Add support for managing a fixed number of retained snapshots

With this change, Restate can be configured to retain a set of recent
snapshots, and automatically delete older snapshots that are no longer
needed. Previously, older snapshots were no longer managed by Retate.
This saves users from having to implement an external lifecycle policy.

When explicit snapshot retention is specified, the reported Archived LSN
will be that of the earliest retained snapshot. Together with the
durability setting, this influences the automatic log trim behavior.
When auto trim respects the Archived LSN, the latest partition snapshot
reference can be (manually) updated to any snapshot within the retention
window, e.g. to deal with snapshot corruption.

Author: pcholakov

Cargo.lock

@@ -68,6 +68,7 @@ rand = { workspace = true }
 serde_json = { workspace = true }
 tempfile = { workspace = true }
 tracing-subscriber = { workspace = true }
+tracing-test = { workspace = true }
 
 [[bench]]
 name = "basic_benchmark"

crates/partition-store/Cargo.toml

@@ -94,7 +94,12 @@ impl Snapshots {
         let archived_lsn = repository
             .get_latest_archived_lsn(partition_id)
             .await
-            .inspect_err(|err| warn!(?partition_id, "Unable to get latest archived LSN: {}", err))
+            .inspect_err(|err| {
+                warn!(
+                    ?partition_id,
+                    "Unable to get archived LSN from snapshot repository: {}", err
+                )
+            })
             .ok()
             .unwrap_or(ArchivedLsn::None);
         db.note_archived_lsn(archived_lsn);