Logstash drop filter for event - logstash

Question

In my log file I have entries like the following:
2014-06-25 12:36:18,176 [10] ((null)) INFO [s=(null)] [u=(null)] Hello from Serilog, running as "David"! [Program]
2014-06-25 12:36:18,207 [10] ((null)) WARN [s=(null)] [u=(null)] =======MyOwnLogger====== Hello from log4net, running as David! [MyOwnLogger]
2014-06-25 12:36:18,209 [10] ((null)) ERROR [s=(null)] [u=(null)] =======MyOwnLogger====== Hello from log4net, running as David! [MyOwnLogger]
which are of loglevel INFO, WARN and ERROR respectively.
What I would like to do is to only output to Elasticsearch those entries which are of ERROR level. Here is my Logstash configuration file:
input {
file {
path => "Somepath/*.log"
}
}
# This filter doesn't work
filter {
if [loglevel] != "error" {
drop { }
}
}
output {
elasticsearch { host => localhost }
stdout {}
}
Effectively, currently nothing gets sent to Elasticsearch. I know it is related to the filter because if it's not there, all the entries get sent to Elastisearch.

Answer 1

Try this grok filter. It is works at me with your logs
filter {
grok {
match => ["message","%{TIMESTAMP_ISO8601:logtime} \[%{NUMBER}\] \(\(%{WORD}\)\) %{WORD:loglevel} %{GREEDYDATA:other}"]
}
if [loglevel]!= "ERROR" {
drop {}
}
}
First, you need to grok the loglevel, then just you can use the field to do if else condition and decide drop or not.