how to free memory used by pdf2json?

[zihuyishi]

I have a server that run four process to handler client side pdf. I found that when client side send a 10mb pdf file, one process will used 400mb memory and never free it. When run it for long time and receive some big pdf, it will take me about 4gb memory, and make other app down. I have a test code like this

const pdfParser = new PDFParser(this, 1);

pdfParser.on('pdfParser_dataReady', pdfData => {
    console.log('--------------raw-----------------');
    console.log(pdfParser.getRawTextContent());
});

pdfParser.loadPDF('/Users/saye/Downloads/Gradle_Recipes_for_Android.pdf');
let server = http.createServer((req, res) => {
    res.write('hello');
    res.end();
});
server.listen(2345);

so what should I do to make memory free