print config on start

server/src/config.rs

@@ -27,6 +27,7 @@ pub struct Config {
 
 fn resolve_datasource(config: &config::Config) -> anyhow::Result<DatasourceConfig> {
     if config.get::<String>("prometheus.url").is_ok() {
+        println!("using Prometheus");
         return Ok(DatasourceConfig::Prometheus(PrometheusConfig {
             url: config.get("prometheus.url")?,
             query: config.get("prometheus.query")?,
@@ -34,6 +35,7 @@ fn resolve_datasource(config: &config::Config) -> anyhow::Result<DatasourceConfi
     }
 
     if config.get::<String>("influx.url").is_ok() {
+        println!("using Influx");
         return Ok(DatasourceConfig::Influx(InfluxConfig {
             url: config.get("influx.url")?,
             org_id: config.get("influx.org_id")?,
@@ -42,7 +44,7 @@ fn resolve_datasource(config: &config::Config) -> anyhow::Result<DatasourceConfi
         }));
     }
 
-    return Err(anyhow::format_err!("no datasource found"));
+    return Err(anyhow::format_err!("please configure a datasource"));
 }
 
 fn resolve_alerting(config: &config::Config) -> anyhow::Result<Option<AlertingConfig>> {
@@ -80,18 +82,32 @@ fn resolve_alerting(config: &config::Config) -> anyhow::Result<Option<AlertingCo
 // config::Environment doesn't support nested configs, e.g. `alerting.type`,
 // so I've copied this from:
 // https://github.com/rust-lang/mdBook/blob/f3e5fce6bf5e290c713f4015947dc0f0ad172d20/src/config.rs#L132
-// so that `__` can be used in env variables instead of `.`, 
+// so that `__` can be used in env variables instead of `.`,
 // e.g. `HASTIC_ALERTING__TYPE` -> alerting.type
 pub fn update_from_env(config: &mut config::Config) {
     let overrides =
         env::vars().filter_map(|(key, value)| parse_env(&key).map(|index| (index, value)));
 
     for (key, value) in overrides {
-        println!("{} => {}", key, value);
         config.set(&key, value).unwrap();
     }
 }
 
+pub fn print_config(config: config::Config) {
+    // TODO: support any nesting level
+    let sections = config.to_owned().cache.into_table().unwrap();
+    for (section_name, values) in sections {
+        match values.clone().into_table() {
+            Err(_) => println!("{} => {}", section_name, values),
+            Ok(section) => {
+                for (key, value) in section {
+                    println!("{}.{} => {}", section_name, key, value);
+                }
+            }
+        }
+    }
+}
+
 fn parse_env(key: &str) -> Option<String> {
     const PREFIX: &str = "HASTIC_";
 
@@ -117,7 +133,8 @@ impl Config {
             config.set("port", 4347).unwrap();
         }
 
-        // TODO: print resulted config (perfectly, it needs adding `derive(Debug)` in `subbeat`'s `DatasourceConfig`)
+        print_config(config.clone());
+
         Ok(Config {
             port: config.get::<u16>("port").unwrap(),
             datasource_config: resolve_datasource(&config)?,