Google Cloud Autoscaler demo

This application is a very simple web server, which responds to get requests by consuming some CPU cycles.
It is part of a demo of the Google Compute Engine Autoscaler.
Link to the Autoscaler tutorial video which refers to this application will follow.

compute/autoscaler/demo/frontend.py

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+# Copyright 2015, Google, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+"""A simple web server which responds to HTTP GET requests by consuming CPU.
+This binary runs in a GCE VM. It serves HTTP requests on port 80. Every request
+with path '/service' consumes 1 core-second of CPU time, with the timeout of
+5 (walltime) seconds. The purpose of this application is to demonstrate how
+Google Compute Engine Autoscaler can scale a web frontend server based on CPU
+utilization.
+The original version of this file is available here:
+https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/compute/
+    autoscaler/demo/tests/test_frontend.py
+"""
+
+import BaseHTTPServer
+from multiprocessing import Process
+import os
+import SocketServer
+import sys
+import time
+
+REQUEST_CPUTIME_SEC = 1.0
+REQUEST_TIMEOUT_SEC = 5.0
+
+
+class CpuBurner(object):
+    def get_walltime(self):
+        return time.time()
+
+    def get_user_cputime(self):
+        return os.times()[0]
+
+    def busy_wait(self):
+        for _ in xrange(100000):
+            pass
+
+    def burn_cpu(self):
+        """Consume REQUEST_CPUTIME_SEC core seconds.
+        This method consumes REQUEST_CPUTIME_SEC core seconds. If unable to
+        complete within REQUEST_TIMEOUT_SEC walltime seconds, it times out and
+        terminates the process.
+        """
+        start_walltime_sec = self.get_walltime()
+        start_cputime_sec = self.get_user_cputime()
+        while (self.get_user_cputime() <
+               start_cputime_sec + REQUEST_CPUTIME_SEC):
+            self.busy_wait()
+            if (self.get_walltime() >
+                    start_walltime_sec + REQUEST_TIMEOUT_SEC):
+                sys.exit(1)
+
+    def handle_http_request(self):
+        """Process a request to consume CPU and produce an HTTP response."""
+        start_time = self.get_walltime()
+        p = Process(target=self.burn_cpu)  # Run in a separate process.
+        p.start()
+        # Force kill after timeout + 1 sec.
+        p.join(timeout=REQUEST_TIMEOUT_SEC + 1)
+        if p.is_alive():
+            p.terminate()
+        if p.exitcode != 0:
+            return (500, "Request failed\n")
+        else:
+            end_time = self.get_walltime()
+            response = "Request took %.2f walltime seconds\n" % (
+                end_time - start_time)
+            return (200, response)
+
+
+class DemoRequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
+    """Request handler for Demo http server."""
+
+    def do_GET(self):
+        """Handle an HTTP GET request."""
+        mapping = {
+            "/": lambda: (200, "OK"),  # Return HTTP 200 response.
+            "/service": CpuBurner().handle_http_request,
+        }
+        if self.path not in mapping:
+            self.send_response(404)
+            self.end_headers()
+            return
+        (code, response) = mapping[self.path]()
+        self.send_response(code)
+        self.end_headers()
+        self.wfile.write(response)
+        self.wfile.close()
+
+
+class DemoHttpServer(SocketServer.ThreadingMixIn,
+                     BaseHTTPServer.HTTPServer):
+    pass
+
+
+if __name__ == "__main__":
+    httpd = DemoHttpServer(("", 80), DemoRequestHandler)
+    httpd.serve_forever()

compute/autoscaler/demo/tests/test_frontend.py

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+# Copyright 2015, Google, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import unittest
+
+from compute.autoscaler.demo import frontend
+
+
+class FakeTime(object):
+    """Fake implementations of GetUserCpuTime, GetUserCpuTime and BusyWait.
+    Each call to BusyWait advances both the cpu and the wall clocks by fixed
+    intervals (cpu_time_step and wall_time_step, respectively). This can be
+    used to simulate arbitrary fraction of CPU time available to the process.
+    """
+    def __init__(self, cpu_time_step=1.0, wall_time_step=1.0):
+        self.cpu_time = 0.0
+        self.wall_time = 0.0
+        self.cpu_time_step = cpu_time_step
+        self.wall_time_step = wall_time_step
+
+    def get_walltime(self):
+        return self.wall_time
+
+    def get_user_cputime(self):
+        return self.cpu_time
+
+    def busy_wait(self):
+        self.wall_time += self.wall_time_step
+        self.cpu_time += self.cpu_time_step
+
+
+class TestHandlers(unittest.TestCase):
+    def setUp(self):
+        self.fake_time = FakeTime()
+        self.cpu_burner = frontend.CpuBurner()
+        self.cpu_burner.get_user_cputime = self.fake_time.get_user_cputime
+        self.cpu_burner.get_walltime = self.fake_time.get_walltime
+        self.cpu_burner.busy_wait = self.fake_time.busy_wait
+
+    # In this test scenario CPU time advances at 25% of the wall time speed.
+    # Given the request requires 1 CPU core second, we expect it to finish
+    # within the timeout (5 seconds) and return success.
+    def test_ok_response(self):
+        self.fake_time.cpu_time_step = 0.25
+        (code, _) = self.cpu_burner.handle_http_request()
+        self.assertEqual(200, code)
+
+    # In this test scenario CPU time advances at 15% of the wall time speed.
+    # Given the request requires 1 CPU core second, we expect it to timeout
+    # after 5 simulated wall time seconds and return error 500.
+    def test_timeout(self):
+        self.fake_time.cpu_time_step = 0.15
+        (code, _) = self.cpu_burner.handle_http_request()
+        self.assertEqual(500, code)
+
+
+if __name__ == '__main__':
+    unittest.main()