Logging to zlib log stream with periodic flushing.

gistfile1.txt

var assert = require('assert');
var zlib = require('zlib');
var gzip = zlib.createGzip();
var fs = require('fs');
var FILENAME = 'log.txt.gz';
var out = fs.createWriteStream(FILENAME);

gzip.pipe(out);

function debug(msg) {
  console.log((new Date()).toISOString() + ' DEBUG> ' + msg);
}

var needs_flush = false;
var is_flushing = false;
var FLUSH_DELAY = 2000;
function doFlush() {
  needs_flush = false;
  debug('caling flush');
  gzip.flush(function() {
    debug('flush finished');
    is_flushing = false;
    if (needs_flush) {
      is_flushing = true;
      setTimeout(doFlush, FLUSH_DELAY);
    }
  });
}

function writeLine(data) {
  debug('calling write');
  gzip.write((new Date()).toISOString() + ' ' + data + '\n', function() {
    debug('write finished');
  });
  needs_flush = true;
  if (!is_flushing) {
    is_flushing = true;
    setTimeout(doFlush, FLUSH_DELAY);
  }
}

setInterval(function() {
  // write some data
  writeLine('A line of data');
}, 500);

var last_size = 0;
setInterval(function() {
  fs.stat('log.txt.gz', function(err, stats) {
    console.log('File size at ' + stats.size);
    assert(stats.size > last_size);
    last_size = stats.size;
  });
}, 5000);

This works on older versions of node (0.6.21), but throws an internal assertion on node 0.9.21