OK, something is definitely not working well with the wildcard patterns. I wonder if it is due to the depth of path? I can't find any documentation about maximum file path depth (although in filebeat docs it mentions something about 8).
Anyway, I can "find" my files if I use this pattern:
path => "/data/tracelogger/tracelogger_data/processed/AP4/10.66.132.23/2019-05-17_20-21-30/cm/log/ris/csv/PerfMon*"
But if I use this pattern it doesn't work (variable expansion wildcard):
path => "/data/tracelogger/tracelogger_data/**/PerfMon*"
Nor this one (explicit wildcards for the fixed path depth):
path => "/data/tracelogger/tracelogger_data/*/*/*/*/*/*/*/*/PerfMon*"
I guess I can try filebeat and see if I can stream the files into logstash to process.