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/*
* librdkafka - The Apache Kafka C/C++ library
*
* Copyright (c) 2015 Magnus Edenhill
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "rdkafka_int.h"
#include "rdkafka_assignor.h"
/**
* Source:
* https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/consumer/RangeAssignor.java
*
* The range assignor works on a per-topic basis. For each topic, we lay out the
* available partitions in numeric order and the consumers in lexicographic
* order. We then divide the number of partitions by the total number of
* consumers to determine the number of partitions to assign to each consumer.
* If it does not evenly divide, then the first few consumers will have one
* extra partition.
*
* For example, suppose there are two consumers C0 and C1, two topics t0 and t1,
* and each topic has 3 partitions, resulting in partitions t0p0, t0p1, t0p2,
* t1p0, t1p1, and t1p2.
*
* The assignment will be:
* C0: [t0p0, t0p1, t1p0, t1p1]
* C1: [t0p2, t1p2]
*/
rd_kafka_resp_err_t
rd_kafka_range_assignor_assign_cb(rd_kafka_t *rk,
const rd_kafka_assignor_t *rkas,
const char *member_id,
const rd_kafka_metadata_t *metadata,
rd_kafka_group_member_t *members,
size_t member_cnt,
rd_kafka_assignor_topic_t **eligible_topics,
size_t eligible_topic_cnt,
char *errstr,
size_t errstr_size,
void *opaque) {
unsigned int ti;
int i;
/* The range assignor works on a per-topic basis. */
for (ti = 0; ti < eligible_topic_cnt; ti++) {
rd_kafka_assignor_topic_t *eligible_topic = eligible_topics[ti];
int numPartitionsPerConsumer;
int consumersWithExtraPartition;
/* For each topic, we lay out the available partitions in
* numeric order and the consumers in lexicographic order. */
rd_list_sort(&eligible_topic->members,
rd_kafka_group_member_cmp);
/* We then divide the number of partitions by the total number
* of consumers to determine the number of partitions to assign
* to each consumer. */
numPartitionsPerConsumer =
eligible_topic->metadata->partition_cnt /
rd_list_cnt(&eligible_topic->members);
/* If it does not evenly divide, then the first few consumers
* will have one extra partition. */
consumersWithExtraPartition =
eligible_topic->metadata->partition_cnt %
rd_list_cnt(&eligible_topic->members);
rd_kafka_dbg(rk, CGRP, "ASSIGN",
"range: Topic %s with %d partition(s) and "
"%d subscribing member(s)",
eligible_topic->metadata->topic,
eligible_topic->metadata->partition_cnt,
rd_list_cnt(&eligible_topic->members));
for (i = 0; i < rd_list_cnt(&eligible_topic->members); i++) {
rd_kafka_group_member_t *rkgm =
rd_list_elem(&eligible_topic->members, i);
int start = numPartitionsPerConsumer * i +
RD_MIN(i, consumersWithExtraPartition);
int length =
numPartitionsPerConsumer +
(i + 1 > consumersWithExtraPartition ? 0 : 1);
if (length == 0)
continue;
rd_kafka_dbg(rk, CGRP, "ASSIGN",
"range: Member \"%s\": "
"assigned topic %s partitions %d..%d",
rkgm->rkgm_member_id->str,
eligible_topic->metadata->topic, start,
start + length - 1);
rd_kafka_topic_partition_list_add_range(
rkgm->rkgm_assignment,
eligible_topic->metadata->topic, start,
start + length - 1);
}
}
return 0;
}
/**
* @brief Initialzie and add range assignor.
*/
rd_kafka_resp_err_t rd_kafka_range_assignor_init(rd_kafka_t *rk) {
return rd_kafka_assignor_add(
rk, "consumer", "range", RD_KAFKA_REBALANCE_PROTOCOL_EAGER,
rd_kafka_range_assignor_assign_cb,
rd_kafka_assignor_get_metadata_with_empty_userdata, NULL, NULL,
NULL, NULL);
}
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