I have scheduled 2 cronjobs for my application.
My Application server is in an autoscaling group and I kept a minimum of 2 instances because of High availability. Everything working is fine but cron job is running multiple times because of 2 instances in autoscaling.
I could not limit the instance size to 1 because already my application in the production environment I prefer to have HA.
How should I have to limit execute cron job on a single instance? or should i have to use other services like AWS Lamda or AWS ELasticBeanstalk
Firstly you should consider whether running the crons on these instances is suitable. If you're trying to keep this highly available and it is directly interacted via customers what will the impact of the crons performance be?
Perhaps consider using a separate autoscaling group or instance with a total of 1 instances to run these crons? You could launch the instance or update the autoscaling group just before the cron needs to run and then automate the shutdown after it has completed.
Otherwise you would need to consider using a locking mechanism for your script. By using this your script write a lock to confirm that it is in process, at the beginning of the script run it would check whether there was any script lock in progress. To further prevent the chance of a collision between multiple servers consider adding jitter (random seconds of sleep) to the start of your script.
Suitable technologies for writing a lock are below:
DynamoDB using strongly consistent reads.
EFS for a Linux application, or FSX for a Windows application.
S3 using strong consistency.
Solutions suggested by Chris Williams sound reasonable if using lambda function is not an option.
One way to simulate cron job is by using CloudWatch Events (now known as EventBridge) in conjunction with AWS Lambda.
First you need to write a Lambda function with the code that needs to be executed on a schedule. Lambda supports cron expressions.
You can then use Schedule Expressions with EventBridge/CloudWatch Event in the same way as a cron tab and mention the Lambda function as target.
you can enable termination protection on of the instance. Attach necessary role & permission for system manager. once the instance is available under managed instance under system manager you can create a schedule event in cloudwatch to run ssm documents. if you are running a bash script convert that to ssm document and set this doc as targate. or you can use shellscript document for running commands
Related
We have an EC2 server that runs cronjobs. Currently there is a crontab on that server that holds the cronjob settings. Everything runs perfectly fine on this server.
Would it be overkill to use AWS Cloudwatch Events to trigger the crons instead? ie create a cloudwatch event that calls a lambda to run a shell command on the EC2 instance.
My thinking is that these would be possible benefits:
no need to manage a crontab file on the EC2 server
easier to activate/deactivate specific cronjobs
looks like there are indeed benefits according to the AWS Docs:
https://aws.amazon.com/blogs/compute/scheduling-ssh-jobs-using-aws-lambda/
Decouple job schedule and AMI: If your cron jobs are part of an AMI, each schedule change requires you to create a new AMI version, and update existing instances running with that AMI. This is both cumbersome and time-consuming. Using scheduled Lambda functions, you can keep the job schedule outside of your AMI and change the schedule on the fly.
Flexible targeting of EC2 instances: By abstracting the job schedule from AMI and EC2 instances, you can flexibly target a subset of your EC2 instance fleet based on tags or other conditions. In this example, we are targeting EC2 instances with the “Environment=Dev” tag.
Intelligent scheduling: With scheduled Lambda functions, you can add custom logic to you abstracted job scheduler.
In my experience it's not an over kill at all. I have used same setup with great success running job(s) (around 50 different jobs) with heavy workload.
My setup was slightly different
The cloudwatch scheduled event was calling a lambda which in turn was putting a messages on a sqs and application in running on ec2 instance(s) was grabbing messages from the sqs and processing them.
The sqs was simply added for robustness.
But this may or may not make sense in your use case.
I have a daily process that needs to digest a tremendous amount of data from two external sources. It normally requires around 28GB or RAM, and a decent amount of processing power. Due to this, an AWS Lambda won't work.
In the meantime, I've been running the process on an EC2 instance. In order to save resources, I've attempted to start the instance using a CloudWatch event. Since no event exists for "StartEC2," I'm kicking off a AWS Lambda instead, which in turn starts the EC2 isntance using Amazon support libraries.
All of this is extremely cumbersome, and I've been looking for a library or pattern that can do what I want. Essentially, I need to start an EC2 instance on a cron/event, deliver a unit of work to it (Shell Script, Java App, whatever), have it run it, then shutdown.
I'd love any suggestions for accomplishing this.
Look into AWS Systems Manager (SSM), you can create an Automation document that will launch the instance, run any custom scripts or tasks, and shut it down again when you're done. You can trigger the SSM Automation with a cron schedule via CloudWatch Events.
You may also want to consider AWS Batch for this type of workload.
