How to get current Function URL (aws-lambda + golang)

Wed, 08 Nov 2023 12:10:16 +0000

When deploying a function lambda that needs details of its own function URL. It's an OAuth Callback, and needs to calculate the redirect. There are possible security issues doing it this way, so will switch to http gateway on launch. In the meantime, though, I ran into a bit of a chicken and egg problem.

In Pulumi, the function URL is created after the function (and even otherwise), I can't pass the output of the lambda (or lambdaFunctionUrl) back in as an environment variable. Fortunately, there is an easy way to pick up the Function URL (or the function name for that matter) - if you know how ;)

```wp-block-syntaxhighlighter-code domainName := request.RequestContext.DomainName funcName := os.Getenv("AWS_LAMBDA_FUNCTION_NAME") return fmt.Sprintf("Domain: %s, funcName: %s", domainName, funcName), nil ```

There are other defined lambda function environment variables as well that you can use.

Including a built artifact in another target (Bazel, golang)

Wed, 01 Nov 2023 19:42:30 +0000

We use pulumi to do IaC and we use a monorepo with Bazel as the build tool. We have out modules set out as following

One of the requirements we have is to build a lambda module and then deploy it. The lambda module is a target being built by Bazel (golang, but shouldn't matter):

```go go_binary( name = "lambda_module", visibility = ["//visibility:public"], ) ```

We then have the iac module, which should get the built version of the above module, so that it can then upload it into lambda

```go go_binary( name = "iac", args = [ "-lambda_module", "$(location //products/productA/module/lambda_module)", ], data = ["//products/productA/module/lambda_module"], visibility = ["//visibility:public"], ) ```

There are two key parameters here to note:

args: We generate the path to the target module using //products/productA/module/lambda_module)
data: We use the data tag to ensure that the built output is included when building/running this target

We then need to use runfiles support within golang to be ablet to identify the correct location for the built binary. The reason this part is complex is to be able to support multiple operating systems. I should caveat that I have only got this working on Linux, but Mac/Win shouldn't be too different.

```go package main import ( _ "embed" "flag" "fmt" "github.com/bazelbuild/rules_go/go/runfiles" "path/filepath" ) func main() { var webhookAuth = flag.String("webhook_auth", "", "bin for webhook_auth") flag.Parse() fmt.Printf("param : %s \n", *webhookAuth) path, err := runfiles.Rlocation(fmt.Sprintf("workspace_name/%s", *webhookAuth)) fmt.Printf("rLoc path: %s, err: %v \n", path, err) symlinks, err := filepath.EvalSymlinks(path) fmt.Printf("evaluated path: %s, err: %v \n", symlinks, err) } ```

We use the flag module to retrieve the path passed in as a runtime parameter

We use runfiles.Rlocation to pick up the "real" path to the file, prepending the workspace name to the start. You can define the workspace name in the root WORKSPACE file with workspace(name = "workspace_name")

Finally, resolve the Symlink to get the actual file path

References

There are similar mechanisms to find the rLocation in other languages, a couple of which are described in its design document

There is some documentation in rules_go around accessing go_binary from go_test which I referenced and updated to get the above example

I found the above link from a stackoverflow post about feeding bazel output to another bazel rule

Aws-Lambda on despatches

How to get current Function URL (aws-lambda + golang)

Including a built artifact in another target (Bazel, golang)

References