Node.js Web Framework benchmarking tool

npm install flod
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A systematic toolchain for benchmarking and comparing Node.js web server frameworks. flod enables developers to compare the performance of different versions of their frameworks and to other frameworks.

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Install using npm:

npm install -g flod

OR by cloning this repository:

git clone https://github.com/spumko/flod.git

Quick Start

If installed globally with -g, the fastest way to try out flod is to run a local benchmark (this currently requires the user to clone the repository to access the files). Here are instructions on how to run a local benchmark on hapi version 1.0.0:

cd examples/hapi@1.0.0
npm install
flod index.js

The above command will run the hapi version 1.0.0 example server and benchmark 100 GET / requests per second for a total of 1000 requests.

To see all of the available options and settings, run:

flod -h


Flod is designed to benchmark web servers. Flod will flood the webserver with a optionally specified number of concurrent requests and measure the latencies of each request until the specific total number of requests has been made.

Benchmarking JavaScript web servers is where flod really shines. With the use of the flod.Probe, flod is able to track useful metrics like memory usage and cpu load during the course of the benchmark.

Tip: If given a large enough range of concurrency levels, Flod can pinpoint the number of requests per second (RPS) your server can handle. Any RPS levels that are rejected by the server will be noted with an 'n/a' under latency. Make use of the -t timeout flag in order to fully understand the behavior of your server under various levels of concurrency.

Local Testing

To run a local JavaScript server benchmark, flod has the following basic syntax:

flod [options] <filename>

where filename is a JavaScript file that starts a web server.

Remote Testing

To perform a benchmark on a remote host, flod has the following basic syntax:

flod [options] <URL>

where URL is a fully formed URL (with protocol http/https, hostname, path (and perhaps a port if not 80)).

If the remote host is running flod.Probe, additional statistics will be printed.


Understanding the Output

Example 1.

$ flod -t 5000 -n 2000 -c 100..500 http://localhost:8000/
This is Flod, version 0.2.0
Copyright 2013 Walmart, http://github.com/spumko/flod

Benchmarking (hold on)...

Server                  Requests/sec  Latency           Memory  Load
----------------------  ------------  ----------------  ------  ----
http://localhost:8000/  100           601.74 ± 319.92               
http://localhost:8000/  200           1280.93 ± 709.25              
http://localhost:8000/  300           n/a                           
http://localhost:8000/  400           n/a                           
http://localhost:8000/  500           n/a

The above example runs five benchmarks from 100 to 500 requests per second on a server running on localhost on port 8000. The acceptable timeout has been set to 5 seconds. The table shows latencies only because this server is not embedded with Flod.Probe.

The latencies are given in the format: average ± standard deviation. See Standard Deviation for more information. If Memory and Load were enabled, they would be displayed in the same format.

We can conclude that this server maxes out at approximately 200 requests per second with a response time centered around ~1 seconds but likely exceeds 3 seconds (two standard deviations)..

Useful Flags and Options

  • -n MAX_REQS - the maximum number of requests to perform at each concurrency level. Defaults to 1000. Must be an integer.
  • -c c1..c2 - the concurrency levels in range notation. Flod will bench c1 requests per second and increment by -i until c2 requests per second. Defaults to 100..100. Must be integers.
  • -i INCREMENT - the increment amount used for concurrency level range. Defaults to 100. Must be an integer.
  • -t TIMEOUT - the time in milliseconds to wait for a request to complete before considering it lost. Defaults to 1500. Must be an integer.
  • -m METHOD - the HTTP method to use for the flood of requests. Defaults to GET. Must be a valid HTTP method string.
  • -u URI - the HTTP path to use for the flood of requests. Defaults to /. Must be a URIEncoded string.
  • -o FILENAME - the filename to output all the benchmark data (written as JSON). Default disabled.
  • --force - forces flod to overwrite -o FILENAME if it already exists


  • flod -c 100..700 -n 10000 index.js - will benchmark index.js in batches of 100, 200, 300, 400, 500, 600, and 700 GET / requests per second. Each batch will run for 10000 requests.
  • flod -p upload.json -m POST -c 100..200 -n 1000 index.js - will benchmark index.js in batches of 100 and 200 requests per second. Each time it will POST to / with the contents of upload.json with the correct headers and mimetypes.

Daemon Mode

To perform a benchmark of a JavaScript server on a different, remote computer, flod can daemonize a server file with the flag --daemon. This allows flod to perform a remote test as shown in Remote Testing.

flod --daemon some_file.js

By default, the server will expose http://localhost:3000.



To provide additional metrics during a JavaScript server benchmark, use the flod Probe.

From within the JS server file, include the following snippet:

var Flod = require('flod');
var probe = new Flod.Probe(server, {server: SERVER, version: VERSION});

where SERVER could be hapi and VERSION could be 1.0.0 - change these to fit your needs.

Probe API

Probe(server, options)
// Interface Example
var Flod = require('flod');
var server = new Hapi.Server(+process.env.port || 3000);
var probe = new Flod.Probe(server, {server: 'hapi', version: '1.8.0'});
  • server - (required) variable pointing to your webserver. Acceptable webservers currently include Hapi, Express, and Restify. See the examples for more information regarding usage.
  • options - (required) the Probe options
    • server - (required) the name of the webserver (hapi, express, restify). Must be a string.
    • version - (required) the version of the webserver being employed. Must be a Semantic Versioning string.
    • manualStart - if set to true, flod will wait for a probe.ready() function call before starting the benchmark. Defaults to null.
// Interface Example
var probe = new Flod.Probe(server, {server: 'hapi', version: '1.8.0'});

The ready function is used in conjunction with the options.manualStart flag. By default, flod will start benchmarking as soon as the server has started listening on a port. By utilizing manual start mode, you can have your server boot up and do some prefetching or preprocessing before the benchmark is executed.

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