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I have a lambda function that reads from DynamoDB and creates a large file (~500M) in /tmp that finally uploaded to s3. Once uploaded the lambda clears the file from /tmp (since there is a high probability that the instance may be reused)

This function takes about 1 minute to execute, even if you ignore the latencies.

In this scenario, when i try to invoke the function again, in < 1m, i have no control if i will have enough space to write to /tmp. My function fails.

Questions: 1. What are the known work arounds in these kind of scenario? (Potentially give more space in /tmp or ensure a clean /tmp is given for each new execution) 2. What are the best practices regarding file creation and management in Lambda? 3. Can i attach another EBS or other storage to Lambda for execution ? 4. Is there a way to have file system like access to s3 so that my function instead of using /tmp can write directly to s3?

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    I don't see why you NEED a file (or file system), especially considering that you're using FaaS/Amazon Lambda. Could you rewrite your code so that the DynamoDB output is streamed to S3 without writing it to disk? Commented Jun 23, 2016 at 11:36
  • There is a lot of processing that needs to be done.not just a simple dump from dynamo to s3 Commented Jun 23, 2016 at 11:44
  • Maybe you're just hitting the limit (512M) then? docs.aws.amazon.com/lambda/latest/dg/limits.html It might help to work in-memory, or add a third service for temporary storage in between. Commented Jun 23, 2016 at 11:49
  • @usama not really, the best way is to clean up after you use it, else may be just clean before use. Commented Oct 11, 2018 at 18:51

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I doubt that two concurrently running instances of AWS Lambda will share /tmp or any other local resource, since they must execute in complete isolation. Your error should have a different explanation. If you mean, that a subsequent invocation of AWS Lambda reuses the same instance, then you should simply clear /tmp on your own.

In general, if your Lambda is a resource hog, you better do that work in an ECS container worker and use the Lambda for launching ECS tasks, as described here.

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I have seen that the function is reused a lot. And have faced issues where the instance is reused. Which means the tmp folder is unavailable at that instance
This answer is correct. Instances are often reused, but not concurrently. Clean up your temp directory when the function finishes -- or just remove any files that are present when it starts (meaning after the handler is invoked, not during initialization, of course) -- and this should not be a problem. +1
This is only a partial answer to the four questions listed and I'm actually interested in the answers to the unanswered ones.
@usama rm -rf /tmp/*
@Leon are you sure? This exert from the AWS states (of the /tmp dir) 'The directory content remains when the Execution Context is frozen, providing transient cache that can be used for multiple invocations'
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You are likely running into the 512 MB /tmp limit of AWS Lambda.

You can improve your performance and address your problem by storing the file in-memory, since the memory limit for Lambda functions can go as high as 1.5 GB.

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The issue i was facing is not technically the limit of tmp size, since the containers are being reused, the tmp is not really empty when i get it, it has some stuff from previous executions.
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Starting March 2022, Lambda now supports increasing /tmp directory's maximum size limit up to 10,240MB. More information available here.

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Now it is even easy, AWS storage can be increased to 10GB named Ephemeral Storage. It is available in general configuration of the AWS lambda functions.

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