MINOR: improve the min.insync.replicas doc

clients/src/main/java/org/apache/kafka/common/config/TopicConfig.java

@@ -181,7 +181,8 @@
         "When used together, <code>min.insync.replicas</code> and <code>acks</code> allow you to enforce greater durability guarantees. " +
         "A typical scenario would be to create a topic with a replication factor of 3, " +
         "set <code>min.insync.replicas</code> to 2, and produce with <code>acks</code> of \"all\". " +
-        "This will ensure that a majority of replicas must persist a write before it's considered successful by the producer and it's visible to consumers.";
+        "This will ensure that a majority of replicas must persist a write before it's considered successful by the producer and it's visible to consumers." +
+        "<p> Note that when the Eligible Leader Replicas feature is enabled, the semantics of this config has small changes. Please refer to <a href=\"#eligible_leader_replicas\">the ELR section</a> for more info.</p>"    ;
 
     public static final String COMPRESSION_TYPE_CONFIG = "compression.type";
     public static final String COMPRESSION_TYPE_DOC = "Specify the final compression type for a given topic. " +

docs/ops.html

@@ -4499,8 +4499,15 @@ <h4 class="anchor-heading"><a id="eligible_leader_replicas_upgrade" class="ancho
 
   <h4 class="anchor-heading"><a id="eligible_leader_replicas_tool" class="anchor-link"></a><a href="#eligible_leader_replicas_tool">Tool</a></h4>
   <p>The ELR fields can be checked through the API DescribeTopicPartitions. The admin client can fetch the ELR info by describing the topics.
-    Also note that, if <code>min.insync.replicas</code> is updated for a topic, the ELR field will be cleaned. If cluster default min ISR is updated,
-    all the ELR fields will be cleaned.</p>
+    Note that when the ELR feature is enabled:
+    <ul>
+      <li>The override of <code>min.insync.replicas</code> in broker-level will be removed.</li>
+      <li>The alter of <code>min.insync.replicas</code> config in broker-level is not allowed.</li>
+      <li>The removal of <code>min.insync.replicas</code> config in cluster-level is not allowed.</li>
+      <li>If <code>min.insync.replicas</code> is updated for a topic, the ELR field will be cleaned.</li>
+      <li>If the cluster default <code>min.insync.replicas</code> is updated, all the ELR fields will be cleaned.</li>
+    </ul>
+  </p>
 
 </script>
 

metadata/src/main/java/org/apache/kafka/controller/ConfigurationControlManager.java

@@ -611,7 +611,7 @@ int getStaticallyConfiguredMinInsyncReplicas() {
 
     /**
      * Generate any configuration records that are needed to make it safe to enable ELR.
-     * Specifically, we need to remove all cluster-level configurations for min.insync.replicas,
+     * Specifically, we need to remove all broker-level configurations for min.insync.replicas,
      * and create a cluster-level configuration for min.insync.replicas. It is always safe to call
      * this function if ELR is already enabled; it will simply do nothing if the necessary
      * configurations already exist.