[local server] Local Server should pass HTTP headers down to the Lambda Runtime

[sebsto]

Describe the bug

When locally invoking a function through the local server, any HTTP header passed to the server are not forwarded to the Lambda Interface Client.

This prevents to test Tenant-ID for example.

curl -v -d @event.json -H "X-Amz-Tenant-Id: 123" http://127.0.0.1:7000/invoke 
*   Trying 127.0.0.1:7000...
* Connected to 127.0.0.1 (127.0.0.1) port 7000
> POST /invoke HTTP/1.1
> Host: 127.0.0.1:7000
> User-Agent: curl/8.7.1
> Accept: */*
> X-Amz-Tenant-Id: 123
> Content-Length: 3107
> Content-Type: application/x-www-form-urlencoded
> 
* upload completely sent off: 3107 bytes
< HTTP/1.1 202 Accepted
< Content-Length: 49
< 
* Connection #0 to host 127.0.0.1 left intact
{"body":"No Tenant ID provided","statusCode":400}%  

This happens here

swift-aws-lambda-runtime/Sources/AWSLambdaRuntime/Lambda+LocalServer.swift

Line 410 in 0305cb3

self.invocationPool.push(LocalServerInvocation(requestId: requestId, request: body))

Expected Behavior

The HTTP headers received by the local server must be passed down to the Lambda Runtime.

Current Behavior

HTTP Headers are not forwarded.

Reproduction Steps

See above

Possible Solution

Change the local server to forward all HTTP headers received to the Lambda runtime client

Additional Information/Context

n/a

AWS SWIFT SDK version used

n/a

Compiler and Version used

n/a

Operating System and version

n/a

[manojmahapatra]

@sebsto I can reproduce this locally.

After diving into the code, here is what I'm thinking as a proposed fix, have the local server forward all headers from /invoke to the runtime while callers may send X-Amz-Tenant-Id. To make this work in local mode, I'm considering mapping: X-Amz-Tenant-Id -> Lambda-Runtime-Aws-Tenant-Id. (would be local server only)

Is that mapping reasonable to include, or should we require callers to send the runtime header explicitly when using the local server?

[sebsto]

Thank you @manojmahapatra for having a look at this.
I wouldn't map anything. I would let users (developers) pass the headers they want / need to their lambda function.

The Lambda-Runtime-Aws-Tenant-Id header is already mapped to context.tenantID here https://github.com/awslabs/swift-aws-lambda-runtime/pull/608/changes#diff-ef121a6bef193ef509b6290e137f0b2db2410508737f96937b3e592802b6fd2e

What is missing is passing the user-provided headers to the Lambda runtime.

curl -H ... -xx-> Local HTTP Server --> Lambda runtime --> Lambda Function

This line is not propagating the headers

[manojmahapatra]

Thank you @sebsto for the insight. I have put together a fix, let me know how it looks.

[sebsto]

fixed by #643
Thank you and congrats for your first contribution.