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-rw-r--r--src/bayou.rs174
1 files changed, 144 insertions, 30 deletions
diff --git a/src/bayou.rs b/src/bayou.rs
index 457a666..47a027a 100644
--- a/src/bayou.rs
+++ b/src/bayou.rs
@@ -5,10 +5,12 @@ use rand::prelude::*;
use serde::{Deserialize, Serialize};
use tokio::io::AsyncReadExt;
-use k2v_client::{BatchReadOp, Filter, K2vClient, K2vValue};
+use k2v_client::{BatchDeleteOp, BatchReadOp, Filter, K2vClient, K2vValue};
use rusoto_core::HttpClient;
use rusoto_credential::{AwsCredentials, StaticProvider};
-use rusoto_s3::{GetObjectRequest, ListObjectsV2Request, S3Client, S3};
+use rusoto_s3::{
+ DeleteObjectRequest, GetObjectRequest, ListObjectsV2Request, PutObjectRequest, S3Client, S3,
+};
use rusoto_signature::Region;
use crate::cryptoblob::*;
@@ -19,8 +21,18 @@ const SAVE_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(3600);
-const CHECKPOINT_MIN_OPS: usize = 16;
+const CHECKPOINT_INTERVAL: Duration = Duration::from_secs(60);
+const CHECKPOINT_MIN_OPS: usize = 4;
+// 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;
pub trait BayouState:
Default + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync + 'static
@@ -76,26 +88,7 @@ impl<S: BayouState> Bayou<S> {
/// Re-reads the state from persistent storage backend
pub async fn sync(&mut self) -> Result<()> {
// 1. List checkpoints
- let prefix = format!("{}/checkpoint/", self.path);
-
- let mut lor = ListObjectsV2Request::default();
- lor.bucket = self.bucket.clone();
- lor.max_keys = Some(1000);
- lor.prefix = Some(prefix.clone());
-
- let checkpoints_res = self.s3.list_objects_v2(lor).await?;
-
- let mut checkpoints = vec![];
- for object in checkpoints_res.contents.unwrap_or_default() {
- if let Some(key) = object.key {
- if let Some(ckid) = key.strip_prefix(&prefix) {
- if let Some(ts) = Timestamp::parse(ckid) {
- checkpoints.push((ts, key));
- }
- }
- }
- }
- checkpoints.sort_by_key(|(ts, _)| *ts);
+ let checkpoints = self.list_checkpoints().await?;
eprintln!("(sync) listed checkpoints: {:?}", checkpoints);
// 2. Load last checkpoint if different from currently used one
@@ -184,10 +177,8 @@ impl<S: BayouState> Bayou<S> {
ops.sort_by_key(|(ts, _)| *ts);
eprintln!("(sync) {} operations", ops.len());
- // if no operations, clean up and return now
- if ops.is_empty() {
- self.history.clear();
- return Ok(());
+ 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)
@@ -205,7 +196,7 @@ impl<S: BayouState> Bayou<S> {
.iter()
.enumerate()
.zip(ops.iter())
- .skip_while(|((i, (ts1, _, _)), (ts2, _))| ts1 == ts2)
+ .skip_while(|((_, (ts1, _, _)), (ts2, _))| ts1 == ts2)
.map(|((i, _), _)| i)
.next()
.unwrap_or(self.history.len());
@@ -292,7 +283,104 @@ impl<S: BayouState> Bayou<S> {
pub async fn checkpoint(&mut self) -> Result<()> {
self.check_recent_sync().await?;
- eprintln!("Mock checkpointing, not implemented");
+ // 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 => {
+ eprintln!("(cp) Oldest operation is too recent to trigger checkpoint");
+ return Ok(());
+ }
+ };
+
+ if i_cp < CHECKPOINT_MIN_OPS {
+ eprintln!("(cp) Not enough old operations to trigger checkpoint");
+ return Ok(());
+ }
+
+ let ts_cp = self.history[i_cp].0;
+ eprintln!(
+ "(cp) we could checkpoint at time {} (index {} in history)",
+ ts_cp.serialize(),
+ i_cp
+ );
+
+ // Check existing checkpoints: if last one is too recent, don't checkpoint again.
+ let existing_checkpoints = self.list_checkpoints().await?;
+ eprintln!("(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
+ {
+ eprintln!(
+ "(cp) last checkpoint is too recent: {}, not checkpointing",
+ last_cp.0.serialize()
+ );
+ return Ok(());
+ }
+ }
+
+ eprintln!("(cp) saving checkpoint at {}", ts_cp.serialize());
+
+ // 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)?;
+
+ let mut por = PutObjectRequest::default();
+ por.bucket = self.bucket.clone();
+ por.key = format!("{}/checkpoint/{}", self.path, ts_cp.serialize());
+ por.body = Some(cryptoblob.into());
+ self.s3.put_object(por).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() {
+ eprintln!("(cp) drop old checkpoint {}", key);
+ let mut dor = DeleteObjectRequest::default();
+ dor.bucket = self.bucket.clone();
+ dor.key = key.to_string();
+ self.s3.delete_object(dor).await?;
+ }
+
+ // Delete corresponding range of operations
+ let ts_ser = existing_checkpoints[last_to_keep].0.serialize();
+ self.k2v
+ .delete_batch(&[BatchDeleteOp {
+ partition_key: &self.path,
+ prefix: None,
+ start: None,
+ end: Some(&ts_ser),
+ single_item: false,
+ }])
+ .await?;
+ }
+
Ok(())
}
@@ -303,6 +391,32 @@ impl<S: BayouState> Bayou<S> {
&self.checkpoint.1
}
}
+
+ // ---- INTERNAL ----
+
+ async fn list_checkpoints(&self) -> Result<Vec<(Timestamp, String)>> {
+ let prefix = format!("{}/checkpoint/", self.path);
+
+ let mut lor = ListObjectsV2Request::default();
+ lor.bucket = self.bucket.clone();
+ lor.max_keys = Some(1000);
+ lor.prefix = Some(prefix.clone());
+
+ let checkpoints_res = self.s3.list_objects_v2(lor).await?;
+
+ let mut checkpoints = vec![];
+ for object in checkpoints_res.contents.unwrap_or_default() {
+ if let Some(key) = object.key {
+ if let Some(ckid) = key.strip_prefix(&prefix) {
+ if let Some(ts) = Timestamp::parse(ckid) {
+ checkpoints.push((ts, key));
+ }
+ }
+ }
+ }
+ checkpoints.sort_by_key(|(ts, _)| *ts);
+ Ok(checkpoints)
+ }
}
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]