Remove duplicates in a logstash array

[SKing]

I have a json String with name / value pairs

{
"A1":"123",
"A2":"225",
"A3":"668",
"A4":"225"
}

Using logstash I can mutate the string and end up with an array by using
mutate {
add_field => {A => "%{A1}")
add_field => {A => "%{A2}")
add_field => {A => "%{A3}")
add_field => {A => "%{A4}")
}

mutate {
remove_field => ["A1", "A2", "A3", "A4"]
}

{
"A": ["123", "225", "668", "225"]
}

I would like to eliminate the duplicates in the array so that I end up with
{
"A": ["123", "225", "668"]
}

I have tried using kv {} with allow_duplicate_values=false
but that would only work if my input data was of the format
{
"A":"123",
"A":"225",
"A":"668",
"A":"225"
}

Looking at this post

Checking if an nested field which is an array contains a value

Hi: I am trying to check if a nested field in the input can be used for conditional checks and how to do it: here is an example logstash config : input { generator { message => '{"metadata": { "origins": [ "192.168.50.91" ] }}' codec => "json" count => 1 } } filter { if [metadata][origins] =~ /192\.168\.50\.91/ { mutate { add_field => [ "router.cisco.hostname", "foo" ] } } } output { stdout { codec => rubydebug } } In the above config, I want to be abl…

it would appear to be some variation on
if [A2] in [A] {
if %{A2} in [A] {

Would appreciate people's help with this.
Thanks

[Jenni]

ruby {
  code => 'event.set("A", event.get("A").uniq)'
}

[SKing]

Thanks Jenni.

Even quicker using the built in plug-ins

if [A1] {
mutate {
add_field => {"A" => "%{A1}"}
}
}
if [A2] {
if !([A]) or !([A2] in [A]) {
mutate {
add_field => {"A" => "%{A2}"}
}
}
}
if [A3] {
if !([A]) or !([A3] in [A]) {
mutate {
add_field => {"A" => "%{A3}"}
}
}
}
if [A4] {
if !([A]) or !([A4] in [A]) {
mutate {
add_field => {"A" => "%{A4}"}
}
}
}