Elasticsearch index/cache not clearing/stuck

I'm using https://github.com/firebase/flashlight to index data for searches

However, this morning I deleted the whole firebase index, so it should be empty (this has worked before, but it seems that when the nodejs app.js crashes in some cases, causing the cache to get "stuck"), but I still see old search results from my nodejs app somehow...

I've tried: 

http://localhost:9200/_cache/clear

and

http://localhost:9200/_flush
http://localhost:9200/firebase/_flush

They all say successful, but still I get old results, out of, seemingly nowhere.

I can also see in the console that it refreshes every 60 seconds, and, deleting the whole firebase has worked before without problems...

I even saw a message housekeeping: found 60 orphans (removing them now) in the console so it should be refreshed by now...

I tried restarting elasticsearch as well as the whole Linux/Debian server...

In the config.js I have two indexes: 

exports.paths = [
   {
      path:  "tags",
      index: "firebase",
      type:  "tag",
      filter: function(data) { return data.name !== 'system'; }
   },
   {
      path:  "tracks",
      index: "firebase",
      type:  "track",
      filter: function(data) { return data.name !== 'system'; }
   }
];

And strangely enough, I have no problem whatsoever when using the 'track' store, instead of using the 'tag' one...

What am I missing here?

// Update !

So, I just deleted the firebase tracks index while the nodejs script was running and the script crashed... Same problem, different index. So the crashing script must cause it... so, how do I clear this stuck cache?

A wild guess, maybe you are not posting the queries correctly. You said you have tried following links:

http://localhost:9200/_cache/clear
http://localhost:9200/_flush
http://localhost:9200/firebase/_flush

If you are accessing the urls from browser it won't clear them. You have to POST them. It is ambiguous from your question if you did it, both GET and POST return same results (showing total, successful and failed). Try this from commandline using curl:

curl -XPOST 'http://localhost:9200/_cache/clear'
curl -XPOST 'http://localhost:9200/_flush'

Or create an AJAX request with JQuery or use fiddler.

Try to optimize your indeces by sending the following POST request to your elasticsearch server:

curl -XPOST 'http://localhost:9200/_optimize?max_num_segments=1&wait_for_merge=true'

It makes lucene really delete the deleted documents from disk and merge indeces.

So I fixed it by simply doing: 

curl -XDELETE localhost:9200/Firebase

Thanks to: https://github.com/elasticsearch/elasticsearch/issues/7541#issuecomment-54724302

I'm guessing Elastic search is not aware (and has not been told) of the relevance of its current index, perhaps the Flashlight script I'm using is not informing it about what the index should have been? But, since this is only necessary when the node script crashes when you suddenly delete your whole firebase index, it should be catchable somehow, but I'm happy that I can at least fix it like this. Rebuilding the index is not a big issue/task right now, but in the future it might be.