Logstash grok multiline; Java stack trace

configuration

input {
        file {

        path => "/root/mult.log"
        start_position => "beginning"
        sincedb_path => "/dev/null"
        codec => multiline{

                 pattern => "^ -%{SPACE}%{TIMESTAMP_ISO8601}"
                 negate => true
                 what => "previous"
        }
}
 }
filter {
    grok {
     match => [
       "message", "(?m)^ -%{SPACE}%{TIMESTAMP_ISO8601:time} \[%{WORD:main}\] %{LOGLEVEL:loglevel}%{SPACE}\(%{JAVACLASS:class}\) %{DATA:mydata}\n(\t)?%{GREEDYDATA:stack}",
       "message", "^ -%{SPACE}%{TIMESTAMP_ISO8601:time} \[%{WORD:main}\] %{LOGLEVEL:loglevel}%{SPACE}\(%{JAVACLASS:class}\) %{GREEDYDATA:mydata}" ]
        break_on_match => false
 }
    date {
    match => [ "timestamp" , "dd/MMM/yyyy:HH:mm:ss Z"]
 }
}

output {
  stdout { codec => rubydebug}
elasticsearch {
    host => "localhost"
  }
}