add member away benchmark

2 files changed, 36 insertions, 1 deletions

diff --git a/docs/development.md b/docs/development.md
index 0b424e3..db89c04 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -21,7 +21,8 @@ The benchmarks are ignored tests named `bench_*`: the document's (writes and syn
 messages, `document/bench.rs`), the remakes' replay (`remake/bench.rs`), and what
 passing changes on costs over the simulated network (`simtest/bench.rs`: messages and
 bytes per write by kind, propagation delays, for a full mesh, a writer behind NAT, two
-transports and partial meshes of 50 and 100 nodes; several minutes, or one scenario
+transports, partial meshes of 50 and 100 nodes, lossy links, and a member away for a
+while; several minutes, or one scenario
 alone with `BENCH_SCENARIO`, part of its name: `BENCH_SCENARIO=NAT`; all at once with
 `BENCH_PARALLEL=1`, faster on many cores, though sharing them makes delays come out
 somewhat higher), and
diff --git a/src/simtest/bench.rs b/src/simtest/bench.rs
index acf91bf..9ffb93c 100644
--- a/src/simtest/bench.rs
+++ b/src/simtest/bench.rs
@@ -52,6 +52,11 @@ struct Scenario {
     net: fn(&Sim, &[String]),
     /// The node that writes in the one-writer workload.
     writer: usize,
+    /// A node that goes away for the middle half of each workload (it is taken off the
+    /// net, as if gone without a word) and comes back, if any: 50 writes at 5 a second,
+    /// 10 s, not long enough to be held dormant (four keepalives, 20 s), so what a node
+    /// that is gone costs before the others notice.
+    away: Option<usize>,
 }
 
 fn sim_only(_: usize) -> &'static [&'static str] {
@@ -101,6 +106,7 @@ const SCENARIOS: &[Scenario] = &[
         on: sim_only,
         net: clean,
         writer: 1,
+        away: None,
     },
     Scenario {
         name: "writer behind NAT (one link), 13 nodes",
@@ -108,6 +114,7 @@ const SCENARIOS: &[Scenario] = &[
         on: sim_only,
         net: writer_behind_nat,
         writer: 1,
+        away: None,
     },
     Scenario {
         name: "two transports, 3 bridges, 30 nodes",
@@ -115,6 +122,7 @@ const SCENARIOS: &[Scenario] = &[
         on: two_transports,
         net: clean,
         writer: 5,
+        away: None,
     },
     Scenario {
         name: "partial mesh, 50 nodes",
@@ -122,6 +130,7 @@ const SCENARIOS: &[Scenario] = &[
         on: sim_only,
         net: clean,
         writer: 1,
+        away: None,
     },
     Scenario {
         name: "partial mesh, lossy and slow links, 50 nodes",
@@ -129,6 +138,7 @@ const SCENARIOS: &[Scenario] = &[
         on: sim_only,
         net: lossy,
         writer: 1,
+        away: None,
     },
     Scenario {
         name: "partial mesh, 100 nodes",
@@ -136,6 +146,15 @@ const SCENARIOS: &[Scenario] = &[
         on: sim_only,
         net: clean,
         writer: 1,
+        away: None,
+    },
+    Scenario {
+        name: "partial mesh, a member away for 10 s, 50 nodes",
+        nodes: 50,
+        on: sim_only,
+        net: clean,
+        writer: 1,
+        away: Some(3),
     },
 ];
 
@@ -349,6 +368,21 @@ async fn run(seed: u64, scenario: &'static Scenario) -> String {
     {
         let start = Totals::of(&nodes);
         for i in 0..WRITES {
+            // The middle half, the node that goes away is gone (writing nothing).
+            if let Some(away) = scenario.away {
+                if i == WRITES / 4 {
+                    sim.net.take_down(&ids[away]);
+                } else if i == WRITES * 3 / 4 {
+                    sim.net.bring_up(&ids[away]);
+                }
+            }
+            let gone = scenario.away.is_some_and(|away| {
+                (WRITES / 4..WRITES * 3 / 4).contains(&i) && away == i % nodes.len()
+            });
+            if writer.is_none() && gone {
+                tokio::time::sleep(WRITE_EVERY).await;
+                continue;
+            }
             let node = &nodes[writer.unwrap_or(i % nodes.len())];
             // A path of each workload's own: writing what is there already changes
             // nothing, and nothing would pass.