feat(cluster): Send flush slots cmd from masters to replicas. (#1484)

This fixes potential data diffs between master and replica upon slot moving

Fixes #1320

src/server/cluster/cluster_family.cc

@@ -18,6 +18,7 @@
 #include "server/conn_context.h"
 #include "server/dflycmd.h"
 #include "server/error.h"
+#include "server/journal/journal.h"
 #include "server/main_service.h"
 #include "server/replica.h"
 #include "server/server_family.h"
@@ -392,7 +393,7 @@ void ClusterFamily::DflyCluster(CmdArgList args, ConnectionContext* cntx) {
     return (*cntx)->SendError(kClusterDisabled);
   }
 
-  if (!cntx->owner()->IsAdmin()) {
+  if (cntx->owner() && !cntx->owner()->IsAdmin()) {
     return (*cntx)->SendError(kDflyClusterCmdPort);
   }
 
@@ -404,6 +405,8 @@ void ClusterFamily::DflyCluster(CmdArgList args, ConnectionContext* cntx) {
     return DflyClusterConfig(args, cntx);
   } else if (sub_cmd == "MYID") {
     return DflyClusterMyId(args, cntx);
+  } else if (sub_cmd == "FLUSHSLOTS") {
+    return DflyClusterFlushSlots(args, cntx);
   }
 
   return (*cntx)->SendError(UnknownSubCmd(sub_cmd, "DFLYCLUSTER"), kSyntaxErrType);
@@ -429,6 +432,59 @@ SlotSet GetDeletedSlots(bool is_first_config, const SlotSet& before, const SlotS
 
 // Guards set configuration, so that we won't handle 2 in parallel.
 Mutex set_config_mu;
+
+void DeleteSlots(const SlotSet& slots) {
+  if (slots.empty()) {
+    return;
+  }
+
+  auto cb = [&](auto*) {
+    EngineShard* shard = EngineShard::tlocal();
+    if (shard == nullptr)
+      return;
+
+    shard->db_slice().FlushSlots(slots);
+  };
+  shard_set->pool()->AwaitFiberOnAll(std::move(cb));
+}
+
+void WriteFlushSlotsToJournal(const SlotSet& slots) {
+  if (slots.empty()) {
+    return;
+  }
+
+  // Build args
+  vector<string> args;
+  args.reserve(slots.size() + 1);
+  args.push_back("FLUSHSLOTS");
+  for (const SlotId slot : slots) {
+    args.push_back(absl::StrCat(slot));
+  }
+
+  // Build view
+  vector<string_view> args_view(args.size());
+  for (size_t i = 0; i < args.size(); ++i) {
+    args_view[i] = args[i];
+  }
+
+  auto cb = [&](auto*) {
+    EngineShard* shard = EngineShard::tlocal();
+    if (shard == nullptr) {
+      return;
+    }
+
+    auto journal = EngineShard::tlocal()->journal();
+    if (journal == nullptr) {
+      return;
+    }
+
+    // Send journal entry
+    journal->RecordEntry(/* txid= */ 0, journal::Op::COMMAND, /* dbid= */ 0,
+                         /* shard_cnt= */ shard_set->size(), make_pair("DFLYCLUSTER", args_view),
+                         false);
+  };
+  shard_set->pool()->AwaitFiberOnAll(std::move(cb));
+}
 }  // namespace
 
 void ClusterFamily::DflyClusterConfig(CmdArgList args, ConnectionContext* cntx) {
@@ -468,17 +524,10 @@ void ClusterFamily::DflyClusterConfig(CmdArgList args, ConnectionContext* cntx)
 
   SlotSet after = tl_cluster_config->GetOwnedSlots();
 
