api: avoid 5xx when stats/events not yet populated (#13424) (#13845)

* api: avoid 5xx when stats/events not yet populated

* Add catching of metrics exception also for retrieve of :queue metrics. No pipelines means no queues created

* Added empty result when no pipelines is present and query for node info API

Co-authored-by: andsel <selva.andre@gmail.com>
(cherry picked from commit a6c0e75b53)

logstash-core/lib/logstash/api/commands/node.rb

@@ -38,6 +38,8 @@ module LogStash
           pipeline_ids.each_with_object({}) do |pipeline_id, result|
             result[pipeline_id] = pipeline(pipeline_id, options)
           end
+        rescue Instrument::MetricStore::MetricNotFound
+          {}
         end
 
         def pipeline(pipeline_id, options={})

logstash-core/lib/logstash/api/commands/stats.rb

@@ -39,6 +39,8 @@ module LogStash
           end
 
           {:events_count => total_queued_events}
+        rescue Instrument::MetricStore::MetricNotFound
+          {}
         end
 
         def jvm
@@ -74,6 +76,9 @@ module LogStash
             [:stats, :events],
             :in, :filtered, :out, :duration_in_millis, :queue_push_duration_in_millis
           )
+        rescue Instrument::MetricStore::MetricNotFound
+          # if the stats/events metrics have not yet been populated, return an empty map
+          {}
         end
 
         def pipeline(pipeline_id = nil, opts={})