Use Flask for Python environment

Flask gives us easy routing support, and simple interface for getting
at request data.

environments/python3/Dockerfile

@@ -1,3 +1,12 @@
-FROM python:3-onbuild
-CMD [ "python", "./server.py" ]
-EXPOSE 8888
+FROM ubuntu:16.04
+
+RUN apt-get update -y
+RUN apt-get install -y python3 python3-pip python3-dev build-essential
+
+COPY . /app
+WORKDIR /app
+RUN pip3 install -r requirements.txt
+
+ENTRYPOINT ["python3"]
+CMD ["server.py"]
+

environments/python3/requirements.txt

@@ -0,0 +1 @@
+Flask===0.11.1

environments/python3/server.py

@@ -1,47 +1,32 @@
 #!/usr/bin/env python
 
 import imp
-from http.server import BaseHTTPRequestHandler, HTTPServer
+
+from flask import Flask
+from flask import request
+from flask import abort
+
+app = Flask(__name__)
 
 codepath = '/userfunc/user'
+
 userfunc = None
 
+@app.route('/specialize', methods=['POST'])
+def load():
+    global userfunc
+    userfunc = (imp.load_source('user', codepath)).main
+    return ""
+
+@app.route('/', methods=['GET', 'POST', 'PUT', 'HEAD', 'OPTIONS', 'DELETE'])
+def f():
+    if userfunc == None:
+        print("Generic container: no requests supported")
+        abort(500)
+    return userfunc()    
+
 #
-# Request context that's passed to user functions
+# TODO: this starts the built-in server, which isn't the most
+# efficient.  We should use something better.
 #
-class Context:
-    def __init__(self, handler):
-        self.handler = handler
-
-class testHTTPServer_RequestHandler(BaseHTTPRequestHandler):
-    def do_POST(self):
-        global userfunc
-        userfunc = (imp.load_source('user', codepath)).main
-        self.send_response(200)
-        self.end_headers()
-        self.wfile.write(bytes("ok\n", "utf8"))
-        return
-
-    # GET
-    def do_GET(self):
-        global userfunc
-        try:
-            print("GET request")
-            ctx = Context(self)
-            message = userfunc(ctx)
-            self.send_response(200)
-            self.end_headers()
-            self.wfile.write(bytes(message, "utf8"))
-            return
-        except:
-            self.send_response(500)
-            self.end_headers()
-
-def run():
-    print('starting server...')
-    server_address = ('0.0.0.0', 8888)
-    httpd = HTTPServer(server_address, testHTTPServer_RequestHandler)
-    httpd.serve_forever()
-
-
-run()
+app.run(host='0.0.0.0', port='8888')

examples/python/hello.py

@@ -1,2 +1,2 @@
-def main(context):
-    return "Hello, world!"
+def main():
+    return "Hello, world!\n"