-  // Delete old slots data.
-  SlotSet deleted_slot_ids = GetDeletedSlots(is_first_config, before, after);
-  if (!deleted_slot_ids.empty()) {
-    auto cb = [&](auto*) {
-      EngineShard* shard = EngineShard::tlocal();
-      if (shard == nullptr)
-        return;
-
-      shard->db_slice().FlushSlots(deleted_slot_ids);
-    };
-    shard_set->pool()->AwaitFiberOnAll(std::move(cb));
+  if (ServerState::tlocal()->is_master) {
+    auto deleted_slots = GetDeletedSlots(is_first_config, before, after);
+    DeleteSlots(deleted_slots);
+    WriteFlushSlotsToJournal(deleted_slots);
   }
 
   return rb->SendOk();
@@ -537,6 +586,26 @@ void ClusterFamily::DflyClusterGetSlotInfo(CmdArgList args, ConnectionContext* c
   }
 }
 
+void ClusterFamily::DflyClusterFlushSlots(CmdArgList args, ConnectionContext* cntx) {
+  SinkReplyBuilder* rb = cntx->reply_builder();
+
+  args.remove_prefix(1);  // Removes "FLUSHSLOTS" subcmd string
+
+  SlotSet slots;
+  slots.reserve(args.size());
+  for (size_t i = 0; i < args.size(); ++i) {
+    unsigned slot;
+    if (!absl::SimpleAtoi(ArgS(args, i), &slot) || (slot > ClusterConfig::kMaxSlotNum)) {
+      return rb->SendError(kSyntaxErrType);
+    }
+    slots.insert(static_cast<SlotId>(slot));
+  }
+
+  DeleteSlots(slots);
+
+  return rb->SendOk();
+}
+
 using EngineFunc = void (ClusterFamily::*)(CmdArgList args, ConnectionContext* cntx);
 
 inline CommandId::Handler HandlerFunc(ClusterFamily* se, EngineFunc f) {

src/server/cluster/cluster_family.h

@@ -46,6 +46,7 @@ class ClusterFamily {
   void DflyClusterConfig(CmdArgList args, ConnectionContext* cntx);
   void DflyClusterGetSlotInfo(CmdArgList args, ConnectionContext* cntx);
   void DflyClusterMyId(CmdArgList args, ConnectionContext* cntx);
+  void DflyClusterFlushSlots(CmdArgList args, ConnectionContext* cntx);
 
   ClusterConfig::ClusterShard GetEmulatedShardInfo(ConnectionContext* cntx) const;
 

src/server/cluster/cluster_family_test.cc

@@ -47,6 +47,10 @@ class ClusterFamilyTest : public BaseFamilyTest {
     EXPECT_LE(absl::Now(), deadline)
         << "Timeout of " << timeout << " reached when expecting condition";
   }
+
+  string GetMyId() {
+    return RunAdmin({"dflycluster", "myid"}).GetString();
+  }
 };
 
 TEST_F(ClusterFamilyTest, DflyClusterOnlyOnAdminPort) {
@@ -474,7 +478,7 @@ TEST_F(ClusterFamilyTest, ClusterGetSlotInfo) {
           "replicas": []
         }
       ])json";
-  string config = absl::Substitute(config_template, RunAdmin({"dflycluster", "myid"}).GetString());
+  string config = absl::Substitute(config_template, GetMyId());
 
   EXPECT_EQ(RunAdmin({"dflycluster", "config", config}), "OK");
 
@@ -528,7 +532,7 @@ TEST_F(ClusterFamilyTest, ClusterSlotsPopulate) {
           "replicas": []
         }
       ])json";
-  string config = absl::Substitute(config_template, RunAdmin({"dflycluster", "myid"}).GetString());
+  string config = absl::Substitute(config_template, GetMyId());
 
   EXPECT_EQ(RunAdmin({"dflycluster", "config", config}), "OK");
 
@@ -563,7 +567,7 @@ TEST_F(ClusterFamilyTest, ClusterConfigDeleteSlots) {
           "replicas": []
         }
       ])json";
-  string config = absl::Substitute(config_template, RunAdmin({"dflycluster", "myid"}).GetString());
+  string config = absl::Substitute(config_template, GetMyId());
 
   EXPECT_EQ(RunAdmin({"dflycluster", "config", config}), "OK");
 
@@ -608,7 +612,7 @@ TEST_F(ClusterFamilyTest, ClusterConfigDeleteSlotsNoCrashOnShutdown) {
           "replicas": []
         }
       ])json";
-  string config = absl::Substitute(config_template, RunAdmin({"dflycluster", "myid"}).GetString());
+  string config = absl::Substitute(config_template, GetMyId());
 
