WIP refactor

1 files changed, 0 insertions, 514 deletions

diff --git a/src/bayou.rs b/src/bayou.rs
deleted file mode 100644
index 9faff5a..0000000
--- a/src/bayou.rs
+++ /dev/null
@@ -1,514 +0,0 @@
-use std::sync::{Arc, Weak};
-use std::time::{Duration, Instant};
-
-use anyhow::{anyhow, bail, Result};
-use log::error;
-use rand::prelude::*;
-use serde::{Deserialize, Serialize};
-use tokio::sync::{watch, Notify};
-
-use crate::cryptoblob::*;
-use crate::login::Credentials;
-use crate::storage;
-use crate::timestamp::*;
-
-const KEEP_STATE_EVERY: usize = 64;
-
-// Checkpointing interval constants: a checkpoint is not made earlier
-// than CHECKPOINT_INTERVAL time after the last one, and is not made
-// if there are less than CHECKPOINT_MIN_OPS new operations since last one.
-const CHECKPOINT_INTERVAL: Duration = Duration::from_secs(6 * 3600);
-const CHECKPOINT_MIN_OPS: usize = 16;
-// HYPOTHESIS: processes are able to communicate in a synchronous
-// fashion in times that are small compared to CHECKPOINT_INTERVAL.
-// More precisely, if a process tried to save an operation within the last
-// CHECKPOINT_INTERVAL, we are sure to read it from storage if it was
-// successfully saved (and if we don't read it, it means it has been
-// definitely discarded due to an error).
-
-// Keep at least two checkpoints, here three, to avoid race conditions
-// between processes doing .checkpoint() and those doing .sync()
-const CHECKPOINTS_TO_KEEP: usize = 3;
-
-const WATCH_SK: &str = "watch";
-
-pub trait BayouState:
-    Default + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync + 'static
-{
-    type Op: Clone + Serialize + for<'de> Deserialize<'de> + std::fmt::Debug + Send + Sync + 'static;
-
-    fn apply(&self, op: &Self::Op) -> Self;
-}
-
-pub struct Bayou<S: BayouState> {
-    path: String,
-    key: Key,
-
-    storage: storage::Store,
-
-    checkpoint: (Timestamp, S),
-    history: Vec<(Timestamp, S::Op, Option<S>)>,
-
-    last_sync: Option<Instant>,
-    last_try_checkpoint: Option<Instant>,
-
-    watch: Arc<K2vWatch>,
-    last_sync_watch_ct: storage::RowRef,
-}
-
-impl<S: BayouState> Bayou<S> {
-    pub async fn new(creds: &Credentials, path: String) -> Result<Self> {
-        let storage = creds.storage.build().await?;
-
-        //let target = k2v_client.row(&path, WATCH_SK);
-        let target = storage::RowRef::new(&path, WATCH_SK);
-        let watch = K2vWatch::new(creds, target.clone()).await?;
-
-        Ok(Self {
-            path,
-            storage,
-            key: creds.keys.master.clone(),
-            checkpoint: (Timestamp::zero(), S::default()),
-            history: vec![],
-            last_sync: None,
-            last_try_checkpoint: None,
-            watch,
-            last_sync_watch_ct: target,
-        })
-    }
-
-    /// Re-reads the state from persistent storage backend
-    pub async fn sync(&mut self) -> Result<()> {
-        let new_last_sync = Some(Instant::now());
-        let new_last_sync_watch_ct = self.watch.rx.borrow().clone();
-
-        // 1. List checkpoints
-        let checkpoints = self.list_checkpoints().await?;
-        tracing::debug!("(sync) listed checkpoints: {:?}", checkpoints);
-
-        // 2. Load last checkpoint if different from currently used one
-        let checkpoint = if let Some((ts, key)) = checkpoints.last() {
-            if *ts == self.checkpoint.0 {
-                (*ts, None)
-            } else {
-                tracing::debug!("(sync) loading checkpoint: {}", key);
-
-                let buf = self
-                    .storage
-                    .blob_fetch(&storage::BlobRef(key.to_string()))
-                    .await?
