In this article we will look at creating a Cloudwatch rule in Amazon Web Services with Cloudformation that will invoke a Lambda function on a timer. In this article we are going to create a Scheduled Event to regularly invoke our Lambda function. The AWS web console or the CLI are quick and easy ways to get Cloudwatch rules setup, but if you are building systems that use integrated AWS services, Cloudwatch can help keep these services organized and in a central location.
In this article we will use Cloudformation to create our Cloudwatch rule. Then we have our first resource object, in this case cloudwatchRuleInvokeLambda. These resource type identifiers can be named as you see fit, but will need to be unique. They will always have the format:.
Description shows in the description field when viewing your Cloudwatch rule, and State is used to enable and disable to rule. ScheduleExpression, in this case of a schedule rule is used to tell how often to invoke the Lamda function.
And finally Targets will be an array of objects that describe the Lambda function to invoke. You can read up on how to use Lambda Qualifiers here. Next is the Input to send to the Lambda function. This will be available in the Event object in your function. Last is the Id, this helps you keep track of the targets your rule calls.
Notice that the Targets object accepts an array.
Amazon CloudWatch EventsのイベントルールでターゲットをAmazon SQSにしてAWS Lambdaでイベントソース…
In our example, we call two different targets using the same rule. In this example, we are calling the same Lambda function, but using Qualifiers to specify calling the ACC qualifier:. This target array can also be used to call other Lambda functions, SQS operations, or other targets that listen to Cloudwatch rules.
You can use this property in Cloudwatch to get information about other objects in your Cloudwatch stack. If you do not recieve an error back from AWS your template is valid. My response looks like this:. Check the Events page in the web console to view logs to see what failed. At this point you cannot update the template for your stack, you must delete the stack and re-create. Target input: Sending data to your Lambda function is important.
Be sure to use the Input property of your target object. From our template that looks like this:. After following this article you should now have a valid Cloudformation template to create a Cloudwatch rule that invokes a Lambda function ever hour. You can expand this template to add other resources to expand your Cloudformation templates.I finally took the plunge and played around with creating a CloudFormation template.
It was actually easier than I thought it would be. So that's a plus. Most CloudFormation scripts are very daunting to view The first part of this template is automating creation of the actual Lambda function, so lets break that down:.
To define a Lambda, we must provide four properties:. All of these properties are things you would supply to a Lambda function if you were creating it through the UI. This should just be your Lambda execution Role. The Code property in this example uses the Fn::Join property to concatinate lines together as the code of your Lambda function. This is sufficient for the simple example I'm showing you here. In reality, you would likely point to an S3 location for your code.
This requires a bit more scripting than the previous sections. From the above, we will create a reference using the logical name of the Lambda function. The last component here is getting the ARN of the event source.
This uses another script Fn::GetAtt which simply retreieves the specified attribute from the resource in the template. Lets start with a template, then I'll break it down.
To define a Lambda, we must provide four properties: Handler - the entrance point to your Lambda Role - the role that the Lambda executes under Runtime - the Runtime to execute the Lambda with Code - how you want to load the code into your Lambda function All of these properties are things you would supply to a Lambda function if you were creating it through the UI.
Amazon SQS as an Event Source to AWS Lambda : A Deep Dive
The reference resolves to the physical ID of the Lambda, which is it's name. Hopefully that provides a bit of a starting point for working with CloudFormation.There are many advantages to using a serverless architecture and there are hundreds of excellent articles extolling its virtues, but one painful downside is the often-slow response time of serverless functions that are infrequently used.AWS CloudFormation Masterclass
This is because on occasion, the container that created the function does not get reused. So on some requests, AWS needs to re-provision a container with your code before it can process the request.
Alas, this has not yet? This is easier than you might expect. From there, go to Events and click Create rule. Then select the Lambda function you want to target from the Targets list and Save. So for the sake of science, I went ahead and created interval timers for 1—15 minutes, as well as 30, 45, and 60 minute intervals for good measure. This should give us a sense of how long AWS keeps these containers warm. Fast forward 8 hours and we have our results.
I was hoping the results would be interesting enough to create a fancy chart, but instead, I found this pattern for all of the functions. Basically, all Lambda functions stayed warm for the duration of the experiment except that sometime around UTC, AWS decided to reset all containers with no regard to whether or not it had been used recently.
Even the 1-hour ping continued to use the same container for several hours in a row image below. If you have any ideas of how we might improve upon these results, or if you have reason to believe these results are not valid for some particular reason, let me know in the comments. Sam Corcos is the co-founder of CarDasha full-service automotive concierge provider that eliminates the hassle of auto service, care, and maintenance.
He is also the author of Learn Phoenixand founder of Sightline Maps. Sign in.
What's New? Get Certified acloud. Use CloudWatch timers to thaw functions and help reduce response times from 3 seconds to a couple hundred milliseconds.
Sam Corcos Follow.If you've got a moment, please tell us what we did right so we can do more of it. Thanks for letting us know this page needs work. We're sorry we let you down. If you've got a moment, please tell us how we can make the documentation better. The AWS::Events::Rule resource creates a rule that matches incoming events and routes them to one or more targets for processing. For more information, see What Is Amazon Eventbridge? A rule must contain at least an EventPattern or ScheduleExpression.
