I'm newbie to AWS Step Functions and AWS Batch. I'm trying to integrate AWS Batch Job with Step Function. AWS Batch Job executes simple python scripts which output string value (High level simplified requirement) . I need to have the python script output available to the next state of the step function. How I should be able to accomplish this. AWS Batch Job output does not contain results of the python script. instead it contains all the container related information with input values.

Example : AWS Batch Job executes python script which output "Hello World". I need "Hello World" available to the next state of the step function to execute a lambda associated with it.

I was able to do it, below is my state machine, I took the sample project for running the batch job Manage a Batch Job (AWS Batch, Amazon SNS) and modified it for two lambdas for passing input/output.

{"Comment": "An example of the Amazon States Language for notification on an AWS Batch job completion","StartAt": "Submit Batch Job","TimeoutSeconds": 3600,"States": {"Submit Batch Job": {"Type": "Task","Resource": "arn:aws:states:::batch:submitJob.sync","Parameters": {"JobName": "BatchJobNotification","JobQueue": "arn:aws:batch:us-east-1:1234567890:job-queue/BatchJobQueue-737ed10e7ca3bfd","JobDefinition": "arn:aws:batch:us-east-1:1234567890:job-definition/BatchJobDefinition-89c42b1f452ac67:1"},"Next": "Notify Success","Catch": [{"ErrorEquals": ["States.ALL"],"Next": "Notify Failure"}]},"Notify Success": {"Type": "Task","Resource": "arn:aws:lambda:us-east-1:1234567890:function:readcloudwatchlogs","Parameters": {"LogStreamName.$": "$.Container.LogStreamName"},"ResultPath": "$.lambdaOutput","Next": "ConsumeLogs"},"ConsumeLogs": {"Type": "Task","Resource": "arn:aws:lambda:us-east-1:1234567890:function:consumelogs","Parameters": {"randomstring.$": "$.lambdaOutput.logs"},"End": true},"Notify Failure": {"Type": "Task","Resource": "arn:aws:states:::sns:publish","Parameters": {"Message": "Batch job submitted through Step Functions failed","TopicArn": "arn:aws:sns:us-east-1:1234567890:StepFunctionsSample-BatchJobManagement17968f39-e227-47ab-9a75-08a7dcc10c4c-SNSTopic-1GR29R8TUHQY8"},"End": true}}
}

The key to read logs was in the Submit Batch Job output which contains LogStreamName, that I passed to my lambda named function:readcloudwatchlogs and read the logs and then eventually passed the read logs to the next function named function:consumelogs. You can see in the attached screenshot consumelogs function printing the logs.

{"Attempts": [{"Container": {"ContainerInstanceArn": "arn:aws:ecs:us-east-1:1234567890:container-instance/BatchComputeEnvironment-4a1593ce223b3cf_Batch_7557555f-5606-31a9-86b9-83321eb3e413/6d11fdbfc9eb4f40b0d6b85c396bb243","ExitCode": 0,"LogStreamName": "BatchJobDefinition-89c42b1f452ac67/default/2ad955bf59a8418893f53182f0d87b4b","NetworkInterfaces": [],"TaskArn": "arn:aws:ecs:us-east-1:1234567890:task/BatchComputeEnvironment-4a1593ce223b3cf_Batch_7557555f-5606-31a9-86b9-83321eb3e413/2ad955bf59a8418893f53182f0d87b4b"},"StartedAt": 1611329367577,"StatusReason": "Essential container in task exited","StoppedAt": 1611329367748}],"Container": {"Command": ["echo","Hello world"],"ContainerInstanceArn": "arn:aws:ecs:us-east-1:1234567890:container-instance/BatchComputeEnvironment-4a1593ce223b3cf_Batch_7557555f-5606-31a9-86b9-83321eb3e413/6d11fdbfc9eb4f40b0d6b85c396bb243","Environment": [{"Name": "MANAGED_BY_AWS","Value": "STARTED_BY_STEP_FUNCTIONS"}],"ExitCode": 0,"Image": "137112412989.dkr.ecr.us-east-1.amazonaws.com/amazonlinux:latest","LogStreamName": "BatchJobDefinition-89c42b1f452ac67/default/2ad955bf59a8418893f53182f0d87b4b","TaskArn": "arn:aws:ecs:us-east-1:1234567890:task/BatchComputeEnvironment-4a1593ce223b3cf_Batch_7557555f-5606-31a9-86b9-83321eb3e413/2ad955bf59a8418893f53182f0d87b4b",
..},
.."Tags": {"resourceArn": "arn:aws:batch:us-east-1:1234567890:job/d36ba07a-54f9-4acf-a4b8-3e5413ea5ffc"}
}

• Read Logs Lambda code:

import boto3client = boto3.client('logs')def lambda_handler(event, context):print(event)response = client.get_log_events(logGroupName='/aws/batch/job',logStreamName=event.get('LogStreamName'))log = {'logs': response['events'][0]['message']}return log

• Consume Logs Lambda Code

import jsonprint('Loading function')def lambda_handler(event, context):print(event)