Inconsistent Solr Learning to Rank Feature Store State - SolrCloud / 7.7

[Doug Turnbull]

Hi all,

In SolrCloud mode, Solr 7.7, I uploaded a feature store, and notice it in
zookeeper under the collection's config. I've tried to upload various
feature store names with the command:

```
 curl -XPUT "http://localhost:8983/solr/collection/schema/feature-store";
--data-binary "@ltr/collection/feature_set.json" -H
'Content-type:application/json'

{
  "responseHeader":{
    "status":0,
    "QTime":19}}
```

The json file contents are:

```
[
    {
      "name" : "title_bm25",
      "class" : "org.apache.solr.ltr.feature.SolrFeature",
      "params" : {
        "q" : "title:(${keywords})"
      }
    },
    {
      "name" : "title_len",
      "class" : "org.apache.solr.ltr.feature.FieldLengthFeature",
      "params" : {
        "field": "title"
      }
    }
]
```

Everytime I curl to see what feature stores exist, I get an inconsistent
response from the node I uploaded to:

```

$ curl -XGET 'http://localhost:8983/solr/collection/schema/feature-store'
{
  "responseHeader":{
    "status":0,
    "QTime":2},
  "featureStores":[]}
(solr/search-v2/pool-v)douglas.turnbull@solr-prod-v2-

$ curl -XGET 'http://localhost:8983/solr/collection/schema/feature-store'
{
  "responseHeader":{
    "status":0,
    "QTime":0},
  "featureStores":[""]}

$ curl -XGET 'http://localhost:8983/solr/collection/schema/feature-store'
{
  "responseHeader":{
    "status":0,
    "QTime":103},
  "featureStores":[]}

$ curl -XGET 'http://localhost:8983/solr/collection/schema/feature-store'
{
  "responseHeader":{
    "status":0,
    "QTime":0},
  "featureStores":["_DEFAULT",
  "_DEFAULT_"]}

$ curl -XGET 'http://localhost:8983/solr/collection/schema/feature-store'
{
  "responseHeader":{
    "status":0,
    "QTime":0},
  "featureStores":["foo", "_DEFAULT_"]}
$ curl -XGET 'http://localhost:8983/solr/collection/schema/feature-store'
{
  "responseHeader":{
    "status":0,
    "QTime":103},
  "featureStores":[]}

```

Similarly when I query for _DEFAULT_ directly:

```
$ curl -XGET 
'http://localhost:8983/solr/collection/schema/feature-store/_DEFAULT_'

reddit-search-config$
{
  "responseHeader":{
    "status":0,
    "QTime":2},
  "features":[]}


$ curl -XGET 
'http://localhost:8983/solr/collection/schema/feature-store/_DEFAULT_'
{
  "responseHeader":{
    "status":0,
    "QTime":1},
  "features":[{
      "name":"title_bm25",
      "class":"org.apache.solr.ltr.feature.SolrFeature",
      "params":{"q":"title:(${keywords})"},
      "store":"_DEFAULT_"},
    {
      "name":"title_len",
      "class":"org.apache.solr.ltr.feature.FieldLengthFeature",
      "params":{"field":"title"},
      "store":"_DEFAULT_"}]}
$ curl -XGET 
'http://localhost:8983/solr/collection/schema/feature-store/_DEFAULT_'

reddit-search-config$
{
  "responseHeader":{
    "status":0,
    "QTime":1},
  "features":[]}
```

Is this a known issue? Seems like a bug, but let me know if there's a
workaround or something I should be doing differently

Thanks
-Doug