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wasmCloud Application Deployment Manager (wadm)

The wasmCloud Application Deployment Manager (wadm) enables declarative wasmCloud applications. It's responsible for managing a set of application deployment specifications, monitoring the current state of an entire lattice, and issuing the appropriate lattice control commands required to close the gap between observed and desired state. It is currently in an alpha release state and undergoing further rigor and testing approaching a production-ready 0.4 version.

Heads Up

Wadm is still in alpha as we continue to tie up a few loose ends. Below is a list of known issues/missing features to be aware of that we plan on addressing by the time we hit 0.4:

The current scaling algorithm is a bit jittery and puts the "eventual" in eventual consistency. It will get to the right number of replicas, but may take a second. We've already identified a fix, but it is in the the wasmCloud host, so we'll need to update things there first
Full e2e tests. There are integration tests, but not full e2e tests in place yet
Full/updated documentation
More examples!

Using wadm

Install

You can deploy wadm by downloading the binary for your host operating system and architecture, and then running it alongside your wasmCloud host. We recommend using wash to run wasmCloud and NATS, and then running wadm afterwards connected to the same NATS connection.

Ensure you have a proper rust toolchain installed to install wash, until we release wash v0.18.0.

```

Install wash

cargo install wash-cli --git https://github.com/wasmcloud/wash --branch feat/wadm0.4support --force ```

```

Install wadm

curl -fLO https://github.com/wasmCloud/wadm/releases/download//wadm---.tar.gz tar -xvf wadm---.tar.gz cd wadm--- ./wadm ```

Setup

wash up -d # Start NATS and wasmCloud in the background wadm # Start wadm

Deploying an application

Take the following manifest and save it locally (you can also download this from echo.yaml):

```yaml apiVersion: core.oam.dev/v1beta1 kind: Application metadata: name: echo annotations: version: v0.0.1 description: "This is my app" spec: components: - name: echo type: actor properties: image: wasmcloud.azurecr.io/echo:0.3.7 traits: - type: spreadscaler properties: replicas: 1 - type: linkdef properties: target: httpserver values: address: 0.0.0.0:8080

- name: httpserver
  type: capability
  properties:
    contract: wasmcloud:httpserver
    image: wasmcloud.azurecr.io/httpserver:0.17.0
  traits:
    - type: spreadscaler
      properties:
        replicas: 1

```

Then, use wadm to put the manifest and deploy it.

wash app put ./echo.yaml wash app deploy echo

🎉 You've just launched your first application with wadm! Try curl localhost:8080/wadm and see the response from the echo WebAssembly module.

When you're done, you can use wadm to undeploy the application.

wash app undeploy echo

Modifying applications

wadm supports upgrading applications by putting new versions of manifests and then deploying them. Try changing the manifest you created above by updating the number of echo replicas.

yaml <<ELIDED>> name: echo annotations: version: v0.0.2 # Note the changed version description: "wasmCloud echo Example" spec: components: - name: echo type: actor properties: image: wasmcloud.azurecr.io/echo:0.3.5 traits: - type: spreadscaler properties: replicas: 10 # Let's run 10! <<ELIDED>>

Then, simply deploy the new version:

wash app put ./echo.yaml wash app deploy echo v0.0.2

If you navigate to the wasmCloud dashboard, you'll see that you now have 10 instances of the echo actor.

Documentation for configuring the spreadscaler to spread actors and providers across multiple hosts in a lattice is forthcoming.

Responsibilities

wadm has a very small set of responsibilities, which actually contributes to its power.

Manage Application Specifications - Manage models consisting of desired state. This includes the creation and deletion and rollback of models to previous versions. Application specifications are defined using the Open Application Model. For more information on wadm's specific OAM features, see our OAM README.
Observe State - Monitor wasmCloud CloudEvents from all hosts in a lattice to build the current state.
Take Compensating Actions - When indicated, issue commands to the lattice control interface to bring about the changes necessary to make the desired and observed state match.

🚧 Advanced

In advanced use cases, wadm is also capable of:

Monitoring multiple lattices
Running multiple replicas to distribute load among multiple processes, or for a high-availability architecture.

🚧 The above functionality is somewhat tested, but not as rigorously as a single instance monitoring a single lattice. Proceed with caution while we do further testing.

API

Interacting with wadm is done over NATS on the root topic wadm.api.{prefix} where prefix is the lattice namespace prefix. For more information on this API, please consult the wadm Reference.

Known Issues/Missing functionality

As this is a new project there are some things we know are missing or buggy. A non-exhaustive list of these can be found below:

Currently the API does not update with the status of each scaler and reconcile action
It is technically possible as things stand right now for a race condition with manifests when a manifest is updated/created and deleted simultaneously. In this case, one of the operations will win and you will end up with a manifest that still exists after you delete it or a manifest that does not exist after you create it. This is a very unlikely scenario as only one person or process is interacting with a specific, but it is possible. If this becomes a problem for you, please let us know and we will consider additional ways of how we can address it.
Manifest validation is not yet implemented. Right now wadm will accept the manifest blindly so long as it can parse it. It will not validate that the model name is valid or if you specified entirely invalid properties. This will be added in a future version.
Nondestructive (e.g. orphaning resources) undeploys are not currently implemented. You can set the field in the request, but it won't do anything

References

The wasmCloud Application Deployment Manager (wadm) originally came from the autonomous lattice controller RFC and then was reworked in version 0.4 in response to the tidying and productioning RFC.