State

The sim.State is a simple key/value in-memory store for the simulator with support for lazy tokens.

Consider a use case where there is an attribute of a simulated service that only gets resolved during initialization (e.g. the exposed port of a container). In order to create such resources, we need a way to obtain a lazy token that gets resolved during simulator initialization. It just so happens that we already have a mechanism like this, but it was not exposed as a public API.

Use the preflight method state.token(key) to obtain a token that can be used to reference the value of the state at runtime.

During simulator app initialization (i.e. cloud.OnDeploy or cloud.Service startup), you must call the inflight method state.set(key, value) to set the runtime value. The value will be available at runtime through the inflight method state.get(key), or via a resolved token.

Usage

Let's say I want to create a simulated service that has property called startTime which returns the time the service was started. This information is also known when the service is actually initialized.

bring cloud;
bring sim;

class MyService {
  startTime: str;

  new() {
    let state = new sim.State();

    new cloud.Service(inflight () => {
      state.set("start", std.Datetime.utcNow().toIso());
    });

    this.startTime = state.token("start");
  }
}

In this example, the startTime property will resolve to a simulator token (something like ${root/MyService/State#attrs.start)}) which can be referenced ("lifted") into inflight context naturally:

let s = new MyService();

new cloud.Function(inflight () => {
  log("service start time is {s}");
});

This creates an implicit dependency between the cloud.Function and MyService such that only when the state start is set, the cloud.Function will be initialized with the actual value.

API Reference

Resources

State

• Implements: ISimulatorResource

Key/value in-memory state for the simulator.

Use the preflight method token(key) to obtain a token that can be used to reference the value of the state at runtime.

During deployment (i.e. cloud.OnDeploy or cloud.Service startup), you must call the inflight method set(key, value) to set the runtime value. The value will be available at runtime through the inflight method get(key) (or resolved as a token).

See tests for examples.

Initializers

bring sim;

new sim.State();

Name	Type	Description

---

Methods

Preflight Methods

Name	Description
token	Returns a token that can be used to retrieve the value of the state after the simulation has run.
toSimulator	Convert this resource to a resource schema for the simulator.

Inflight Methods

Name	Description
get	Gets the runtime state of this object.
set	Sets the state of runtime a runtime object.
tryGet	Checks if runtime state exists for this object and returns it's value.

---

token

token(key: str): str

Returns a token that can be used to retrieve the value of the state after the simulation has run.

key^Required

• Type: str

The object key retrieved through the inflight state.get().

---

toSimulator

toSimulator(): ToSimulatorOutput

Convert this resource to a resource schema for the simulator.

get

inflight get(key: str): Json

Gets the runtime state of this object.

Throws if there is no value for the given key.

key^Required

• Type: str

The object's key.

---

set

inflight set(key: str, value: Json): void

Sets the state of runtime a runtime object.

key^Required

• Type: str

The object's key.

---

value^Required

• Type: Json

The object's value.

---

tryGet

inflight tryGet(key: str): Json?

Checks if runtime state exists for this object and returns it's value.

If no value exists, returns nil.

key^Required

• Type: str

The object's key.

---

Static Functions

Name	Description
onLiftType	A hook called by the Wing compiler once for each inflight host that needs to use this type inflight.
toInflight	Generates an asynchronous JavaScript statement which can be used to create an inflight client for a resource.

---

onLiftType

bring sim;

sim.State.onLiftType(host: IInflightHost, ops: MutArray<str>);

A hook called by the Wing compiler once for each inflight host that needs to use this type inflight.

The list of requested inflight methods needed by the inflight host are given by ops.

This method is commonly used for adding permissions, environment variables, or other capabilities to the inflight host.

host^Required

• Type: IInflightHost

---

ops^Required

• Type: MutArray<str>

---

toInflight

bring sim;

sim.State.toInflight(obj: IResource);

Generates an asynchronous JavaScript statement which can be used to create an inflight client for a resource.

NOTE: This statement must be executed within an async context.

obj^Required

• Type: IResource

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Properties

Name	Type	Description
node	constructs.Node	The tree node.

---

node^Required

node: Node;

• Type: constructs.Node

The tree node.

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