fix: stream memory counting during snapshot loading (#4346)

* fix: stream memory counting during snapshot loading

src/server/dragonfly_test.cc

@@ -802,6 +802,25 @@ TEST_F(DflyEngineTest, DebugObject) {
   EXPECT_THAT(resp.GetString(), HasSubstr("encoding:listpack"));
 }
 
+TEST_F(DflyEngineTest, StreamMemInfo) {
+  for (int i = 1; i < 2; ++i) {
+    Run({"XADD", "test", std::to_string(i), "var", "val" + std::to_string(i)});
+  }
+
+  int64_t stream_mem_first = GetMetrics().db_stats[0].memory_usage_by_type[OBJ_STREAM];
+  EXPECT_GT(stream_mem_first, 0);
+
+  auto dump = Run({"dump", "test"});
+  Run({"del", "test"});
+  Run({"restore", "test", "0", facade::ToSV(dump.GetBuf())});
+
+  int64_t stream_mem_second = GetMetrics().db_stats[0].memory_usage_by_type[OBJ_STREAM];
+
+  // stream_mem_first != stream_mem_second due to a preallocation in XADD command (see
+  // STREAM_LISTPACK_MAX_PRE_ALLOCATE)
+  EXPECT_GT(stream_mem_second, 0);
+}
+
 // TODO: to test transactions with a single shard since then all transactions become local.
 // To consider having a parameter in dragonfly engine controlling number of shards
 // unconditionally from number of cpus. TO TEST BLPOP under multi for single/multi argument case.

src/server/rdb_load.cc

@@ -50,6 +50,7 @@ extern "C" {
 #include "server/serializer_commons.h"
 #include "server/server_state.h"
 #include "server/set_family.h"
+#include "server/stream_family.h"
 #include "server/transaction.h"
 #include "strings/human_readable.h"
 
@@ -703,6 +704,7 @@ void RdbLoaderBase::OpaqueObjLoader::CreateZSet(const LoadTrace* ltrace) {
 
 void RdbLoaderBase::OpaqueObjLoader::CreateStream(const LoadTrace* ltrace) {
   stream* s;
+  StreamMemTracker mem_tracker;
   if (config_.append) {
     if (!EnsureObjEncoding(OBJ_STREAM, OBJ_ENCODING_STREAM)) {
       return;
@@ -848,6 +850,7 @@ void RdbLoaderBase::OpaqueObjLoader::CreateStream(const LoadTrace* ltrace) {
   if (!config_.append) {
     pv_->InitRobj(OBJ_STREAM, OBJ_ENCODING_STREAM, s);
   }
+  mem_tracker.UpdateStreamSize(*pv_);
 }
 
 void RdbLoaderBase::OpaqueObjLoader::HandleBlob(string_view blob) {

src/server/stream_family.cc

@@ -27,6 +27,18 @@ namespace dfly {
 using namespace facade;
 using namespace std;
 
+StreamMemTracker::StreamMemTracker() {
+  start_size_ = zmalloc_used_memory_tl;
+}
+
+void StreamMemTracker::UpdateStreamSize(PrimeValue& pv) const {
+  const size_t current = zmalloc_used_memory_tl;
+  int64_t diff = static_cast<int64_t>(current) - static_cast<int64_t>(start_size_);
+  pv.AddStreamSize(diff);
+  // Under any flow we must not end up with this special value.
+  DCHECK(pv.MallocUsed() != 0);
+}
+
 namespace {
 
 struct Record {
@@ -612,24 +624,6 @@ int StreamTrim(const AddTrimOpts& opts, stream* s) {
   return 0;
 }
 
-class StreamMemTracker {
- public:
-  StreamMemTracker() {
-    start_size_ = zmalloc_used_memory_tl;
-  }
-
-  void UpdateStreamSize(PrimeValue& pv) const {
-    const size_t current = zmalloc_used_memory_tl;
-    int64_t diff = static_cast<int64_t>(current) - static_cast<int64_t>(start_size_);
-    pv.AddStreamSize(diff);
-    // Under any flow we must not end up with this special value.
-    DCHECK(pv.MallocUsed() != 0);
-  }
-
- private:
-  size_t start_size_{0};
-};
-
 OpResult<streamID> OpAdd(const OpArgs& op_args, const AddTrimOpts& opts, CmdArgList args) {
   DCHECK(!args.empty() && args.size() % 2 == 0);
   auto& db_slice = op_args.GetDbSlice();

src/server/stream_family.h

@@ -15,6 +15,19 @@ namespace dfly {
 class CommandRegistry;
 struct CommandContext;
 
