Logstash output question

Hi all,
i'd like to know if it's possibile to write some custom text inside of a file, during a csv upload inside elastic search

Logstash doesn't send files to Elasticsearch. It sends JSON documents, in your case created from CSV files. Do you want to create additional fields/properties in the JSON document created from each CSV line, or what do you want to accomplish?

beside sending JSONs to ES, i'd like to write a text file with the processed csv name and the number of records correctly uploaded n ES, i need this to manage csv reports better

Didn't you ask the same question a few days ago? I don't think there's a simple way of doing it. But can't you extract that information from ES instead? If you save the CSV filename in a field you can aggregate on the filename field and get back the document count per filename.

okay, but don't you have any idea about how this could be achieved? if you could give me some place to start it would be better, otherwise i am willing to hear some other reccomendation about how to execute it from ES, as you just mentioned. thank you

Use a terms aggregation to query ES and get back a table of how many documents there are for each CSV file.

ok thanks, but there's another issue: every time i load records inside an index through csv not ALL of them gets adeed, many of these get to update pre-existing records, so it turns out to be difficult to assess that everything went at it should or if there have been any errors/exceptions