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Discussion on: Create AWS Lambda Function Triggered By S3 Notification Event

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samzoozi profile image
Ali Zonoozi

Is there a way to do this using chalice with CDK integration? when I try deploying using cdk deploy command I get the following error:

Unable to package chalice apps that @app.on_s3_event decorator. CloudFormation does not support modifying the event notifications of existing buckets. You can deploy this app using chalice deploy.

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baotran2207 profile image
baotran2207 • Edited

With current version , we can not use on_s3_event with cdk deploy. The only option i think is s3 event -> sqs/sns -> chalice.on_sqs_message . There is one cons is that we need to filter the prefix/suffix by ourself in on_sqs_message handler .

I assume you follow the cdk deploy tutorial

This is example chalice stack infrastructure/stacks/chaliceapp.py

from aws_cdk import (
    aws_s3,
    aws_sns, ## you can notify sns
    aws_sqs, ## you can notify sqs
    aws_s3_notifications as aws_s3_noti,
)
from chalice.cdk import Chalice
RUNTIME_SOURCE_DIR = os.path.join(
    os.path.dirname(os.path.dirname(__file__)), os.pardir, "runtime"
)

class ChaliceApp(cdk.Stack):
     def __init__(self, scope, id, **kwargs):
         self.sqs_generic = aws_sqs.Queue(self, "mysqs")
         self.bucket = s3.Bucket(self, "MyBucket")
         self.chalice = Chalice(
             self,
            "BaoTranBackend",
            source_dir=RUNTIME_SOURCE_DIR,
            stage_config={
                "lambda_memory_size": 256,
                "environment_variables": {
                    "S3_MAIN_BUCKET": self.bucket.bucket_name,
                    "SQS_GENERIC" : self.sqs_generic.queue_name,
                }
            },
        )
         self.chalice_role = self.chalice.get_role("DefaultRole")
         self.bucket.grant_read_write(self.chalice_role)
          self.bucket.add_event_notification(aws_s3.EventType.OBJECT_CREATED_PUT, aws_s3_noti.SqsDestination(self.sqs_generic))
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Then in your runtime/app.py , you can receive the sqs message :

from chalice import Chalice
app = Chalice(app_name='chalice-backend')
@sqs_events.on_sqs_message(
    queue=os.environ.get("SQS_GENERIC", ""),
    batch_size=1)
def handle_sqs_message(event):
    print('Trigger generic')
    print("dict ", event.to_dict())

    for record in event:
        print(record, 'in event')
        logger.info(f" in even ! Detail {record} ")
    ## with the bucket and the key , you can open boto3 session and implement logic here 

app.register_blueprint(sqs_events) ## remember to register events
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And after deployment, upload a file to s3 then in cloudwatch , there would be something like this

Image description

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vumdao profile image
🚀 Vu Dao 🚀

Unfortunately I migrated all my chalice projects to fully CDK :)