CODEWITHSUNDEEP
amazon-web-servicesaws-lambdaamazon-cloudwatch
Prashantm
Prashantm

Reputation: 71

Call concurrent instances of AWS lambda on Cloud watch event rule

I have one cloud watch event set per minute which triggers AWS Lambda.I have set concurrent executions of lambda to 10 however it's only triggering a single instance per minute. I want it to run 10 concurrent instances per minute.

Upvotes: 3

Views: 743

Answers (1)

TantrixRobotBoy
TantrixRobotBoy

Reputation: 629

Concurrency in Lambda is managed pretty differently from what you expect. In your case you want a single CloudWatch Event to trigger multiple instances each minute. However, Concurrency in Lambda is working as follows: think you have CloudWatch Event triggering your Lambda and also other AWS services (e.g. S3 and DynamoDB) which trigger your Lambda. What happens when one of your triggers activate the Lambda is that a Lambda instance is active and is consumed until the Lambda finishes its work/computation. During that period of time, the total concurrency units will be decreased by one. At that very moment if another trigger activates the Lambda, the total concurrency units will be decreased again. And this will happen until your Lambda instances are being executed.

So, in your case there will be always a single event (CloudWatch) triggering a single Lambda instance, causing the system not to trigger multiple instances, as for its operation this is the correct way to work. In other words, you do not want to increase concurrent lambda execution to 10 (or whatever) to reach your goal of running 10 parallel instances per minute.

In order to do so, it's probably better for you to create a Lambda orchestrator which calls multiple instances of your Lambda and then setting the Lambda Concurrency in this last Lambda higher than 10 (if you do not want the Lambda to throttle). This way is also pretty good in order to manage the execution of your multiple instances and to catch errors atomically with a greater error flow control.

You can refer to this article in order to get the Lambda Concurrency behavior. The implementation of Lambda orchestrator to manage the multiple instances execution, instead is pretty straightforward.

Upvotes: 3

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