I’m working on an Phoenix application which does external requests. My first approach was using HTTPotion 2.2.2, which looked more stable, with only 1 opened issue on Github. After doing some benchmarks, I got surprised how different the results are.

The application I used as example works like a proxy. If I do a POST request to my application http://my_phoenix_app.com/1, the application does a request to http://requestb.in/1 in another process using spawn and saves the result, including the request duration, headers and body on database.

I used ab (Apache Benchmark) to test the requests and the command I used was:

ab -p json_file.txt -T 'application/json' -c CONCURRENCY -n REQUESTS https://myapp.herokuapp.com/api/webhooks/1

Where json_file.txt content is {"first_name":"Jony"} and CONCURRENCY and REQUESTS have the values below.

HTTPotion 2.2.2

# requests concurrency failed requests/second
1 2000 400 1225 109.46
2 800 150 429 108.48
3 800 80 385 85.14
4 800 40 223 56.72
  • 100% of HTTPotion failures were exceptions (HTTPotion.HTTPError) retry_later, apparently thrown by ibrowse, and it is harder to handle.

Then I changed to HTTPoison and got a much better result.

HTTPoison 0.8.2

# requests concurrency failed requests/second
1 2000 400 6 124.66
  • The 6 errors were {:error, %HTTPoison.Error{id: nil, reason: :closed}}.

I repeated the process many times with both libraries and didn’t get expressive differences.

It is only a hobby application hosted on heroku free.

I received a feedback on Slack group that I can change HTTPotion default settings to improve number of connections, max queue per connection, etc. I will check it and add the numbers here.


I changed ibrowse configuration for HTTPotion and the result is impressive!

response = HTTPotion.post "http://example.com", [
  ibrowse: [max_sessions: 100, max_pipeline_size: 10]]
# requests concurrency failed requests/second
1 4000 4000 18 67.03
2 4000 3500 7 63.80
3 4000 2500 5 77.54
4 4000 1500 8 72.53
5 4000 1000 4 71.98
6 3000 600 4 69.17
7 2000 400 6 62.95

Since I got a much better result using this configuration, I used the same values for requests and concurrency as in #1 using HTTPoison, and the results are similar.

Most of the failures are related to SSL handshake failed (5) which looks like is something internal to heroku.

Now I am curious to compare heroku dynos 2x vs 1x and improvements on database. I may do it in a future post.