Allow user to specify host bind address (#44)

Signed-off-by: Mihai Puha <mihai.puha@criticaltechnologies.ro>
Co-authored-by: Mihai Puha <mihai.puha@criticaltechnologies.ro>

Author: puhamihai

README.md

@@ -52,6 +52,7 @@ Available options
 ```
 Usage: gluster-metrics-exporter [OPTIONS]
     --metrics-path=URL               Metrics Path (default: /metrics)
+    --host-binding                   Exporter bind address (default: 0.0.0.0)
     -p PORT, --port=PORT             Exporter Port (default: 9713)
     --cluster=NAME                   Cluster identifier
     --gluster-host=NAME              Gluster Host to replace `localhost` from the peer command output (default: hostname)

src/args.cr

@@ -16,6 +16,10 @@ module GlusterMetricsExporter
         @@config.metrics_path = url
       end
 
+      parser.on("--host-binding=HOST", "Bind to specific IP address (default: #{@@config.host_binding})") do |host|
+        @@config.host_binding = host
+      end
+
       parser.on("-p PORT", "--port=PORT", "Exporter Port (default: #{@@config.port})") do |port|
         @@config.port = port.to_i
       end

src/config.cr

@@ -5,6 +5,7 @@ module GlusterMetricsExporter
     include YAML::Serializable
 
     property metrics_path = "/metrics",
+      host_binding = "0.0.0.0",
       port = 9713,
       gluster_executable_path = "/usr/sbin/gluster",
       log_level = "info",

src/gluster-metrics-exporter.cr

@@ -77,6 +77,7 @@ module GlusterMetricsExporter
 
     Crometheus.default_registry.path = @@config.metrics_path
     Kemal.config.port = @@config.port
+    Kemal.config.host_binding = @@config.host_binding
     Kemal.config.logger = ExporterAPILogHandler.new
     Kemal.run
   end