I changed the output to console and verified that
filebeat is actually examining the logs and there are hundreds of lines that should be sent to Logstash.
The only error messages that
journalctl shows are about empty files being ignored.
I've verified with
tcpdump that over 30 seconds go by without any messages being sent.
I upgraded from
8.12.0 but that had no effect.
There was a burst of traffic at 00:00 UTC of nearly 14k lines in 1 minute, which is a normal amount of traffic, but the next minute it was back down to 210 lines.
Where else can I look to diagnose this?
The problem only started on Wednesday, though I can't find any change that might have stopped the flow of logs. The configs are working fine in another DC, but 1 DC that we have is missing millions of log lines.