added export doc-comments

crates/api-grub/src/export.rs

@@ -6,6 +6,32 @@ use std::env;
 use anyhow::Result;
 use log::{info, error};
 
+/// An entity which handles DB connections.
+/// 
+/// This struct is used to be a layer between API-grab workers
+/// and the `pool` of DB connections to save grabbing processes statuses 
+/// (now `PostgreSQL`, slowly migrating to `ClickHouse` support)
+/// 
+/// # Examples
+/// 
+/// ```
+/// use api-grub::export::Expoter;
+/// 
+/// let exporter = Expoter::init();
+/// 
+/// assert!(exporter.get_connection_from_pool().is_some());
+/// ```  
+/// 
+/// # Hint: 
+/// 
+/// - use `export_data` method to export metrics to DB
+/// 
+/// - use `export_metrics` method to export metrics (`PrometehusMetrics` 
+/// type) to the Prometehus exporter (`$EXPORTER_URL`)
+/// 
+/// - use `export_metrics_extended` method to export metrics (
+/// `*PrometehusMetricsExtended*` type with `desc` field) to the 
+/// Prometehus exporter (`$EXPORTER_URL`)
 pub struct Exporter {
     pool : Option<Pool>,
 }