fix(syslog): a row from before the name split, last seen as a device, stays that device's (#6096)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/syslog/receiver.py

@@ -249,6 +249,15 @@ async def store_lines(session, lines: list[Received]) -> None:
     sources = {(s.address, s.sender): s for s in (await session.execute(
         select(SyslogSource).where(SyslogSource.address.in_(addresses)))).scalars()}
     new = [k for k in by_sender if k not in sources]
+    for key in [k for k in new if k[1]]:
+        # A row from before devices at Docker's address were told apart by
+        # name, last seen under this one, is this device: it keeps its state
+        # and name rather than a new row being offered beside it.
+        before = sources.get((key[0], ""))
+        if before is not None and before.hostname_seen == key[1]:
+            before.sender = key[1]
+            sources[key] = sources.pop((key[0], ""))
+            new.remove(key)
     if new:
         known = (await session.execute(select(func.count()).select_from(SyslogSource))).scalar_one()
         for key in new:

tests/integration/test_syslog.py

@@ -99,6 +99,20 @@ def test_devices_through_dockers_address_are_told_apart_by_name(app, monkeypatch
             got = sorted((r.address, r.sender, r.lines_total, r.last_line) for r in rows)
             assert got == [("10.0.0.2", "AsusNAS", 2, "d"), ("10.0.0.2", "SynNAS", 2, "c"),
                            ("10.9.0.1", "", 1, "e")]
+            await s.execute(delete(SyslogSource))
+            await s.commit()
+        # A row from before the split, last seen under a device's name, is that device's.
+        async with app.db_sessionmaker() as s:
+            async with s.begin():
+                s.add(SyslogSource(address="10.0.0.3", state="accepted", name="DS923", hostname_seen="DS923",
+                                   first_seen_at=now, last_seen_at=now, lines_total=3))
+        async with app.db_sessionmaker() as s:
+            async with s.begin():
+                await receiver.store_lines(s, [line("10.0.0.3", "DS923", "f"), line("10.0.0.3", "util", "g")])
+        async with app.db_sessionmaker() as s:
+            rows = (await s.execute(select(SyslogSource))).scalars().all()
+            got = sorted((r.sender, r.state, r.name, r.lines_total) for r in rows)
+            assert got == [("DS923", "accepted", "DS923", 4), ("util", "offered", "", 1)]
         async with app.db_sessionmaker() as s:
             async with s.begin():
                 await s.execute(delete(SyslogSource))