Reputation: 553

Restarting AWS lambda function to clear cache

I have a AWS Lambda function that creates an object from a s3 call in cold start. I then hold the object in the cache while the function is warm to keep load times down. When files are changed in s3, I have a trigger to run the lambda, but not all the running instances of lambda restart and pull from s3.

Is there a way to bring down all instances of lambda forcing a full cold start?

Also, I don't want to use python.

Upvotes: 55

Answers (11)

Sajjad Ali Vayani

Reputation: 1

Updating description from AWS console will do the job. My use case was, I was storing SSM parameter in static variable in lambda function as a cache. I updated the value of ssm parameter and updated the description of lambda from AWS console, the updated value reflected in lambda.

Upvotes: 0

Paul Şular

Reputation: 155

Following Renato Byrro's answer I made a lambda function using JavaScript AWS SDK to restart another lambda function by updating the description.

import { LambdaClient, UpdateFunctionConfigurationCommand } from '@aws-sdk/client-lambda';

const forceLambdaRestart = async event => {
    try {
        const client = new LambdaClient({
            region: 'your region here',
            credentials: {
                accessKeyId: 'your access key id',
                secretAccessKey: 'your secret access key',
            },
        });

        const command = new UpdateFunctionConfigurationCommand({
            FunctionName: event.functionName,
            Description: `forced update ${Date.now()}`,
        });

        const data = await client.send(command);

        console.log(data);
        return data;
    } catch (error) {
        console.error(error);
        return error;
    }
};

forceLambdaRestart();

It seems like that is enough to restart the lambda and clear in-memory cache.

Upvotes: 1

Nilesh

Reputation: 127

The simplest answer for this question I found is. Make some changes in function like adding a simple comment line or removing any white space and then redeploy the function.

It will clear the cache while deploying.

Upvotes: 2

johncurrier

Reputation: 493

Simply add a new environment variable and / or change an existing one. I created one named BOGUS and gave it a number that I increment whenever I want to force a cold start.

Upvotes: 11

Jochem Schulenklopper

Reputation: 6914

In addition to some of the valid answers above: I happened to run an experiment on the (average) AWS Lambda instance lifetime. I could not find instances that ran for much longer than (on average) two hours: https://xebia.com/blog/til-that-aws-lambda-terminates-instances-preemptively/.

TL;DR: AWS Lambda is preemptively terminating instances (even those handling traffic) after two hours, with a standard deviation of 30 minutes.

Upvotes: 4

user3041539

Reputation: 628

Easiest way I found was changing something in Basic Settings like timeout:

I've upped+1 by a second, saved, and the function got refreshed

Upvotes: 13

Baked Inhalf

Reputation: 3735

I made an Answer based on my comment and verification from @DejanVasic

aws lambda update-function-configuration --function-name "myLambda" --description "foo"

This will force the next invokation of the lambda to "cold start".

To verify:

@timestamp, @message | sort @timestamp desc | limit 1000 | filter @message like "cold_start:true"

Upvotes: 45

Ludicrous

Reputation: 61

If you are using the Lambda versioning system, another way to do this is by publishing a new version and using an alias to direct all traffic to it.

Here's an example:

Publish version: aws lambda publish-version --function-name your-function-name-here

Update the alias pointing to the new version: aws lambda update-alias --function-name your-function-name-here --name alias-name-here --function-version 123 (use the function version in the output message from the first command above)

Upvotes: 4

Renato Byrro

Reputation: 3784

Use the UpdateFunctionCode API endpoint to force a refresh of all containers. AWS SDKs wrap this up to make it easier for you to call the API using your preferred language.

Upvotes: 15