How to remove all fields with NULL value in Logstash filter

Question

I am reading checkpoint log file with csv format with logstash and some fields have null value.

i want to remove all fields with null value.

i can not foresee exactly which fields(keys) will have null value because i have 150 columns in the csv file and i dont want check each one of them.

is it possible to do a dynamic filter in logstash that will remove any fields with null value?

my logstash configuration file look like that:

input {
  stdin { tags => "checkpoint" } 
   file {
   type => "file-input"
   path =>  "D:\Browser Downloads\logstash\logstash-1.4.2\bin\checkpoint.csv"
   sincedb_path => "D:\Browser Downloads\logstash\logstash-1.4.2\bin\sincedb-access2"
   start_position => "beginning"
   tags => ["checkpoint","offline"]
  }
}
filter {
 if "checkpoint" in [tags] {
        csv {
        columns => ["num","date","time","orig","type","action","alert","i/f_name","i/f_dir","product","Internal_CA:","serial_num:","dn:","sys_message:","inzone","outzone","rule","rule_uid","rule_name","service_id","src","dst","proto","service","s_port","dynamic object","change type","message_info","StormAgentName","StormAgentAction","TCP packet out of state","tcp_flags","xlatesrc","xlatedst","NAT_rulenum","NAT_addtnl_rulenum","xlatedport","xlatesport","fw_message","ICMP","ICMP Type","ICMP Code","DCE-RPC Interface UUID","rpc_prog","log_sys_message","scheme:","Validation log:","Reason:","Serial num:","Instruction:","fw_subproduct","vpn_feature_name","srckeyid","dstkeyid","user","methods:","peer gateway","IKE:","CookieI","CookieR","msgid","IKE notification:","Certificate DN:","IKE IDs:","partner","community","Session:","L2TP:","PPP:","MAC:","OM:","om_method:","assigned_IP:","machine:","reject_category","message:","VPN internal source IP","start_time","connection_uid","encryption failure:","vpn_user","Log ID","message","old IP","old port","new IP","new port","elapsed","connectivity_state","ctrl_category","description","description ","severity","auth_status","identity_src","snid","src_user_name","endpoint_ip","src_machine_name","src_user_group","src_machine_group","auth_method","identity_type","Authentication trial","roles","dst_user_name","dst_machine_name","spi","encryption fail reason:","information","error_description","domain_name","termination_reason","duration"]
      #  remove_field => [ any fields with null value] how to do it please 
        separator => "|"
        }
    # drop csv header
        if [num] == "num" and [date] == "date" and [time] == "time" and [orig] == "orig" {
        drop { }
    }
    }
  }

}
output {
   stdout {
    codec => rubydebug 
  }
   file {
      path => "output.txt"
   }

HERE I ATTACH SOME LOGS EXAMPLE:

num|date|time|orig|type|action|alert|i/f_name|i/f_dir|product|Internal_CA:|serial_num:|dn:|sys_message:|inzone|outzone|rule|rule_uid|rule_name|service_id|src|dst|proto|service|s_port|dynamic object|change type|message_info|StormAgentName|StormAgentAction|TCP packet out of state|tcp_flags|xlatesrc|xlatedst|NAT_rulenum|NAT_addtnl_rulenum|xlatedport|xlatesport|fw_message|ICMP|ICMP Type|ICMP Code|DCE-RPC Interface UUID|rpc_prog|log_sys_message|scheme:|Validation log:|Reason:|Serial num:|Instruction:|fw_subproduct|vpn_feature_name|srckeyid|dstkeyid|user|methods:|peer gateway|IKE:|CookieI|CookieR|msgid|IKE notification:|Certificate DN:|IKE IDs:|partner|community|Session:|L2TP:|PPP:|MAC:|OM:|om_method:|assigned_IP:|machine:|reject_category|message:|VPN internal source IP|start_time|connection_uid|encryption failure:|vpn_user|Log ID|message|old IP|old port|new IP|new port|elapsed|connectivity_state|ctrl_category|description|description |severity|auth_status|identity_src|snid|src_user_name|endpoint_ip|src_machine_name|src_user_group|src_machine_group|auth_method|identity_type|Authentication trial|roles|dst_user_name|dst_machine_name|spi|encryption fail reason:|information|error_description|domain_name|termination_reason|duration
0|8Jun2012|16:33:35|10.0.0.1|log|keyinst||daemon|inbound|VPN-1 & FireWall-1|started|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 1|8Jun2012|16:36:34|10.0.0.1|log|keyinst||daemon|inbound|VPN-1 & FireWall-1|started|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 2|8Jun2012|16:52:39|10.0.0.1|log|keyinst||daemon|inbound|VPN-1 & FireWall-1|Certificate initialized|86232|CN=fw-KO,O=sc-KO.KO.dc.obn8cx|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 3|8Jun2012|16:52:39|10.0.0.1|log|keyinst||daemon|inbound|VPN-1 & FireWall-1|Initiated certificate is now valid|86232|CN=fw-KO,O=sc-KO.KO.dc.obn8cx|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 4|8Jun2012|16:55:44|10.0.0.1|log|keyinst||daemon|inbound|VPN-1 & FireWall-1|Issued empty CRL 1|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
20|8Jun2012|16:58:28|10.0.0.1|log|accept||eth1|inbound|VPN-1 & FireWall-1|||||Internal|External|1|{2A42C8CD-148D-4809-A480-3171108AD6C7}||domain-udp|192.168.100.1|198.32.64.12|udp|53|1036|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Answer 1

