"Univeral Lambda" for Zig

This a Zig 0.11 project intended to be used as a package to turn a zig program into a function that can be run as:

• A command line executable
• A standalone web server
• An AWS Lambda function
• A shared library in flexilib
• Cloudflare (TODO/Planned)
• etc

Usage - Development

From an empty directory, with Zig 0.11 installed:

zig init-exe

Create a build.zig.zon with the following contents:

.{
    .name = "univeral-zig-example",
    .version = "0.0.1",

    .dependencies = .{
        .universal_lambda_build = .{
            .url = "https://git.lerch.org/lobo/universal-lambda-zig/archive/ea730c50a50faddf4af719bbb3d8d5fac09e0c19.tar.gz",
            .hash = "1220be3a235a6506dbfef0ba6705e728eebabf9af2b33364aead1c30cdcde353f357",
        },
        .flexilib = .{
            .url = "https://git.lerch.org/lobo/flexilib/archive/c44ad2ba84df735421bef23a2ad612968fb50f06.tar.gz",
            .hash = "122051fdfeefdd75653d3dd678c8aa297150c2893f5fad0728e0d953481383690dbc",
        },
    },
}

Due to limitations in the build apis related to relative file paths, the dependency name currently must be "universal_lambda_build". Also, note that the flexilib dependency is required at all times. This requirement may go away with zig 0.12 (see #17135) and/or changes to this library.

Build.zig:

• Add an import at the top:

const configureUniversalLambdaBuild = @import("universal_lambda_build").configureBuild;

• Set the return of the build function to return !void rather than void
• Add a line to the build script, after any modules are used, but otherwise just after adding the exe is fine:

try configureUniversalLambdaBuild(b, exe);

This will provide most of the magic functionality of the package, including several new build steps to manage the system, and a new import to be used.

main.zig

The build changes above will add a module called 'universal_lambda_handler'. Add an import:

const universal_lambda = @import("universal_lambda_handler");

Add a handler to be executed. This must be public, and named 'handler'. If you don't want to do that, name it whatever you want, and provide a public const, e.g. pub const handler=myActualFunctionName. The handler must follow this signature:

pub fn handler(allocator: std.mem.Allocator, event_data: []const u8, context: universal_lambda.Context) ![]const u8

Let the package know about your handler in your main function, like so:

try universal_lambda.run(null, handler);

The first parameter above is an allocator. If you have a specific handler you would like to use, you may specify it. Otherwise, an appropriate allocator will be created and used. Currently this is an ArenaAllocator wrapped around an appropriate base allocator, so your handler does not require deallocation.

Note that for flexilib builds, the main function is ignored and the handler is called directly. This is unique to flexilib.

A fully working example of usage is at https://git.lerch.org/lobo/universal-lambda-example/.

Usage - Building

The build configuration will add the following build steps when building with Linux:

  awslambda_package            Package the function
  awslambda_deploy             Deploy the function
  awslambda_iam                Create/Get IAM role for function
  awslambda_run                Run the app in AWS lambda
  standalone_server            Run the function in its own web server
  flexilib                     Create a flexilib dynamic library

AWS Lambda is not currently available if building with other operating systems, as that set of build steps utilize system commands using the AWS CLI. This is likely to change in the future to enable other operating systems.

To run as an executable, a simple zig build will build, or zig build run will run as expected. zig build standalone_server run will also build/run as a standalone web server.

Limitations

This is currently a minimal viable product. The biggest current limitation is that context is not currently implemented. This is important to see command line arguments, http headers and the like.

Other limitations include standalone web server port customization, main function not called under flexilib, and linux/aws cli requirements for Linux.