utilities for archiving snapshots (#3224)

# Description of Changes

Adds utilities for marking and deleting snapshot directories that have
been archived

# API and ABI breaking changes

<!-- If this is an API or ABI breaking change, please apply the
corresponding GitHub label. -->

None

# Expected complexity level and risk

<!--
How complicated do you think these changes are? Grade on a scale from 1
to 5,
where 1 is a trivial change, and 5 is a deep-reaching and complex
change.

This complexity rating applies not only to the complexity apparent in
the diff,
but also to its interactions with existing and future code.

If you answered more than a 2, explain what is complex about the PR,
and what other components it interacts with in potentially concerning
ways. -->

1

# Testing

<!-- Describe any testing you've done, and any testing you'd like your
reviewers to do,
so that you're confident that all the changes work as expected! -->

Testing will be handled by the patch that adds archival

crates/paths/src/server.rs

@@ -206,6 +206,11 @@ path_type! {
     SnapshotDirPath: dir
 }
 
+path_type! {
+    /// An archived snapshot directory. `{data-dir}/replica/$replica_id/snapshots/$tx_offset.archived_snapshot`
+    ArchivedSnapshotDirPath: dir
+}
+
 impl SnapshotDirPath {
     pub fn snapshot_file(&self, tx_offset: u64) -> SnapshotFilePath {
         let file_name = format!("{tx_offset:0>20}.snapshot_bsatn");
@@ -221,6 +226,12 @@ impl SnapshotDirPath {
         fs::rename(self, invalid_path)
     }
 
+    pub fn rename_as_archived(&self) -> io::Result<ArchivedSnapshotDirPath> {
+        let path = self.0.with_extension("archived_snapshot");
+        fs::rename(self, &path)?;
+        Ok(ArchivedSnapshotDirPath(path))
+    }
+
     pub fn tx_offset(&self) -> Option<u64> {
         self.0
             .file_stem()

crates/snapshot/src/lib.rs

@@ -30,7 +30,7 @@ use spacetimedb_fs_utils::{
     lockfile::{Lockfile, LockfileError},
 };
 use spacetimedb_lib::Identity;
-use spacetimedb_paths::server::{SnapshotDirPath, SnapshotFilePath, SnapshotsPath};
+use spacetimedb_paths::server::{ArchivedSnapshotDirPath, SnapshotDirPath, SnapshotFilePath, SnapshotsPath};
 use spacetimedb_paths::FromPathUnchecked;
 use spacetimedb_primitives::TableId;
 use spacetimedb_sats::{bsatn, de::Deserialize, ser::Serialize};
@@ -40,6 +40,7 @@ use spacetimedb_table::{
     page_pool::PagePool,
     table::Table,
 };
+use std::fs;
 use std::{
     collections::BTreeMap,
     collections::HashMap,
@@ -145,6 +146,9 @@ pub const SNAPSHOT_FILE_EXT: &str = "snapshot_bsatn";
 /// File extension of snapshots which have been marked invalid by [`SnapshotRepository::invalidate_newer_snapshots`].
 pub const INVALID_SNAPSHOT_DIR_EXT: &str = "invalid_snapshot";
 
+/// File extension of snapshots which have been archived
+pub const ARCHIVED_SNAPSHOT_EXT: &str = "archived_snapshot";
+
 #[derive(Clone, Serialize, Deserialize)]
 /// The hash and refcount of a single blob in the blob store.
 struct BlobEntry {
@@ -890,6 +894,27 @@ impl SnapshotRepository {
             }))
     }
 
+    /// Return an interator of [`ArchivedSnapshotDirPath`] for all the archived snapshot directories on disk
+    pub fn all_archived_snapshots(&self) -> Result<impl Iterator<Item = ArchivedSnapshotDirPath>, SnapshotError> {
+        Ok(self
+            .root
+            // Item = Result<DirEntry>
+            .read_dir()?
+            // Item = DirEntry
+            .filter_map(Result::ok)
+            // Item = PathBuf
+            .map(|dirent| dirent.path())
+            // Ignore entries not shaped like snapshot directories.
+            .filter(|path| path.extension() == Some(OsStr::new(ARCHIVED_SNAPSHOT_EXT)))
+            // Item = ArchivedSnapshotDirPath
+            .map(ArchivedSnapshotDirPath::from_path_unchecked))
+    }
+
+    /// Delete an archived snapshot from disk
+    pub fn remove_archived_snapshot(path: &ArchivedSnapshotDirPath) -> Result<(), SnapshotError> {
+        fs::remove_dir_all(path).map_err(SnapshotError::Io)
+    }
+
     /// Return the `TxOffset` of the highest-offset complete snapshot in the repository.
     ///
     /// Does not verify that the snapshot of the returned `TxOffset` is valid and uncorrupted,