-                    .value;
-                tracing::debug!("(sync) checkpoint body length: {}", buf.len());
-
-                let ck = open_deserialize::<S>(&buf, &self.key)?;
-                (*ts, Some(ck))
-            }
-        } else {
-            (Timestamp::zero(), None)
-        };
-
-        if self.checkpoint.0 > checkpoint.0 {
-            bail!("Loaded checkpoint is more recent than stored one");
-        }
-
-        if let Some(ck) = checkpoint.1 {
-            tracing::debug!(
-                "(sync) updating checkpoint to loaded state at {:?}",
-                checkpoint.0
-            );
-            self.checkpoint = (checkpoint.0, ck);
-        };
-
-        // remove from history events before checkpoint
-        self.history = std::mem::take(&mut self.history)
-            .into_iter()
-            .skip_while(|(ts, _, _)| *ts < self.checkpoint.0)
-            .collect();
-
-        // 3. List all operations starting from checkpoint
-        let ts_ser = self.checkpoint.0.to_string();
-        tracing::debug!("(sync) looking up operations starting at {}", ts_ser);
-        let ops_map = self
-            .storage
-            .row_fetch(&storage::Selector::Range {
-                shard: &self.path,
-                sort_begin: &ts_ser,
-                sort_end: WATCH_SK,
-            })
-            .await?;
-
-        let mut ops = vec![];
-        for row_value in ops_map {
-            let row = row_value.row_ref;
-            let sort_key = row.uid.sort;
-            let ts = sort_key
-                .parse::<Timestamp>()
-                .map_err(|_| anyhow!("Invalid operation timestamp: {}", sort_key))?;
-
-            let val = row_value.value;
-            if val.len() != 1 {
-                bail!("Invalid operation, has {} values", val.len());
-            }
-            match &val[0] {
-                storage::Alternative::Value(v) => {
-                    let op = open_deserialize::<S::Op>(v, &self.key)?;
-                    tracing::trace!("(sync) operation {}: {:?}", sort_key, op);
-                    ops.push((ts, op));
-                }
-                storage::Alternative::Tombstone => {
-                    continue;
-                }
-            }
-        }
-        ops.sort_by_key(|(ts, _)| *ts);
-        tracing::debug!("(sync) {} operations", ops.len());
-
-        if ops.len() < self.history.len() {
-            bail!("Some operations have disappeared from storage!");
-        }
-
-        // 4. Check that first operation has same timestamp as checkpoint (if not zero)
-        if self.checkpoint.0 != Timestamp::zero() && ops[0].0 != self.checkpoint.0 {
-            bail!(
-                "First operation in listing doesn't have timestamp that corresponds to checkpoint"
-            );
-        }
-
-        // 5. Apply all operations in order
-        // Hypothesis: before the loaded checkpoint, operations haven't changed
-        // between what's on storage and what we used to calculate the state in RAM here.
-        let i0 = self
-            .history
-            .iter()
-            .zip(ops.iter())
-            .take_while(|((ts1, _, _), (ts2, _))| ts1 == ts2)
-            .count();
-
-        if ops.len() > i0 {
-            // Remove operations from first position where histories differ
-            self.history.truncate(i0);
-
-            // Look up last calculated state which we have saved and start from there.
-            let mut last_state = (0, &self.checkpoint.1);
-            for (i, (_, _, state_opt)) in self.history.iter().enumerate().rev() {
-                if let Some(state) = state_opt {
-                    last_state = (i + 1, state);
-                    break;
-                }
-            }
-
-            // Calculate state at the end of this common part of the history
-            let mut state = last_state.1.clone();
-            for (_, op, _) in self.history[last_state.0..].iter() {
-                state = state.apply(op);
-            }
-
-            // Now, apply all operations retrieved from storage after the common part
-            for (ts, op) in ops.drain(i0..) {
-                state = state.apply(&op);
-                if (self.history.len() + 1) % KEEP_STATE_EVERY == 0 {
-                    self.history.push((ts, op, Some(state.clone())));
-                } else {
-                    self.history.push((ts, op, None));
-                }
-            }
-
-            // Always save final state as result of last operation
-            self.history.last_mut().unwrap().2 = Some(state);
-        }
-
-        // Save info that sync has been done
-        self.last_sync = new_last_sync;
-        self.last_sync_watch_ct = new_last_sync_watch_ct;
-        Ok(())
-    }
-
-    /// Does a sync() if either of the two conditions is met:
-    /// - last sync was more than CHECKPOINT_INTERVAL/5 ago
-    /// - a change was detected
-    pub async fn opportunistic_sync(&mut self) -> Result<()> {
-        let too_old = match self.last_sync {
-            Some(t) => Instant::now() > t + (CHECKPOINT_INTERVAL / 5),
-            _ => true,
-        };
-        let changed = self.last_sync_watch_ct != *self.watch.rx.borrow();
-        if too_old || changed {
-            self.sync().await?;
-        }
-        Ok(())
-    }
-
-    pub fn notifier(&self) -> std::sync::Weak<Notify> {
-        Arc::downgrade(&self.watch.learnt_remote_update)
-    }
-
-    /// Applies a new operation on the state. Once this function returns,
-    /// the operation has been safely persisted to storage backend.
-    /// Make sure to call `.opportunistic_sync()` before doing this,
-    /// and even before calculating the `op` argument given here.
