Update max message size default (#1458)

Author: kbatuigas

modules/develop/pages/config-topics.adoc

@@ -223,7 +223,7 @@ CONFIGS
 KEY                           VALUE                          SOURCE
 cleanup.policy                delete                         DYNAMIC_TOPIC_CONFIG
 compression.type              producer                       DEFAULT_CONFIG
-max.message.bytes             1048576                        DEFAULT_CONFIG
+max.message.bytes             20971520                       DEFAULT_CONFIG
 message.timestamp.type        CreateTime                     DEFAULT_CONFIG
 redpanda.datapolicy           function_name:  script_name:   DEFAULT_CONFIG
 redpanda.remote.delete        true                           DEFAULT_CONFIG

modules/reference/pages/properties/cluster-properties.adoc

@@ -2795,7 +2795,7 @@ Time between cluster join retries in milliseconds.
 
 === kafka_batch_max_bytes
 
-Maximum size of a batch processed by the server. If the batch is compressed, the limit applies to the compressed batch size.
+The default maximum batch size for topics if the topic property xref:reference:properties/topic-properties.adoc[`message.max.bytes`] is not set. If the batch is compressed, the limit applies to the compressed batch size.
 
 *Unit:* bytes
 

modules/reference/pages/properties/topic-properties.adoc

@@ -293,15 +293,19 @@ The maximum size of a message or batch of a topic. If a compression type is enab
 
 If `max.message.bytes` is set to a positive value, it overrides the cluster property xref:./cluster-properties.adoc#kafka_batch_max_bytes[`kafka_batch_max_bytes`] for the topic.
 
+Set an upper limit for `max.message.bytes` using the cluster property config_ref:kafka_max_message_size_upper_limit_bytes,true,properties/cluster-properties[`kafka_max_message_size_upper_limit_bytes`].
+
 *Type:* integer
 
 *Unit:* bytes
 
 *Accepted values:* [`1`, `2147483647`]
 
-*Default:* null
+*Default:* 1048576 (1 MiB)
 
-*Related cluster property:* xref:./cluster-properties.adoc#kafka_batch_max_bytes[`kafka_batch_max_bytes`]
+*Related cluster properties:* 
+- xref:./cluster-properties.adoc#kafka_batch_max_bytes[`kafka_batch_max_bytes`]
+- xref:./cluster-properties.adoc#kafka_max_message_size_upper_limit_bytes[`kafka_max_message_size_upper_limit_bytes`]
 
 **Related topics**: