sqs-dg-2009-02-01
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Amazon Simple Queue Service Developer Guide<br />
Message Lifecycle<br />
Extending a Message's Visibility Timeout<br />
When you receive a message from the queue, you might find the visibility timeout for the queue is<br />
insufficient to fully process and delete that message. Amazon SQS allows you to extend the visibility<br />
timeout for that particular message. When you extend the visibility timeout, Amazon SQS overwrites the<br />
original timeout value and the new value begins at the time you changed it.<br />
For example, let's say the timeout for the queue is 30 seconds, and you receive a message. Once you're<br />
20 seconds into the timeout for that message (i.e., you have 10 seconds left), you extend it by 60 seconds<br />
by calling ChangeMessageVisibility with VisibilityTimeoutset to 60 seconds.You have then changed<br />
the remaining visibility timeout from 10 seconds to 60 seconds.<br />
The extension you request is not stored in memory for that message. If for some reason you don't delete<br />
the message and the message is received again, the visibility timeout for the message the next time it's<br />
received is the overall value for the queue and not the extended value you previously set.<br />
Terminating a Message's Visibility Timeout<br />
When you receive a message from the queue, you might find that you actually don't want to process and<br />
delete that message. Amazon SQS allows you to terminate the visibility timeout for a specific message,<br />
which immediately makes the message visible to other components in the system to process. To do this,<br />
you call ChangeMessageVisibility with VisibilityTimeout=0 seconds.<br />
API Actions Related to Visibility Timeout<br />
The following table lists the API actions to use to manipulate the visibility timeout.<br />
To do this...<br />
Set the visibility timeout for a queue<br />
Get the visibility timeout for a queue<br />
Set the visibility timeout for the received messages without<br />
affecting the queue's visibility timeout<br />
Extending or terminating a message's visibility timeout<br />
Use this action<br />
SetQueueAttributes<br />
GetQueueAttributes<br />
ReceiveMessage and set the<br />
VisibilityTimeout parameter to the<br />
value you want<br />
ChangeMessageVisibility<br />
Message Lifecycle<br />
The following diagram and process describe the lifecycle of an Amazon SQS message, called Message<br />
A, from creation to deletion. Assume that a queue already exists.<br />
API Version <strong>2009</strong>-<strong>02</strong>-<strong>01</strong><br />
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