aquatic: print stats about number of peers per torrent

Cargo.lock

@@ -24,6 +24,7 @@ version = "0.1.0"
 dependencies = [
  "bittorrent_udp",
  "dashmap",
+ "histogram",
  "indexmap",
  "mimalloc",
  "mio",
@@ -244,6 +245,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "histogram"
+version = "0.6.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "12cb882ccb290b8646e554b157ab0b71e64e8d5bef775cd66b6531e52d302669"
+
 [[package]]
 name = "humansize"
 version = "1.1.0"

TODO.md

@@ -15,12 +15,6 @@
 * Performance
     * cpu-target=native good?
     * mialloc good?
-    * use DashMap readable view when accessing torrent stats and possibly
-      also after modification of announcing peer and during collection
-      of response peers
-* Statistics
-    * Print stats for number of peers per torrent (median, 95th, 99th
-      percentile.) Use histogram crate?
 * bittorrent_udp
     * ParseError enum maybe, with `Option<TransactionId>`
     * Avoid allocating in conversion to bytes, send in a mutable buffer

aquatic/Cargo.toml

@@ -14,6 +14,7 @@ name = "aquatic"
 [dependencies]
 bittorrent_udp = { path = "../bittorrent_udp" }
 dashmap = "3"
+histogram = "0.6"
 indexmap = "1"
 mimalloc = { version = "0.1", default-features = false }
 mio = { version = "0.7", features = ["udp", "os-poll", "os-util"] }

aquatic/src/lib/lib.rs

@@ -1,6 +1,8 @@
 use std::sync::atomic::Ordering;
 use std::time::Duration;
 
+use histogram::Histogram;
+
 pub mod common;
 pub mod config;
 pub mod handlers;
@@ -55,6 +57,34 @@ pub fn run(){
                     responses_per_second,
                     requests_per_readable_event
                 );
+
+                let mut peers_per_torrent = Histogram::new();
+
+                for torrent in state.torrents.iter(){
+                    let num_seeders = torrent.num_seeders.load(Ordering::SeqCst);
+                    let num_leechers = torrent.num_leechers.load(Ordering::SeqCst);
+
+                    let num_peers = (num_seeders + num_leechers) as u64;
+
+                    if let Err(err) = peers_per_torrent.increment(num_peers){
+                        eprintln!("error incrementing peers_per_torrent histogram: {}", err)
+                    }
+                }
+
+                if peers_per_torrent.entries() != 0 {
+                    println!(
+                        "peers per torrent: min: {}, p50: {}, p75: {}, p90: {}, p99: {}, p999: {}, max: {}",
+                        peers_per_torrent.minimum().unwrap(),
+                        peers_per_torrent.percentile(50.0).unwrap(),
+                        peers_per_torrent.percentile(75.0).unwrap(),
+                        peers_per_torrent.percentile(90.0).unwrap(),
+                        peers_per_torrent.percentile(99.0).unwrap(),
+                        peers_per_torrent.percentile(99.9).unwrap(),
+                        peers_per_torrent.maximum().unwrap(),
+                    );
+
+                    println!();
+                }
             }
         });
     }