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Websockets in Django

Q & A

What are websocket? Why do we need it?
Quoting from wikipedia,
"WebSocket is a computer communications protocol, providing full-duplex communication channels over a single TCP connection. The WebSocket protocol was standardized by the IETF as RFC 6455 in 2011, and the WebSocket API in Web IDL is being standardized by the W3C."
WebSockets are used for streaming messages. To implement real-time notification we need to stream messages from the server to the client without a refresh or making an HTTP request from the client. Hence websockets.

How do we implement websockets in django?
We will be using django-channels (channels) for websockets. Django, by default does not support websocket. Channels is a django project which allows Django to handle websockets, HTTP and HTTP2 requests. But how does channels implement websockets in WSGI server (gunicorn) which does not support websockets. Simple we don't. Instead, we will be using Daphne, an interface server designed fo…
Recent posts

Table Schema

Continuing my last post.
When using SQL database a very important aspect is the table schema. What is the best schema for a table. I feel we can never say this definitely we can only try making it better. We had 2 choice when deciding on the schema for the notification app.  One notification table for all types of notification (Owner, Group and Watching)Three notification table for 3 types of notification We decided to go with the second option. You ask why. The needs of the three notification are totally different. For example, owner notification needs to be related to User table while Group notification needs to be related to the group table. If we had used option 1 we would have many columns with null values for a large set of rows (remember this is SQL not NoSQL) creating a table with sparse data. Owner notification table schema is as follows:
Column NameData TypeData RangeDescriptionmessageStringNotification messagetypeEnumcreate, upload, update, deleteType of notificationowne…

Django + Kafka

Q & A of connecting Apache Kafka and Django
Problem #1 Kafka consumer should always be listening for new messages in the queue. The consumer should be running in parallel to GraphSpace app (producer). Solution There are multiple ways to do this. We create another Django project say called "GraphSpace notification consumer" which starts along the GraphSpace application and establishes a connection with Kafka. This is an overkill for a simple consumer.We can use celery for multi-threading. Celery itself uses Redis or RabbitMQ as a queue for tasks. This setup might work for a large scale multi-threading system but for a simple setup of running a consumer this is a overkill. We will be running 2 queues (Redis and Kafka), one for queuing task and another for queuing content. I tried this setup with the following architecture:
I will recommend keeping the architecture simple, run the consumer code on a different thread in daemon mode. Problem #2 Where to start this consumer th…

Kafka Clients 101

In this post, we will look at packages to build a real time notification system for GraphSpace. GraphSpace is built in Django. The requirements for our system are Decoupled from the main app ,i.e, should be non-blockingUse Apache Kafka as the message queue systemFollow a producer-consumer architecture with broker, KafkaAble to handle different types of notification: Group, Owner and Watching The above requirements can be satisfied if we have a package that can connect to Kafka, have an ability to handle different types of notification and is non-blocking. To handle different type of notifications we can have producers and consumers send and receive messages with different topics. So the package we need should be able to dynamically do so. Instead of having say 10 producers for 10 topics and establishing 10 connections to Kafka, it is better we have 1 producer which can send messages with 10 different topics. Similarly 1 consumer should be able to subscribe to 10 different topics. By m…

Project Introduction

Notification System for GraphSpace
Organization: National Resource for Network Biology (NRNB)
GraphSpace is an user-friendly web-based platform that collaborating research groups can utilize for storage, interaction, and network sharing. A GraphSpace user can import graphs created in Cytoscape, upload them through a REST API, interact with them by customizing and saving layouts, share them within and between groups of collaborators, search for different graphs, and organize them using tags. These functions are enabled through GraphSpace’s comprehensive REST API, which allows users to communicate programmatically.

Notifications are integral to all web applications as they are the means to tracking all important information. It is most optimal when a notification system is decoupled from the main application flow, because we can have a clear distinction between the utilities of the two applications. In this project, there are three primary types of notifications that need to be implement…