A gist that stress tests levelUP by inserting lots of batch files containing JSON. This can be configured to create a "memory leak" in levelUP.

levelUpStressTest.js

//fergusmcdowall@gmail.com
//A very simple stress test for levelUP
//make lots of LorumIpsum json files, put them into batches, and then
//cram as many of them as possible into LevelUP

//At the time of writing (15 aug 2013) this will create a memory leak

//adjust size of batches here
var totalBatchFiles = 300;
var totalDocsPerBatchFile = 100;
var totalFieldsPerDoc = 10;
var totalSentencesPerField = 50;

var loremIpsum = require('lorem-ipsum');
var levelup = require('levelup');
var db = levelup('./db',
                 {valueEncoding: 'json'})



for (var i = 0; i < totalBatchFiles; i++) {
  var batch = [];
  for (var j = 0; j < totalDocsPerBatchFile; j++) {
    var value = {};
    var key = i + '~' + j;
    for (var k = 0; k < totalFieldsPerDoc; k++) {
      var fieldText = loremIpsum({
        count: totalSentencesPerField, 
        units: 'sentences',
        sentenceLowerBound: 5,
        sentenceUpperBound: 15,
        paragraphLowerBound: 3,
        paragraphUpperBound: 7,
        format: 'plain',
        random: Math.random   
      });
      var fieldIndex = loremIpsum({
        count: 1, 
        units: 'words',
        format: 'plain',
        random: Math.random   
      });
      value[fieldIndex] = fieldText;
    }
    batch.push({
      type: 'put',
      key: key,
      value: value});
    console.log(key);
  }
  insertBatch(i, batch);
}

function insertBatch(id, thisBatch) {
  console.log('queueing batch ' + id);
  db.batch(thisBatch, function (err) {
    console.log('inserted batch ' + id);
    if (err) return console.log('Ooops!', err);
    return;
  });
}

package.json

{
  "name": "LevelUpStressTest",
  "description": "a module that creates pretent JSON files an inserts them into levelUP",
  "version": "0.1.1",
  "engines": {
    "node": ">=0.4.10"
  },
  "dependencies": {
    "lorem-ipsum": "*",
    "levelup": "*",
    "leveldown": "*"
  },
  "author": "Fergus McDowall <fergusmcdowall@gmail.com>"
}

my version with some breathing space for V8, in the above version there is absolutely no room for the callbacks to get back in to the event loop.

//fergusmcdowall@gmail.com
//A very simple stress test for levelUP
//make lots of LorumIpsum json files, put them into batches, and then
//cram as many of them as possible into LevelUP

//At the time of writing (15 aug 2013) this will create a memory leak

//adjust size of batches here
var totalBatchFiles = 30000;
var totalDocsPerBatchFile = 100;
var totalFieldsPerDoc = 10;
var totalSentencesPerField = 50;

var loremIpsum = require('lorem-ipsum');
var levelup = require('levelup');
var db = levelup('./db',
                 {valueEncoding: 'json'})

var batches = 0
var inserted = 0
var queued = 0


function doBatch () {
  var batch = [];
  for (var j = 0; j < totalDocsPerBatchFile; j++) {
    var value = {};
    var key = batches + '~' + j;
    for (var k = 0; k < totalFieldsPerDoc; k++) {
      var fieldText = loremIpsum({
        count: totalSentencesPerField, 
        units: 'sentences',
        sentenceLowerBound: 5,
        sentenceUpperBound: 15,
        paragraphLowerBound: 3,
        paragraphUpperBound: 7,
        format: 'plain',
        random: Math.random   
      });
      var fieldIndex = loremIpsum({
        count: 1, 
        units: 'words',
        format: 'plain',
        random: Math.random   
      });
      value[fieldIndex] = fieldText;
    }
    batch.push({
      type: 'put',
      key: key,
      value: value});
    //console.log(key);
  }
  insertBatch(batches, batch);
  if (++batches < totalBatchFiles)
    setImmediate(doBatch)
}
db.on('ready', doBatch)

setInterval(function () {
  console.log(queued, inserted, process.memoryUsage())
}, 5000)

function insertBatch(id, thisBatch) {
  queued++
  //console.log('queueing batch ' + id);
  db.batch(thisBatch, function (err) {
    queued--
    inserted++
    //console.log('inserted batch ' + id);
    if (err) return console.log('Ooops!', err);
    return;
  });
}

for convenience: link back to issue Level/levelup#171