feat(common): Add a cross-process lock generation.

This patch adds `CrossProcessLockGeneration`. A lock generation is
an integer incremented each time the lock is taken by another holder.
If the generation changes, it means the lock is _poisoned_. This
_poisoning_ aspect is going to be expanded in the next patches. This
patch focuses on the introduction of this _generation_.

The `CrossProcessLock::try_lock_once` method, and
the `TryLock::try_lock` method, both returns a
`Option<CrossProcessLockGeneration>` instead of a `bool`: `true` is
replaced by `Some(_)`, `false` by `None`.

Author: Hywan

crates/matrix-sdk-base/src/event_cache/store/integration_tests.rs

@@ -1304,57 +1304,57 @@ macro_rules! event_cache_store_integration_tests_time {
                 let store = get_event_cache_store().await.unwrap().into_event_cache_store();
 
                 let acquired0 = store.try_take_leased_lock(0, "key", "alice").await.unwrap();
-                assert!(acquired0);
+                assert_eq!(acquired0, Some(1)); // first lock generation
 
                 // Should extend the lease automatically (same holder).
                 let acquired2 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
-                assert!(acquired2);
+                assert_eq!(acquired2, Some(1)); // same lock generation
 
                 // Should extend the lease automatically (same holder + time is ok).
                 let acquired3 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
-                assert!(acquired3);
+                assert_eq!(acquired3, Some(1)); // same lock generation
 
                 // Another attempt at taking the lock should fail, because it's taken.
                 let acquired4 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(!acquired4);
+                assert!(acquired4.is_none()); // not acquired
 
                 // Even if we insist.
                 let acquired5 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(!acquired5);
+                assert!(acquired5.is_none()); // not acquired
 
                 // That's a nice test we got here, go take a little nap.
                 sleep(Duration::from_millis(50)).await;
 
                 // Still too early.
                 let acquired55 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(!acquired55);
+                assert!(acquired55.is_none()); // not acquired
 
                 // Ok you can take another nap then.
                 sleep(Duration::from_millis(250)).await;
 
                 // At some point, we do get the lock.
                 let acquired6 = store.try_take_leased_lock(0, "key", "bob").await.unwrap();
-                assert!(acquired6);
+                assert_eq!(acquired6, Some(2)); // new lock generation!
 
                 sleep(Duration::from_millis(1)).await;
 
                 // The other gets it almost immediately too.
                 let acquired7 = store.try_take_leased_lock(0, "key", "alice").await.unwrap();
-                assert!(acquired7);
+                assert_eq!(acquired7, Some(3)); // new lock generation!
 
                 sleep(Duration::from_millis(1)).await;
 
-                // But when we take a longer lease...
+                // But when we take a longer lease…
                 let acquired8 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(acquired8);
+                assert_eq!(acquired8, Some(4)); // new lock generation!
 
                 // It blocks the other user.
                 let acquired9 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
-                assert!(!acquired9);
+                assert!(acquired9.is_none()); // not acquired
 
                 // We can hold onto our lease.
                 let acquired10 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(acquired10);
+                assert_eq!(acquired10, Some(4)); // same lock generation
             }
         }
     };

crates/matrix-sdk-base/src/event_cache/store/memory_store.rs

@@ -19,13 +19,16 @@ use std::{
 
 use async_trait::async_trait;
 use matrix_sdk_common::{
-    cross_process_lock::memory_store_helper::try_take_leased_lock,
+    cross_process_lock::{
+        CrossProcessLockGeneration,
+        memory_store_helper::{Lease, try_take_leased_lock},
+    },
     linked_chunk::{
         ChunkIdentifier, ChunkIdentifierGenerator, ChunkMetadata, LinkedChunkId, Position,
         RawChunk, Update, relational::RelationalLinkedChunk,
     },
 };
-use ruma::{EventId, OwnedEventId, RoomId, events::relation::RelationType, time::Instant};
+use ruma::{EventId, OwnedEventId, RoomId, events::relation::RelationType};
 use tracing::error;
 
 use super::{
@@ -43,7 +46,7 @@ pub struct MemoryStore {
 
 #[derive(Debug)]
 struct MemoryStoreInner {
-    leases: HashMap<String, (String, Instant)>,
+    leases: HashMap<String, Lease>,
     events: RelationalLinkedChunk<OwnedEventId, Event, Gap>,
 }
 
