Web Backend Engineering

Contributors: Mandy He and RJ Kretscmar.

The information in this file will reflect different assumptions, instructions, and other meta-data of our project.

Design Decisions:

* We will be using vanilla Flask for the web framework.
* We will be using ScyllaDB, A Cassandra type of wide columndatabase.
* We will be using a Linux-like directory structure for our project. (See Project Structure for more information)

Project Structure:

* etc/ will contain all of the configuration files.
* bin/ will contain all of the scripts to aid in the project.
* app/ will contain all of the python code to our microservices.
  -xspf.py
  -users.py
  -tracks.py
  -playlists.py
  -desc.py
* lib/ will contain various libraries (or libary-type files).
* var/ will contain various changing files; we keeps the project 2 Sqlite3 database files there.
* media/ will contain the individual music files and the album art.
* docs/ contains screenshots for memcached before/afteer and microservices operations screenshots.

Database Structure:

The keyspace of "xspf" has 2 Cassandra tables as follows. Visit ../docs/cqlsh-creating-tables-and-verify-tables.txt to view two tables structures.

• users_by_username
• playlists_by_playlist_id_and_username

Environment

- Flask
- foreman
- dot-env
- Jinja2
- requests
- memcached and pymemcache
- Docker
- ScyllaDB
- Cassandra
- DataStax's Python Driver for Apache Canssandra
- MinIO Object Storage
- Kong API Gateway

Steps to generate a XSPF playlist:

1. start the scylla database from any directory, then verify it do start:
```
$docker start scylla
$docker exec -it scylla nodetool status
```
2. Start the memcache server running on local host with port number of 11211
```
sudo service memcached start
```
record the memcache statistics before and after the xspf service uses memcache.
```
$ telnet localhost 11211
  stats
```
3. Run the 4 backend microservices and the xspf playlist service, migrate to the bin/ directory, run the Procfile through foreman of "foreman start", the 4 microservices will run three instances each all on separate ports. To get the xspf playlist xml output, visit:
http://127.0.0.1:5400/playlist/1
  ```
  foreman start
  ```
  ports assignments are:
  ```
  21:31:46 users.1     |  * Running on http://127.0.0.1:5200/
  21:31:46 tracks.1    |  * Running on http://127.0.0.1:5000/
  21:31:46 playlists.1 |  * Running on http://127.0.0.1:5100/
  21:31:46 desc.1      |  * Running on http://127.0.0.1:5300/
  ```

4. Run xspf.py from ./app/xspf.py as follows. The service is running on http://127.0.0.1:5400/playlist/1. The output file is xspf-playlist_1.xml.
```
python3 xspf.py
```
5. Media data has been saved to MiNIO remote server. To start MINIO: go to /Minio folder with executable file and sub-folders, then to go terminal, and run minio as the following:
```
   ./minio server start object storage server
```
  Minio server will run at http://127.0.0.1:9000, and mp3 files are stored in the folder of /tracks
  Use the following credentials to access the minio server bucket:
  ```
     -AccessKey: 54AUW87M5DUD0B9UBR1X
     -SecretKey: s28mRRzRRhJcJv84MxzEyNaVt2nTwejSkWuGoBr8
  ```

Query Screenshots

There are some saved screenshots during the CRUD process from each microservices' http endpoints. They are under ../docs/

• users
• playlists
• tracks
• desc
• memcached
• xspf playlists xml

xspf Microservice:

xspf.py: To generate a xspf playlist, the script is located in /app/xspf.py. Go to /app folder, from terminal, run "python xspf.py", it will run in local host. run this endpoint: http://127.0.0.1:5400/playlist/1. The sample playlist xml file is xspf-playlist.xml.

Tracks Microservice:

tracks.py: To learn more about the Tracks API and how to use it, please refer to the root page of the microservice after starting it up. It will have the most up-to-date information on all the new features and a general guide on how to use it.

Playlist Microservice:

playlists.py: To learn more about the Playlist API and how to use it, please refer to the root page of the microservice after starting it up. It will have the most up-to-date information on all the new features and a general guide on how to use it.

Users Microservice:

users.py: python scripts to crate datatable, table, create new user, update user password, delete user, view user profile

Description Microservices

desc.py: python script to set and retrieve a user's description of a track.