Tarmac

Build Serverless Microservices with WebAssembly Functions

Tarmac is a lightweight, open-source application server that simplifies building microservices using WebAssembly (WASM) functions. With Tarmac, you can quickly write and deploy a single function as a standalone microservice. Or you can use Tarmac's ability to run multi-function services to create a purpose-built serverless platform.

Tarmac delivers more than just a lightweight application server for WebAssembly functions. It offers built-in support for key-value stores like Redis and Cassandra, traditional SQL databases like MySQL and Postgres, and fundamental capabilities like mutual TLS authentication and observability. With Tarmac, you can easily focus on writing your functions while benefiting from a robust suite of integrations for building modern distributed services.

Quick Start

Tarmac makes it easy to get started with building complex functions. This Go function is an excellent example of its simplicity. Its payload reversal logic leverages a key:value datastore for caching, demonstrating how effortless it is to create complex functionality with very little code.

// Tac is a small, simple Go program that is an example WASM module for Tarmac. This program will accept a Tarmac
// server request, log it, and echo back the payload in reverse.
package main

import (
	"fmt"
	"github.com/madflojo/tarmac/pkg/sdk"
)

var tarmac *sdk.Tarmac

func main() {
	var err error

	// Initialize the Tarmac SDK
	tarmac, err = sdk.New(sdk.Config{Handler: Handler})
	if err != nil {
		return
	}
}

// Handler is the custom Tarmac Handler function that will receive a payload and
// must return a payload along with a nil error.
func Handler(payload []byte) ([]byte, error) {
	var err error

	// Log it
	tarmac.Logger.Trace(fmt.Sprintf("Reversing Payload: %s", payload))

	// Check Cache
	key := string(payload)
	rsp, err := tarmac.KV.Get(key)
	if err != nil || len(payload) < 1 {
		// Flip it and reverse
		if len(payload) > 0 {
			for i, n := 0, len(payload)-1; i < n; i, n = i+1, n-1 {
				payload[i], payload[n] = payload[n], payload[i]
			}
		}
		rsp = payload

		// Store in Cache
		err = tarmac.KV.Set(key, payload)
		if err != nil {
			tarmac.Logger.Error(fmt.Sprintf("Unable to cache reversed payload: %s", err))
			return rsp, nil
		}
	}

	// Return the payload
	return rsp, nil
}

To start running this function, navigate to our examples directory and run the make build command. The make build command compiles the code and generates a WebAssembly module.

$ cd example/tac/go
$ make build

Once compiled, you can run this function as a standalone microservice using the following Docker command.

$ docker run -p 8080:8080 \
  -e "APP_ENABLE_TLS=false" -e "APP_LISTEN_ADDR=0.0.0.0:8080" \
  -v `pwd`/functions:/functions madflojo/tarmac

With Tarmac now running, we can access our WASM function using any HTTP Client such as curl.

$ curl -v --data "Tarmac Example" http://localhost:8080

That's it! You can write and deploy functions in Go, Rust, AssemblyScript, Swift, or Zig with Tarmac. For more advanced functions, check out our developer guides.

Multi-Function Services

While users of Tarmac can build standalone microservices with a single function quickly, it shines with multi-function services. Tarmac's ability to run multiple functions means you can create purpose-built serverless platforms or full-featured distributed services with the developer experience of serverless functions.

To get started with multi-function services, you must provide a tarmac.json configuration file (via the WASM_FUNCTION_CONFIG configuration parameter) that lists the Functions to load and the various protocols and routes to expose as endpoints. Below is a sample tarmac.json configuration file.

{
  "services": {
    "my-service": {
      "name": "my-service",
      "functions": {
        "function1": {
          "filepath": "/path/to/function1.wasm"
        },
        "function2": {
          "filepath": "/path/to/function2.wasm"
        }
      },
      "routes": [
        {
          "type": "http",
          "path": "/function1",
          "methods": ["GET"],
          "function": "function1"
        },
        {
          "type": "http",
          "path": "/function2",
          "methods": ["POST"],
          "function": "function2"
        }
      ]
    }
  }
}

Each function has its own code base but shares the same service namespace and configurations in a multi-function service configuration.

In the example above, we have a service named my-service with function1 and function2 functions. Each function has a .wasm file at /path/to/function1.wasm and /path/to/function2.wasm.

To define the routes for each function, add a route object to the routes array with the type set to http and the function set to the function's name.

In addition to the http route type, Tarmac also supports scheduled_task routes that execute a function at a specific interval. The frequency parameter specifies the interval (in seconds).

{
  "type": "scheduled_task",
  "function": "function1",
  "frequency": 10
}

With Tarmac's support for multiple functions, you can quickly build complex, distributed services by dividing your service into smaller, more manageable pieces.

Architecture

Tarmac is a serverless platform that enables users to define and execute WebAssembly Functions. When Tarmac receives requests, it forwards them to WebAssembly Functions, which act as request handlers. The communication between Tarmac and WebAssembly Functions is via WebAssembly Procedure Calls (waPC).

By leveraging waPC, WebAssembly Functions can interact with Tarmac's core capabilities. Capabilities include performing callbacks to the Tarmac server to access key-value stores, interact with SQL databases, or make HTTP requests to downstream services.

To provide a streamlined developer experience, Tarmac offers a Go SDK that simplifies the usage of waPC. The SDK abstracts away the complexity of using waPC, allowing developers to focus on writing their functions and leveraging Tarmac's features.

With Tarmac, users can build a simple microservice (depicted below).

Or, users can build complex Serverless platforms to enable multiple use cases.

Contributing

We are thrilled that you are interested in contributing to Tarmac and helping to make it even better! To get started, please check out our contributing guide for information on how to submit bug reports, feature requests, and code contributions.