feat(server): Implement MEMORY MALLOC-STATS command (#363)

Signed-off-by: Roman Gershman <roman@dragonflydb.io>

Signed-off-by: Roman Gershman <roman@dragonflydb.io>

src/server/CMakeLists.txt

@@ -15,7 +15,7 @@ cxx_link(dfly_transaction uring_fiber_lib dfly_core strings_lib)
 add_library(dragonfly_lib  channel_slice.cc command_registry.cc
             config_flags.cc conn_context.cc debugcmd.cc dflycmd.cc
             generic_family.cc hset_family.cc json_family.cc
-            list_family.cc main_service.cc  rdb_load.cc rdb_save.cc replica.cc
+            list_family.cc main_service.cc memory_cmd.cc rdb_load.cc rdb_save.cc replica.cc
             snapshot.cc script_mgr.cc server_family.cc malloc_stats.cc
             set_family.cc stream_family.cc string_family.cc
             zset_family.cc version.cc bitops_family.cc container_utils.cc)

src/server/memory_cmd.cc

@@ -0,0 +1,68 @@
+// Copyright 2022, DragonflyDB authors.  All rights reserved.
+// See LICENSE for licensing terms.
+//
+
+#include "server/memory_cmd.h"
+
+#include <absl/strings/str_cat.h>
+#include <mimalloc.h>
+
+#include "facade/error.h"
+#include "server/server_state.h"
+
+using namespace std;
+using namespace facade;
+
+namespace dfly {
+
+namespace {
+
+void MiStatsCallback(const char* msg, void* arg) {
+  string* str = (string*)arg;
+  absl::StrAppend(str, msg);
+}
+
+bool MiArenaVisit(const mi_heap_t* heap, const mi_heap_area_t* area, void* block, size_t block_size,
+                  void* arg) {
+  string* str = (string*)arg;
+
+  absl::StrAppend(str, "block_size ", block_size, ", reserved ",
+                  area->reserved, ", comitted ", area->committed,
+                  ", used: ", area->used * block_size, "\n");
+
+  return true;
+};
+
+}  // namespace
+
+MemoryCmd::MemoryCmd(ServerFamily* owner, ConnectionContext* cntx) : sf_(*owner), cntx_(cntx) {
+}
+
+void MemoryCmd::Run(CmdArgList args) {
+  string_view sub_cmd = ArgS(args, 1);
+  if (sub_cmd == "USAGE") {
+    // dummy output, in practice not implemented yet.
+    return (*cntx_)->SendLong(1);
+  } else if (sub_cmd == "MALLOC-STATS") {
+    return MallocStats();
+  }
+
+  string err = UnknownSubCmd(sub_cmd, "MEMORY");
+  return (*cntx_)->SendError(err, kSyntaxErrType);
+}
+
+void MemoryCmd::MallocStats() {
+  string str;
+  absl::StrAppend(&str, "___ Begin mimalloc statistics ___\n");
+  mi_stats_print_out(MiStatsCallback, &str);
+
+  absl::StrAppend(&str, "\nArena statistics from a single thread:\n");
+  mi_heap_t* data_heap = ServerState::tlocal()->data_heap();
+  mi_heap_visit_blocks(data_heap, false /* visit all blocks*/, MiArenaVisit, &str);
+
+  absl::StrAppend(&str, "--- End mimalloc statistics ---\n");
+
+  return (*cntx_)->SendBulkString(str);
+}
+
+}  // namespace dfly

src/server/memory_cmd.h

@@ -0,0 +1,26 @@
+// Copyright 2022, DragonflyDB authors.  All rights reserved.
+// See LICENSE for licensing terms.
+//
+
+#pragma once
+
+#include "server/conn_context.h"
+
+namespace dfly {
+
+class ServerFamily;
+
+class MemoryCmd {
+ public:
+  MemoryCmd(ServerFamily* owner, ConnectionContext* cntx);
+
+  void Run(CmdArgList args);
+
+ private:
+  void MallocStats();
+
+  ServerFamily& sf_;
+  ConnectionContext* cntx_;
+};
+
+}  // namespace dfly

src/server/server_family.cc

@@ -31,6 +31,7 @@ extern "C" {
 #include "server/error.h"
 #include "server/journal/journal.h"
 #include "server/main_service.h"
+#include "server/memory_cmd.h"
 #include "server/rdb_load.h"
 #include "server/rdb_save.h"
 #include "server/replica.h"
@@ -1015,13 +1016,10 @@ void ServerFamily::Debug(CmdArgList args, ConnectionContext* cntx) {
 
 void ServerFamily::Memory(CmdArgList args, ConnectionContext* cntx) {
   ToUpper(&args[1]);
-  string_view sub_cmd = ArgS(args, 1);
-  if (sub_cmd == "USAGE") {
-    return (*cntx)->SendLong(1);
-  }
 
-  string err = UnknownSubCmd(sub_cmd, "MEMORY");
+  MemoryCmd mem_cmd{this, cntx};
-  return (*cntx)->SendError(err, kSyntaxErrType);
+
+  return mem_cmd.Run(args);
 }
 
 void ServerFamily::Save(CmdArgList args, ConnectionContext* cntx) {