[Packetbeat] High CPU usage in PGSQL Decoder

[andrewkroh]

Packetbeat is using a lot of CPU time while processing pgsql protocol data. CPU profiling shows that much of this time can be attributed to the copious logging statements (even while debug logging is off).

(pprof) list isSpecialPgsqlCommand
Total: 29.95s
ROUTINE ======================== github.com/elastic/beats/packetbeat/protos/pgsql.isSpecialPgsqlCommand in github.com/elastic/beats/packetbeat/protos/pgsql/parse.go
     6.47s     26.23s (flat, cum) 87.58% of Total
             .          .    680:       // Startup Message
     2.89s     19.27s    681:       logp.Debug("pgsqldetailed", "Startup Message, length=%d", length)
     1.02s      1.02s    682:       return true, length, startupMessage