1 files changed, 50 insertions, 9 deletions

diff --git a/src/dbwrapper.cpp b/src/dbwrapper.cpp
index ac122a3545..ca446c92fe 100644
--- a/src/dbwrapper.cpp
+++ b/src/dbwrapper.cpp
@@ -72,6 +72,31 @@ public:
     }
 };
 
+static void SetMaxOpenFiles(leveldb::Options *options) {
+    // On most platforms the default setting of max_open_files (which is 1000)
+    // is optimal. On Windows using a large file count is OK because the handles
+    // do not interfere with select() loops. On 64-bit Unix hosts this value is
+    // also OK, because up to that amount LevelDB will use an mmap
+    // implementation that does not use extra file descriptors (the fds are
+    // closed after being mmaped).
+    //
+    // Increasing the value beyond the default is dangerous because LevelDB will
+    // fall back to a non-mmap implementation when the file count is too large.
+    // On 32-bit Unix host we should decrease the value because the handles use
+    // up real fds, and we want to avoid fd exhaustion issues.
+    //
+    // See PR #12495 for further discussion.
+
+    int default_open_files = options->max_open_files;
+#ifndef WIN32
+    if (sizeof(void*) < 8) {
+        options->max_open_files = 64;
+    }
+#endif
+    LogPrint(BCLog::LEVELDB, "LevelDB using max_open_files=%d (default=%d)\n",
+             options->max_open_files, default_open_files);
+}
+
 static leveldb::Options GetOptions(size_t nCacheSize)
 {
     leveldb::Options options;
@@ -79,17 +104,18 @@ static leveldb::Options GetOptions(size_t nCacheSize)
     options.write_buffer_size = nCacheSize / 4; // up to two write buffers may be held in memory simultaneously
     options.filter_policy = leveldb::NewBloomFilterPolicy(10);
     options.compression = leveldb::kNoCompression;
-    options.max_open_files = 64;
     options.info_log = new CBitcoinLevelDBLogger();
     if (leveldb::kMajorVersion > 1 || (leveldb::kMajorVersion == 1 && leveldb::kMinorVersion >= 16)) {
         // LevelDB versions before 1.16 consider short writes to be corruption. Only trigger error
         // on corruption in later versions.
         options.paranoid_checks = true;
     }
+    SetMaxOpenFiles(&options);
     return options;
 }
 
 CDBWrapper::CDBWrapper(const fs::path& path, size_t nCacheSize, bool fMemory, bool fWipe, bool obfuscate)
+    : m_name(fs::basename(path))
 {
     penv = nullptr;
     readoptions.verify_checksums = true;
@@ -156,11 +182,30 @@ CDBWrapper::~CDBWrapper()
 
 bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
 {
+    const bool log_memory = LogAcceptCategory(BCLog::LEVELDB);
+    double mem_before = 0;
+    if (log_memory) {
+        mem_before = DynamicMemoryUsage() / 1024.0 / 1024;
+    }
     leveldb::Status status = pdb->Write(fSync ? syncoptions : writeoptions, &batch.batch);
     dbwrapper_private::HandleError(status);
+    if (log_memory) {
+        double mem_after = DynamicMemoryUsage() / 1024.0 / 1024;
+        LogPrint(BCLog::LEVELDB, "WriteBatch memory usage: db=%s, before=%.1fMiB, after=%.1fMiB\n",
+                 m_name, mem_before, mem_after);
+    }
     return true;
 }
 
+size_t CDBWrapper::DynamicMemoryUsage() const {
+    std::string memory;
+    if (!pdb->GetProperty("leveldb.approximate-memory-usage", &memory)) {
+        LogPrint(BCLog::LEVELDB, "Failed to get approximate-memory-usage property\n");
+        return 0;
+    }
+    return stoul(memory);
+}
+
 // Prefixed with null character to avoid collisions with other keys
 //
 // We must use a string constructor which specifies length so that we copy
@@ -199,14 +244,10 @@ void HandleError(const leveldb::Status& status)
 {
     if (status.ok())
         return;
-    LogPrintf("%s\n", status.ToString());
-    if (status.IsCorruption())
-        throw dbwrapper_error("Database corrupted");
-    if (status.IsIOError())
-        throw dbwrapper_error("Database I/O error");
-    if (status.IsNotFound())
-        throw dbwrapper_error("Database entry missing");
-    throw dbwrapper_error("Unknown database error");
+    const std::string errmsg = "Fatal LevelDB error: " + status.ToString();
+    LogPrintf("%s\n", errmsg);
+    LogPrintf("You can use -debug=leveldb to get more complete diagnostic messages\n");
+    throw dbwrapper_error(errmsg);
 }
 
 const std::vector<unsigned char>& GetObfuscateKey(const CDBWrapper &w)