# Ruby exceptions logstash
**URL:** https://discuss.elastic.co/t/ruby-exceptions-logstash/276829
**Category:** Logstash
**Created:** [June 23, 2021, 5:27pm UTC](https://discuss.elastic.co/t/ruby-exceptions-logstash/276829 "2021-06-23T17:27:46Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Roberto\_B](https://discuss.elastic.co/u/Roberto_B)
#### Post date: [June 23, 2021, 5:27pm UTC](https://discuss.elastic.co/t/ruby-exceptions-logstash/276829/1 "2021-06-23T17:27:46Z")
Hi all,
i'm in trouble with Ruby exceptions i get 2 types of exceptions:
```auto
[ERROR][logstash.filters.ruby][windows-patching][7da18e5397d31e1f8d249dc2ef273bcbcc32d26e064f064c3138ef1bcbc3c2a0] Ruby exception occurred:
undefined method `scan' for nil:NilClass
[ERROR][logstash.filters.ruby][windows-patching][e0a2523135310fc00c1030f2da81c2f3b28e517f8b2c21c12101e9d813e448ce] Ruby exception occurred: undefined method `[]' for nil:NilClass
```
I've this kind of ruby filter
```auto
filter{
ruby {
code => "
if event.get('Patches available').nil?
event.remove('[Patches available]')
end
"
}
}
filter{
ruby {
code => "
if event.get('Patches installed').nil?
event.remove('[Patches installed]')
end
"
}
}
#Questo modulo standardizza il campo Installable Errata e Applicable Errata togliendo "" [] \ lo splitta e produce un array di stringhe
filter {
mutate {
gsub => [
"Patches available", "[\[\]]", "",
"Patches available", "\"", ""
]
}
ruby { code => 'event.set("Patches available", event.get("Patches available").scan(/\(\w+\)/))' }
}
filter {
mutate {
gsub => [
"Patches installed", "[\[\]]", "",
"Patches installed", "\"", ""
]
}
ruby { code => 'event.set("Patches installed", event.get("Patches installed").scan(/\(\w+\)/))' }
}
filter{
ruby {
code => "
if event.get('Patches available').nil?
event.set('N_Patches_available', 0)
event.remove('[Patches available]')
else
event.set('N_Patches_available', (event.get('Patches available').length))
end
"
}
}
filter{
ruby {
code => "
if event.get('Patches installed').nil?
event.set('N_Patches_installed', 0)
event.remove('[Patches installed]')
else
event.set('N_Patches_installed', (event.get('Patches installed').length))
end
"
}
}
```
Maybe the problem is due to the fact that in some case one of the field is empty so "scan" cannnot scan any data?
I would like to totaly remove the field if it is nil and\or to avoid exceptions. Do you know of to do that? Someting like a " if not event.nil? " ?! I'm not a Ruby expert.
KR
Roberto
---
### Author:  [@Badger](https://discuss.elastic.co/u/Badger)
#### Post date: [June 23, 2021, 6:19pm UTC](https://discuss.elastic.co/t/ruby-exceptions-logstash/276829/2 "2021-06-23T18:19:24Z")
Your first two ruby filters potentially delete the field [Patches available], but after running the mutate you unconditionally call ruby code which runs .scan on its value. That is going to result in that "undefined method `scan' for nil:NilClass" exception.
You could try wrapping the mutate and 3rd ruby filter in
```
if [Patches available] {
...
}
```
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 21, 2021, 6:19pm UTC](https://discuss.elastic.co/t/ruby-exceptions-logstash/276829/3 "2021-07-21T18:19:54Z")
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