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Upon each partition assignment calculation, the full partition assignments are preserved for each consumer (as user data). This is specially helpful when a consumer group leader, who is in charge of performing the partition assignment, dies and the leadership has to be given to some other group member; which, because of the mentioned preserved assignment, . In such circumstances, the new leader has access to what the most recent partition assignment was for the consumer groupand can easily take over the rebalance that is triggered when the former leader disappears, and also future rebalances.

Example 1

Suppose there are three consumers C₀, C₁, C₂, four topics t₀, t₁, t₂, t₃, and each topic has 2 partitions, resulting in partitions t₀p₀, t₀p₁, t₁p₀, t₁p₁, t₂p₀, t₂p₁, t₃p₀, t₃p₁. Each consumer is subscribed to all three topics.

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