[Filestore] issue-3687: implement pagination during ListNodes for local filestore

cloud/filestore/config/server.proto

@@ -123,6 +123,9 @@ message TLocalServiceConfig
 
     // Trust guest kernel to check user permissions for fuse operations
     optional bool GuestOnlyPermissionsCheckEnabled = 21;
+
+    // Max entries each ListNodes will return
+    optional uint32 MaxResponseEntries = 22;
 }
 
 ////////////////////////////////////////////////////////////////////////////////

cloud/filestore/libs/service_local/config.cpp

@@ -37,6 +37,7 @@ constexpr TDuration AsyncHandleOpsPeriod = TDuration::MilliSeconds(50);
     xxx(ServerWriteBackCacheEnabled, bool,          false                     )\
     xxx(DontPopulateNodeCacheWhenListingNodes, bool, false                    )\
     xxx(GuestOnlyPermissionsCheckEnabled,      bool, false                    )\
+    xxx(MaxResponseEntries,          ui32,          10000                     )\
 // FILESTORE_SERVICE_CONFIG
 
 #define FILESTORE_SERVICE_DECLARE_CONFIG(name, type, value)                    \

cloud/filestore/libs/service_local/config.h

@@ -51,6 +51,8 @@ class TLocalFileStoreConfig
     bool GetDontPopulateNodeCacheWhenListingNodes() const;
 
     bool GetGuestOnlyPermissionsCheckEnabled() const;
+
+    ui32 GetMaxResponseEntries() const;
 };
 
 }   // namespace NCloud::NFileStore

cloud/filestore/libs/service_local/fs_node.cpp

@@ -5,6 +5,7 @@
 #include <cloud/filestore/libs/diagnostics/critical_events.h>
 
 #include <util/generic/guid.h>
+#include <util/stream/format.h>
 
 namespace NCloud::NFileStore {
 
@@ -205,7 +206,16 @@ NProto::TListNodesResponse TLocalFileSystem::ListNodes(
         return TErrorResponse(ErrorInvalidParent(request.GetNodeId()));
     }
 
-    auto entries = parent->List();
+    uint64_t offset = 0;
+    auto& cookie = request.GetCookie();
+    if (cookie) {
+        if (!TryFromString(cookie, offset)) {
+            return TErrorResponse(ErrorInvalidArgument());
+        }
+    }
+
+    auto listRes = parent->List(offset, Config->GetMaxResponseEntries());
+    auto& entries = listRes.DirEntries;
 
     NProto::TListNodesResponse response;
     response.MutableNames()->Reserve(entries.size());
@@ -237,6 +247,7 @@ NProto::TListNodesResponse TLocalFileSystem::ListNodes(
         ConvertStats(entry.second, *response.MutableNodes()->Add());
     }
 
+    response.SetCookie(ToString(listRes.DirOffset));
     return response;
 }
 

cloud/filestore/libs/service_local/index.cpp

@@ -90,9 +90,21 @@ TString TIndexNode::ReadLink() const
     return NLowLevel::ReadLink(NodeFd);
 }
 
-TVector<std::pair<TString, TFileStat>> TIndexNode::List(bool ignoreErrors)
+TVector<NLowLevel::TDirEntry> TIndexNode::List(bool ignoreErrors)
 {
-    return NLowLevel::ListDirAt(NodeFd, ignoreErrors);
+    auto res = NLowLevel::ListDirAt(
+        NodeFd,
+        0,   // start at beginning of dir
+        0,   // don't limit number of entries
+        ignoreErrors);
+
+    return std::move(res.DirEntries);
+}
+
+NLowLevel::TListDirResult
+TIndexNode::List(uint64_t offset, size_t entriesLimit, bool ignoreErrors)
+{
+    return NLowLevel::ListDirAt(NodeFd, offset, entriesLimit, ignoreErrors);
 }
 
 TFileStat TIndexNode::Stat()

cloud/filestore/libs/service_local/index.h

@@ -67,7 +67,9 @@ class TIndexNode
     TIndexNodePtr CreateSymlink(const TString& name, const TString& target);
     TIndexNodePtr CreateSocket(const TString& name, int flags);
 
-    TVector<std::pair<TString, TFileStat>> List(bool ignoreErrors = false);
+    TVector<NLowLevel::TDirEntry> List(bool ignoreErrors = false);
+    NLowLevel::TListDirResult
+    List(uint64_t offset, size_t entriesLimit, bool ignoreErrors = false);
 
     void Rename(
         const TString& name,

cloud/filestore/libs/service_local/lowlevel.cpp

@@ -297,8 +297,10 @@ TFileSystemStat StatFs(const TFileHandle& handle)
     return GetFileSystemStat(fs);
 }
 
-TVector<std::pair<TString, TFileStat>> ListDirAt(
+TListDirResult ListDirAt(
     const TFileHandle& handle,
+    uint64_t offset,
+    size_t entriesLimit,
     bool ignoreErrors)
 {
     auto fd = openat(Fd(handle), ".", O_RDONLY);
@@ -320,7 +322,11 @@ TVector<std::pair<TString, TFileStat>> ListDirAt(
         }
     };
 
