I cannot get python lambda to return binary data. The node-template for thumbnail images works fine but I cannot get a python lambda to work. Below is the relevant lines from my lambda. The print("image_data " + image_64_encode)
line prints a base64 encoded image to the logs.
def lambda_handler(event, context): img_base64 = event.get('base64Image') if img_base64 is None: return respond(True, "No base64Image key") img = base64.decodestring(img_base64) name = uuid.uuid4() path = '/tmp/{}.png'.format(name) print("path " + path) image_result = open(path, 'wb') image_result.write(img) image_result.close() process_image(path) image_processed_path = '/tmp/{}-processed.png'.format(name) print("image_processed_path " + image_processed_path) image_processed = open(image_processed_path, 'rb') image_processed_data = image_processed.read() image_processed.close() image_64_encode = base64.encodestring(image_processed_data) print("image_data " + image_64_encode) return respond(False, image_64_encode) def respond(err, res): return { 'statusCode': '400' if err else '200', 'body': res, 'headers': { 'Content-Type': 'image/png', }, 'isBase64Encoded': 'true' }
Any pointers to what I'm doing wrong?
The Lambda execution environment is based on a specific Amazon Linux AMI and kernel version. Any native binaries that are used in a Lambda deployment package must be compiled in this environment, and only 64-bit binaries are supported.
Returning a valueIf you use the RequestResponse invocation type, such as Synchronous invocation, AWS Lambda returns the result of the Python function call to the client invoking the Lambda function (in the HTTP response to the invocation request, serialized into JSON).
You can't do that. Your file handle only has meaning in the context of your lambda function, it means nothing outside of it.
Following all the steps above didn't work on my case, because having the binary support for content-type = */*
will convert all responses to binary.
My case:
Multiple lambda functions returning json (text), just a single lambda returning a binary file. All have lambda proxy enabled.
The lambdas are in an API Gateway
The API Gateway is behind CloudFront
Hint: I have notice an important information in the API Gateway -> Settings
Quoting:
API Gateway will look at the Content-Type and Accept HTTP headers to decide how to handle the body.
This means that the Content-Type response header must match Accept request header
Solution:
Set Binary Media Types in API gateway to your mime type: image/jpg
In your HTTP request set Accept: image/jpg
In your HTTP response set Content-Type: image/jpg
{ "isBase64Encoded": True, "statusCode": 200, "headers": { "content-type": "image/jpg"}, "body": base64.b64encode(content_bytes).decode("utf-8") }
On the new screen, you have to add Accept header to Whitelist.
Note 1: If you have multiple file types, you must add them all to Binary Media Types in the API gateway settings
Note 2: For those coming from serverless and want to set the binary types when deploying your lambdas, then check this post: setting binary media types for API gateway
plugins: - serverless-apigw-binary custom: apigwBinary: types: - 'image/jpeg'
The serverless.yml file for cloudfront should contain:
resources: WebAppCloudFrontDistribution: Type: AWS::CloudFront::Distribution Properties: DistributionConfig: ... CacheBehaviors: ... - #API calls ... ForwardedValues: ... Headers: - Authorization - Accept
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With