Method write

src/slave/container_loggers/logrotate.cpp:195–233

Writes the buffer from stdin to the leading log file. When the number of written bytes exceeds `--max_size`, the leading log file is rotated. When the number of log files exceed `--max_files`, the oldest log file is deleted.

  // log file is rotated.  When the number of log files exceed `--max_files`,
  // the oldest log file is deleted.
  Try<Nothing> write(size_t readSize)
  {
    // Rotate the log file if it will grow beyond the `--max_size`.
    if (bytesWritten + readSize > flags.max_size.bytes()) {
      rotate();
    }

    // If the leading log file is not open, open it.
    // NOTE: We open the file in append-mode as `logrotate` may sometimes fail.
    if (leading.isNone()) {
      Try<int> open = os::open(
          flags.log_filename.get(),
          O_WRONLY | O_CREAT | O_APPEND | O_CLOEXEC,
          S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

      if (open.isError()) {
        return Error(
            "Failed to open '" + flags.log_filename.get() +
            "': " + open.error());
      }

      leading = open.get();
    }

    // Write from stdin to `leading`.
    // NOTE: We do not exit on error here since we are prioritizing
    // clearing the STDIN pipe (which would otherwise potentially block
    // the container on write) over log fidelity.
    Try<Nothing> result =
      os::write(leading.get(), string(buffer, readSize));

    if (result.isError()) {
      std::cerr << "Failed to write: " << result.error() << std::endl;
    }

    bytesWritten += readSize;

    return Nothing();
  }

  // Calls `logrotate` on the leading log file and resets the `bytesWritten`.
  void rotate()