-    pub async fn push(&mut self, op: S::Op) -> Result<()> {
-        tracing::debug!("(push) add operation: {:?}", op);
-
-        let ts = Timestamp::after(
-            self.history
-                .last()
-                .map(|(ts, _, _)| ts)
-                .unwrap_or(&self.checkpoint.0),
-        );
-
-        let row_val = storage::RowVal::new(
-            storage::RowRef::new(&self.path, &ts.to_string()),
-            seal_serialize(&op, &self.key)?,
-        );
-        self.storage.row_insert(vec![row_val]).await?;
-        self.watch.propagate_local_update.notify_one();
-
-        let new_state = self.state().apply(&op);
-        self.history.push((ts, op, Some(new_state)));
-
-        // Clear previously saved state in history if not required
-        let hlen = self.history.len();
-        if hlen >= 2 && (hlen - 1) % KEEP_STATE_EVERY != 0 {
-            self.history[hlen - 2].2 = None;
-        }
-
-        self.checkpoint().await?;
-
-        Ok(())
-    }
-
-    /// Save a new checkpoint if previous checkpoint is too old
-    pub async fn checkpoint(&mut self) -> Result<()> {
-        match self.last_try_checkpoint {
-            Some(ts) if Instant::now() - ts < CHECKPOINT_INTERVAL / 5 => Ok(()),
-            _ => {
-                let res = self.checkpoint_internal().await;
-                if res.is_ok() {
-                    self.last_try_checkpoint = Some(Instant::now());
-                }
-                res
-            }
-        }
-    }
-
-    async fn checkpoint_internal(&mut self) -> Result<()> {
-        self.sync().await?;
-
-        // Check what would be the possible time for a checkpoint in the history we have
-        let now = now_msec() as i128;
-        let i_cp = match self
-            .history
-            .iter()
-            .enumerate()
-            .rev()
-            .skip_while(|(_, (ts, _, _))| {
-                (now - ts.msec as i128) < CHECKPOINT_INTERVAL.as_millis() as i128
-            })
-            .map(|(i, _)| i)
-            .next()
-        {
-            Some(i) => i,
-            None => {
-                tracing::debug!("(cp) Oldest operation is too recent to trigger checkpoint");
-                return Ok(());
-            }
-        };
-
-        if i_cp < CHECKPOINT_MIN_OPS {
-            tracing::debug!("(cp) Not enough old operations to trigger checkpoint");
-            return Ok(());
-        }
-
-        let ts_cp = self.history[i_cp].0;
-        tracing::debug!(
-            "(cp) we could checkpoint at time {} (index {} in history)",
-            ts_cp.to_string(),
-            i_cp
-        );
-
-        // Check existing checkpoints: if last one is too recent, don't checkpoint again.
-        let existing_checkpoints = self.list_checkpoints().await?;
-        tracing::debug!("(cp) listed checkpoints: {:?}", existing_checkpoints);
-
-        if let Some(last_cp) = existing_checkpoints.last() {
-            if (ts_cp.msec as i128 - last_cp.0.msec as i128)
-                < CHECKPOINT_INTERVAL.as_millis() as i128
-            {
-                tracing::debug!(
-                    "(cp) last checkpoint is too recent: {}, not checkpointing",
-                    last_cp.0.to_string()
-                );
-                return Ok(());
-            }
-        }
-
-        tracing::debug!("(cp) saving checkpoint at {}", ts_cp.to_string());
-
-        // Calculate state at time of checkpoint
-        let mut last_known_state = (0, &self.checkpoint.1);
-        for (i, (_, _, st)) in self.history[..i_cp].iter().enumerate() {
-            if let Some(s) = st {
-                last_known_state = (i + 1, s);
-            }
-        }
-        let mut state_cp = last_known_state.1.clone();
-        for (_, op, _) in self.history[last_known_state.0..i_cp].iter() {
-            state_cp = state_cp.apply(op);
-        }
-
-        // Serialize and save checkpoint
-        let cryptoblob = seal_serialize(&state_cp, &self.key)?;
-        tracing::debug!("(cp) checkpoint body length: {}", cryptoblob.len());
-
-        let blob_val = storage::BlobVal::new(
-            storage::BlobRef(format!("{}/checkpoint/{}", self.path, ts_cp.to_string())),
-            cryptoblob.into(),
-        );
-        self.storage.blob_insert(blob_val).await?;
-
-        // Drop old checkpoints (but keep at least CHECKPOINTS_TO_KEEP of them)
-        let ecp_len = existing_checkpoints.len();
-        if ecp_len + 1 > CHECKPOINTS_TO_KEEP {
-            let last_to_keep = ecp_len + 1 - CHECKPOINTS_TO_KEEP;
-
-            // Delete blobs
-            for (_ts, key) in existing_checkpoints[..last_to_keep].iter() {
-                tracing::debug!("(cp) drop old checkpoint {}", key);
-                self.storage
-                    .blob_rm(&storage::BlobRef(key.to_string()))
-                    .await?;
-            }
-
-            // Delete corresponding range of operations
-            let ts_ser = existing_checkpoints[last_to_keep].0.to_string();
-            self.storage
-                .row_rm(&storage::Selector::Range {
-                    shard: &self.path,
-                    sort_begin: "",
-                    sort_end: &ts_ser,
-                })
-                .await?
