if "iris-uat" in "%{[openshift][kubernetes][namespace_name]}" {
You cannot use a sprintf reference in a conditional. This is a substring match.
if "iris-uat" in "[openshift][kubernetes][namespace_name]" {
That is a also substring match against a string, so if "ift][kuber" in "[openshift][kubernetes][namespace_name]" { would evaluate to true, but that never will.
if "iris-uat" in [openshift][kubernetes][namespace_name] {
I would expect that to work. Instead of showing us the result from an index search can you show us an event output from logstash with
output { stdout { codec => rubydebug } }