[kafka] branch trunk updated: MINOR: Clarify impact of num.replica.fetchers (#12153)

[jg...@apache.org]

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The following commit(s) were added to refs/heads/trunk by this push:
     new 06051988a2e MINOR: Clarify impact of num.replica.fetchers (#12153)
06051988a2e is described below

commit 06051988a2e3e6593eca21d8decbd59f2af46f90
Author: Joel Hamill <11...@users.noreply.github.com>
AuthorDate: Mon May 16 09:38:06 2022 -0700

    MINOR: Clarify impact of num.replica.fetchers (#12153)
    
    The documentation for `num.replica.fetchers` should emphasize the fact that the count applies to each source broker individually. Also mention the tradeoff.
    
    Reviewers: Jason Gustafson <ja...@confluent.io>
---
 core/src/main/scala/kafka/server/KafkaConfig.scala | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/core/src/main/scala/kafka/server/KafkaConfig.scala b/core/src/main/scala/kafka/server/KafkaConfig.scala
index 5942b164ea4..8588828d4f2 100755
--- a/core/src/main/scala/kafka/server/KafkaConfig.scala
+++ b/core/src/main/scala/kafka/server/KafkaConfig.scala
@@ -900,8 +900,10 @@ object KafkaConfig {
     "will still be returned to ensure that progress can be made. As such, this is not an absolute maximum. The maximum " +
     "record batch size accepted by the broker is defined via <code>message.max.bytes</code> (broker config) or " +
     "<code>max.message.bytes</code> (topic config)."
-  val NumReplicaFetchersDoc = "Number of fetcher threads used to replicate messages from a source broker. " +
-  "Increasing this value can increase the degree of I/O parallelism in the follower broker."
+  val NumReplicaFetchersDoc = "Number of fetcher threads used to replicate records from each source broker. The total number of fetchers " +
+  "on each broker is bound by <code>num.replica.fetchers</code> multiplied by the number of brokers in the cluster." +
+  "Increasing this value can increase the degree of I/O parallelism in the follower and leader broker at the cost " +
+  "of higher CPU and memory utilization."
   val ReplicaFetchBackoffMsDoc = "The amount of time to sleep when fetch partition error occurs."
   val ReplicaHighWatermarkCheckpointIntervalMsDoc = "The frequency with which the high watermark is saved out to disk"
   val FetchPurgatoryPurgeIntervalRequestsDoc = "The purge interval (in number of requests) of the fetch request purgatory"