@@ -75,7 +78,7 @@ impl EventCacheStore for MemoryStore {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> Result<bool, Self::Error> {
+    ) -> Result<Option<CrossProcessLockGeneration>, Self::Error> {
         let mut inner = self.inner.write().unwrap();
 
         Ok(try_take_leased_lock(&mut inner.leases, lease_duration_ms, key, holder))

crates/matrix-sdk-base/src/event_cache/store/mod.rs

@@ -28,7 +28,8 @@ mod memory_store;
 mod traits;
 
 use matrix_sdk_common::cross_process_lock::{
-    CrossProcessLock, CrossProcessLockError, CrossProcessLockGuard, TryLock,
+    CrossProcessLock, CrossProcessLockError, CrossProcessLockGeneration, CrossProcessLockGuard,
+    TryLock,
 };
 pub use matrix_sdk_store_encryption::Error as StoreEncryptionError;
 use ruma::{
@@ -192,7 +193,7 @@ impl TryLock for LockableEventCacheStore {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> std::result::Result<bool, Self::LockError> {
+    ) -> std::result::Result<Option<CrossProcessLockGeneration>, Self::LockError> {
         self.0.try_take_leased_lock(lease_duration_ms, key, holder).await
     }
 }

crates/matrix-sdk-base/src/event_cache/store/traits.rs

@@ -17,6 +17,7 @@ use std::{fmt, sync::Arc};
 use async_trait::async_trait;
 use matrix_sdk_common::{
     AsyncTraitDeps,
+    cross_process_lock::CrossProcessLockGeneration,
     linked_chunk::{
         ChunkIdentifier, ChunkIdentifierGenerator, ChunkMetadata, LinkedChunkId, Position,
         RawChunk, Update,
@@ -46,7 +47,7 @@ pub trait EventCacheStore: AsyncTraitDeps {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> Result<bool, Self::Error>;
+    ) -> Result<Option<CrossProcessLockGeneration>, Self::Error>;
 
     /// An [`Update`] reflects an operation that has happened inside a linked
     /// chunk. The linked chunk is used by the event cache to store the events
@@ -191,7 +192,7 @@ impl<T: EventCacheStore> EventCacheStore for EraseEventCacheStoreError<T> {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> Result<bool, Self::Error> {
+    ) -> Result<Option<CrossProcessLockGeneration>, Self::Error> {
         self.0.try_take_leased_lock(lease_duration_ms, key, holder).await.map_err(Into::into)
     }
 

crates/matrix-sdk-base/src/media/store/integration_tests.rs

@@ -1337,57 +1337,57 @@ macro_rules! media_store_integration_tests_time {
                 let store = get_media_store().await.unwrap();
 
                 let acquired0 = store.try_take_leased_lock(0, "key", "alice").await.unwrap();
-                assert!(acquired0);
+                assert_eq!(acquired0, Some(1)); // first lock generation
 
                 // Should extend the lease automatically (same holder).
                 let acquired2 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
-                assert!(acquired2);
+                assert_eq!(acquired2, Some(1)); // same lock generation
 
                 // Should extend the lease automatically (same holder + time is ok).
                 let acquired3 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
-                assert!(acquired3);
+                assert_eq!(acquired3, Some(1)); // same lock generation
 
                 // Another attempt at taking the lock should fail, because it's taken.
                 let acquired4 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(!acquired4);
+                assert!(acquired4.is_none()); // not acquired
 
                 // Even if we insist.
                 let acquired5 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(!acquired5);
+                assert!(acquired5.is_none()); // not acquired
 
                 // That's a nice test we got here, go take a little nap.
                 sleep(Duration::from_millis(50)).await;
 
                 // Still too early.
                 let acquired55 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(!acquired55);
+                assert!(acquired55.is_none()); // not acquired
 
                 // Ok you can take another nap then.
                 sleep(Duration::from_millis(250)).await;
 
                 // At some point, we do get the lock.
                 let acquired6 = store.try_take_leased_lock(0, "key", "bob").await.unwrap();
-                assert!(acquired6);
+                assert_eq!(acquired6, Some(2)); // new lock generation!
 
                 sleep(Duration::from_millis(1)).await;
 
                 // The other gets it almost immediately too.
                 let acquired7 = store.try_take_leased_lock(0, "key", "alice").await.unwrap();
-                assert!(acquired7);
+                assert_eq!(acquired7, Some(3)); // new lock generation!
 
                 sleep(Duration::from_millis(1)).await;
 
-                // But when we take a longer lease...
+                // But when we take a longer lease…
                 let acquired8 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(acquired8);
+                assert_eq!(acquired8, Some(4)); // new lock generation!
 
