NATS KeyValue Messaging

This is a Wasm component example, which, using NATS KeyValue and Messaging providers, demonstrates the following operations:

• Performs a variety of wasi:keyvalue store and atomics interfaces operations, using either one or two NATS buckets.

  • The bucket names are passed as provider configuration data (i.e. under target_config attribute), via the component named link definitions.

    • The example can work with either one, or two link definitions, demonstrating how to provide multiple configuration sets to the provider, and switch between them.

  • The link names, which identify the target buckets are passed as component configuration data. They're used to reference the target buckets for keyvalue operations.

  • For the increment function, the delta value is received by subscribing to a NATS subject, which its name is passed as part of wasmcloud-messaging provider configuration data (under source_config attribute).

• The results of operations are published to another NATS subject, which the name is also passed as component configuration data.

• The results are also logged and can be viewed in the ~/.wash/downloads/wascloud.log.

The delete operation is the equivalent of issuing the NATS cli command nats kv purge <bucket-name> <key-name>.

Prerequisites

• cargo 1.78

• wash 0.29.2

• wadm 0.12.2 (only if multiple links used)

• nats cli 0.1.4

Building

From the root directory of this example issue the following command:

bash

wash build

Running with wasmCloud

The NATS buckets used must exist, before running the example; so, run the following cli commands to ensure wasmCloud is running, and we have new buckets, which we can watch:

shell

# Start wasmCloud
wash up --detach

# Add 2 new NATS KV buckets
nats kv add WASMCLOUD
nats kv add WASMLAND

# Deploy the example
wash app deploy ./wadm.yaml
wash app get

# Watch the newly created NATS buckets for changes:
nats kv watch WASMCLOUD &
nats kv watch WASMLAND &

# In a different terminal window, subscribe to the topic, which the example component would publish retrieved key-value pair:
nats sub 'nats.demo'

# In another terminal window, trigger the component's operations, by publishing the delta of the counter key:
nats pub 'nats.atomic.delta' 100

Adding Capabilities

To learn how to extend this example with additional capabilities, see the Adding Capabilities section of the wasmCloud documentation.