A dead letter queue is a special form of message queue, used to process messages that are unable to be normally consumed in a centralized manner. If a message fails to be properly consumed after a certain number of retry attempts, TDMQ for RocketMQ will determine that this message cannot be consumed in the current situation and send it to the dead letter queue.
In actual situations, messages may become unconsumable due to extended periods of service downtime or network disconnections. In such situations, messages are not discarded immediately, but the dead letter queue engages in extended persistence processing for such messages. Upon identifying an appropriate solution, users can create a consumer subscription to the dead letter queue in order to process messages that cannot be process at the time.
Query Restrictions
You can query messages from the past three days at most.
Feature Description
If a message is sent to the dead letter queue, it will not be consumed by consumers normally. You can query messages from the past three days at most. Please process dead letter messages within three days after they are generated. Otherwise, these messages may be deleted.
A dead letter queue contains all the dead letter messages generated in every topic within a single group. If there are no dead letter messages in a group, no dead letter queues will be created and dead letter messages cannot be found.
Directions:
1. Log in to the TDMQ for RocketMQ console, and then click on Dead Letter Message Query in the left sidebar.
2. On the message query page, select the region and follow the on-screen instructions to enter the query conditions.
Time Range: Choose your desired time period for conducting the query. You can choose the last 30 minutes, last hour, last 6 hours, last 24 hours, last 3 days, or a customized time range.
Present Cluster: Choose the cluster that contains the dead letter message to be queried.
Group: Choose the group that contains the dead letter message to be queried.
Message ID: It is optional.
If you leave the Message ID field blank, the query is a fuzzy search. Queries can be conducted in batch according to Group ID and time range in which the dead letter messages are generated.
If you specify Message ID, the query is an exact search. Group ID and Message ID will be used to precisely locate any message.
3. Click Query. The list below will show all the results of the search in pages.
4. You can select multiple dead letter messages and click Batch Resend Messages at the top left corner to resend these messages to the original retry queue. Alternatively, you can click Resend Message under the operations column of a single message to resend a particular dead letter message. Messages that have been resent will be delivered to the retry queue of the original queue and will not be immediately deleted from the dead letter queue. These messages will only be deleted after their lifecycle (three days) expires.
5. Find the message in which you want to view its content or parameters, and click View Details under the operation column. Then you can view the basic information, content (message body), and parameters of the message.
6. Click View Message Trace under the operation column, or select Message Trace on the tab bar in the details page. Then you can view the message trace of the message. For details, see the Message Trace Query Results.
You will see that when a dead letter message is resent, the consumption status changes to Dead Letter Redelivery Completed.
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