Add initial news reader example (#4348)

doc/source/example-newsreader.rst

@@ -0,0 +1,29 @@
+News Reader
+===========
+
+This document shows how to implement a simple news reader using Ray. The reader
+consists of a simple Vue.js `frontend`_ and a backend consisting of a Flask
+server and a Ray actor. View the `code for this example`_.
+
+To run this example, you will need to install NPM and a few python dependencies.
+
+.. code-block:: bash
+
+  pip install atoma
+  pip install flask
+
+
+To use this example you need to
+
+* In the ``ray/examples/newsreader`` directory, start the server with
+  ``python server.py``.
+* Clone the client code with ``git clone https://github.com/ray-project/qreader``
+* Start the client with ``cd qreader;  npm install; npm run dev``
+* You can now add a channel by clicking "Add channel" and for example pasting
+  ``http://news.ycombinator.com/rss`` into the field.
+* Star some of the articles and dump the database by running
+  ``sqlite3 newsreader.db`` in a terminal in the ``ray/examples/newsreader``
+  directory and entering ``SELECT * FROM news;``.
+
+.. _`frontend`: https://github.com/saqueib/qreader
+.. _`code for this example`: https://github.com/ray-project/ray/tree/master/examples/newsreader

doc/source/index.rst

@@ -115,6 +115,7 @@ Ray comes with libraries that accelerate deep learning and reinforcement learnin
    example-rl-pong.rst
    example-policy-gradient.rst
    example-parameter-server.rst
+   example-newsreader.rst
    example-resnet.rst
    example-a3c.rst
    example-lbfgs.rst

examples/newsreader/server.py

@@ -0,0 +1,85 @@
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+import atoma
+from flask import Flask, jsonify, request
+from flask_cors import CORS
+import requests
+import sqlite3
+
+import ray
+
+
+@ray.remote
+class NewsServer(object):
+
+    def __init__(self):
+        self.conn = sqlite3.connect("newsreader.db")
+        c = self.conn.cursor()
+        c.execute("""CREATE TABLE IF NOT EXISTS news
+                     (title text, link text,
+                     description text, published timestamp,
+                     feed url, liked bool)""")
+        self.conn.commit()
+
+    def retrieve_feed(self, url):
+        response = requests.get(url)
+        feed = atoma.parse_rss_bytes(response.content)
+        items = []
+        c = self.conn.cursor()
+        for item in feed.items:
+            items.append({"title": item.title,
+                          "link": item.link,
+                          "description": item.description,
+                          "description_text": item.description,
+                          "pubDate": str(item.pub_date)})
+            c.execute("""INSERT INTO news (title, link, description,
+                         published, feed, liked) values
+                         (?, ?, ?, ?, ?, ?)""", (
+                         item.title, item.link, item.description,
+                         item.pub_date, feed.link, False))
+        self.conn.commit()
+
+        return {"channel": {"title": feed.title,
+                            "link": feed.link,
+                            "url": feed.link},
+                "items": items}
+
+    def like_item(self, url, is_faved):
+        c = self.conn.cursor()
+        if is_faved:
+            c.execute("UPDATE news SET liked = 1 WHERE link = ?", (url,))
+        else:
+            c.execute("UPDATE news SET liked = 0 WHERE link = ?", (url,))
+        self.conn.commit()
+
+
+# instantiate the app
+app = Flask(__name__)
+app.config.from_object(__name__)
+
+# enable CORS
+CORS(app)
+
+
+@app.route("/api", methods=["POST"])
+def dispatcher():
+    req = request.get_json()
+    method_name = req["method_name"]
+    method_args = req["method_args"]
+    if hasattr(dispatcher.server, method_name):
+        method = getattr(dispatcher.server, method_name)
+        # Doing a blocking ray.get right after submitting the task
+        # might be bad for performance if the task is expensive.
+        result = ray.get(method.remote(*method_args))
+        return jsonify(result)
+    else:
+        return jsonify(
+            {"error": "method_name '" + method_name + "' not found"})
+
+
+if __name__ == "__main__":
+    ray.init(num_cpus=2)
+    dispatcher.server = NewsServer.remote()
+    app.run()