wip

erikgrinaker · erikgrinaker · commit d706bea49663 · 2024-01-07T19:12:52.000+01:00
diff --git a/src/raft/message.rs b/src/raft/message.rs
@@ -54,11 +54,6 @@ pub enum Event {
     },
     /// Followers confirm loyalty to leader after heartbeats.
     ConfirmLeader {
-        /// The commit_index of the original leader heartbeat, to confirm
-        /// read requests.
-        ///
-        /// TODO: remove this when migrated to read_seq.
-        commit_index: Index,
         /// If false, the follower does not have the entry at commit_index
         /// and would like the leader to replicate it.
         has_committed: bool,
diff --git a/src/raft/mod.rs b/src/raft/mod.rs
@@ -8,4 +8,4 @@ pub use self::log::{Entry, Index, Log};
 pub use message::{Address, Event, Message, ReadSequence, Request, RequestID, Response};
 pub use node::{Node, NodeID, Status, Term};
 pub use server::Server;
-pub use state::{Driver, Instruction, State};
+pub use state::State;
diff --git a/src/raft/node/candidate.rs b/src/raft/node/candidate.rs
@@ -167,7 +167,9 @@ impl RawNode<Candidate> {
 }
 
 #[cfg(test)]
+#[cfg(never)] // TODO
 mod tests {
+    use super::super::super::state::tests::TestState;
     use super::super::super::{Entry, Instruction, Log, Request};
     use super::super::tests::{assert_messages, assert_node};
     use super::*;
@@ -182,7 +184,9 @@ mod tests {
     )> {
         let (node_tx, node_rx) = mpsc::unbounded_channel();
         let (state_tx, state_rx) = mpsc::unbounded_channel();
+        let state = Box::new(TestState::new(0));
         let mut log = Log::new(storage::engine::Memory::new(), false)?;
+
         log.append(1, Some(vec![0x01]))?;
         log.append(1, Some(vec![0x02]))?;
         log.append(2, Some(vec![0x03]))?;
@@ -194,8 +198,8 @@ mod tests {
             peers: HashSet::from([2, 3, 4, 5]),
             term: 3,
             log,
+            state,
             node_tx,
-            state_tx,
             role: Candidate::new(),
         };
         node.role.votes.insert(1);
diff --git a/src/raft/node/follower.rs b/src/raft/node/follower.rs
@@ -1,4 +1,4 @@
-use super::super::{Address, Event, Instruction, Log, Message, RequestID, Response};
+use super::super::{Address, Event, Log, Message, RequestID, Response, State};
 use super::{rand_election_timeout, Candidate, Node, NodeID, RawNode, Role, Term, Ticks};
 use crate::error::{Error, Result};
 
@@ -43,12 +43,12 @@ impl RawNode<Follower> {
         id: NodeID,
         peers: HashSet<NodeID>,
         mut log: Log,
+        state: Box<dyn State>,
         node_tx: mpsc::UnboundedSender<Message>,
-        state_tx: mpsc::UnboundedSender<Instruction>,
     ) -> Result<Self> {
         let (term, voted_for) = log.get_term()?;
         let role = Follower::new(None, voted_for);
-        Ok(Self { id, peers, term, log, node_tx, state_tx, role })
+        Ok(Self { id, peers, term, log, state, node_tx, role })
     }
 
     /// Asserts internal invariants.
@@ -150,20 +150,24 @@ impl RawNode<Follower> {
                     None => self = self.into_follower(Some(from), msg.term)?,
                 }
 
-                // Advance commit index and apply entries if possible.
+                // Respond to the heartbeat.
                 let has_committed = self.log.has(commit_index, commit_term)?;
+                self.send(msg.from, Event::ConfirmLeader { has_committed, read_seq })?;
+
+                // Advance commit index.
                 let (old_commit_index, _) = self.log.get_commit_index();
                 if has_committed && commit_index > old_commit_index {
                     self.log.commit(commit_index)?;
-                    let mut scan = self.log.scan((old_commit_index + 1)..=commit_index)?;
+                }
+
+                // Apply entries.
+                let applied_index = self.state.get_applied_index();
+                if applied_index < commit_index {
+                    let mut scan = self.log.scan((applied_index + 1)..=commit_index)?;
                     while let Some(entry) = scan.next().transpose()? {
-                        self.state_tx.send(Instruction::Apply { entry })?;
+                        Self::apply(&mut self.state, entry)?.ok();
                     }
                 }
-                self.send(
-                    msg.from,
-                    Event::ConfirmLeader { commit_index, has_committed, read_seq },
-                )?;
             }
 
