linkedin/kafka-tools

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from kafka.tools.assigner.actions import ActionModule
from kafka.tools.exceptions import NotEnoughReplicasException


class ActionDemote(ActionModule):
    name = "demote"
    helpstr = "Force a broker to relinquish leadership wherever it is safe to do so. This is done by reordering " \
        "replica lists and then performing a PLE."

    def __init__(self, args, cluster):
        super(ActionDemote, self).__init__(args, cluster)

    @classmethod
    def _add_args(cls, parser):
        parser.add_argument(
            '-b', '--brokers', type=int, help='List of broker ids to demote', required=True, nargs='*')
        parser.add_argument('-t', '--topics', required=False, nargs='*',
                            help='Optional list of topics to use. If not specified, leadership of all topics lead by the brokers to demote will be changed.')

    def process_cluster(self):
        # Randomize a broker list to use for new replicas once. We'll round robin it from here
        brokers_to_demote = set(self.args.brokers)
        topics_to_consider = self.args.topics and set(self.args.topics) or None

        for partition in self.cluster.partitions(self.args.exclude_topics):
            if topics_to_consider and partition.topic.name not in topics_to_consider:
                continue

            if all(b.id in brokers_to_demote for b in partition.replicas):
                msg = 'Topic {0} partition {1} only has replicas in the list of brokers to be demoted: {2}'.format(
                    partition.topic.name,
                    str(partition.num),
                    ', '.join(str(b.id) for b in partition.replicas))
                raise NotEnoughReplicasException(msg)

            while partition.replicas[0].id in brokers_to_demote:
                broker = partition.replicas[0]
                partition.remove_replica(broker)
                partition.add_replica(broker)