Using if else in logstash filter

Hi everyone,

i'd like to ask, is it possible to use OR operator in if else statement in logstash filter?

so, i want to delete the event that has value "VoIP-Null0", "Null0", and "Loopback0" in data.ifDescr field. i already apply configuration like this to delete them

csv {
separator => ","
skip_header => true
columns => ["timestamp","host","data.ifDescr","data.ifInOctets","data.ifOutOctets"]

if [data][ifDescr] == "VoIP-Null0" or [data][ifDescr] == "Null0" or [data][ifDescr] == "Loopback0"{
drop { }

but there's no change. the event are still exist. even in the logstash log, there is no error
can you show me how to solve this? thank you

Yes it is supported AND OR... Check docs

Check in LS ruby debugger real the field name "data.ifInOctets" or [data][ifDescr].
I haven't tried, but should be different names in CSV. Also is useful,not mandatory, to have () in log. operations

columns => ["timestamp","host","[data][ifDescr]","[data][ifInOctets]","[data][ifOutOctets]"]

if ( ([data][ifDescr] == "VoIP-Null0") or ([data][ifDescr] == "Null0") or ([data][ifDescr] == "Loopback0") ) {
drop { }

Thank you for the response. i'll try your suggestion later. because I tried my luck before and it worked. hahaha. i change it from

if [data][ifDescr] == "VoIP-Null0" or [data][ifDescr] == "Null0" or [data][ifDescr] == "Loopback0"{
drop { }


if [data.ifDescr] == "VoIP-Null0" or [data.ifDescr] == "Null0" or [data.ifDescr] == "Loopback0"{
drop { }

I didn't think it would work. Once again, thank you

data.ifDescr - single field name
[data][ifDescr] - nested field

You should avoid using dots in fields name as this can lead to confusion because they work in different ways in Logstash and Elasticsearch.

In Logstash, using data.ifDescr means a field with a literal dot in its name, you have this:

{ "data.ifDescr": "value" }

In elasticsearch in scripts or ingest pipelines, using data.ifDescr would mean a json object named data with a nested field named ifDescr.

Something like this:

{ "data": { "ifDescr": "value" } }

In your case, if you named your field as data.ifDescr, then you should use [data.ifDescr] in your conditional.

But the recommendation is to change your csv filter and condtional to the ones that @Rios shared.

1 Like

Thanks for the explanation @leandrojmp . i also want to ask something about if else. is it good to use conditional statement this many?

or is it better if i make it like this?

if "Crypto" in [data][ifDescr] or "Bluetooth" in [data][ifDescr] or "unrouted" in [data][ifDescr]{
drop { }
else if "VoIP" in [data][ifDescr] or "Null" in [data][ifDescr] or "Loopback" in [data][ifDescr]{
drop { }

I'm afraid if I use conditional statements like above picture, it will affect logstash performance. Thank you

It makes no difference and will have zero impact in the performance.

But if the value of the field [data][ifDescr] is a single keyword you can improve your conditional and make it more readable.

if [data][ifDescr] in ["Crypto", "Bluetooth", "unrouted", "VoIP", "Null", "Loopback"] {
    drop {}

Thanks a lot for the solution @leandrojmp and Thank you for the help @Rios

actually that is some keyword of the value. because the value of the field is unrouted Vlan 56 (for example) if the value is not a single keyword, how do i improve my conditional?

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