                 // It blocks the other user.
                 let acquired9 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
-                assert!(!acquired9);
+                assert!(acquired9.is_none()); // not acquired
 
                 // We can hold onto our lease.
                 let acquired10 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
-                assert!(acquired10);
+                assert_eq!(acquired10, Some(4)); // same lock generation
             }
         }
     };

crates/matrix-sdk-base/src/media/store/memory_store.rs

@@ -20,12 +20,13 @@ use std::{
 
 use async_trait::async_trait;
 use matrix_sdk_common::{
-    cross_process_lock::memory_store_helper::try_take_leased_lock, ring_buffer::RingBuffer,
-};
-use ruma::{
-    MxcUri, OwnedMxcUri,
-    time::{Instant, SystemTime},
+    cross_process_lock::{
+        CrossProcessLockGeneration,
+        memory_store_helper::{Lease, try_take_leased_lock},
+    },
+    ring_buffer::RingBuffer,
 };
+use ruma::{MxcUri, OwnedMxcUri, time::SystemTime};
 
 use super::Result;
 use crate::media::{
@@ -48,7 +49,7 @@ pub struct MemoryMediaStore {
 #[derive(Debug)]
 struct MemoryMediaStoreInner {
     media: RingBuffer<MediaContent>,
-    leases: HashMap<String, (String, Instant)>,
+    leases: HashMap<String, Lease>,
     media_retention_policy: Option<MediaRetentionPolicy>,
     last_media_cleanup_time: SystemTime,
 }
@@ -110,7 +111,7 @@ impl MediaStore for MemoryMediaStore {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> Result<bool, Self::Error> {
+    ) -> Result<Option<CrossProcessLockGeneration>, Self::Error> {
         let mut inner = self.inner.write().unwrap();
 
         Ok(try_take_leased_lock(&mut inner.leases, lease_duration_ms, key, holder))

crates/matrix-sdk-base/src/media/store/mod.rs

@@ -32,7 +32,8 @@ use std::fmt;
 use std::{ops::Deref, sync::Arc};
 
 use matrix_sdk_common::cross_process_lock::{
-    CrossProcessLock, CrossProcessLockError, CrossProcessLockGuard, TryLock,
+    CrossProcessLock, CrossProcessLockError, CrossProcessLockGeneration, CrossProcessLockGuard,
+    TryLock,
 };
 use matrix_sdk_store_encryption::Error as StoreEncryptionError;
 pub use traits::{DynMediaStore, IntoMediaStore, MediaStore, MediaStoreInner};
@@ -172,7 +173,7 @@ impl TryLock for LockableMediaStore {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> std::result::Result<bool, Self::LockError> {
+    ) -> std::result::Result<Option<CrossProcessLockGeneration>, Self::LockError> {
         self.0.try_take_leased_lock(lease_duration_ms, key, holder).await
     }
 }

crates/matrix-sdk-base/src/media/store/traits.rs

@@ -17,7 +17,7 @@
 use std::{fmt, sync::Arc};
 
 use async_trait::async_trait;
-use matrix_sdk_common::AsyncTraitDeps;
+use matrix_sdk_common::{AsyncTraitDeps, cross_process_lock::CrossProcessLockGeneration};
 use ruma::{MxcUri, time::SystemTime};
 
 #[cfg(doc)]
@@ -41,7 +41,7 @@ pub trait MediaStore: AsyncTraitDeps {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> Result<bool, Self::Error>;
+    ) -> Result<Option<CrossProcessLockGeneration>, Self::Error>;
 
     /// Add a media file's content in the media store.
     ///
@@ -313,7 +313,7 @@ impl<T: MediaStore> MediaStore for EraseMediaStoreError<T> {
         lease_duration_ms: u32,
         key: &str,
         holder: &str,
-    ) -> Result<bool, Self::Error> {
+    ) -> Result<Option<CrossProcessLockGeneration>, Self::Error> {
         self.0.try_take_leased_lock(lease_duration_ms, key, holder).await.map_err(Into::into)
     }