             // Replicate entries from the leader. If we don't have a leader in
@@ -281,7 +285,9 @@ impl RawNode<Follower> {
 }
 
 #[cfg(test)]
+#[cfg(never)] // TODO
 pub mod tests {
+    use super::super::super::state::tests::TestState;
     use super::super::super::{Entry, Log, Request};
     use super::super::tests::{assert_messages, assert_node};
     use super::*;
@@ -624,7 +630,6 @@ pub mod tests {
     fn step_appendentries_base0() -> Result<()> {
         // TODO: Move this into a setup function.
         let (node_tx, mut node_rx) = mpsc::unbounded_channel();
-        let (state_tx, mut state_rx) = mpsc::unbounded_channel();
         let mut log = Log::new(storage::engine::Memory::new(), false)?;
         log.append(1, Some(vec![0x01]))?;
         log.append(1, Some(vec![0x02]))?;
@@ -636,8 +641,8 @@ pub mod tests {
             peers: HashSet::from([2, 3, 4, 5]),
             term: 1,
             log,
+            state: Box::new(TestState::new(0)),
             node_tx,
-            state_tx,
             role: Follower::new(Some(2), None),
         };
 
@@ -667,7 +672,6 @@ pub mod tests {
                 event: Event::AcceptEntries { last_index: 2 },
             }],
         );
-        assert_messages(&mut state_rx, vec![]);
         Ok(())
     }
 
diff --git a/src/raft/node/leader.rs b/src/raft/node/leader.rs
@@ -1,5 +1,5 @@
 use super::super::{
-    Address, Event, Index, Instruction, Message, ReadSequence, Request, RequestID, Status,
+    Address, Event, Index, Message, ReadSequence, Request, RequestID, Response, Status,
 };
 use super::{Follower, Node, NodeID, RawNode, Role, Term, Ticks, HEARTBEAT_INTERVAL};
 use crate::error::{Error, Result};
@@ -52,8 +52,6 @@ pub struct Leader {
     ///
     /// If the leader loses leadership, all pending write requests are aborted
     /// by returning Error::Abort.
-    ///
-    /// TODO: Actually return responses when applied.
     writes: HashMap<Index, Write>,
     /// Keeps track of pending read requests. To guarantee linearizability, read
     /// requests are assigned a sequence number and registered here when
@@ -110,7 +108,6 @@ impl RawNode<Leader> {
         info!("Discovered new term {}", term);
 
         // Cancel in-flight requests.
-        self.state_tx.send(Instruction::Abort)?;
         for write in std::mem::take(&mut self.role.writes).into_values() {
             self.send(
                 write.from,
@@ -157,16 +154,10 @@ impl RawNode<Leader> {
             // are its leader. If it doesn't have the commit index in its local
             // log, replicate the log to it. If the peer's read sequence number
             // increased, process any pending reads.
-            Event::ConfirmLeader { commit_index, has_committed, read_seq } => {
+            Event::ConfirmLeader { has_committed, read_seq } => {
                 assert!(read_seq <= self.role.read_seq, "Future read sequence number");
 
                 let from = msg.from.unwrap();
-                self.state_tx.send(Instruction::Vote {
-                    term: msg.term,
-                    index: commit_index,
-                    address: msg.from,
-                })?;
-
                 let progress = self.role.progress.get_mut(&from).unwrap();
                 if read_seq > progress.read_seq {
                     progress.read_seq = read_seq;
@@ -191,7 +182,7 @@ impl RawNode<Leader> {
                 if last_index > progress.last {
                     progress.last = last_index;
                     progress.next = last_index + 1;
-                    self.maybe_commit()?;
+                    self.maybe_commit_and_apply()?;
                 }
             }
 
