Memory leak in NodeJS + GCloud logging

I have been finding memory leak in our production code for 2 weaks. At the end I reproduced the memory leak with simple nodejs server and gcloud logging api.

Nodejs server is the same as inside Nodejs Getting Started Guide

'use strict';

const http = require('http');

const hostname = '127.0.0.1';
const port = 3000;

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello World\n');
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

module.exports = server;

I write every request headers to gcloud logging:

'use strict';

const app = require('./app.js');

const gcloud  = require('gcloud')({
    keyFilename: 'my-key-file',
    projectId: 'my-project-id'
});

const logging = gcloud.logging();

const logs = logging.log('log-bucket');

const resource = {
  type: 'logging_log',
  labels: {
    name: 'clear_node_logs',
  }
};

app.on('request', function onServerRequest(req, res) {
    const entry = logs.entry(resource, req.headers);

    logs.info(entry, logHandler);
});

function logHandler(err) {
    if (err) {
        console.log(err);
    }
}

If I make 300k requests to this server I get the following memory usage

As you can see the memory leaks. At the end I get OutOfMemory exception.

If I log the same amount of data inside setInterval function the memory doesn't leak.

What could be the source of that leak in such a simple application?

Our dependency, gRPC, had a memory leak which was originally reported here: https://github.com/GoogleCloudPlatform/google-cloud-node/issues/1414

A fix was recently released in gRPC, and we will be releasing versions of google-cloud and affected submodules today.