bluelens

bluelens

bluelens makes music recommendations to its users based on the users' social activities.

Table of Content

• Introduction
• Getting Started
• API Design
• Security
• Data Model
• Development
• ACI Image
• License

Introduction

Our fictional client has asked us to build a music recommendation system for his customers. The system shall make music recommendations based on a user's listening history and who they follow.

The following is the list of rules to determine the recommendations:

• History of all the music a user has heard before.
• Followees of user. And maybe even followees of the followees.
• Preferences to be given to songs that are new to the user.

The objectives of this project is to experiment with goa. In particular, we will be using goa to:

• Auto-generate server and client code,
• Define custom media types,
• Secure API endpoints using Basic Authentication and API key,
• Generate API swagger documents,
• Logging HTTP requests,
• Build websocket endpoints,
• Timeout middleware with context,
• Encrypt data transmission over HTTPS.

The acbuild is used to build an ACI container image of blued, which can be run with rkt. Refer to the ACI Image section.

Getting Started

The following is the list of prerequisites to build this project:

1. Install glide
2. Set the ${PACKAGE_ROOT} in the Makefile to match your project package.
3. Install goagen using this command: make goagen
4. Create a self-signed certificate. This content is ignored by git: make tls

To build the server and client, use the all target of the Makefile:

$ make

Run the blued binary to start the server:

$ sudo ./blued -apikey=<apikey> -user=<user> -password=<password> -private tls/localhost.key -cert tls/localhost.crt
2017/03/28 11:14:13 [INFO] mount ctrl=Music action=Create route=POST /bluelens/music security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=Music action=List route=GET /bluelens/music security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=Music action=Show route=GET /bluelens/music/:id security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=Recommendations action=Recommend route=GET /bluelens/recommendations/:userID/:limit security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=Swagger files=cmd/blued/swagger/swagger.json route=GET /bluelens/swagger.json
2017/03/28 11:14:13 [INFO] mount ctrl=Swagger files=cmd/blued/swagger/swagger.yaml route=GET /bluelens/swagger.yaml
2017/03/28 11:14:13 [INFO] mount ctrl=User action=Create route=POST /bluelens/user security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=User action=Follow route=POST /bluelens/user/:id/follows/:followeeID security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=User action=List route=GET /bluelens/user security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=User action=Listen route=POST /bluelens/user/:id/listen/:musicID security=APIKey
2017/03/28 11:14:13 [INFO] mount ctrl=User action=Show route=GET /bluelens/user/:id security=APIKey
2017/03/28 11:14:13 [INFO] listen transport=https addr=:443

Note that the server is started with sudo in order to bind the process to port 443. The Swagger docs for the endpoints can be found in https://localhost/bluelens/swagger.json and https://localhost/bluelens/swagger.yaml

blued supports the following flags:

$ blued -h
  -apikey string
        Key used for API key authentication
  -cert string
        Path to the TLS cert file (default "tls/cert.pem")
  -followees string
        Path to read user's followees data from (default "etc/followees.json")
  -history string
        Path to read user's history data from (default "etc/history.json")
  -music string
        Path to read music data from (default "etc/music.json")
  -password string
        Password used for HTTP Basic Authentication
  -private string
        Path to the TLS private key file (default "tls/key.pem")
  -timeout duration
        Request timeout in seconds. Default to 10s. (default 10s)
  -user string
        Username used for HTTP Basic Authentication

In goa 1.1.0, the auto-generated client doesn't work with TLS.

To interact with the blued server, use curl:

# view all music resources
$ curl --cacert tls/localhost.crt -H "Authorization: Bearer <apikey>" https://localhost/bluelens/music

# view all user resources
$ curl --cacert tls/localhost.crt -H "Authorization: Bearer <apikey>" https://localhost/bluelens/user

# make 10 recommendations for user-01
$ curl --cacert tls/localhost.crt -H "Authorization: Bearer <apikey>" https://localhost/bluelens/recommendations/user-01/10

API Design

The design/design.go contains all the endpoints specifications. The Swagger doc is accessible at https://localhost/bluelens/swagger.json and https://localhost/bluelens/swagger.yaml

Security

All request and responses messages are transmitted over HTTPS. The make tls target can be used to generate a self-signed certificate and private key. To change the transporatation scheme to HTTP, update the design/design.go specification, and update the server's service (in cmd/blued/main.go) to use the Golang http.ListenAndServer() API.

In addition, the endpoints authorization scheme are detailed below:

Data Model

This system is constrained by the following pre-defined data model:

• music: Has an ID and a list of tags (see etc/music.json),
• user: Has an ID, follows N other users (see etc/follows.json), has heard Y musics in the past (see etc/listen.json).

Development

This project uses glide to manage its dependencies, and goa to generate the server and client code.

Use the Makefile all target to install the dependencies, run the test, autogenerate and build the server an client code.

$ make

Take a look at the Makefile for other convenient targets that help with daily development tasks such as test, codegen, server/build, client/build etc.

