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Not only the sticky assignor preserves more assignments, it also results in a more balanced assignment.

Example 3

There are two consumers C₀, C₁, and two topics t₀, t₁, with 2 partitions each. Therefore, the partitions are t₀p₀, t₀p₁,t₁p₀, t₁p₁. Both consumers are subscribed to both topics.

The range, round robin, and sticky assignors all result in the following assignment:

Now, if consumer C₂ subscribed to both topics comes on board, the range assignor would produce the following (which is not a fair assignment):

The round robin assignor would produce this (which is not the stickies assignment):

The sticky assignor would move one of the partitions to the new consumer producing something like this (preserving 3 partition assignments):

The Algorithm

The inputs to the sticky partition assignment algorithm are

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