Warrior_EA/Database/DatabaseVersionManager.mqh

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class CDatabaseVersionManager
  {
private:
   //--- Read/Update both open this FILE_COMMON version file with the same 5-attempt/1s-sleep retry,
   //--- differing only in the open flags and the "reading"/"writing" noun in the log line.
   // FILE_SHARE_READ|FILE_SHARE_WRITE required - this file is FILE_COMMON (shared across every
   // chart instance/symbol), so without share flags a second instance's open can be blocked by
   // the first's exclusive handle, exhausting these retries and (via the ERROR sentinel below)
   // potentially triggering a version-mismatch CleanDirectory() that wipes the shared DB folder.
   int               OpenVersionFileWithRetry(string versionFilePath, int openFlags, string verb)
     {
      int fileHandle = INVALID_HANDLE; // Initialize to a safe value
      int attempts = 0;
      while(attempts < 5)
        {
         fileHandle = FileOpen(versionFilePath, openFlags);
         if(fileHandle != INVALID_HANDLE)
           {
            break; // Success, break out of the loop
           }
         Print("Retry " + IntegerToString(attempts + 1) + " failed to open file for " + verb + ": " + versionFilePath + " (error " + IntegerToString(GetLastError()) + ")");
         Sleep(1000); // Wait for a second before retrying
         attempts++;
        }
      if(fileHandle == INVALID_HANDLE)
         Print("Failed to open file for " + verb + " after retries: " + versionFilePath + " (error " + IntegerToString(GetLastError()) + ")");
      return fileHandle;
     }

public:
   string            ReadStoredDbVersion(string versionFilePath)
     {
      if(!FileIsExist(versionFilePath, FILE_COMMON))
         return "NA";
      int fileHandle = OpenVersionFileWithRetry(versionFilePath, FILE_COMMON | FILE_READ | FILE_SHARE_READ | FILE_SHARE_WRITE, "reading");
      if(fileHandle == INVALID_HANDLE)
         return "ERROR";
      string dbVersion = FileReadString(fileHandle);
      FileClose(fileHandle);
      return dbVersion;
     }

   bool              UpdateStoredDbVersion(string versionFilePath, string dbVersion)
     {
      int fileHandle = OpenVersionFileWithRetry(versionFilePath, FILE_COMMON | FILE_WRITE | FILE_SHARE_READ | FILE_SHARE_WRITE, "writing");
      if(fileHandle == INVALID_HANDLE)
         return false;
      FileWriteString(fileHandle, dbVersion);
      FileClose(fileHandle);
      return true;
     }
  };
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