[BUG] No minimum validation for top_n_size setting

[dzane17]

What is the bug?

There is no minimum for top_n_size setting. Users can set the value to 0 or negative value which does not make sense.

Add minimum constant here -

query-insights/src/main/java/org/opensearch/plugin/insights/settings/QueryInsightsSettings.java

Line 63 in 84e6b75

public static final int MAX_N_SIZE = 100;

Update validator function here -

query-insights/src/main/java/org/opensearch/plugin/insights/core/service/TopQueriesService.java

Line 139 in 84e6b75

if (size > QueryInsightsSettings.MAX_N_SIZE) {

How can one reproduce the bug?

% curl -XPUT "localhost:9200/_cluster/settings?pretty&flat_settings" -H 'Content-Type: application/json' -d '{"transient":{"search.insights.top_queries.latency.top_n_size": "-1"}}' 
{
  "acknowledged" : true,
  "persistent" : { },
  "transient" : {
    "search.insights.top_queries.latency.top_n_size" : "-1"
  }
}

What is the expected behavior?

We should reject all requests which attempt to update less than some minimum value, probably 1.

[ansjcy]

[Triage]
@dzane17 Thanks for filing this issue.

[ansjcy]

This is fixed as part of #13.