run scheduled task in AWS without cron

Currently I have a single server in amazon where I put all my cronjobs. I want to eliminate this single point of failure, and expose all my tasks as web services. I'd like to expose the services behind a VPC ELB to a few servers that will run the tasks when called.

Is there some service that Amazon (AWS) offers that can run a reoccurring job (really call a webservice) at scheduled intervals? I'd really like to be able to keep the cron functionality in terms of time/day specification, but farm out the HA of the driver (thing that calls endpoints at the right time) to AWS.

I like how SQS offers web endpoint(s), but from what I can tell you cant schedule them. SWF doesn't seem to be a good fit either.

AWS announced support for scheduled functions in Lambda at its 2015 re:Invent conference. With this feature users can execute Lambda functions on a scheduled basis using a cron-like syntax. The Lambda docs show an example of using Python to perform scheduled events.

Currently, the minimum resolution that a scheduled lambda can run at is 1 minute (the same as cron, but not as fine grained as systemd timers).

The Lambder project helps to simplify the use of scheduled functions on Lambda.

λ Gordon's cron example has perhaps the simplest interface for deploying scheduled lambda functions.

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Original answer, saved for posterity.

As Eric Hammond and others have stated, there is no native AWS service for scheduled tasks. There are only workarounds and half solutions as mentioned in other answers.

To recap the current options:

• The single-instance autoscale group that starts and stops on a schedule, as described by Eric Hammond.
• Using a Simple Workflow Service timer, which is not at all intuitive. This case study mentions that JPL used SWF to build a distributed cron, but there are no implementation details. There is also a reference to a code example buried in the SWF code samples.
• Run it yourself using something like cronlock.
• Use something like the Unreliable Town Clock (UTC) to run Lambda functions on a schedule. Remember that Lambda cannot currently access resources within a VPC

Hopefully a better solution will come along soon.

Introducing Events in AWS Cloudwatch

You can schedule by minute, hourly, days or using CRON expression using console and without Lambda or any programming.

I just scheduled my ASP.net WEB API(HTTP Post) using SNS HTTP endpoint to execute every minute and it's working perfectly.

> Is there some service that Amazon (AWS) offers that can run a reoccurring job at scheduled intervals?

This is one of a few single points of failure that people (including me) keep mentioning when designing architectures with AWS. Until Amazon solves it with a service, here's a hack I've published which is actively used by some companies.

AWS Auto Scaling can run and terminate instances using a recurring schedule specified in the cron format.

http://docs.amazonwebservices.com/AutoScaling/latest/APIReference/API_PutScheduledUpdateGroupAction.html

You can have the instance automatically run a process on startup.

If you don't know how long the job will last, you can set things up so that your job terminates the instance when it has completed.

Here's an article I wrote that walks through exact commands needed to set this up:

> Running EC2 Instances on a Recurring Schedule with Auto Scaling
> http://alestic.com/2011/11/ec2-schedule-instance

Starting a whole instance just to kick off a set of jobs seems a bit like overkill, but if it's a t1.micro, then it only costs a couple pennies.

That t1.micro doesn't have to do the actual work either. Your instance could inject messages into SQS or through SNS so that the other redundant servers pick up the tasks.

This a hosted third party site that can regularly call scheduled scripts on your domain.

This will not work if you need your script to run in the shell, and not as Apache.

Sounds like this might be useful to you: http://docs.aws.amazon.com/datapipeline/latest/DeveloperGuide/dp-using-task-runner.html

> Task Runner is a task agent application that polls AWS Data Pipeline > for scheduled tasks and executes them on Amazon EC2 instances, Amazon > EMR clusters, or other computational resources, reporting status as it > does so. Depending on your application, you may choose to: > > * Allow AWS Data Pipeline to install and manage one or more Task Runner > applications for you on computational resources that it manages > automatically. In this case, you do not need to install or configure > Task Runner as described in this section. This is the recommended > configuration. > > * Manually install and configure Task Runner on a computational resource > such as a long-running EC2 instance or a physical server. To do so, > use the procedures in this section. > > * Develop and install a custom task agent instead of Task Runner. The > procedures for doing so will depend on the implementation of the > custom task agent.

Amazon has introducted Lambda last year for NodeJS, yesterday Amazon added the features Scheduled Functions, VPC Support, and Python Support.

By leveraging Scheduled Function - a proper replacement for CRON can be attained.

More Info - http://aws.amazon.com/lambda/details/

As of August 2020, Amazon has moved the Lambda/CloudWatch events to a service called EventBridge (https://aws.amazon.com/eventbridge/). It was launched in July 2019, after most of the answers to this question.

Looks like this is a relatively new option from AWS BeanStalk:

https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features-managing-env-tiers.html#worker-periodictasks

Basically, they act like regular SQS receivers, but they're called on a cron schedule instead of in response to a SQS message.

SWF is a Web service from AWS that can be used to schedule tasks. Most of the work goes into specifying what a task and a schedule is.

http://milindparikh.blogspot.com/2015/07/introducing-diksha-aws-lambda-function.html is a scalable scheduler written against SWF.

CloudWatch Events are great, but there is a limit on their number. If you need a scale and willing to sacrifice the precision you could use DynamoDB's TTL as a timer.

The idea is to put items into a DynamoDB table with a TTL set to the time you need to run a task. DynamoDB will delete those items somewhere around the specified time (within 48 hours of expiration). Those deleted items will appear in the DynamoDB stream, associated with a table. A lambda function could listen the stream and take appropriate actions upon the deletions.

Read more in "DynamoDB TTL as an ad-hoc scheduling mechanism" by theburningmonk.com.

The AWS Elastic Load Balancers will ping your instances to check that they're healthy. You can add your cron-like tasks to the script that the ELB is pinging, and it will execute very regularly.

You'd want to add some logic so that each tasks is executed the right amount of times and at the right interval, but this could be accomplished with a database table that tracks executions. Each time the ELB pings your server, your server would check the database to see if any job is pending, and then execute that job.

The ELB will timeout if the script takes too long to execute, so it's important to not create a situation where your ELB health check will take many seconds to process the cron tasks. To overcome this, you can employ the AWS Simple Notification Service. Your ELB health check script can simply publish a message to an SNS topic, and then that topic can deliver the message via an HTTP request to your web server.

In other words: ELB pings your EC2 instance... EC2 instance checks for pending jobs and sends a message to SNS if any are found... SNS notifies your app via HTTP... The HTTP call from SNS is what actually processes the cron job