Use gamma distribution for all load testers

aquatic_http_load_test/src/common.rs

@@ -1,6 +1,6 @@
 use std::sync::{atomic::AtomicUsize, Arc};
 
-use rand_distr::Pareto;
+use rand_distr::Gamma;
 
 pub use aquatic_http_protocol::common::*;
 pub use aquatic_http_protocol::request::*;
@@ -29,7 +29,7 @@ pub struct Statistics {
 pub struct LoadTestState {
     pub info_hashes: Arc<Vec<InfoHash>>,
     pub statistics: Arc<Statistics>,
-    pub pareto: Arc<Pareto<f64>>,
+    pub gamma: Arc<Gamma<f64>>,
 }
 
 #[derive(PartialEq, Eq, Clone, Copy)]

aquatic_http_load_test/src/config.rs

@@ -33,24 +33,6 @@ impl aquatic_common::cli::Config for Config {
     }
 }
 
-#[derive(Clone, Debug, PartialEq, TomlConfig, Deserialize)]
-#[serde(default, deny_unknown_fields)]
-pub struct TorrentConfig {
-    pub number_of_torrents: usize,
-    /// Pareto shape
-    ///
-    /// Fake peers choose torrents according to Pareto distribution.
-    pub torrent_selection_pareto_shape: f64,
-    /// Probability that a generated peer is a seeder
-    pub peer_seeder_probability: f64,
-    /// Probability that a generated request is a announce request, as part
-    /// of sum of the various weight arguments.
-    pub weight_announce: usize,
-    /// Probability that a generated request is a scrape request, as part
-    /// of sum of the various weight arguments.
-    pub weight_scrape: usize,
-}
-
 impl Default for Config {
     fn default() -> Self {
         Self {
@@ -68,14 +50,33 @@ impl Default for Config {
     }
 }
 
+#[derive(Clone, Debug, PartialEq, TomlConfig, Deserialize)]
+#[serde(default, deny_unknown_fields)]
+pub struct TorrentConfig {
+    pub number_of_torrents: usize,
+    /// Probability that a generated peer is a seeder
+    pub peer_seeder_probability: f64,
+    /// Probability that a generated request is a announce request, as part
+    /// of sum of the various weight arguments.
+    pub weight_announce: usize,
+    /// Probability that a generated request is a scrape request, as part
+    /// of sum of the various weight arguments.
+    pub weight_scrape: usize,
+    /// Peers choose torrents according to this Gamma distribution shape
+    pub torrent_gamma_shape: f64,
+    /// Peers choose torrents according to this Gamma distribution scale
+    pub torrent_gamma_scale: f64,
+}
+
 impl Default for TorrentConfig {
     fn default() -> Self {
         Self {
             number_of_torrents: 10_000,
             peer_seeder_probability: 0.25,
-            torrent_selection_pareto_shape: 2.0,
             weight_announce: 5,
             weight_scrape: 0,
+            torrent_gamma_shape: 0.2,
+            torrent_gamma_scale: 100.0,
         }
     }
 }

aquatic_http_load_test/src/main.rs

@@ -6,7 +6,7 @@ use ::glommio::LocalExecutorBuilder;
 use aquatic_common::cpu_pinning::glommio::{get_worker_placement, set_affinity_for_util_worker};
 use aquatic_common::cpu_pinning::WorkerIndex;
 use rand::prelude::*;
-use rand_distr::Pareto;
+use rand_distr::Gamma;
 
 mod common;
 mod config;
@@ -47,12 +47,16 @@ fn run(config: Config) -> ::anyhow::Result<()> {
         info_hashes.push(InfoHash(rng.gen()));
     }
 
-    let pareto = Pareto::new(1.0, config.torrents.torrent_selection_pareto_shape).unwrap();
+    let gamma = Gamma::new(
+        config.torrents.torrent_gamma_shape,
+        config.torrents.torrent_gamma_scale,
+    )
+    .unwrap();
 
     let state = LoadTestState {
         info_hashes: Arc::new(info_hashes),
         statistics: Arc::new(Statistics::default()),
-        pareto: Arc::new(pareto),
+        gamma: Arc::new(gamma),
     };
 
     let tls_config = create_tls_config().unwrap();

aquatic_http_load_test/src/utils.rs

@@ -2,7 +2,7 @@ use std::sync::Arc;
 
 use rand::distributions::WeightedIndex;
 use rand::prelude::*;
-use rand_distr::Pareto;
+use rand_distr::Gamma;
 
 use crate::common::*;
 use crate::config::*;
@@ -69,12 +69,12 @@ fn create_scrape_request(config: &Config, state: &LoadTestState, rng: &mut impl
 
 #[inline]
 fn select_info_hash_index(config: &Config, state: &LoadTestState, rng: &mut impl Rng) -> usize {
-    pareto_usize(rng, &state.pareto, config.torrents.number_of_torrents - 1)
+    gamma_usize(rng, &state.gamma, config.torrents.number_of_torrents - 1)
 }
 
 #[inline]
-fn pareto_usize(rng: &mut impl Rng, pareto: &Arc<Pareto<f64>>, max: usize) -> usize {
-    let p: f64 = pareto.sample(rng);
+fn gamma_usize(rng: &mut impl Rng, gamma: &Arc<Gamma<f64>>, max: usize) -> usize {
+    let p: f64 = gamma.sample(rng);
     let p = (p.min(101.0f64) - 1.0) / 100.0;
 
     (p * max as f64) as usize