add delay in hasher and rng

dockercoins/hasher/hasher.rb

@@ -6,6 +6,8 @@ set :bind, '0.0.0.0'
 set :port, 80
 
 post '/' do
+    # Simulate a bit of delay
+    sleep 0.1
     content_type 'text/plain'
     "#{Digest::SHA2.new().update(request.body.read)}"
 end

dockercoins/rng/rng.py

@@ -1,6 +1,7 @@
 from flask import Flask, Response
 import os
 import socket
+import time
 
 app = Flask(__name__)
 
@@ -19,6 +20,8 @@ def index():
 
 @app.route("/<int:how_many_bytes>")
 def rng(how_many_bytes):
+    # Simulate a little bit of delay
+    time.sleep(0.1)
     return Response(
         os.read(urandom, how_many_bytes),
         content_type="application/octet-stream")

www/htdocs/index.html

@@ -361,7 +361,6 @@ Let's repeat the tests with smaller data.
 .exercise[
 
 - Open http://[yourVMaddr]:8000/ (from a browser)
-- Click on the (few) available buttons
 
 ]
 
@@ -430,6 +429,16 @@ We have available resources.
 - Docker Compose supports scaling
 - It doesn't deal with load balancing
 - For services that *do not* accept connections, that's OK
+- Let's scale `worker` and see what happens!
+
+.exercise[
+
+- Run `docker-compose scale worker=4`
+
+- See the impact on CPU load (with top/htop),
+  <br/>and on compute speed (with web UI)
+
+]
 
 # Scaling HTTP on a single node