Elastic channels support large-scale chat experiences with up to 1-million members. Typical uses include watch parties for sporting or political events. You can use elastic channels only in the US East (N. Virginia) region.
An elastic channel consists of a single channel with a common configuration, plus a varying—or elastic—number of sub-channels. The configuration also includes minimum and maximum thresholds for the members in the sub-channels.
For example, say you create an elastic channel with 100 sub-channels, and for the sub-channels you set a low threshold of 500 members and a high threshold of 10,000 members. When users join this example channel, the system automatically assigns them to a single sub-channel until the member count exceeds 10,000. At that point, the system creates a new sub-channel and adds any new members there. As users leave, the system deletes sub-channels and distributes members across the remaining sub-channels.
Splitting the audience across sub-channels makes conversations easier for participants to follow. Moderators also have reduced workloads, because they only need to watch some of the sub-channels. In addition, moderators can use the built-in tools that elastic channels provide. For example, moderators can ban users from a channel, create moderators, and use channel flows to automatically moderate all the messages in the channel.
For more information about Amazon Chime SDK Messaging quotas, refer to Messaging Quotas in the Amazon Chime SDK General Reference.
Topics
Managing elastic channel members for Amazon Chime SDK meetings
Sending elastic channel messages in Amazon Chime SDK meetings
Understanding WebSocket system messages in elastic channels for Amazon Chime SDK meetings
Using Kinesis streams to receive system messages for Amazon Chime SDK meetings
Testing elastic channels for Amazon Chime SDK meetings in our demo app
Prerequisites
You must have the following to use elastic channels.
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Knowledge of Amazon Chime SDK Messaging functionality, such as managing channels, and sending and receiving messages.
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The ability to invoke the Amazon Chime SDK Messaging APIs.
Elastic channel concepts
To use elastic channels effectively, you must understand these concepts.
- Sub-channels
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Elastic channels divide their members into logical containers called sub-channels. When you add an
AppInstanceUserto an elastic channel, the user becomes a member of a sub-channel. That user can send and receive messages, but only with other members of that sub-channel. The system never allows messages from one sub-channel to appear in other sub-channels. - Scaling
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To support user engagement, every sub-channel must meet a minimum membership requirement. You provide that value when you create an elastic channel. As users join or leave an event, the system transfers members to different sub-channels, which makes the overall channel "elastic." Sub-channels run the following scaling actions.
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SCALE_OUT – When a new elastic channel membership request comes in and all sub-channels are full, the system scales out by creating a new sub-channel, and then transferring memberships from existing sub-channels to the new sub-channel.
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SCALE_IN – When a sub-channel membership count goes below the minimum requirement, and another sub-channel has the capacity to accommodate all the members of the first sub-channel, a
SCALE_INevent transfers those memberships, and then deletes the sub-channel and all messages.
Note
If you need to access messages from channels that have been deleted, you must first turn on message streaming. For more information, refer to Streaming messaging data in Amazon Chime SDK messaging.
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- Member transfer
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This occurs when membership balancing moves an
AppInstanceUserfrom one sub-channel to another. TheAppInstanceUserstill belongs to the elastic channel after the transfer. However, the new sub-channel contains different memberships and messages, so the messages sent by theAppInstanceUserafter the transfer go to those different members. Membership balancing does not affect moderator memberships.
Note
Elastic channels don't support hidden memberships, membership preferences, and read message timestamps.
Additional supported features
Elastic channels also support these messaging features.
