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Commit fd3ab2f

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djmailhotandrewsg
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Demo webserver for managed instances tutorial (GoogleCloudPlatform#2077)
* Add compute/managed-instances/demo/webserver.py as tutorial sample code * Update managed-instances demo webserver to run with Python3 * Lint fixes for managed-instances demo webserver * Python3 fixes for managed-instances demo webserver * Update managed-instances demo webserver to use Flask * Add copywrite header * managed instances demo Flask app refactor long lines * managed instances demo app actually uses PORT_NUMBER global * managed instances demo app fix gethostname reference * Add comments to managed instances demo app
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‎compute/managed-instances/demo/app.py

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# Copyright 2019, Google, Inc.
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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Flask app to be used as an interactive demonstration of autohealing.
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Exposes a simple UI showing basic server stats and a toggle button to
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simulate a healthy/unhealthy server status for any attached health check.
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Attached health checks should query the '/health' path.
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"""
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from flask import Flask, make_response, render_template
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from re import sub
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from requests import get
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from socket import gethostname
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PORT_NUMBER = 80
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app = Flask(__name__)
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healthy = True
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@app.route('/')
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def index():
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"""Returns the demo UI."""
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global healthy
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return render_template('index.html',
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hostname=gethostname(),
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zone=_get_zone(),
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template=_get_template(),
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healthy=healthy)
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@app.route('/health')
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def health():
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"""Returns the simulated 'healthy'/'unhealthy' status of the server.
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Returns:
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HTTP status 200 if 'healthy', HTTP status 500 if 'unhealthy'
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"""
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global healthy
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template = render_template('health.html', healthy=healthy)
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return make_response(template, 200 if healthy else 500)
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@app.route('/makeHealthy')
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def make_healthy():
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"""Sets the server to simulate a 'healthy' status."""
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global healthy
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healthy = True
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template = render_template('index.html',
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hostname=gethostname(),
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zone=_get_zone(),
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template=_get_template(),
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healthy=True)
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response = make_response(template, 302)
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response.headers['Location'] = '/'
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return response
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@app.route('/makeUnhealthy')
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def make_unhealthy():
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"""Sets the server to simulate an 'unhealthy' status."""
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global healthy
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healthy = False
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template = render_template('index.html',
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hostname=gethostname(),
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zone=_get_zone(),
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template=_get_template(),
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healthy=False)
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response = make_response(template, 302)
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response.headers['Location'] = '/'
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return response
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def _get_zone():
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"""Gets the GCE zone of this instance.
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Returns:
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str: The name of the zone if the zone was successfully determined.
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Empty string otherwise.
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"""
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r = get('http://metadata.google.internal/'
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'computeMetadata/v1/instance/zone',
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headers={'Metadata-Flavor': 'Google'})
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if r.status_code == 200:
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return sub(r'.+zones/(.+)', r'\1', r.text)
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else:
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return ''
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def _get_template():
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"""Gets the GCE instance template of this instance.
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Returns:
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str: The name of the template if the template was successfully
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determined and this instance was built using an instance template.
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Empty string otherwise.
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"""
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r = get('http://metadata.google.internal/'
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'computeMetadata/v1/instance/attributes/instance-template',
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headers={'Metadata-Flavor': 'Google'})
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if r.status_code == 200:
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return sub(r'.+instanceTemplates/(.+)', r'\1', r.text)
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else:
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return ''
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if __name__ == "__main__":
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app.run(debug=False, port=PORT_NUMBER)

‎compute/managed-instances/demo/requirements.txt

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flask==1.0

‎compute/managed-instances/demo/templates/health.html

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<div style="font-family: verdana; font-weight: bold; font-size: 40px">
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{% if healthy %}
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<span>HTTP/1.0 200 OK</span>
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{% else %}
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<span>HTTP/1.0 500 Internal Server Error</span>
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{% endif %}
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</div>

‎compute/managed-instances/demo/templates/index.html

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<html>
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<head>
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<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0-rc.2/css/materialize.min.css">
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<script src="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0-rc.2/js/materialize.min.js"></script>
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</head>
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<body>
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<table class="striped">
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<colgroup>
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<col width="200">
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</colgroup>
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<tbody>
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<tr>
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<td>Hostname:</td>
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<td><b>{{ hostname }}</b></td>
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</tr>
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<tr>
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<td>Zone:</td>
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<td><b>{{ zone }}</b></td>
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</tr>
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<tr>
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<td>Template:</td>
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<td><b>{{ template }}</b></td>
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</tr>
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<tr>
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<td>Health status:</td>
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{% if healthy %}
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<td><span class="btn green">healthy</span></td>
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{% else %}
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<td><span class="btn red">unhealthy</span></td>
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{% endif %}
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</tr>
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<tr>
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<td>Actions:</td>
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<td>
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{% if healthy %}
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<a class="btn blue" href="/makeUnhealthy">Make unhealthy</a>
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{% else %}
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<a class="btn blue" href="/makeHealthy">Make healthy</a>
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{% endif %}
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<a class="btn blue" href="/health">Check health</a>
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</td>
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</tr>
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</tbody>
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</table>
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</body>
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</html>

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