Function readNewChunk

scripts/telemetry-otlp-export.js:199–254

(filePath, storedOffset)

// it is left for the next run. When the file shrank below the stored offset
// (truncation or rotation) the offset resets to 0.
function readNewChunk(filePath, storedOffset) {
  if (!fs.existsSync(filePath)) {
    return { lines: [], nextOffset: 0, reset: storedOffset > 0 };
  }

  const size = fs.statSync(filePath).size;
  let offset = storedOffset;
  let reset = false;
  if (size < offset) {
    offset = 0;
    reset = true;
  }
  if (size === offset) {
    return { lines: [], nextOffset: offset, reset };
  }

  const buffer = Buffer.alloc(size - offset);
  const fd = fs.openSync(filePath, 'r');
  try {
    fs.readSync(fd, buffer, 0, buffer.length, offset);
  } finally {
    fs.closeSync(fd);
  }

  const chunk = buffer.toString('utf8');
  const segments = chunk.split('\n');
  let rawLines;
  let consumedBytes;

  if (chunk.endsWith('\n')) {
    rawLines = segments.slice(0, -1);
    consumedBytes = buffer.length;
  } else {
    const tail = segments[segments.length - 1];
    let tailParses = false;
    try {
      JSON.parse(tail);
      tailParses = true;
    } catch (error) {
      tailParses = false;
    }
    if (tailParses) {
      rawLines = segments;
      consumedBytes = buffer.length;
    } else {
      rawLines = segments.slice(0, -1);
      consumedBytes = buffer.length - Buffer.byteLength(tail, 'utf8');
    }
  }

  const lines = rawLines
    .map((line) => (line.endsWith('\r') ? line.slice(0, -1) : line))
    .filter((line) => line.trim() !== '');

  return { lines, nextOffset: offset + consumedBytes, reset };
}

function loadState(stateFile) {