   EXPECT_EQ(RunAdmin({"dflycluster", "config", config}), "OK");
 
@@ -659,7 +663,7 @@ TEST_F(ClusterFamilyTest, ClusterConfigDeleteSomeSlots) {
           "replicas": []
         }
       ])json";
-  string config = absl::Substitute(config_template, RunAdmin({"dflycluster", "myid"}).GetString());
+  string config = absl::Substitute(config_template, GetMyId());
 
   EXPECT_EQ(RunAdmin({"dflycluster", "config", config}), "OK");
 
@@ -733,6 +737,34 @@ TEST_F(ClusterFamilyTest, Keyslot) {
             CheckedInt({"cluster", "keyslot", "123{def}456"}));
 }
 
+TEST_F(ClusterFamilyTest, FlushSlots) {
+  EXPECT_EQ(Run({"debug", "populate", "100", "key", "4", "slots", "0", "1"}), "OK");
+
+  EXPECT_THAT(RunAdmin({"dflycluster", "getslotinfo", "slots", "0", "1"}),
+              RespArray(ElementsAre(RespArray(ElementsAre(IntArg(0), "key_count", Not(IntArg(0)),
+                                                          "total_reads", _, "total_writes", _)),
+                                    RespArray(ElementsAre(IntArg(1), "key_count", Not(IntArg(0)),
+                                                          "total_reads", _, "total_writes", _)))));
+
+  ExpectConditionWithinTimeout([&]() {
+    return RunAdmin({"dflycluster", "flushslots", "0"}) == "OK";
+  });
+
+  EXPECT_THAT(RunAdmin({"dflycluster", "getslotinfo", "slots", "0", "1"}),
+              RespArray(ElementsAre(RespArray(ElementsAre(IntArg(0), "key_count", IntArg(0),
+                                                          "total_reads", _, "total_writes", _)),
+                                    RespArray(ElementsAre(IntArg(1), "key_count", Not(IntArg(0)),
+                                                          "total_reads", _, "total_writes", _)))));
+
+  EXPECT_EQ(RunAdmin({"dflycluster", "flushslots", "0", "1"}), "OK");
+
+  EXPECT_THAT(RunAdmin({"dflycluster", "getslotinfo", "slots", "0", "1"}),
+              RespArray(ElementsAre(RespArray(ElementsAre(IntArg(0), "key_count", IntArg(0),
+                                                          "total_reads", _, "total_writes", _)),
+                                    RespArray(ElementsAre(IntArg(1), "key_count", IntArg(0),
+                                                          "total_reads", _, "total_writes", _)))));
+}
+
 TEST_F(ClusterFamilyTest, ClusterCrossSlot) {
   string config_template = R"json(
       [
@@ -751,7 +783,7 @@ TEST_F(ClusterFamilyTest, ClusterCrossSlot) {
           "replicas": []
         }
       ])json";
-  string config = absl::Substitute(config_template, RunAdmin({"dflycluster", "myid"}).GetString());
+  string config = absl::Substitute(config_template, GetMyId());
 
   EXPECT_EQ(RunAdmin({"dflycluster", "config", config}), "OK");
   EXPECT_EQ(Run({"SET", "key", "value"}), "OK");
@@ -767,7 +799,7 @@ TEST_F(ClusterFamilyTest, ClusterCrossSlot) {
   EXPECT_THAT(Run({"MGET", "key{tag}", "key2{tag}"}), RespArray(ElementsAre("value", "value2")));
 }
 
-class ClusterFamilyEmulatedTest : public BaseFamilyTest {
+class ClusterFamilyEmulatedTest : public ClusterFamilyTest {
  public:
   ClusterFamilyEmulatedTest() {
     SetTestFlag("cluster_mode", "emulated");
@@ -786,17 +818,17 @@ TEST_F(ClusterFamilyEmulatedTest, ClusterInfo) {
 
