chore(torture): address multiple left todos

+ more sophisticated new key generation
+ more sophisticated value generation
+ use the `max_rollback_blocks` cli argument as nomt option
  for `max_rollback_log_len`

Author: gabriele-0201

torture/src/agent.rs

@@ -234,7 +234,12 @@ impl Agent {
         o.path(workdir.join("nomt_db"));
         o.bitbox_seed(init.bitbox_seed);
         o.hashtable_buckets(500_000);
-        o.rollback(init.rollback);
+        if let Some(n_commits) = init.rollback {
+            o.rollback(true);
+            o.max_rollback_log_len(n_commits);
+        } else {
+            o.rollback(false);
+        }
         let nomt = Nomt::open(o)?;
         Ok(Self {
             workdir,

torture/src/message.rs

@@ -47,7 +47,8 @@ pub struct InitPayload {
     /// Only used upon creation a new NOMT db.
     pub bitbox_seed: [u8; 16],
     /// Whether the agent is supposed to handle rollbacks.
-    pub rollback: bool,
+    /// If `Some`, the maximum amount of supported blocks in a single rollback is specified.
+    pub rollback: Option<u32>,
 }
 
 /// The parameters for the [`ToAgent::Commit`] message.

torture/src/supervisor/cli.rs

@@ -99,9 +99,9 @@ pub struct WorkloadParams {
     ///
     /// The effective number of commits used for each rollback is randomly generated in the range
     /// 0..max_rollback_commits.
-    #[clap(default_value = "10")]
+    #[clap(default_value = "100")]
     #[arg(long = "max-rollback-commits")]
-    pub max_rollback_commits: usize,
+    pub max_rollback_commits: u32,
 
     /// Whether to ensure the correct application of the changest after every commit.
     #[clap(default_value = "false")]

torture/src/supervisor/controller.rs

@@ -33,7 +33,7 @@ impl SpawnedAgentController {
         workdir: String,
         workload_id: u64,
         bitbox_seed: [u8; 16],
-        rollback: bool,
+        rollback: Option<u32>,
     ) -> Result<()> {
         // Assign a unique ID to the agent.
         static AGENT_COUNT: AtomicUsize = AtomicUsize::new(0);

torture/src/supervisor/workload.rs

@@ -28,6 +28,9 @@ struct Biases {
     /// When generating a key, whether it should be one that was appeared somewhere or a brand new
     /// key.
     new_key: f64,
+    /// Distribution used when generating a new key to decide how many bytes needs to be shared
+    /// with an already existing key.
+    new_key_distribution: WeightedIndex<usize>,
     /// When executing a workload iteration, this is the probability of executing a commit.
     commit: u8,
     /// When executing a workload iteration, this is the probability of executing a commit
@@ -53,10 +56,27 @@ impl Biases {
             panic!("Sum of `commit-crash`, `rollback` and `rollback-crash` must be lower than 100");
         };
 
+        // When generating a new key to be inserted in the database,
+        // this distribution will generate the key.
+        // There is a 25% chance that the key is completely random,
+        // half of the 25% chance that the first byte will be shared with an existing key,
+        // one third of the 25% chance that two bytes will be shared with an existing key,
+        // and so on.
+        //
+        // There are:
+        // + 25% probability of having a key with 0 shared bytes.
+        // + 48% probability of having a key with 1 to 9 shared bytes.
+        // + 27% probability of having a key with more than 10 shared bytes.
+        //
+        // UNWRAP: provided iterator is not empty, no item is lower than zero
+        // and the total sum is greater than one.
+        let new_key_distribution = WeightedIndex::new((1usize..33).map(|x| (32 * 32) / x)).unwrap();
+
         Self {
             delete: (delete as f64) / 100.0,
             overflow: (overflow as f64) / 100.0,
             new_key: (new_key as f64) / 100.0,
+            new_key_distribution,
             commit,
             commit_crash,
             rollback,
@@ -147,10 +167,8 @@ impl WorkloadState {
 