Rules with EventPattern are triggered when a matching event is observed. Rules with ScheduleExpression self-trigger based on the given schedule. A rule can have both an EventPattern and a ScheduleExpressionin which case the rule triggers on matching events as well as on a schedule. However, EventBridge uses an exact match in event patterns and rules. Be sure to use the correct ARN characters when creating event patterns so that they match the ARN syntax in the event that you want to match.
Update requires : No interruption. The event bus to associate with this rule. If you omit this, the default event bus is used.
Update requires : Replacement. Describes which events are routed to the specified target. When using CloudFormation, you must enclose each part of the event pattern in square brackets, as follows:. A rule must contain either EventPattern or ScheduleExpression.
The name of the rule. If you specify a name, you can't perform updates that require replacement of this resource. You can perform updates that require no or some interruption. If you must replace the resource, specify a new name. If you're setting an event bus in another account as the target and that account granted permission to your account through an organization instead of directly by the account ID, you must specify a RoleArn with proper permissions in the Target structure, instead of here in this parameter.If you've got a moment, please tell us what we did right so we can do more of it.
Thanks for letting us know this page needs work. We're sorry we let you down. If you've got a moment, please tell us how we can make the documentation better. You can configure triggers to invoke a function in response to resource lifecycle events, respond to incoming HTTP requests, consume events from a queue, or run on a schedule. The structure of the event document is different for each event type, and contains data about the resource or request that triggered the function.
Lambda runtimes convert the event into an object and pass it to your function. The Lambda runtime converts the event document into an object and passes it to your function handler. For compiled languages, Lambda provides definitions for event types in a library. See the following topics for more information. For services that generate a queue or data stream, you create an event source mapping in Lambda and grant Lambda permission to access the other service in the execution role.
Lambda reads data from the other service, creates an event, and invokes your function. Other services invoke your function directly. You grant the other service permission in the function's resource-based policyand configure the other service to generate events and invoke your function.
Depending on the service, the invocation can be synchronous or asynchronous. For synchronous invocation, the other service waits for the response from your function and might retry on errors. AWS Step Functions. For asynchronous invocation, Lambda queues the event before passing it to your function. The other service gets a success response as soon as the event is queued and isn't aware of what happens afterwards.
Did this page help you? Thanks for letting us know we're doing a good job! Example Event from an Application Load Balancer. Document Conventions. Best Practices.Comment 0. SQS as an event source to Lambda is a game changer. I can now send all my event-based messages, logs, and analytics from my iOS application directly to an SQS queue. What has changed is the managed backend resources for consuming content sent to the queue. After you are up and running, follow along for a deeper dive into this serverless event-driven architecture.
Simple Queue Service SQS is scalable, low latency, offers unlimited throughput, at-least-once-delivery, batching, server-side encryption, serverless messaging service. This could be done with short polling or long polling. Either way, it was a service you, as a developer, had to build, monitor, scale, and maintain. You even had to write logic to know when to back off polling and know when to delete a message or let it go back into the queue.
It was a hacked way of event-driven development. Think of it like building your own webhook for an API. Not an easy solution. The source queue is NOT triggering your Lambda function.
Now that SQS is an event source to Lambda, all that heavy lifting of managing message polling and deleting has been offloaded to the Lambda service, which is now your SQS consumer. Lambda is doing the scaling of consumers of YOUR SQS queue for messages, receiving messages, and passing those messages to your Lambda function, and then deleting those messages when your Lambda function successfully handles the message s received.
Using AWS Lambda with Other Services
This is all explained in more detail here. Thanks for the sketch, Jerry Hargrove! If you already know enough about SQS as an event source and how the AWS Lambda integration works, skip the preamble and move onto Get Started using the included end-to-end CloudFormation template and then come back for a deeper dive. Click on the template to launch the CloudFormation console to begin building your stack. The template defaults to the US West Oregon region us-west For testing fun, I put in a parameter for you to provide your mobile number so that you will receive an SMS text message whenever an SQS message arrives in the queue.
This for testing purposes only. The phone number is stored as an environment variable for the Lambda function. If Node. In the Amazon SQS consolesend messages to the queue.One of them is running some background jobs in scheduled intervals. It collects metrics and logs from your resources. You can take actions by defining targets to these events. You can create a rule to trigger an AWS Lambda function whenever this event happens. This type of events are triggered when a change occurs on your AWS resources.
On the other hand, you can also define event rules that self-trigger regularly and configure a target action to do some regular work. Hence, when this event is triggered at the specified time or interval you defined, your function or state machine is executed. These types of events are called scheduled Amazon CloudWatch Events and we will make example of them in this blog post. By the way, Amazon EventBridge is the new version of CloudWatch events, a serverless event bus service.
It also allows you to build an event-driven architecture and integrate your SaaS applications with AWS resources easier. I will also show you how you can use Amazon EventBridge console to create scheduled events. This type of usage is very similar to the cron jobs you define on your Linux servers.
But this time, it will be serverless and you will not need to pay for the idle time your servers run. For example, you can configure an event to be triggered on every Monday at in GMT. You have less control in rate definitions. It starts from the time you create the event and calculates the next trigger time according to its creation time.
To do this. Next, you will see the event rule form in which Event pattern is selected. It is for the resource originated events that we discussed above. Hence, for scheduled events, you need to select Schedule option. You will see that rate expression is enabled by default when you enable Schedule option.
There are two information you need to provide to define a fixed rate: The interval and its unit. The unit can be minutes, hours and days.