Code Layout

Server

The server code are found in the cmd/blued. The controller code and main.go are generated once by goagen. As long as they remain in the cmd/blued folder, subsequent goagen execution will not re-generate them. All the code found in the cmd/blued/app sub-folder are re-generated by goagen in subsequent execution. To force the controller code or main.go to be re-generated, run the Make server/codegen target with the CODEGEN_MAIN_OPTS variable set to --force:

$ CODEGEN_MAIN_OPTS=--force make server/codegen

Client

The client code are found in the cmd/blue folder. The CLI main.go is located in the cmd/blue/tool/blue sub-folder. To force the main.go to be re-generated, delete it then run the Make client/codengen target:

$ make client/codegen

ACI Image With rkt

The acbuild.sh script uses acbuild to build an ACI container image for blued. This image can then be run with rkt.

$ API_KEY=<api_key> BASIC_AUTH_USERNAME=<username> BASIC_AUTH_PASSWORD=<password> make aci
$ sudo rkt run --insecure-options=image --net=host build/blued-1.0.0-linux-amd64.aci
[18762.694938] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=Music action=Create route=POST /bluelens/music security=APIKey
[18762.695191] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=Music action=List route=GET /bluelens/music security=APIKey
[18762.695349] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=Music action=Show route=GET /bluelens/music/:id security=APIKey
[18762.695516] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=Recommendations action=Recommend route=GET /bluelens/recommendations/:userID/:limit security=APIKey
[18762.695691] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=Swagger files=cmd/blued/swagger/swagger.json route=GET /bluelens/swagger.json
[18762.695881] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=Swagger files=cmd/blued/swagger/swagger.yaml route=GET /bluelens/swagger.yaml
[18762.696132] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=User action=Create route=POST /bluelens/user security=APIKey
[18762.696279] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=User action=Follow route=POST /bluelens/user/:id/follows/:followeeID security=APIKey
[18762.696486] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=User action=List route=GET /bluelens/user security=APIKey
[18762.696658] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=User action=Listen route=POST /bluelens/user/:id/listen/:musicID security=APIKey
[18762.696804] blued[5]: 2017/04/06 19:59:51 [INFO] mount ctrl=User action=Show route=GET /bluelens/user/:id security=APIKey
[18762.696953] blued[5]: 2017/04/06 19:59:51 [INFO] listen transport=https addr=:443

Notice that the rkt pod is started with a host bridge network so that the endpoints are accessible at https://localhost. Also, the self-signed cert generated by the make tls target uses localhost as the CN.

Use curl to access the endpoints. For example,

$ curl -H "Authorization: Bearer <api_key>" --cacert tls/localhost.crt https://localhost/bluelens/music
[{"href":"/bluelens/music/song-01","id":"song-01","tags":["jazz","old school","instrumental"]},{"href":"/bluelens/music/song-02","id":"song-02","tags":["samba","60s"]},{"href":"/bluelens/music/song-03","id":"song-03","tags":["rock","alternative"]},{"href":"/bluelens/music/song-04","id":"song-04","tags":["rock","alternative"]},{"href":"/bluelens/music/song-05","id":"song-05","tags":["folk","instrumental"]},{"href":"/bluelens/music/song-06","id":"song-06","tags":["60s","rock","old school"]},{"href":"/bluelens/music/song-07","id":"song-07","tags":["alternative","dance"]},{"href":"/bluelens/music/song-08","id":"song-08","tags":["electronic","pop"]},{"href":"/bluelens/music/song-09","id":"song-09","tags":["60s","rock"]},{"href":"/bluelens/music/song-10","id":"song-10","tags":["60s","jazz"]},{"href":"/bluelens/music/song-11","id":"song-11","tags":["samba"]},{"href":"/bluelens/music/song-12","id":"song-12","tags":["jazz","instrumental"]},{"href":"/bluelens/music/song-13","id":"song-13","tags":["80s","old school","dance"]},{"href":"/bluelens/music/song-14","id":"song-14","tags":[""]},{"href":"/bluelens/music/song-15","id":"song-15","tags":["soft rock","90s","international"]},{"href":"/bluelens/music/song-16","id":"song-16","tags":["pop","soundtrack"]},{"href":"/bluelens/music/song-17","id":"song-17","tags":["jazz","billboard","90s"]},{"href":"/bluelens/music/song-18","id":"song-18","tags":["pop","80s","international"]},{"href":"/bluelens/music/song-19","id":"song-19","tags":["soundtrack","old school"]},{"href":"/bluelens/music/song-20","id":"song-20","tags":["90s","jazz"]}]

To access the swagger docs,

curl -H "Authorization: Bearer <api_key>" --cacert tls/localhost.crt https://admin:admin@localhost/bluelens/swagger.json
{"swagger":"2.0","info":{"title":"The bluelens API","description":"This API provides a set of endpoints to manage users' followees, music history and recommendations.","license":{"name":"MIT","url":"https://github.com/ihcsim/bluelens/blob/master/LICENSE"},"version":""},"host":"localhost","schemes":["https"],"consumes":["application/json"],"produces":["application/json"],"paths":{"/bluelens/music":{"get":{"tags":["music"],"summary":"list music","description":"List up to N music resources. N can be adjusted using the 'limit' and 'offset' parameters.","operationId":"music#list","parameters":[{"name":"limit","in":"query","required":false,"type":"integer","default":20},{"name":"offset","in":"query","required":false,"type":"integer","default":0}],"responses":{"200":{"description":"OK","schema":{"$ref":"#/definitions/BluelensMusicCollection"}},"401":{"description":"Unauthorized"},"500":{"description":"Internal Server Error","schema":{"$ref":"#/definitions/error"}}}
...

LICENSE

Refer the LICENSE file.