Dmitry Pekar created KAFKA-1792:
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Summary: change behavior of --generate to produce assignment
config with fair replica distribution and minimal number of reassignments
Key: KAFKA-1792
URL: https://issues.apache.org/jira/browse/KAFKA-1792
Project: Kafka
Issue Type: Sub-task
Reporter: Dmitry Pekar
Current implementation produces fair replica distribution between specified
list of brokers. Unfortunately, it doesn't take
into account current replica assignment.
So if we have, for instance, 3 brokers id=[0..2] and are going to add fourth
broker id=3,
generate will create an assignment config which will redistribute replicas
fairly accross brokers [0..3]
in the same way as those partitions were created from scratch.
It will not take into consideration current replica assignment and accordingly
will not try to minimize number
of replica moves between brokers.
As proposed by Joe Stein this should be improved. New output of improved
--generate algorithm should suite following requirements:
fairness of replica distribution - every broker will have R or R+1 replicas
assigned;
minimum of reassignments - number of replica moves between brokers will be
minimal;
Example.
Consider following replica distribution per brokers [0..3] (we just added
brokers 2 and 3):
broker - 0, 1, 2, 3
replicas - 7, 6, 0, 0
The new algorithm will produce following assignment:
broker - 0, 1, 2, 3
replicas - 4, 3, 3, 3
moves - -3, -3, +3, +3
It will be fair and number of moves will be 6, which is minimal for specified
initial distribution.
The scope of this issue is:
design an algorithm matching the above requirements;
implement this algorithm and unit tests;
test it manually using different initial assignments;
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