-    TVector<std::pair<TString, TFileStat>> results;
+    if (offset) {
+        seekdir(dir, offset);
+    }
+
+    TListDirResult res;
 
     errno = 0;
     while (auto* entry = readdir(dir)) {
@@ -332,22 +338,34 @@ TVector<std::pair<TString, TFileStat>> ListDirAt(
         if (ignoreErrors) {
             try {
                 auto stat = StatAt(handle, name);
-                results.emplace_back(std::move(name), stat);
+                res.DirEntries.emplace_back(std::move(name), stat);
             } catch (const TServiceError& err) {
                 errno = 0;
                 continue;
             }
         } else {
             auto stat = StatAt(handle, name);
-            results.emplace_back(std::move(name), stat);
+            res.DirEntries.emplace_back(std::move(name), stat);
+        }
+
+        if (entriesLimit && --entriesLimit == 0) {
+            break;
         }
     }
 
     Y_ENSURE_EX(errno == 0, TServiceError(GetSystemErrorCode())
         << "failed to list: "
         << LastSystemErrorText());
 
-    return results;
+    long loc = telldir(dir);
+
+    Y_ENSURE_EX(loc != -1, TServiceError(GetSystemErrorCode())
+        << "failed to telldir: "
+        << LastSystemErrorText());
+
+    res.DirOffset = loc;
+
+    return res;
 }
 
 ////////////////////////////////////////////////////////////////////////////////

cloud/filestore/libs/service_local/lowlevel.h

@@ -105,6 +105,16 @@ struct TOpenOrCreateResult
 
 ////////////////////////////////////////////////////////////////////////////////
 
+using TDirEntry = std::pair<TString, TFileStat>;
+
+struct TListDirResult
+{
+    TVector<TDirEntry> DirEntries;
+    uint64_t DirOffset = 0;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
 TFileHandle Open(const TString& path, int flags, int mode);
 TFileHandle Open(const TFileHandle& handle, int flags, int mode);
 TFileHandle OpenAt(
@@ -144,8 +154,10 @@ TFileStat Stat(const TFileHandle& handle);
 TFileStat StatAt(const TFileHandle& handle, const TString& name);
 TFileSystemStat StatFs(const TFileHandle& handle);
 
-TVector<std::pair<TString, TFileStat>> ListDirAt(
+TListDirResult ListDirAt(
     const TFileHandle& handle,
+    uint64_t offset,
+    size_t entriesLimit,
     bool ignoreErrors);
 
 //

cloud/filestore/libs/service_local/lowlevel_ut.cpp

@@ -58,6 +58,62 @@ Y_UNIT_TEST_SUITE(TLowlevelTest)
         res = NLowLevel::OpenOrCreateAt(node, "2.txt", O_WRONLY, 0755);
         UNIT_ASSERT(!res.WasCreated);
     }
+
+    Y_UNIT_TEST(ShouldDoIterativeListDir)
+    {
+        const TTempDir TempDir;
+        auto rootNode = NLowLevel::Open(TempDir.Name(), O_PATH, 0);
+
+        int nodesCount = 10;
+        TSet<TString> entryNames;
+        for (int i = 0; i < nodesCount; i++) {
+            if (i == 0) {
+                auto name = "dir_" + ToString(i);
+                entryNames.insert(name);
+                NLowLevel::MkDirAt(rootNode, name, 0755);
+            } else {
+                auto name = "file_" + ToString(i);
+                entryNames.insert(name);
+                NLowLevel::OpenAt(
+                    rootNode,
+                    name,
+                    O_CREAT | O_WRONLY,
+                    0755);
+            }
+        }
+
+        auto savedEntryNames = entryNames;
+        auto checkListDirResult =
+            [&](NLowLevel::TListDirResult& res, size_t expectedEntriesCount)
+        {
+            UNIT_ASSERT_EQUAL(res.DirEntries.size(), expectedEntriesCount);
+            for (auto& entry: res.DirEntries) {
+                UNIT_ASSERT_EQUAL_C(
+                    1,
+                    entryNames.count(entry.first),
+                    TStringBuilder() << entry.first << " missing");
+                entryNames.erase(entry.first);
+            }
+        };
+
+        auto res = NLowLevel::ListDirAt(rootNode, 0, 5, false);
+        checkListDirResult(res, 5);
+
+        res = NLowLevel::ListDirAt(rootNode, res.DirOffset, 3, false);
+        checkListDirResult(res, 3);
+
+        res = NLowLevel::ListDirAt(rootNode, res.DirOffset, 2, false);
+        checkListDirResult(res, 2);
+
+        res = NLowLevel::ListDirAt(rootNode, res.DirOffset, 2, false);
+        checkListDirResult(res, 0);
+
+        // with limit 0 all nodes should be read
+        entryNames = savedEntryNames;
+        res = NLowLevel::ListDirAt(rootNode, 0, 0, false);
+        checkListDirResult(res, 10);
+
+    }
 };
 
 }   // namespace NCloud::NFileStore

cloud/filestore/libs/service_local/session.h

@@ -164,7 +164,7 @@ class TSession
             } catch (...) {
                 STORAGE_ERROR(
                     "Failed to open Handle, HandleId=" << it->HandleId <<
-                    ", NodeId" << it->NodeId <<
+                    ", NodeId=" << it->NodeId <<
                     ", Exception=" << CurrentExceptionMessage());
                 HandleTable->DeleteRecord(it.GetIndex());
                 continue;