levelup writeStream doesn't pause when behind. this leads to huge memory leaks importing lots of data especially from stdin.

leak_levelup.js

var level = require('levelup')
, db = level('./streamtest.db')


var dbws = db.createWriteStream()
, c = 0
, start = Date.now()
, intervalCount = 0
, bytes = 0
, paused = false
;

dbws.on('pause',function(){
  console.log('paused.');
  paused = true;
}).on('drain',function(){
  console.log('drained.');
  paused = false;
});

// generate 10000 key values per ms
(function fn(){

  if(paused) return setImmediate(fn);

  var s = Date.now(), values = 0,key,value;
  while(s == Date.now() || values > 10000){
    values++;

    key = 'a_key_'+(++c);
    value = '{"time":'+s+',"updated":'+s+',"id":'+c+',"number":1,"string":"some important string value"}';
    dbws.write({key:key,value:value});

    bytes += key.length+value.length;
  }
  intervalCount += values;
  setImmediate(fn);
})()

interval = setInterval(function(){
  console.log(c/(Date.now()-start),'values per ms. ',intervalCount,' since last interval ',bytes,' bytes and ',c,' rows written so far.');
  intervalCount = 0;
},1000);