refactor: derive last_accessed_at from claimed_at to unify timestamp tracking

src/cashet/redis_store.py

@@ -120,7 +120,7 @@ def _encode_commit(commit: Commit) -> bytes:
         "tags": commit.tags,
         "created_at": commit.created_at.isoformat(),
         "claimed_at": commit.claimed_at.isoformat(),
-        "last_accessed_at": datetime.now(UTC).isoformat(),
+        "last_accessed_at": commit.claimed_at.isoformat(),
     }
     return json.dumps(d, separators=(",", ":")).encode()
 

src/cashet/store.py

@@ -271,9 +271,8 @@ def blob_exists(self, hash: str) -> bool:
 
     def put_commit(self, commit: Commit) -> None:
         conn = self._connect(immediate=True)
-        now = datetime.now(UTC).isoformat()
         try:
-            self._put_commit_row(conn, commit, now)
+            self._put_commit_row(conn, commit, commit.claimed_at.isoformat())
             conn.execute("COMMIT")
         except Exception:
             conn.execute("ROLLBACK")
@@ -329,8 +328,7 @@ def _put_commit_row(
 
     def find_by_fingerprint(self, fingerprint: str) -> Commit | None:
         conn = self._connect()
-        now = datetime.now(UTC)
-        now_iso = now.isoformat()
+        now_iso = datetime.now(UTC).isoformat()
         row = conn.execute(
             """SELECT * FROM commits
                WHERE fingerprint = ? AND status IN ('completed', 'cached')
@@ -341,10 +339,6 @@ def find_by_fingerprint(self, fingerprint: str) -> Commit | None:
         ).fetchone()
         if row is None:
             return None
-        conn.execute(
-            "UPDATE commits SET last_accessed_at = ? WHERE hash = ?",
-            (now_iso, row["hash"]),
-        )
         return self._row_to_commit(row)
 
     def find_running_by_fingerprint(self, fingerprint: str) -> Commit | None:

tests/test_async_client.py

@@ -315,6 +315,49 @@ def do_thing(x: int) -> int:
         assert do_thing.__doc__ == "A docstring."
         assert hasattr(do_thing, "_cashet_wrapped_func")
 
+    async def test_last_accessed_at_derived_from_claimed_at(
+        self, async_client: AsyncClient
+    ) -> None:
+        def work() -> int:
+            return 42
+
+        ref = await async_client.submit(work)
+        assert await ref.load() == 42
+
+        conn = async_client.store._core._connect()
+        row = conn.execute(
+            "SELECT claimed_at, last_accessed_at FROM commits WHERE hash = ?",
+            (ref.commit_hash,),
+        ).fetchone()
+        assert row["claimed_at"] == row["last_accessed_at"]
+
+    async def test_cache_hit_does_not_shift_last_accessed_at(
+        self, async_client: AsyncClient
+    ) -> None:
+        def work() -> int:
+            return 42
+
+        ref1 = await async_client.submit(work)
+        assert await ref1.load() == 42
+
+        conn = async_client.store._core._connect()
+        row_before = conn.execute(
+            "SELECT last_accessed_at FROM commits WHERE hash = ?",
+            (ref1.commit_hash,),
+        ).fetchone()
+        la_before = row_before["last_accessed_at"]
+
+        ref2 = await async_client.submit(work)
+        assert await ref2.load() == 42
+
+        row_after = conn.execute(
+            "SELECT last_accessed_at FROM commits WHERE hash = ?",
+            (ref1.commit_hash,),
+        ).fetchone()
+        la_after = row_after["last_accessed_at"]
+
+        assert la_before == la_after
+
 
 class TestAsyncContextManager:
     async def test_async_with(self) -> None:

tests/test_store.py

@@ -1099,6 +1099,45 @@ def make_bytes(n: int) -> bytes:
         client.gc(older_than=timedelta(days=1), max_size_bytes=1)
         assert client.stats()["total_commits"] == 0
 
+    def test_last_accessed_at_derived_from_claimed_at(self, client: Client) -> None:
+        def work() -> int:
+            return 42
+
+        ref = client.submit(work)
+        assert ref.load() == 42
+
+        conn = client.store._connect()
+        row = conn.execute(
+            "SELECT claimed_at, last_accessed_at FROM commits WHERE hash = ?",
+            (ref.commit_hash,),
+        ).fetchone()
+        assert row["claimed_at"] == row["last_accessed_at"]
+
+    def test_cache_hit_does_not_shift_last_accessed_at(self, client: Client) -> None:
+        def work() -> int:
+            return 42
+
+        ref1 = client.submit(work)
+        assert ref1.load() == 42
+
+        conn = client.store._connect()
+        row_before = conn.execute(
+            "SELECT last_accessed_at FROM commits WHERE hash = ?",
+            (ref1.commit_hash,),
+        ).fetchone()
+        la_before = row_before["last_accessed_at"]
+
+        ref2 = client.submit(work)
+        assert ref2.load() == 42
+
+        row_after = conn.execute(
+            "SELECT last_accessed_at FROM commits WHERE hash = ?",
+            (ref1.commit_hash,),
+        ).fetchone()
+        la_after = row_after["last_accessed_at"]
+
+        assert la_before == la_after
+
 
 class TestTTL:
     def test_ttl_roundtrip(self, client: Client) -> None: