Add note about 2.x dlq has a default 30s ackTimeout policy in messaging.md (#985)

Author: geniusjoe

docs/concepts-messaging.md

@@ -344,6 +344,7 @@ The dead letter producerName uses this format:
 :::note
 - For Pulsar 2.6.x and 2.7.x, the default dead letter topic uses the format of `<subscriptionname>-DLQ`. If you upgrade from 2.6.x~2.7.x to 2.8.x or later, you need to delete historical dead letter topics and retry letter partitioned topics. Otherwise, Pulsar continues to use original topics, which are formatted with `<subscriptionname>-DLQ`.
 - It is not recommended to use `<subscriptionname>-DLQ` because if multiple topics under the same namespace have the same subscription, then dead message topic names for multiple topics might be the same, which will result in mutual consumptions.
+- From Pulsar 2.3.x to 2.10.x, Java SDK dead letter policy will set a 30 seconds acknowledgment timeout when there is no user defined acknowledgment timeout. This default timeout policy has been removed since 3.0.x.
 :::
 
 Use the Java client to specify the name of the dead letter topic.

versioned_docs/version-3.0.x/concepts-messaging.md

@@ -330,6 +330,7 @@ The default dead letter topic uses this format:
 :::note
 - For Pulsar 2.6.x and 2.7.x, the default dead letter topic uses the format of `<subscriptionname>-DLQ`. If you upgrade from 2.6.x~2.7.x to 2.8.x or later, you need to delete historical dead letter topics and retry letter partitioned topics. Otherwise, Pulsar continues to use original topics, which are formatted with `<subscriptionname>-DLQ`.
 - It is not recommended to use `<subscriptionname>-DLQ` because if multiple topics under the same namespace have the same subscription, then dead message topic names for multiple topics might be the same, which will result in mutual consumptions.
+- From Pulsar 2.3.x to 2.10.x, Java SDK dead letter policy will set a 30 seconds acknowledgment timeout when there is no user defined acknowledgment timeout. This default timeout policy has been removed since 3.0.x.
 :::
 
 Use the Java client to specify the name of the dead letter topic.

versioned_docs/version-3.3.x/concepts-messaging.md

@@ -342,6 +342,7 @@ The dead letter producerName uses this format:
 :::note
 - For Pulsar 2.6.x and 2.7.x, the default dead letter topic uses the format of `<subscriptionname>-DLQ`. If you upgrade from 2.6.x~2.7.x to 2.8.x or later, you need to delete historical dead letter topics and retry letter partitioned topics. Otherwise, Pulsar continues to use original topics, which are formatted with `<subscriptionname>-DLQ`.
 - It is not recommended to use `<subscriptionname>-DLQ` because if multiple topics under the same namespace have the same subscription, then dead message topic names for multiple topics might be the same, which will result in mutual consumptions.
+- From Pulsar 2.3.x to 2.10.x, Java SDK dead letter policy will set a 30 seconds acknowledgment timeout when there is no user defined acknowledgment timeout. This default timeout policy has been removed since 3.0.x.
 :::
 
 Use the Java client to specify the name of the dead letter topic.

versioned_docs/version-4.0.x/concepts-messaging.md

@@ -342,6 +342,7 @@ The dead letter producerName uses this format:
 :::note
 - For Pulsar 2.6.x and 2.7.x, the default dead letter topic uses the format of `<subscriptionname>-DLQ`. If you upgrade from 2.6.x~2.7.x to 2.8.x or later, you need to delete historical dead letter topics and retry letter partitioned topics. Otherwise, Pulsar continues to use original topics, which are formatted with `<subscriptionname>-DLQ`.
 - It is not recommended to use `<subscriptionname>-DLQ` because if multiple topics under the same namespace have the same subscription, then dead message topic names for multiple topics might be the same, which will result in mutual consumptions.
+- From Pulsar 2.3.x to 2.10.x, Java SDK dead letter policy will set a 30 seconds acknowledgment timeout when there is no user defined acknowledgment timeout. This default timeout policy has been removed since 3.0.x.
 :::
 
 Use the Java client to specify the name of the dead letter topic.