Logstash indexing JSON array but not JSON objects individually

Question

I'm sending logs over TCP using Node.js. The logs are ingested when sent as a JSON array (only the commented line without the loop). But if I iterate over the array and send them individually, only the first log is ingested. The rest don't even show up in the logstash logs. I need to send them individually so Logstash can parse them to their respective indices in Elasticsearch which it cannot identify when sent as an array.

const client = new net.Socket();
client.connect(LOGSTASH_PORT, LOGSTASH_HOST, () => {

    for (const event of allEvents) {
      const success = client.write(JSON.stringify(event), (error) => {
        if (error) {
          console.error('Error writing to socket:', error);
        } else {
          console.log('Data written successfully');
        }
      });
    }

    //const success = client.write(JSON.stringify(allEvents));

    client.end();
});

No error response in both cases so checking for drain event does not help. This is what my Logstash config looks like

input {
    tcp {
        port => "5400"
        codec =>"json"
    }
}

filter {

}

output {
 stdout { codec => json }
 elasticsearch {
   index => "<some index name>"
   hosts=> "${ELASTIC_HOSTS}"
   user=> "${ELASTIC_USER}"
   password=> "${ELASTIC_PASSWORD}"
   cacert=> "<some path>"
 }
}

I've tried the json_lines codec but that does not help. The problem could be with client.write() not finishing the operation before the next iteration starts but it does not send an error.

Answer 1

Ok so I figured out the fix. Change the input codec to json_lines and manually insert a new line in the string after writing a JSON object. This is what the change looks like

 const success = client.write(JSON.stringify(event) + "\n")

This looks like a hacky solution but hey it works. All I can think of for this happening is the client.write() not treating the message as a single unit after each loop iteration.