 TEST_F(ClusterFamilyEmulatedTest, ClusterShards) {
   EXPECT_THAT(Run({"cluster", "shards"}),
-              RespArray(ElementsAre("slots",                                                      //
-                                    RespArray(ElementsAre(IntArg(0), IntArg(16383))),             //
-                                    "nodes",                                                      //
-                                    RespArray(ElementsAre(                                        //
-                                        RespArray(ElementsAre(                                    //
-                                            "id", RunAdmin({"dflycluster", "myid"}).GetString(),  //
-                                            "endpoint", "fake-host",                              //
-                                            "ip", "fake-host",                                    //
-                                            "port", IntArg(6379),                                 //
-                                            "role", "master",                                     //
-                                            "replication-offset", IntArg(0),                      //
+              RespArray(ElementsAre("slots",                                           //
+                                    RespArray(ElementsAre(IntArg(0), IntArg(16383))),  //
+                                    "nodes",                                           //
+                                    RespArray(ElementsAre(                             //
+                                        RespArray(ElementsAre(                         //
+                                            "id", GetMyId(),                           //
+                                            "endpoint", "fake-host",                   //
+                                            "ip", "fake-host",                         //
+                                            "port", IntArg(6379),                      //
+                                            "role", "master",                          //
+                                            "replication-offset", IntArg(0),           //
                                             "health", "online")))))));
 }
 
@@ -807,13 +839,12 @@ TEST_F(ClusterFamilyEmulatedTest, ClusterSlots) {
                                     RespArray(ElementsAre(  //
                                         "fake-host",        //
                                         IntArg(6379),       //
-                                        RunAdmin({"dflycluster", "myid"}).GetString())))));
+                                        GetMyId())))));
 }
 
 TEST_F(ClusterFamilyEmulatedTest, ClusterNodes) {
   EXPECT_THAT(Run({"cluster", "nodes"}),
-              RunAdmin({"dflycluster", "myid"}).GetString() +
-                  " fake-host:6379@6379 myself,master - 0 0 0 connected 0-16383\r\n");
+              GetMyId() + " fake-host:6379@6379 myself,master - 0 0 0 connected 0-16383\r\n");
 }
 
 }  // namespace

src/server/replica.cc

@@ -3,6 +3,8 @@
 //
 #include "server/replica.h"
 
+#include "absl/strings/match.h"
+
 extern "C" {
 #include "redis/rdb.h"
 }
@@ -1348,7 +1350,24 @@ bool Replica::TransactionData::AddEntry(journal::ParsedEntry&& entry) {
 }
 
 bool Replica::TransactionData::IsGlobalCmd() const {
-  return commands.size() == 1 && commands.front().cmd_args.size() == 1;
+  if (commands.size() > 1) {
+    return false;
+  }
+
+  auto& command = commands.front();
+  if (command.cmd_args.empty()) {
+    return false;
+  }
+
+  auto& args = command.cmd_args;
+  if (absl::EqualsIgnoreCase(ToSV(args[0]), "FLUSHDB"sv) ||
+      absl::EqualsIgnoreCase(ToSV(args[0]), "FLUSHALL"sv) ||
+      (absl::EqualsIgnoreCase(ToSV(args[0]), "DFLYCLUSTER"sv) &&
+       absl::EqualsIgnoreCase(ToSV(args[1]), "FLUSHSLOTS"sv))) {
+    return true;
+  }
+
+  return false;
 }
 
 Replica::TransactionData Replica::TransactionData::FromSingle(journal::ParsedEntry&& entry) {

tests/dragonfly/cluster_test.py

@@ -378,9 +378,8 @@ async def test_cluster_replica_sets_non_owned_keys(df_local_factory):
 
     await push_config(replica_config, [c_replica_admin])
 
-    # The replica should have deleted the key.
-    # Note: this is not the long-term intended behavior. It will change after we fix #1320.
-    assert await c_replica.execute_command("dbsize") == 0
+    # The replica should *not* have deleted the key.
+    assert await c_replica.execute_command("dbsize") == 1
 
     # Set another key on the master, which it owns but the replica does not own.
     await c_master.set("key2", "value");
@@ -388,7 +387,7 @@ async def test_cluster_replica_sets_non_owned_keys(df_local_factory):
 
