutron_base_url:?}/v2.0/qos/policies/$policy_id/minimum_bandwidth_rules/$rule_id" \
| json_pp

lajoskatona told me he's looking into the server side of this bug, the next update may be coming from him.