-        }
-
-        Ok(())
-    }
-
-    pub fn state(&self) -> &S {
-        if let Some(last) = self.history.last() {
-            last.2.as_ref().unwrap()
-        } else {
-            &self.checkpoint.1
-        }
-    }
-
-    // ---- INTERNAL ----
-
-    async fn list_checkpoints(&self) -> Result<Vec<(Timestamp, String)>> {
-        let prefix = format!("{}/checkpoint/", self.path);
-
-        let checkpoints_res = self.storage.blob_list(&prefix).await?;
-
-        let mut checkpoints = vec![];
-        for object in checkpoints_res {
-            let key = object.0;
-            if let Some(ckid) = key.strip_prefix(&prefix) {
-                if let Ok(ts) = ckid.parse::<Timestamp>() {
-                    checkpoints.push((ts, key.into()));
-                }
-            }
-        }
-        checkpoints.sort_by_key(|(ts, _)| *ts);
-        Ok(checkpoints)
-    }
-}
-
-// ---- Bayou watch in K2V ----
-
-struct K2vWatch {
-    target: storage::RowRef,
-    rx: watch::Receiver<storage::RowRef>,
-    propagate_local_update: Notify,
-    learnt_remote_update: Arc<Notify>,
-}
-
-impl K2vWatch {
-    /// Creates a new watch and launches subordinate threads.
-    /// These threads hold Weak pointers to the struct;
-    /// they exit when the Arc is dropped.
-    async fn new(creds: &Credentials, target: storage::RowRef) -> Result<Arc<Self>> {
-        let storage = creds.storage.build().await?;
-
-        let (tx, rx) = watch::channel::<storage::RowRef>(target.clone());
-        let propagate_local_update = Notify::new();
-        let learnt_remote_update = Arc::new(Notify::new());
-
-        let watch = Arc::new(K2vWatch {
-            target,
-            rx,
-            propagate_local_update,
-            learnt_remote_update,
-        });
-
-        tokio::spawn(Self::background_task(Arc::downgrade(&watch), storage, tx));
-
-        Ok(watch)
-    }
-
-    async fn background_task(
-        self_weak: Weak<Self>,
-        storage: storage::Store,
-        tx: watch::Sender<storage::RowRef>,
-    ) {
-        let (mut row, remote_update) = match Weak::upgrade(&self_weak) {
-            Some(this) => (this.target.clone(), this.learnt_remote_update.clone()),
-            None => return,
-        };
-
-        while let Some(this) = Weak::upgrade(&self_weak) {
-            tracing::debug!(
-                "bayou k2v watch bg loop iter ({}, {})",
-                this.target.uid.shard,
-                this.target.uid.sort
-            );
-            tokio::select!(
-                // Needed to exit: will force a loop iteration every minutes,
-                // that will stop the loop if other Arc references have been dropped
-                // and free resources. Otherwise we would be blocked waiting forever...
-                _ = tokio::time::sleep(Duration::from_secs(60)) => continue,
-
-                // Watch if another instance has modified the log
-                update = storage.row_poll(&row) => {
-                    match update {
-                        Err(e) => {
-                            error!("Error in bayou k2v wait value changed: {}", e);
-                            tokio::time::sleep(Duration::from_secs(30)).await;
-                        }
-                        Ok(new_value) => {
-                            row = new_value.row_ref;
-                            if let Err(e) = tx.send(row.clone()) {
-                                tracing::warn!(err=?e, "(watch) can't record the new log ref");
-                                break;
-                            }
-                            tracing::debug!(row=?row, "(watch) learnt remote update");
-                            this.learnt_remote_update.notify_waiters();
-                        }
-                    }
-                }
-
-                // It appears we have modified the log, informing other people
-                _ = this.propagate_local_update.notified() => {
-                    let rand = u128::to_be_bytes(thread_rng().gen()).to_vec();
-                    let row_val = storage::RowVal::new(row.clone(), rand);
-                    if let Err(e) = storage.row_insert(vec![row_val]).await
-                    {
-                        tracing::error!("Error in bayou k2v watch updater loop: {}", e);
-                        tokio::time::sleep(Duration::from_secs(30)).await;
-                    }
-                }
-            );
-        }
-        // unblock listeners
-        remote_update.notify_waiters();
-        tracing::info!("bayou k2v watch bg loop exiting");
-    }
-}