log-buffer

Buffer calls to console.log, console.warn, etc. for high performance logging

Description

Calls to console.log, console.error, etc. are synchronous, and as such, will block the event loop while the data is being written to a file, terminal, socket, pipe, etc.

This module provides a seamless, drop-in buffer for all calls to these functions, and flushes them when the buffers exceed a certain size (8k by default).

See Known Issues for timing concerns with this module.

Example

require('log-buffer');
console.log('Hello'); // buffered
console.log('world'); // buffered
// flushed at exit or 8k of data

Even though there are 2 calls to console.log, this example only writes to a file descriptor once.

Customization

You can specify an alternative buffer size to use for automatic flushing like this:

require('log-buffer')(4096); // buffer will flush at 4k

This module also exposes the flush function used to flush all buffers, so if you would like you can manually invoke a flush. Also, you can specify an interval to automatically flush all buffers so logs don't get held in memory indefinitely.

var logbuffer = require('log-buffer');
setInteval(function() {
  logbuffer.flush();
}, 5000); // flush every 5 seconds

Benchmark

Counting to a million, logging each iteration, without buffering

$ time node examples/count.js > /dev/null

real    0m4.658s
user    0m4.406s
sys     0m0.337s

Counting to a million, logging each iteration, with buffering (8k)

$ time node examples/bcount.js > /dev/null

real    0m1.903s
user    0m1.920s
sys     0m0.027s

A 2.4x increase

Install

npm install log-buffer

Tests

npm test

Known Issues

• All buffers are flushed when flush is called (whether automatically or manually). Because of this, calls to different console family functions may return out of order.

Example:

require('log-buffer');
console.log(1);
console.error(2);
console.log(3);

yields

1
3
2

1 and 3 are both written to stdout and 2 is written stderr. The priority order in flushing is ['warn', 'log', 'error', 'info']

License

MIT Licensed