     # See that the key exists in both replica and master
     assert await c_master.execute_command("dbsize") == 2
-    assert await c_replica.execute_command("dbsize") == 1
+    assert await c_replica.execute_command("dbsize") == 2
 
     # The replica should still reply with MOVED, despite having that key.
     try:
@@ -397,6 +396,118 @@ async def test_cluster_replica_sets_non_owned_keys(df_local_factory):
     except redis.exceptions.ResponseError as e:
         assert re.match(r"MOVED \d+ localhost:1111", e.args[0])
 
+    await push_config(replica_config, [c_master_admin])
+    await asyncio.sleep(0.5)
+    assert await c_master.execute_command("dbsize") == 0
+    assert await c_replica.execute_command("dbsize") == 0
+
+
+@dfly_args({"proactor_threads": 4, "cluster_mode": "yes"})
+async def test_cluster_flush_slots_after_config_change(df_local_factory):
+    # Start and configure cluster with 1 master and 1 replica, both own all slots
+    master = df_local_factory.create(port=BASE_PORT, admin_port=BASE_PORT+1000)
+    replica = df_local_factory.create(port=BASE_PORT+1, admin_port=BASE_PORT+1001)
+    df_local_factory.start_all([master, replica])
+
+    c_master = aioredis.Redis(port=master.port)
+    c_master_admin = aioredis.Redis(port=master.admin_port)
+    master_id = await get_node_id(c_master_admin)
+
+    c_replica = aioredis.Redis(port=replica.port)
+    c_replica_admin = aioredis.Redis(port=replica.admin_port)
+    replica_id = await get_node_id(c_replica_admin)
+
+    config = f"""
+      [
+        {{
+          "slot_ranges": [
+            {{
+              "start": 0,
+              "end": 16383
+            }}
+          ],
+          "master": {{
+            "id": "{master_id}",
+            "ip": "localhost",
+            "port": {master.port}
+          }},
+          "replicas": [
+            {{
+              "id": "{replica_id}",
+              "ip": "localhost",
+              "port": {replica.port}
+            }}
+          ]
+        }}
+      ]
+    """
+    await push_config(config, [c_master_admin, c_replica_admin])
+
+    await c_master.execute_command("debug", "populate", "100000");
+    assert await c_master.execute_command("dbsize") == 100_000
+
+    # Setup replication and make sure that it works properly.
+    await c_replica.execute_command("REPLICAOF", "localhost", master.port)
+    await check_all_replicas_finished([c_replica], c_master)
+    assert await c_replica.execute_command("dbsize") == 100_000
+
+    resp = await c_master_admin.execute_command("dflycluster", "getslotinfo", "slots", "0")
+    assert resp[0][0] == 0
+    slot_0_size = resp[0][2]
+    print(f'Slot 0 size = {slot_0_size}')
+    assert slot_0_size > 0
+
+    config = f"""
+      [
+        {{
+          "slot_ranges": [
+            {{
+              "start": 1,
+              "end": 16383
+            }}
+          ],
+          "master": {{
+            "id": "{master_id}",
+            "ip": "localhost",
+            "port": {master.port}
+          }},
+          "replicas": [
+            {{
+              "id": "{replica_id}",
+              "ip": "localhost",
+              "port": {replica.port}
+            }}
+          ]
+        }},
+        {{
+          "slot_ranges": [
+            {{
+              "start": 0,
+              "end": 0
+            }}
+          ],
+          "master": {{
+            "id": "other-master",
+            "ip": "localhost",
+            "port": 9000
+          }},
+          "replicas": [
+            {{
+              "id": "other-replica",
+              "ip": "localhost",
+              "port": 9001
+            }}
+          ]
+        }}
+      ]
+    """
+    await push_config(config, [c_master_admin, c_replica_admin])
+
+    await asyncio.sleep(0.5)
+
+    assert await c_master.execute_command("dbsize") == (100_000 - slot_0_size)
+    assert await c_replica.execute_command("dbsize") == (100_000 - slot_0_size)
+
 
 @dfly_args({"proactor_threads": 4, "cluster_mode": "yes"})
 async def test_cluster_native_client(df_local_factory):