Ruby filter can meet your requirement.

input {
        stdin {
        }
}

filter {
        csv {
                columns => ["num","date","time","orig","type","action","alert","i/f_name","i/f_dir","product","Internal_CA:","serial_num:","dn:","sys_message:","inzone","outzone","rule","rule_uid","rule_name","service_id","src","dst","proto","service","s_port","dynamic object","change type","message_info","StormAgentName","StormAgentAction","TCP packet out of state","tcp_flags","xlatesrc","xlatedst","NAT_rulenum","NAT_addtnl_rulenum","xlatedport","xlatesport","fw_message","ICMP","ICMP Type","ICMP Code","DCE-RPC Interface UUID","rpc_prog","log_sys_message","scheme:","Validation log:","Reason:","Serial num:","Instruction:","fw_subproduct","vpn_feature_name","srckeyid","dstkeyid","user","methods:","peer gateway","IKE:","CookieI","CookieR","msgid","IKE notification:","Certificate DN:","IKE IDs:","partner","community","Session:","L2TP:","PPP:","MAC:","OM:","om_method:","assigned_IP:","machine:","reject_category","message:","VPN internal source IP","start_time","connection_uid","encryption failure:","vpn_user","Log ID","message","old IP","old port","new IP","new port","elapsed","connectivity_state","ctrl_category","description","description ","severity","auth_status","identity_src","snid","src_user_name","endpoint_ip","src_machine_name","src_user_group","src_machine_group","auth_method","identity_type","Authentication trial","roles","dst_user_name","dst_machine_name","spi","encryption fail reason:","information","error_description","domain_name","termination_reason","duration"]
                separator => "|"
        }
        ruby {
                code => "
                        hash = event.to_hash
                        hash.each do |k,v|
                                if v == nil
                                        event.remove(k)
                                end
                        end
                "
        }
}

output {
    stdout { codec => rubydebug }
}

You can use ruby plugin to filter all the field with nil value (null in Ruby)

Updated:

This is my environment: Windows server 2008 and Logstash 1.4.1. Your logs sample is work at me! I have updated the configuration, input and output.

Input

2|8Jun2012|16:52:39|10.0.0.1|log|keyinst||daemon|inbound|VPN-1 & FireWall-1|Certificate initialized|86232|CN=fw-KO,O=sc-KO.KO.dc.obn8cx|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Output:

{
        "@version" => "1",
      "@timestamp" => "2015-03-12T00:30:34.123Z",
            "host" => "BENLIM",
             "num" => "2",
            "date" => "8Jun2012",
            "time" => "16:52:39",
            "orig" => "10.0.0.1",
            "type" => "log",
          "action" => "keyinst",
        "i/f_name" => "daemon",
         "i/f_dir" => "inbound",
         "product" => "VPN-1 & FireWall-1",
    "Internal_CA:" => "Certificate initialized",
     "serial_num:" => "86232",
             "dn:" => "CN=fw-KO,O=sc-KO.KO.dc.obn8cx"
}

Answer 2

Check the skip_empty_columns option of the csv filter - was really helpful in my use case. :)

Usage:

skip_empty_columns => true