Currently working on an environment requirement where we are to push the same file out to multiple EC2 instances running Windows on a scheduled interval. As it stands now, I see a few options and have tried each:
Windows Task Manager: run a basic task on a set schedule invoking the S3 Sync CLI tool
Cons I can see here include: setting up the task on each EC2 instance (there are many).
Lambda: scheduled lambda job that utilizes SSM to run commands on each server in a resource group
Cons: introducing another layer required to execute this task.
Run Command: using an AWS-RunRemoteScript document, run the script (stored in S3) bucket on target instances.
Cons: I'm not positive you can automate these commands on a schedule without adding another layer.
What is the most scalable path forward? Thanks in advance for your help.
Using the Run Command feature of AWS Systems Manager together with either the Maintenance Window feature of AWS Systems Manager or using CloudWatch Events to schedule the execution of Run Command should be useful here.
If you also tag instances appropriately, you can use the tag targeting feature of Run Command to ensure that all instances run the command (including new instances launched in the future as long as they are tagged).
/Mats
I have a Docker image containing Python code and third-party binary executables. There are only outbound network requests. The image must run hourly and each execution lasts ~3 minutes.
I can:
Use an EC2 instance and schedule hourly execution via cron
Create a CloudWatch Event/Rule to run an ECS Task Defintion hourly
Setup an Elastic Beanstalk environment and schedule hourly deployment of the image
In all of these scenarios, an EC2 instance is running 24/7 and I am being charged for extended periods of no usage.
How do I accomplish scheduling the starting of an existing EC2 instance hourly and the stopping of said instance after the completion of my docker image?
Here's one approach I can think of. It's very high-level, and omits some details, but conceptually it would work just fine. You'll also need to consider the Identity & Access Management (IAM) Roles used:
CloudWatch Event Rule to trigger the Step Function
AWS Step Function to trigger the Lambda function
AWS Lambda function to start up EC2 instances
EC2 instance polling the Step Functions service for Activity Tasks
Create a CloudWatch Event Rule to schedule a periodic task, using a cron expression
The Target of the CloudWatch Event Rule is an AWS Step Function
The AWS Step Function State Machine starts by triggering an AWS Lambda function, which starts the EC2 instance
The next step in the Step Functions State Machine invokes an Activity Task, representing the Docker container that needs to execute
The EC2 instance has a script running on it, which polls the Activity Task for work
The EC2 instance executes the Docker container, waits for it to finish, and sends a completion message to the Step Functions Activity Task
The script running on the EC2 instance shuts itself down
The AWS Step Function ends
Keep in mind that a potentially better option would be to spin up a new EC2 instance every hour, instead of simply starting and stopping the same instance. Although you might get better startup performance by starting an existing instance vs. launching a new instance, you'll also have to spend time to maintain the EC2 instance like a pet: fix issues if they crop up, or patch the operating system periodically. In today's world, it's a commonly accepted practice that infrastructure should be disposable. After all, you've already packaged up your application into a Docker container, so you most likely don't have overly specific expectations around which host that container is actually being executed on.
Another option would be to use AWS Fargate, which is designed to run Docker containers, without worrying about spinning up and managing container infrastructure.
AWS Step Functions
AWS Fargate
Blog: AWS Fargate: An Overview
Creating a CloudWatch Event Rule that triggers on a schedule
I'm running a instance in amazon AWS and it runs non-stop everyday. I'm using ubuntu ec2 instance which is running Apache, Mirthconnect tool and LAMP server. I want to run this instance only on particular time duration of a day. I prefer not use any additional AWS services such as cloud-watch . Is there a way we could acheive this?.
The major purpose is for using Mirthconnect fetching data from mysql database
There are 3 solutions.
AWS Data Pipeline - You can schedule the instance start/stop just like cron. It will cost you one hour of t1.micro instance for every start/stop
AWS Lambda - Define a lambda function that gets triggered at a pre defined time. Your lambda function can start/stop instances. Your cost will be very minimal or $0
Write a shell script and run it as a cron job or run it on demand. The script will have AWS CLI command to start and stop the instance.
I used Data Pipeline for a long time before moving to Lambda. Data Pipeline is very trivial. Just paste the AWS CLI commands to stop and start instances. Lambda is more involved.
I guess for that you'll need another machine which is on 24x7. On which you can write cron job in python using boto or any other language like bash.
I don't see how you start a instance in stopped state without using any other machine.
Or you can have a simple raspberry pi on at your home which does the ON-OFF work for you using AWS CLI or simple Python. How about that? ;)