Behaviour of Scheduled Job (Cron) when a previous job is running and new one is triggered

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Behaviour of Scheduled Job (Cron) when a previous job is running and new one is triggered

RajivBansal-2486 351

I have a job scheduled in container app jobs to execute after every 5 minutes.

Suppose a job is triggered at 11:00 a.m. Now before this finished another job is triggered at 11:05. What will happen to the previously running job. Will it get terminated or will both will run in parallel or will new job won't be scheduled. Please let me know how to control this behaviour.

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Answer 1

Sai Prabhu Naveen Parimi 2,590 Microsoft External Staff Moderator

RajivBansal-2486

When a new instance of your scheduled job is triggered while a previous one is still running, the outcome depends on your Azure Container Apps Job configuration.

Default Behavior – Runs in Parallel

By default, Azure Container Apps Jobs allow multiple instances to run simultaneously. So if your job starts at 11:00 AM and is still running when the next one is triggered at 11:05 AM, both will run in parallel unless limits are set.

For more details, check the official Microsoft documentation: https://learn.microsoft.com/en-us/azure/container-apps/jobs?tabs=azure-cli#scheduled-jobs

Summary

-->By default, jobs run in parallel.
--> You can limit concurrency so only one job runs at a time.

If the answer is helpful, please click Accept Answer and kindly upvote it. If you have any further questions about this answer, please click Comment.

Sai Prabhu Naveen Parimi 2,590 Reputation points Microsoft External Staff Moderator

2025-03-11T04:17:05.82+00:00

RajivBansal-2486

Just checking in to see if my previous response answered your question about the behavior of scheduled jobs in Azure Container Apps. If you have any further questions, feel free to ask!
RajivBansal-2486 351 Reputation points

2025-03-11T05:50:37.29+00:00

@Sai Prabhu Naveen Parimi

Thanks for the response. I checked the documentation and didn't found any configuration named maxConcurrentJobs. Do you mean parallelism? Will setting parallelism alone would be sufficient or is any other configuration need to be set.

Also I didn't found anything like singleton job type. Please refer me to the relevant documentation
Sai Prabhu Naveen Parimi 2,590 Reputation points Microsoft External Staff Moderator

2025-03-12T05:47:51.0533333+00:00

RajivBansal-2486

You're right—there isn’t a setting called maxConcurrentJobs in Azure Container Apps. The relevant setting here is parallelism

Let me know if you need any further clarification!
Sai Prabhu Naveen Parimi 2,590 Reputation points Microsoft External Staff Moderator

2025-03-13T08:42:09.81+00:00

RajivBansal-2486

Just following up to see if you had any further questions regarding parallelism in Azure Container Apps. Let me know if you need any clarification or assistance!
RajivBansal-2486 351 Reputation points

2025-03-13T08:59:39.0266667+00:00

@Sai Prabhu Naveen Parimi : It would be helpful if you can tell a bit about the behavior. Suppose parallelism is set to 1. One job starts at 11:00 a.m. It is still running and another job has to be scheduled for 11:05 a.m. Will this job be scheduled or will it be discarded.

Sai Prabhu Naveen Parimi 2,590 Microsoft External Staff Moderator

RajivBansal-2486

Great question! By default, parallelism is set to 1 in Azure Container Apps Jobs. This means that each scheduled job runs with a single instance at a time. If a new job is triggered while the previous one is still running, the first job continues running until it completes, and the new job starts independently, causing both jobs to run at the same time.

Example Scenario (Job Runs Every 5 Minutes, Each Execution Takes 7 Minutes)

Time	With `parallelism: 1` (Default)	With `parallelism: 2`
11:00 AM	Job 1 starts (1 instance running)	Job 1 starts (2 instances running)
11:00 AM	Job 1 starts (1 instance running)	Job 1 starts (2 instances running)
11:05 AM	Job 2 starts (Job 1 still running)	Job 2 starts (Job 1 still running but finishes faster)
11:07 AM	Job 1 completes	Job 1 already completed
11:10 AM	Job 3 starts (Job 2 still running)	Job 3 starts (Job 2 already completed)
11:12 AM	Job 2 completes	-

Comparison Table: parallelism: 1 vs. parallelism: 2

Setting	`parallelism: 1`	`parallelism: 2`
Instances per execution	1	2
Effect on job execution speed	Slower (only one instance processing work)	Faster (work split between two instances)
Resource usage	Lower	Higher
Billing impact	Lower (fewer resources used)	Higher (more instances running)
Best suited for	Light workloads, cost-saving scenarios	Heavy workloads, performance-critical jobs

Synopsis

Default behavior: parallelism is set to 1, meaning only one instance runs per job execution.
Job execution: A running job does not stop when a new one starts; it continues until completion.
Overlapping jobs: If job execution time exceeds the schedule interval, jobs will run in parallel.
Increasing parallelism: Allows multiple instances within a single execution, speeding up processing but consuming more resources.

Let me know if this is helpful! Please click "Accept Answer" and consider giving it an upvote. If you have any additional questions, feel free to click "Comment."

RajivBansal-2486 351 Reputation points

2025-03-15T07:07:31.15+00:00

Hi Sai Prabhu Naveen Parimi,

Thanks for the response. My requirement is that concurrent instances of job should not run i.e. only one instance of a job should run at a given time. If previous instance is not finished, new job should not be scheduled.

Is it possible to achieve using any configuration in Azure Container Jobs
Sai Prabhu Naveen Parimi 2,590 Reputation points Microsoft External Staff Moderator

2025-03-18T09:27:17.56+00:00

RajivBansal-2486

Currently, this functionality is not supported in Azure Container Apps. I’d recommend submitting a feature request on feedback.azure.com so the product team can consider adding it in future updates.

In the meantime, I’ll check internally with our team to see if there are any alternative solutions or undocumented options to achieve this behavior. I’ll update you as soon as I have more details.

Let me know if you have any other questions!
Sai Prabhu Naveen Parimi 2,590 Reputation points Microsoft External Staff Moderator

2025-04-01T00:48:04.0966667+00:00

RajivBansal-2486We checked with our internal team, and they have confirmed that this functionality is not currently supported in Azure Container Apps.

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Behaviour of Scheduled Job (Cron) when a previous job is running and new one is triggered

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