Lamux is a HTTP multiplexer for AWS Lambda Function aliases.
Usage: lamux --function-name=STRING --domain-suffix=STRING [flags]
Flags:
-h, --help Show context-sensitive help.
--port=8080 Port to listen on ($LAMUX_PORT)
--function-name=STRING Name of the Lambda function to proxy ($LAMUX_FUNCTION_NAME)
--domain-suffix=STRING Domain suffix to accept requests for ($LAMUX_DOMAIN_SUFFIX)
--upstream-timeout=30s Timeout for upstream requests ($LAMUX_UPSTREAM_TIMEOUT)Lamux runs an HTTP server that listens on a specified port and forwards requests to a specified Lambda function aliases. The Lambda function alias is identified by its name, and the domain suffix is used to determine which requests should be forwarded to it.
For example, if you run lamux with --function-name=example and --domain-suffix=example.com, it will forward requests to foo.example.com to the Lambda function aliased example:foo.
The forwarded Lambda functions should process Function URLs payload, but these functions do not need Function URLs settings.
| Request URL | Lambda Function | Alias |
|---|---|---|
http://foo.example.com/ |
example |
foo |
http://bar.example.com/ |
example |
bar |
Lambda alias names allow alphanumeric characters, hyphens, and underscores, but domain names do not allow underscores. And more, lamux uses - as a delimiter between the alias and the function name.
- alias name pattern:
^[a-zA-Z0-9]+$(-and_are not allowed) - function name allows:
^[a-zA-Z0-9-_]+$(-is allowed,_is not allowed)
You can route requests to any Lambda function by specifying the --function-name set to *.
In this case, Lamux will forward requests to the Lambda function aliased myalias-my-func.example.com to the Lambda function my-func aliased as myalias.
| Request URL | Lambda Function | Alias |
|---|---|---|
http://foo-bar.example.com/ |
bar |
foo |
http://foo-baz.example.com/ |
baz |
foo |
http://bar-baz.example.com/ |
baz |
bar |
Lamux can work as a Lambda FunctionURLs. But in this case, Lamux cannot use the Host header because the Lambda function should be accessed via FunctionURLs (e.g., ***.lambda-url.us-east-1.on.aws). So, Lamux uses the X-Forwarded-Host header to determine which requests should be forwarded to the Lambda function.
You may use CloudFront to forward requests to Lamux running on FunctionURLs. In this case, you should set the X-Forwarded-Host header to the original Host header value by Cloud Front Functions(CFF).
// CloudFront Function for setting X-Forwarded-Host header in viewer request
async function handler(event) {
const request = event.request;
request.headers['x-forwarded-host'] = { value: request.headers['host'].value };
return request;
}The lamux binary is a standalone executable. You can run it on your local machine or deploy it to AWS Lambda bootstrap for custom runtimes (provided.al2023 or provided.al2).
All settings can be specified via command-line flags or environment variables.
AWS region to use.
Lamux must have the IAM policy, which can lambda:InvokeFunction.
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "lambda:InvokeFunction",
"Resource": "*",
}
]
}If you want to restrict the functions to invoke, you must set an IAM Policy to specify the Lambda function to be invoked.
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "lambda:InvokeFunction",
"Resource": [
"arn:aws:lambda:us-east-1:123456789012:function:foo:*",
"arn:aws:lambda:us-east-1:123456789012:function:bar:*",
],
}
]
}If lamux runs on Lambda Function URLs, you should attach the appropriate execution policy to the Lambda function's role. (e.g., AWSLambdaBasicExecutionRole managed policy)
Port to listen on. Default is 8080. This setting is ignored when lamux running on AWS Lambda Function URLs.
Name of the Lambda function to proxy. This setting is required.
If you set --function-name to *, Lamux will route requests to any Lambda function. In this case, the Lambda function and alias are determined by the hostname.
Domain suffix to accept requests for. This setting is required.
Timeout for upstream requests. Default is 30s.
This setting is affected by the Lambda function timeout. If the Lambda function timeout is less than the --upstream-timeout, it will time out before the --upstream-timeout.
MIT
Fujiwara Shunichiro