+class CompactObj;
+using PrimeValue = CompactObj;
+
+class StreamMemTracker {
+ public:
+  StreamMemTracker();
+
+  void UpdateStreamSize(PrimeValue& pv) const;
+
+ private:
+  size_t start_size_{0};
+};
+
 class StreamFamily {
  public:
   static void Register(CommandRegistry* registry);

tests/dragonfly/memory_test.py

@@ -6,6 +6,7 @@ from . import dfly_args
 from .instance import DflyInstance, DflyInstanceFactory
 
 
+@pytest.mark.slow
 @pytest.mark.opt_only
 @pytest.mark.parametrize(
     "type, keys, val_size, elements",
@@ -23,7 +24,10 @@ from .instance import DflyInstance, DflyInstanceFactory
 # memory it might force the gh runner to run out of memory (since OOM killer might not even
 # get a chance to run).
 @dfly_args({"proactor_threads": 4, "maxmemory": "5gb"})
-async def test_rss_used_mem_gap(df_server: DflyInstance, type, keys, val_size, elements):
+async def test_rss_used_mem_gap(df_factory, type, keys, val_size, elements):
+    dbfilename = f"dump_{tmp_file_name()}"
+    instance = df_factory.create(dbfilename=dbfilename)
+    instance.start()
     # Create a Dragonfly and fill it up with `type` until it reaches `min_rss`, then make sure that
     # the gap between used_memory and rss is no more than `max_unaccounted_ratio`.
     min_rss = 3 * 1024 * 1024 * 1024  # 3gb
@@ -35,7 +39,7 @@ async def test_rss_used_mem_gap(df_server: DflyInstance, type, keys, val_size, e
     if type == "STREAM":
         max_unaccounted = max_unaccounted * 3
 
-    client = df_server.client()
+    client = instance.client()
     await asyncio.sleep(1)  # Wait for another RSS heartbeat update in Dragonfly
 
     cmd = f"DEBUG POPULATE {keys} k {val_size} RAND TYPE {type} ELEMENTS {elements}"
@@ -44,19 +48,27 @@ async def test_rss_used_mem_gap(df_server: DflyInstance, type, keys, val_size, e
 
     await asyncio.sleep(2)  # Wait for another RSS heartbeat update in Dragonfly
 
-    info = await client.info("memory")
+    async def check_memory():
-    logging.info(f'Used memory {info["used_memory"]}, rss {info["used_memory_rss"]}')
+        info = await client.info("memory")
-    assert info["used_memory"] > min_rss, "Weak testcase: too little used memory"
+        logging.info(f'Used memory {info["used_memory"]}, rss {info["used_memory_rss"]}')
-    delta = info["used_memory_rss"] - info["used_memory"]
+        assert info["used_memory"] > min_rss, "Weak testcase: too little used memory"
-    # It could be the case that the machine is configured to use swap if this assertion fails
+        delta = info["used_memory_rss"] - info["used_memory"]
-    assert delta > 0
+        # It could be the case that the machine is configured to use swap if this assertion fails
-    assert delta < max_unaccounted
+        assert delta > 0
+        assert delta < max_unaccounted
 
-    if type != "STRING" and type != "JSON":
+        if type != "STRING" and type != "JSON":
-        # STRINGs keep some of the data inline, so not all of it is accounted in object_used_memory
+            # STRINGs keep some of the data inline, so not all of it is accounted in object_used_memory
-        # We have a very small over-accounting bug in JSON
+            # We have a very small over-accounting bug in JSON
-        assert info["object_used_memory"] > keys * elements * val_size
+            assert info["object_used_memory"] > keys * elements * val_size
-        assert info["used_memory"] > info["object_used_memory"]
+            assert info["used_memory"] > info["object_used_memory"]
+
+    await check_memory()
+
+    await client.execute_command("SAVE", "DF")
+    await client.execute_command("DFLY", "LOAD", f"{dbfilename}-summary.dfs")
+
+    await check_memory()
 
 
 @pytest.mark.asyncio