docs: adjust metrics documentation

Inform that metrics may now only be used under crate feature 'metrics'.
Mention new metrics in documentation and show an example
how to collect them.
Adjust examples to include new metrics.

docs/source/metrics/metrics.md

@@ -1,5 +1,7 @@
 # Driver metrics
 
+This feature is available only under the crate feature `metrics`.
+
 During operation the driver collects various metrics.
 
 They can be accessed at any moment using `Session::get_metrics()`
@@ -11,6 +13,9 @@ They can be accessed at any moment using `Session::get_metrics()`
 * Total number of paged queries
 * Number of errors during paged queries
 * Number of retries
+* Latency histogram statistics (min, max, mean, standard deviation, percentiles)
+* Rates of queries per second in various time frames
+* Number of active connections, and connection and request timeouts
 
 ### Example
 ```rust
@@ -29,6 +34,27 @@ println!(
     "99.9 latency percentile: {}",
     metrics.get_latency_percentile_ms(99.9).unwrap()
 );
+
+let snapshot = metrics.get_snapshot().unwrap();
+println!("Min: {}", snapshot.min);
+println!("Max: {}", snapshot.max);
+println!("Mean: {}", snapshot.mean);
+println!("Standard deviation: {}", snapshot.stddev);
+println!("Median: {}", snapshot.median);
+println!("75th percentile: {}", snapshot.percentile_75);
+println!("95th percentile: {}", snapshot.percentile_95);
+println!("98th percentile: {}", snapshot.percentile_98);
+println!("99th percentile: {}", snapshot.percentile_99);
+println!("99.9th percentile: {}", snapshot.percentile_99_9);
+
+println!("Mean rate: {}", metrics.get_mean_rate());
+println!("One minute rate: {}", metrics.get_one_minute_rate());
+println!("Five minute rate: {}", metrics.get_five_minute_rate());
+println!("Fifteen minute rate: {}", metrics.get_fifteen_minute_rate());
+
+println!("Total connections: {}", metrics.get_total_connections());
+println!("Connection timeouts: {}", metrics.get_connection_timeouts());
+println!("Requests timeouts: {}", metrics.get_request_timeouts());
 # Ok(())
 # }
 ```

examples/basic.rs

@@ -100,6 +100,27 @@ async fn main() -> Result<()> {
         metrics.get_latency_percentile_ms(99.9).unwrap()
     );
 
+    let snapshot = metrics.get_snapshot().unwrap();
+    println!("Min: {}", snapshot.min);
+    println!("Max: {}", snapshot.max);
+    println!("Mean: {}", snapshot.mean);
+    println!("Standard deviation: {}", snapshot.stddev);
+    println!("Median: {}", snapshot.median);
+    println!("75th percentile: {}", snapshot.percentile_75);
+    println!("95th percentile: {}", snapshot.percentile_95);
+    println!("98th percentile: {}", snapshot.percentile_98);
+    println!("99th percentile: {}", snapshot.percentile_99);
+    println!("99.9th percentile: {}", snapshot.percentile_99_9);
+
+    println!("Mean rate: {}", metrics.get_mean_rate());
+    println!("One minute rate: {}", metrics.get_one_minute_rate());
+    println!("Five minute rate: {}", metrics.get_five_minute_rate());
+    println!("Fifteen minute rate: {}", metrics.get_fifteen_minute_rate());
+
+    println!("Total connections: {}", metrics.get_total_connections());
+    println!("Connection timeouts: {}", metrics.get_connection_timeouts());
+    println!("Requests timeouts: {}", metrics.get_request_timeouts());
+
     println!("Ok.");
 
     Ok(())