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Compiler targets

When working with the Wing programming language, an integral part of the compilation process is the use of compiler targets. In essence, compiler targets specify how and where your application is deployed. They determine both the cloud environment and the provisioning engine that the code will be deployed to.

Targets​

You can view the list of available compiler targets with the wing compile --help command. Here is an example of the output:

wing compile --help
Usage: wing compile [options] <entrypoint>

Compiles a Wing program

Arguments:
  entrypoint                 program .w entrypoint

Options:
  -t, --target <target>      Target platform (choices: "tf-aws", "tf-azure", "tf-gcp", "sim", "awscdk", default: "sim")
  -p, --plugins [plugin...]  Compiler plugins
  -h, --help                 display help for command

In the Options section, there are several choices for --target, such as tf-aws, tf-azure, sim, awscdk etc. The differences between the compiler targets are described in the [CLI user manual].

These targets contain a combination of provisioning engine and cloud environment in their names. The only exception is sim, which is a special target for testing and simulation applications locally.

Portability​

The Wing Cloud Library has several classes representing abstracted cloud resources, whose APIs are not specific to a single cloud provider. This allows you to write code that can be deployed to any supported cloud environment or provisioning engine.

Here's an example of a portable code snippet:

bring cloud;

let bucket = new cloud.Bucket();

Each resource needs a dedicated implementation to work on a given compiler target. A catalog of which resources are supported on each cloud can be found here.

Provisioning engines​

Provisioning is the process of setting up and creating infrastructure, and the provisioning engine is the driver behind this deployment. Common engines used in the Wing compilation process include Terraform and AWS CDK, with support for more planned (tracking issue).

Since a cloud provider may support more than one provisioning engine, a Wing target represents both the provisioning engine and the cloud destination. For instance, tf-aws signifies the use of Terraform for AWS deployment, while tf-gcp indicates Terraform for Google Cloud deployment.

Target-specific code​

There might be times when you need to write code that is specific to a compiler target. For instance, you may want to activate a verbose logging service only when testing locally to save on cloud log storage costs.

With the Wing util library, you can access environment variables. The WING_TARGET environment variable contains the current compiler target, which you can use to conditionally run target-specific code. See the example below:

bring cloud;
bring util;

let invocationCounter = new cloud.Counter();
let queue = new cloud.Queue();

queue.setConsumer(inflight (msg: str) => {
  invocationCounter.inc();
});

new cloud.Function(inflight ()=> { 
  // push a message to queue
  queue.push("m");
  // sleep according to target 
  if util.env("WING_TARGET") == "sim" {
    log("Running on Simulator, sleeping for 1s");
    util.sleep(1s);
  } else {
    log("Running on the cloud, sleeping for 30s");
    util.sleep(30s);
  }
  log("Function invoked ${invocationCounter.peek()} times");
});

In this example, we want to sleep briefly for the Simulator target and for 30 seconds for cloud targets, this is achieved using the WING_TARGET environment variable.

Compiler plugins​

Compiler plugins serve to extend the capabilities of the Wing compiler. They offer customization for the compilation output, such as infrastructure definitions. For instance, a compiler plugin can be employed to enforce a specific tagging convention on all resources within the resulting infrastructure.

Learn more about compiler plugins here