Messaging Service Concept

Core Value

StraaS messaging service are dedicated to build a messaging sdk for live broadcasting, OTT, education and all kinds of applications needing a stable and scalable messaging platform to support hundreds of thousands concurrent user interacting in a single chat.

To fit in OTT scenarios, StraaS also provides management UI from our iframe sdk. Our management functions including delete inappropriate message, blocked specific users, add manager ...etc to help our customers could have better messaging experience.

In following sections, we will explain some design rationale through to help our clients have better understandings of our technology.

2 channel of messages

In StraaS messaging service, we define to types of messaging to fit to different applications. Theses 2 types are

1. text channel
2. data channel

The main differences of these 2 types are provided as following.

Text Channel

This kind of messages are limited by the input interval, user privilege and each user will have different kinds of privilege in input interval (e.g.: the managers are not limited by input interval). To manage the user text, most of the control, censorship and logic is designed for this channel.

Data Channel (Web, ios, Android)

This kind of messages are used to broadcast data and are not subjected to the input interval and user privilege.

And for data in data channel, there are 2 more different types of data to send, raw data and aggregated data:

1. raw data: Raw data are used to broadcast json to users, e.g.: the current live shopping item for eCommerce. This kind of data could transports larger data size (2048 characters), and the available rps is smaller than others.
2. aggregated data: Aggregated data is designed for data which is highly correlated and could be compressed into a smaller size. This kind of data could have higher input rate, but the receiver could received constant frequency, by which the UI performance could be significantly improved. When using data channel, the sent key will be aggregated and the receiver method would receive the aggregated data in specific period, the receive data is a in json formate like: {"key": "like", "n": "20"}.

Summary

In summary, the properties are in following table.

	text channel	data channel-raw data	data channel-aggregated data
User Privilege	O	X	X
Transporting Size	120	2048	100
Input Rate	medium	low	high
Received Rate	medium	low	constant

Chat Metadata

Messaging service provides metadata API for you to store arbitrary data associated to a chat room. For example, you could store detail profile of the chat room owner. Metadata is stored in key and JSON value pairs, it could be retrieved through messaging SDK and server-side API.

There are 2 types of metadata, broadcasting and none-broadcasting: Any changes of broadcasting metadata will be synchronized to clients immediately through messaging SDK. None-broadcasting metadata needs to be query manually and accept lower change frequency, but it can carry much larger data.

In summary, the properties are in following table.

	broadcast	none-broadcast
Retrieving	Active server push	Manual query
Transporting Size	1024	4096
Change Rate	high	low

Roles of Messaging Service

To provide different management privileges for different users, we offer role to define the preset of privilege.

Following tables provide an overview of the role-privilege mappings.

User Operations

	promote NORMAL(member) to be MODERATOR	demote MODERATOR to be NORMAL(member)"	block NORMAL	revive blocked user
LOCAL_MANAGER	O	O	O	O
MODERATOR	X	X	O	O
NORMAL(member)	X	X	X	X
NORMAL(guest)	X	X	X	X
BLOCKED	X	X	X	X
Note that, only NORMAL user could be blocked/un-blocked

Message Operations

	chat in chatWriteMode:ALL	chat in chatWriteMode:LOGIN	chat in chatWriteMode: ANCHOR	remove message	flush all messages	skip interval	pin/unpin message
LOCAL_MANAGER	O	O	O	O	O	O	O
MODERATOR	O	O	O	O	O	O	O
NORMAL(member)	O	O	X	X	X	X	X
NORMAL(guest)	O	X	X	X	X	X	X
BLOCKED	X	X	X	X	X	X	X

Chat Operations

	change chatWriteMode
LOCAL_MANAGER	O
MODERATOR	O
NORMAL(member)	X
NORMAL(guest)	X
BLOCKED	X

Chat Meta Operations

	Set
LOCAL_MANAGER	O
MODERATOR	O
NORMAL(member)	X
NORMAL(guest)	X
BLOCKED	X

Banned Word Mechanism

By setting banned words in the chatroom, our service would blocked msg automatically. This is useful when there are not enough moderators in the chatroom to monitor.

Step

1. When server gets an input msg, first it uses jieba library to segment the text.
2. compare those segments with pre-defined banned words to check if there is exactly match
3. server returns http code 422 when it detects banned words in msg

Refer to api section to utilize this functionality