If a logic app is scheduled to run once a day. And at the run, it finds 20 messages sitting in Azure Service Bus. How does it process them? One by one? or in parallel? And how long does that take? Moreover, how many messages can sit in azure service bus a in one time waiting for logic app to process them? Thanks.

Hi @Fareeha Sattar Shaikh Greetings! Welcome to Microsoft Q&A forum. Thank you for posting this question here. The Azure Logic App Service App Connector has a method Get messages from a queue which processes messages in batches and can be iterated over in the Logic app. The action item has a parameter Maximum message count which can be set from the Logic app designer. The default value for this parameter is 20. If you set a trigger to run the Logic App once a day, the app will process the messages in the queue based on the limit set to this parameter, on FIFO approach, and leave the rest in the queue. And how long does that take? If you are just reading out the messages, this should not take long. The entire logic app workflow process time depends on the different actions configured in the workflow. how many messages can sit in azure service bus a in one time waiting for logic app to process them This depends on couple of factors - Max Size of the Queue and Message time to live. When the Max size of the queue is reached, it will no longer process new messages. The default time to live for a message is 14 days since the time they get added in the queue. Once a message is past this time, it might get deleted from the queue and can no longer be retrieved. Please refer the documentation Azure Service Bus - Message expiration (Time to Live) for more details on this. Hope this answers your questions! Please let me know if you need any additional details. If the response helped, please do click Accept Answer and Yes for the answer provided. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.

How logic app process multiple messages in an Azure Service Bus?

Accepted answer

LeelaRajeshSayana-MSFT 15,556 Reputation points Microsoft Employee

2024-09-18T22:27:15.0666667+00:00

Hi @Fareeha Sattar Shaikh Greetings! Welcome to Microsoft Q&A forum. Thank you for posting this question here.

The Azure Logic App Service App Connector has a method Get messages from a queue which processes messages in batches and can be iterated over in the Logic app. The action item has a parameter Maximum message count which can be set from the Logic app designer.

The default value for this parameter is 20. If you set a trigger to run the Logic App once a day, the app will process the messages in the queue based on the limit set to this parameter, on FIFO approach, and leave the rest in the queue.

And how long does that take?

If you are just reading out the messages, this should not take long. The entire logic app workflow process time depends on the different actions configured in the workflow.

how many messages can sit in azure service bus a in one time waiting for logic app to process them

This depends on couple of factors - Max Size of the Queue and Message time to live. When the Max size of the queue is reached, it will no longer process new messages. The default time to live for a message is 14 days since the time they get added in the queue. Once a message is past this time, it might get deleted from the queue and can no longer be retrieved. Please refer the documentation Azure Service Bus - Message expiration (Time to Live) for more details on this.

Hope this answers your questions! Please let me know if you need any additional details.

If the response helped, please do click Accept Answer and Yes for the answer provided. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.
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1 person found this answer helpful.
Fareeha Sattar Shaikh 65 Reputation points

2024-09-19T08:33:25.6766667+00:00

Hi @LeelaRajeshSayana-MSFT

Thanks for your response. But what if I am using the trigger of When a message is received in topic (auto complete)?

Will the behavior be any different?

LeelaRajeshSayana-MSFT 15,556 Reputation points Microsoft Employee

2024-09-24T21:49:32.74+00:00

Hi @Fareeha Sattar Shaikh Apologies for the delayed response. If you use this approach, you should not have to worry about messages living in the queue and end up not being consumed. The logic app workflow gets triggered for every message that is received to the queue and can be processed without having to wait for an entire day for the message getting processed.

Please be cautious to not send any messages from the logic app workflow to the queue when using this trigger as it would result in an infinite loop.

If the response helped, please do click Accept Answer and Yes for the answer provided. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.

Fareeha Sattar Shaikh 65 Reputation points

2024-09-30T09:33:05.5633333+00:00

Hi @LeelaRajeshSayana-MSFT

But if the Logic App is scheduled to run once in a day. Lets say 8 PM daily. And the service bus of TOPIC has received many messages in it through out the day. So when the Logic App runs at 8 PM, will it run for each message received? How long will it take to process the messages?

And what if there are too many messages, can the logic app be stuck as well?

Fareeha Sattar Shaikh 65 Reputation points

2024-09-30T09:37:00.41+00:00

Hi @LeelaRajeshSayana-MSFT

But what if Logic app is scheduled to run daily at 8 PM once a day. So what if the service bus of type TOPIC receives many messages in it throughout the day. When the logic app runs at 8 PM how will it process those many messages? One by one? And what if the quantity of messages is in thousands? Is there a possibility that logic app will be stuck?

LeelaRajeshSayana-MSFT 15,556 Reputation points Microsoft Employee

2024-09-30T20:53:27.0766667+00:00

Hi @Fareeha Sattar Shaikh If you decide to go with recurrence trigger in stead of When a message is received in topic (auto complete), you will have to choose one of the options available from the supported list of actions by the connector. For topic, you would have to go with Get messages from a topic subscription (peek-lock) action which does have a Maximum message count which the action will process similar to queue processing.

The logic app flow will be the similar to that of a queue as mentioned in the answer above.

Fareeha Sattar Shaikh 65 Reputation points

2024-10-02T16:02:39.18+00:00

Hi @LeelaRajeshSayana-MSFT

But when I use the trigger of when a message is received in topic (auto complete)

even then I have to select the recurrence of the trigger.

LeelaRajeshSayana-MSFT 15,556 Reputation points Microsoft Employee

2024-10-02T20:19:29.2833333+00:00

Hi @Fareeha Sattar Shaikh Thank you for the follow up question. This timer is basically to check how often you would like to the Topic for messages. The trigger automatically provides you access to the Message sent to the Topic. You can access the message body by reading the Content from the returned properties of the Trigger as follows

You wouldn't need another action such as Get messages from a topic subscription (peek-lock) in this case to read the messages out of a topic. If you set this trigger timer to run once an hour and there are 25 messages delivered to the topic, the logic app will be run 25 instances parallelly at the mentioned time and the messages will be processed in FIFO order.

Hope this clarifies things. Please let us know if you have any additional questions or need further clarification.

If it answers your query, please do click Accept Answer and Yes for the answer, as it might be beneficial to other community members reading this thread. Thank you
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