An overview of Zaqar's persistent transport implementation

Zaqar is the messaging and notifications service for OpenStack that allow users to build scalable, reliable and high-performing applications. It has a REST API that can be used by developers to transport messages between different components in their cloud applications through different communication patterns, such as producer/consumer or publisher/subscriber.

In Zaqar's v1, only a WSGI controller is available as a transport solution. This controller is enough for most of the use cases required by users like, for example, task distribution, broadcasting and point to point messaging.

But when the storage and recovery of messages is incremented to rates over 10.000 messages per second -- in cases like activity tracking in a website or log aggregation -- this transport is very inefficient.

To accomplish an adequate performance for this type of loads is necessary the implementation of a streaming interface. That is, long living connections with minimum overhead in which the messages can be freely pushed.

The websocket driver, the latest addition to the Zaqar project, aims to cover this use cases.

Transcript

1. AN OVERVIEW OF ZAQAR’S PERSISTENT TRANSPORT IMPLEMENTATION Cindy Pallares Quezada Victoria Martinez de la Cruz October 29th, 2015
2. WHAT IS ZAQAR?
3. 3 TL;DR Messaging and Notifications for OpenStack To produce an OpenStack messaging service that affords a variety of distributed application patterns in an efficient, scalable and highly-available manner, and to create and maintain associated Python libraries and documentation. What is Zaqar? Mission statement
4. 4 What is Zaqar? ...and in OpenStack itself!* It aims to connect applications running on the cloud... *for certain scenarios… don’t get too excited Main goal
5. 5 What is Zaqar? - It’s not like RabbitMQ or QPID - It’s not a queue service - It’s not an email service What Zaqar is not
6. 6 Multitenant What is Zaqar? Component based Messaging patterns Main features
7. 7 Notifications What is Zaqar? Message delivery guarantee Horizontally scalable Main features
8. 8 Messaging for the cloud Self-healing applications Intercloud communication Data processing What is Zaqar? Some use cases
9. 9 Zaqar architecture Client 1 Client 2 Client 3 Client N Transport Protocol API Storage
10. 10 Storage MongoDB SQLAlchemy Redis Transport WSGI Juno Kilo Zaqar architecture Storage backends and transmission mechanisms supported over time Liberty Storage MongoDB SQLAlchemy (mgmt only) Redis Swift (TBD) Transport WSGI Websocket Mitaka Storage MongoDB SQLAlchemy (mgmt only) Redis Transport WSGI Websocket (beta) Storage MongoDB SQLAlchemy (mgmt only) Redis Transport WSGI Websocket
11. PERSISTENT TRANSPORT
12. 12 WSGI works well for the majority of the use cases… … but when an streaming interface is required, the WSGI transport is not the best. Why we need persistent transport
13. 13 Persistent transport Long-lived connections with minimal overhead - Raw TCP - HTTP long polling - Websocket - WAMP (Web Application Messaging Protocol)
14. 14 Websocket This technology provides a full-duplex communication channel over a single TCP socket - Efficient - Simple - Firewall friendly - Standard
15. 15 Design Several aspects to define - Message format - Message serialization - Connection protocol and security - Third-party libraries to use
16. { “action”: “”, “headers”: {}, “body”: {} } 16 Message format - Action: queue_create - Headers: X-Project-ID, Client-ID, X-Auth-Token, Date, Accept, User-Agent - Body: {“queue_name”: “mitaka”} How should the message structure look like?
17. 17 Message serialization - JSON - Protocol Buffers - MsgPack - Cap ‘n’ Proto How to achieve practicality and performance?
18. 18 Connection protocol and security - Connection protocol. Websocket uses port 80 or 443. Websockets requests are interpreted as an HTTP GET. - Security. Websocket has its secure version (wss). This is complemented with the usage of Keystone auth tokens. How we do transactions and ensure they are safe?
19. 19 - Autobahn - SockJS - SocketIO - ws4py Third party libraries What libraries are we going to use in our implementation?
20. ZAQAR WEBSOCKET API
21. 21 Zaqar Websocket API Features supported - Queues - Messages - Claims - Subscriptions
22. # Queue creation {“action”: “queue_create”, “headers”: {}, “body”: {“queue_name”: “samplequeue”}} # Message post {“action”: “message_post”, “headers”: {}, “body”: {“queue_name”: “samplequeue”, “messages”: [{“body”: “message1”, “ttl”: 3600}, ...]}} # Claim creation {“action”: “claim_create”, “headers”: {}, “body”: {“queue_name”: “samplequeue”, “limit”: 10, “ttl”: 300, “grace”: 300}} # Subscription creation {“action”: “subscription_create”, “headers”: {}, “body”: {“queue_name”: “samplequeue”, “subscriber”: “sampleclient”, “ttl”: 300, “options”: {}}} 22 Zaqar Websocket API Queues, messages, claims and subscription creation
23. 23 Zaqar Websocket API Future work - Binary support - Message serialization
24. HORIZON USE CASE
25. 25 Horizon use case HTTP long polling for table updates
26. 26 Horizon use case Zaqar websocket for table updates Horizon Zaqar Ceilometer Nova Cinder Neutron Glance
27. Q&A @vkmc @cindy_pallares