logstash:how to use environment variables in input host - elasticsearch

Question

I wanna print 'host source' to output. For this goal, local or global variables is necessary. But I wanna not use the global variables like 'export ...'.
So before the input{}, I put the host in metadata then use in 'input{}'.
Like below:
filter{
environment{
add_field =>{
"[#metadata][TEMP]" => "127.0.0.1"
}
}
}
input{
udp{
host => "%{[#metadata][TEMP]}"
port => "10000"
}
}
output{
udp{
host => "127.0.0.1"
port => "10001"
}
}
But logstash is not running then log is like below:
[WARN ][logstash.inputs.udp ] UDP listener died {:exception=>#<SocketError: bind: name or service not known>known>
So how can solve this problem??

Answer 1

Let me try the answer your question in two steps.
The error message
Your config file is malformed. The workflow is always like this:
# This is a comment. You should use comments to describe
# parts of your configuration.
input {
...
}
filter {
...
}
output {
...
}
That is why you get the error message, your filter is in the wrong place and not applied before the input.
Multiple input sources
If you want to add information to your events depending on which input is used, you can add a type during input handling. Here is an example config file:
input {
file {
type => "file"
path => "/var/log/some_name.log"
}
udp{
type => "udp"
host => "127.0.0.1"
port => "10001"
}
}
filter {
# can be omitted, if not used
}
output {
udp{
host => "127.0.0.1"
port => "10001"
}
}
The type is stored as part of the event itself, so you can also use the type to search for it in Kibana.