[25.3] Client monitoring (#1389)

Co-authored-by: Gellért Peresztegi-Nagy <gellert.nagy@redpanda.com>

Author: kbatuigas

modules/ROOT/nav.adoc

@@ -161,7 +161,7 @@
 *** xref:manage:cluster-maintenance/disk-utilization.adoc[]
 *** xref:manage:cluster-maintenance/manage-throughput.adoc[Manage Throughput]
 *** xref:manage:cluster-maintenance/compaction-settings.adoc[Compaction Settings]
-*** xref:manage:cluster-maintenance/configure-availability.adoc[]
+*** xref:manage:cluster-maintenance/configure-client-connections.adoc[]
 *** xref:manage:cluster-maintenance/partition-recovery.adoc[Forced Partition Recovery]
 *** xref:manage:cluster-maintenance/nodewise-partition-recovery.adoc[Node-wise Partition Recovery]
 ** xref:manage:security/index.adoc[Security]

modules/get-started/pages/release-notes/redpanda.adoc

@@ -7,6 +7,10 @@ This topic includes new content added in version {page-component-version}. For a
 * xref:redpanda-cloud:get-started:whats-new-cloud.adoc[]
 * xref:redpanda-cloud:get-started:cloud-overview.adoc#redpanda-cloud-vs-self-managed-feature-compatibility[Redpanda Cloud vs Self-Managed feature compatibility]
 
+== Connected client monitoring
+
+You can view details about Kafka client connections using the Admin API ListKafkaConnections endpoint. This allows you to view detailed information about about active client connections on a cluster, and identify and troubleshoot problematic clients. For more information, see xref:manage:monitoring.adoc#identify-high-throughput-clients[Monitor Redpanda].
+
 == New Admin API endpoints 
 
 Redpanda v25.3 introduces a new API style for the Admin API, powered by https://connectrpc.com/docs/introduction[ConnectRPC]. New Redpanda features and operations in v25.3 are available as ConnectRPC services, allowing you to use autogenerated Protobuf clients in addition to using HTTP clients such as `curl`. 
@@ -23,4 +27,4 @@ Existing Admin API endpoints from versions earlier than 25.3 remain supported, a
 Redpanda Schema Registry now supports an import mode that allows you to import existing schemas and retain their current IDs and version numbers. Import mode is useful when migrating from another schema registry. 
 
 Starting with this release, import mode must be used when importing schemas. Read-write mode no longer allows specifying a schema ID and version when registering a schema.
-See xref:manage:schema-reg/schema-reg-api.adoc#set-schema-registry-mode[Use the Schema Registry API] for more information.
+See xref:manage:schema-reg/schema-reg-api.adoc#set-schema-registry-mode[Use the Schema Registry API] for more information.

…-maintenance/configure-availability.adoc …enance/configure-client-connections.adocmodules/manage/pages/cluster-maintenance/configure-availability.adoc renamed to modules/manage/pages/cluster-maintenance/configure-client-connections.adoc modules/manage/pages/cluster-maintenance/configure-availability.adoc renamed to modules/manage/pages/cluster-maintenance/configure-client-connections.adoc

@@ -1,10 +1,36 @@
 = Configure Client Connections
 :description: Learn about guidelines for configuring client connections in Redpanda clusters for optimal availability.
 :page-categories: Management, Networking
+:page-aliases: manage:cluster-maintenance:configure-availability.adoc
 // tag::single-source[]
 
 Optimize the availability of your clusters by configuring and tuning properties.
 
+// Don't display ListKafkaConnections in Cloud docs until support is added
+ifdef::env-cloud[]
+TIP: Before you configure connection limits or reconnection settings, start by gathering detailed data about your client connections. Use the xref:reference:public-metrics-reference.adoc#redpanda_rpc_active_connections[`redpanda_rpc_active_connections` metric] to view current Kafka client connections.
+endif::[]
+ifndef::env-cloud[]
+[TIP]
+====
+Before you configure connection limits or reconnection settings, start by gathering detailed data about your client connections. 
+
+* Internal metrics that follow the `vectorized_kafka_rpc_.*connect.*` naming pattern provide details on Kafka client connection activity. For example, xref:reference:internal-metrics-reference.adoc#vectorized_kafka_rpc_active_connections[`vectorized_kafka_rpc_active_connections`] reports the current number of active connections.
+* For Redpanda v25.3 and later, use the Admin API ListKafkaConnections endpoint to identify:
++
+-- 
+** Which clients and applications are connected
+** Long-lived connections and long-running requests
+** Connections with no activity 
+** Whether any clients are causing excessive load
+--
++
+By reviewing connection details, you can make informed decisions about tuning connection limits and troubleshooting issues.
+
+See also: link:/api/doc/admin/v2/operation/operation-redpanda-core-admin-v2-clusterservice-listkafkaconnections[ListKafkaConnections reference], xref:manage:monitoring.adoc#throughput[Monitor Redpanda]
+====
+endif::[]
+
 == Limit client connections
 
 To mitigate the risk of a client creating too many connections and using too many system resources, you can configure a Redpanda cluster to impose limits on the number of client connections that can be created.
@@ -70,7 +96,7 @@ NOTE: If you find a high load of unexpected connections from multiple IP address
 * Redpanda may modify this property during internal operations.
 * Availability incidents caused by misconfiguring this feature are excluded from the Redpanda Cloud SLA.
 
-endif::env-cloud[]
+endif::[]
 
 == Configure client reconnections
 
@@ -87,6 +113,9 @@ Additionally, you can use Kafka properties to control message retry behavior. De
 * `retries`: Number of times a producer can retry sending a message before marking it as failed. The default value is 2147483647 for Kafka >= 2.1, or 0 for Kafka \<= 2.0.
 * `retry.backoff.ms`: Amount of time to wait before attempting to retry a failed request to a given topic partition. The default is 100 milliseconds.
 
-See also: xref:develop:produce-data/configure-producers.adoc[Configure Producers]
+== See also
+
+- xref:develop:produce-data/configure-producers.adoc[Configure Producers]
+- xref:manage:cluster-maintenance/manage-throughput.adoc[Manage Throughput]
 
 // end::single-source[]