maxShardsPerNode always over-riden by autoscaling?

[Gus Heck]

I had a 8.0.0 cluster strangely put 2 shards on the same node and then 3 on
the same node the next collection I created. Both had maxShardsPerNode set
to 1 (and it still shows in cluster_state.json).

After some research I found https://jira.apache.org/jira/browse/SOLR-11239

The 8x documentation says nothing about this in the vicinity of the
maxShardsPerNode attribute, and when I checked I found that by default the
cluster comes with 2 listeners and two triggers (.auto_add_replicas and
.scheduled_maintenance). (they seem to be hard coded for automatic addition
in OverSeerTriggerThread:

@Override
public void run() {
  int lastZnodeVersion = znodeVersion;

  // we automatically add a trigger for auto add replicas if it does not
exists already
  // we also automatically add a scheduled maintenance trigger
  while (!isClosed)  {
    try {
      if (Thread.currentThread().isInterrupted()) {
        log.warn("Interrupted");
        break;
      }
      AutoScalingConfig autoScalingConfig =
cloudManager.getDistribStateManager().getAutoScalingConfig();
      AutoScalingConfig updatedConfig =
withAutoAddReplicasTrigger(autoScalingConfig);
      updatedConfig = withScheduledMaintenanceTrigger(updatedConfig);

So I think this means that it's not possible for maxShardsPerNode to ever
have an effect?

If so, we need to formally remove it and provide a clear example of how to
achieve the same effect with the autoscaling framework referenced from the
place where this attribute was documented.

-Gus