How to append to a file in Node?

Question

I am trying to append a string to a log file. However writeFile will erase the content each time before writing the string.

fs.writeFile(\'log.txt\'         


        

Answer 1

My approach is rather special. I basically use the WriteStream solution but without actually 'closing' the fd by using stream.end(). Instead I use cork/uncork. This got the benefit of low RAM usage (if that matters to anyone) and I believe it's more safe to use for logging/recording (my original use case).

Following is a pretty simple example. Notice I just added a pseudo for loop for showcase -- in production code I am waiting for websocket messages.

var stream = fs.createWriteStream("log.txt", {flags:'a'});
for(true) {
  stream.cork();
  stream.write("some content to log");
  process.nextTick(() => stream.uncork());
}

uncork will flush the data to the file in the next tick.

In my scenario there are peaks of up to ~200 writes per second in various sizes. During night time however only a handful writes per minute are needed. The code is working super reliable even during peak times.