     /// Returns a KeyValueChange with a new key, a deleted or a modified one.
     fn gen_key_value_change(&mut self) -> KeyValueChange {
-        // TODO: sophisticated key generation.
-        //
-        // - Pick a key that was already generated before, but generate a key that shares some bits.
         let mut key = [0; 32];
+        // Generate a Delete KeyValueChange
         if !self.committed.state.is_empty() && self.rng.gen_bool(self.biases.delete) {
             loop {
                 self.rng.fill_bytes(&mut key);
@@ -160,15 +178,31 @@ impl WorkloadState {
             }
         }
 
-        if self.committed.state.is_empty() || self.rng.gen_bool(self.biases.new_key) {
+        // Generate a new key KeyValueChange
+        if self.committed.state.is_empty() {
+            self.rng.fill_bytes(&mut key);
+            return KeyValueChange::Insert(key, self.gen_value());
+        }
+
+        if self.rng.gen_bool(self.biases.new_key) {
             loop {
                 self.rng.fill_bytes(&mut key);
+
+                let Some(next_key) = self.committed.state.get_next(&key).map(|(k, _)| *k) else {
+                    continue;
+                };
+
+                let common_bytes =
+                    self.rng.sample(self.biases.new_key_distribution.clone()) as usize;
+                key[..common_bytes].copy_from_slice(&next_key[..common_bytes]);
+
                 if !self.committed.state.contains_key(&key) {
                     return KeyValueChange::Insert(key, self.gen_value());
                 }
             }
         }
 
+        // Generate an update KeyValueChange
         loop {
             self.rng.fill_bytes(&mut key);
             if let Some((next_key, _)) = self.committed.state.get_next(&key) {
@@ -178,14 +212,12 @@ impl WorkloadState {
     }
 
     fn gen_value(&mut self) -> Vec<u8> {
-        // TODO: sophisticated value generation.
-        //
-        // - Different power of two sizes.
-        // - Change it to be a non-even.
+        // MAX_LEAF_VALUE_SIZE is 1332,
+        // thus every value size bigger than this will create an overflow value.
         let len = if self.rng.gen_bool(self.biases.overflow) {
-            32 * 1024
+            self.rng.gen_range(1333..32 * 1024)
         } else {
-            32
+            self.rng.gen_range(1..1333)
         };
         let mut value = vec![0; len];
         self.rng.fill_bytes(&mut value);
@@ -233,7 +265,7 @@ pub struct Workload {
     /// Whether to randomly sample the state after every crash or rollback.
     sample_snapshot: bool,
     /// The max number of commits involved in a rollback.
-    max_rollback_commits: usize,
+    max_rollback_commits: u32,
     /// If `Some` there are rollbacks waiting to be applied.
     scheduled_rollbacks: ScheduledRollbacks,
 }
@@ -455,16 +487,8 @@ impl Workload {
         Ok(())
     }
 
-    fn commits_to_rollback(&mut self) -> usize {
-        // TODO: n_commits should also depend on the max rollback supported by NOMT.
-        std::cmp::min(
-            self.state.rng.gen_range(1..self.max_rollback_commits) as usize,
-            self.state.committed.sync_seqn as usize,
-        )
-    }
-
     async fn schedule_rollback(&mut self, should_crash: bool) -> anyhow::Result<()> {
-        let n_commits_to_rollback = self.commits_to_rollback();
+        let n_commits_to_rollback = self.state.rng.gen_range(1..self.max_rollback_commits) as usize;
         if n_commits_to_rollback == 0 {
             trace!("No available commits to perform rollback with");
             return Ok(());
@@ -593,7 +617,6 @@ impl Workload {
         let agent_died_or_timeout = timeout(TOLERANCE, agent.died()).await;
         self.agent.take().unwrap().teardown().await;
         if let Err(Elapsed { .. }) = agent_died_or_timeout {
-            // TODO: flag for investigation.
             return Err(anyhow::anyhow!("agent did not die"));
         }
 
@@ -740,7 +763,11 @@ impl Workload {
         assert!(self.agent.is_none());
         controller::spawn_agent_into(&mut self.agent).await?;
         let workdir = self.workdir.path().display().to_string();
-        let rollback = self.state.biases.rollback > 0;
+        let rollback = if self.state.biases.rollback > 0 {
+            Some(self.max_rollback_commits)
+        } else {
+            None
+        };
         self.agent
             .as_mut()
             .unwrap()