Since now, I have started Logstash by running the command:
/usr/share/logstash/bin/logstash --path.settings /etc/logstash/ --path.data sensor39 -f /etc/logstash/conf.d/logstash-config.conf
and it successfully sent all of the logs and I could see them on the dashboard.
But now, I have configured the Logstash service unit file to this:
ExecStart=/usr/share/logstash/bin/logstash --path.settings /etc/logstash --path.data sensor39 -f /etc/logstash/conf.d/logstash-config.conf
so that I can just start the Logstash service in order to send the logs. The problem is that only a few of the logs can be seen now on the dashboard.
Why does this happen and how can I fix it? Please, help.