Queue modes
- Last UpdatedJun 29, 2026
- 2 minute read
Each message received by a module enters an input queue, except when queues are disabled. In most cases, messages stay briefly until they are picked up for processing. However, there are times when messages may build up in the queue due to the following reasons:
-
An output module is waiting on a slow external system.
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A burst of messages are created by a module in the flow. For example, a module is looping over messages in an array.
The following table lists the queue mode settings used to control what actions are taken when the input queue gets full.
Note: The default size for input queues is 100 messages, which is sufficient for most situations.
|
Queue mode setting |
Description |
|---|---|
|
Wait |
This default setting instructs the previous module to wait (back pressure) until there is space in the queue to add the message. Use this setting when message bursts are moderate and the flow can handle the average incoming message rate. In remote sessions, the system can show warnings when a queue becomes full, even in Wait mode. This is acceptable in certain situations. For example, when using an Array Split module. If warnings occur across all modules back to the first module in a flow, the flow cannot handle the average message rate. In this case, adjust the queue settings. In this mode, deployed flows do not report warnings for full queues because this is typically not an issue. |
|
Drop Newest |
This setting instructs a module to drop the latest message added to a queue in order to make room for adding a new message. |
|
Drop Oldest |
This setting instructs a module to drop the oldest message added to the queue in order to make room for adding a new message. |
|
Drop Write |
This setting instructs the module to drop the pending new message. All existing messages in the queue will remain. |