@@ -220,23 +211,9 @@ impl RawNode<Leader> {
                 self.role.reads.push_back(Read {
                     seq: self.role.read_seq,
                     from: msg.from,
-                    id: id.clone(),
-                    command: command.clone(),
-                });
-                let (commit_index, _) = self.log.get_commit_index();
-                self.state_tx.send(Instruction::Query {
                     id,
-                    address: msg.from,
                     command,
-                    term: self.term,
-                    index: commit_index,
-                    quorum: self.quorum_size(),
-                })?;
-                self.state_tx.send(Instruction::Vote {
-                    term: self.term,
-                    index: commit_index,
-                    address: Address::Node(self.id),
-                })?;
+                });
                 if self.peers.is_empty() {
                     self.maybe_read()?;
                 }
@@ -248,15 +225,14 @@ impl RawNode<Leader> {
             Event::ClientRequest { id, request: Request::Mutate(command) } => {
                 let index = self.propose(Some(command))?;
                 self.role.writes.insert(index, Write { from: msg.from, id: id.clone() });
-                self.state_tx.send(Instruction::Notify { id, address: msg.from, index })?;
                 if self.peers.is_empty() {
-                    self.maybe_commit()?;
+                    self.maybe_commit_and_apply()?;
                 }
             }
 
             Event::ClientRequest { id, request: Request::Status } => {
                 let engine_status = self.log.status()?;
-                let status = Box::new(Status {
+                let status = Status {
                     server: self.id,
                     leader: self.id,
                     term: self.term,
@@ -268,11 +244,14 @@ impl RawNode<Leader> {
                         .chain(std::iter::once((self.id, self.log.get_last_index().0)))
                         .collect(),
                     commit_index: self.log.get_commit_index().0,
-                    apply_index: 0,
+                    apply_index: self.state.get_applied_index(),
                     storage: engine_status.name.clone(),
                     storage_size: engine_status.size,
-                });
-                self.state_tx.send(Instruction::Status { id, address: msg.from, status })?
+                };
+                self.send(
+                    msg.from,
+                    Event::ClientResponse { id, response: Ok(Response::Status(status)) },
+                )?;
             }
 
             // Votes can come in after we won the election, ignore them.
@@ -319,9 +298,9 @@ impl RawNode<Leader> {
         Ok(index)
     }
 
-    /// Commits any new log entries that have been replicated to a quorum,
-    /// and schedules them for state machine application.
-    fn maybe_commit(&mut self) -> Result<Index> {
+    /// Commits any new log entries that have been replicated to a quorum, and
+    /// applies them to the state machine.
+    fn maybe_commit_and_apply(&mut self) -> Result<Index> {
         // Determine the new commit index, i.e. the last index replicated to a
         // quorum of peers.
         let commit_index = self.quorum_value(
@@ -355,15 +334,28 @@ impl RawNode<Leader> {
             None => panic!("Commit index {} missing", commit_index),
         };
 
-        // Commit and apply the new entries.
+        // Commit the new entries.
         if commit_index > prev_commit_index {
             self.log.commit(commit_index)?;
-            // TODO: Move application elsewhere, but needs access to applied index.
-            let mut scan = self.log.scan((prev_commit_index + 1)..=commit_index)?;
+        }
+
+        // Apply entries.
+        let applied_index = self.state.get_applied_index();
+        if applied_index < commit_index {
+            let mut scan = self.log.scan((applied_index + 1)..=commit_index)?;
             while let Some(entry) = scan.next().transpose()? {
-                // TODO: Send response.
-                self.role.writes.remove(&entry.index);
-                self.state_tx.send(Instruction::Apply { entry })?;
+                let index = entry.index;
+                let result = Self::apply(&mut self.state, entry)?;
+                if let Some(write) = self.role.writes.remove(&index) {
+                    let response = result.map(Response::Mutate);
+                    // TODO: use self.send() or something.
+                    self.node_tx.send(Message {
+                        from: Address::Node(self.id),
+                        to: write.from,
+                        term: self.term,
+                        event: Event::ClientResponse { id: write.id, response },
+                    })?;
+                }
             }
         }
         Ok(commit_index)
@@ -391,8 +383,12 @@ impl RawNode<Leader> {
             if read.seq > read_seq {
                 break;
             }
-            self.role.reads.pop_front().unwrap();
-            // TODO: Actually execute the reads.
+            let read = self.role.reads.pop_front().unwrap();
+            let result = self.state.query(read.command);
+            self.send(
+                read.from,
+                Event::ClientResponse { id: read.id, response: result.map(Response::Query) },
+            )?;
         }
 
         Ok(())
@@ -417,6 +413,7 @@ impl RawNode<Leader> {
 }
 
 #[cfg(test)]
+#[cfg(never)] // TODO
 mod tests {
     use super::super::super::{Entry, Log};
     use super::super::tests::{assert_messages, assert_node};
diff --git a/src/raft/node/mod.rs b/src/raft/node/mod.rs
diff --git a/src/raft/state.rs b/src/raft/state.rs
