Trouble getting Logstash to pick up an environment variable

[jclose (Jason)]

I am consistently getting an error with trying to pick up the environment variable within my input config file.

Here is what I have:

input {
    redis {
        data_type => "list"
        key => "syslog"
        host => "${REDIS_HOST}"
        add_field => { "logstash_host" => '${HOSTNAME}'
                       "log_source" => "redis"
                       "msg_src" => "%{[type]}" }
        tags =>  [ "syslog", "redis" ]
    }
}

It isn't picking up the REDIST_HOST or the HOSTNAME variables. I have added them to the /etc/default/logstash file (this is Ubuntu 16.04). I have even tried doing it via a shell script inside of /etc/profile.d

I have tried with both export REDIS="10.2.2.2" and just REDIS="10.2.2.2" and neither is working.

The error I get is the following:

[2018-02-07T15:19:49,562][ERROR][logstash.agent ] Failed to execute action {:action=>LogStash::PipelineAction::Create/pipeline_id:main, :exception=>"LogStash::ConfigurationError", :message=>"Cannot evaluate ${REDIS_HOST}. Environment variable REDIS_HOST is not set and there is no default value given.", :backtrace...

I start via a service (sudo service logstash start). What am I doing wrong?

[aberrantCode (Erik W)]

Does it work correctly if you run it from the command line with the "--allow-env" switch?

[jclose (Jason)]

I just tried this both, putting both the export and leaving the export out of the /etc/default/logstash file, and the error didn't show up.

I think I have figured out what I was doing wrong.

I was trying to set something inside the /etc/default/logstash file using another, global environment variable. Apparently, it wasn't picking that up.

I'm guessing this was the issue. Apologize for not checking this part more thoroughly.