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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 dies and the leadership has to be given to some other group member. ; which, because of the mentioned preserved assignment, has access to what the most recent partition assignment was for the consumer group.

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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