Puppet variables set in exec environment not accessible elsewhere in the class

I'm trying to configure a logging figuration with log paths based on a check to see if that log file exists. However, the if statements always return true even though I know /var/log/hermes/hermes.log doesn't exist. I have tested the exec {"service_log_check" onlyif is working so it's something to do with the if statement. I had thought about adding within each exec something like environment => ["FOO=true" and then changing the if statement to if $FOO == true but it appears that variables set within exec environment are only accessible within the exec not the whole class. It's driving me crazy!!! We are using puppet v3.7

class hermes::fluentd($service_name='hermes', $logs='/var/log/test/test.log') {

exec {"service_log_check":
  command => '/bin/true',
  onlyif => '/usr/bin/test -e /var/log/hermes/hermes.log',
}

exec {"service_log_json_check":
  command => '/bin/true',
  onlyif => '/usr/bin/test -e /var/log/hermes/hermes-json.log',
}

exec {"request_log_check":
  command => '/bin/true',
  onlyif => '/usr/bin/test -e /var/log/hermes/request.log',
}

if service_log_check {
    $service_logs = "/var/log/${service_name}/${service_name}.log"
}
else { $service_logs = []
}

if service_log_json_check {
    $service_json_logs = "/var/log/${service_name}/${service_name}-json.log"
}
else { $service_json_logs = []
}

if request_log_check {
    $service_request_logs = "/var/log/${service_name}/request.log"
}
else
{ $service_request_logs = []
}

$logs_to_tail = [$logs, $service_logs, $service_json_logs, $service_request_logs]


file { "/etc/td-agent/config.d/${service_name}_service_logs.conf":
    ensure => present,
    content => template('service_logs.conf.erb'),
    owner  => td-agent,
    group  => td-agent,
    mode   => '0775'
}

}