fuddle

⚠ Fuddle is still in development

What is Fuddle?

Fuddle is a service registry that can be used for client side service discovery and cluster observability.

Unlike server side service discovery, where requests are simply load balanced across a set of nodes in a service, client side service discovery gives developers control. Using a Fuddle SDK nodes can register themselves, query the set of nodes in the cluster and subscribe to changes.

Each registered node includes a set of fixed attributes (ID, service, locality and revision), and application defined metadata which may be updated and propagated to other nodes in the cluster.

Features

• Service registry: Nodes register with the service registry to make themselves known to the rest of the cluster
• Service discovery: Nodes can lookup other nodes in the cluster, filter based on service, locality and metadata, and subscribe to updates when the set of matching nodes changes
• Cluster observability: The cluster and individual nodes can be inspected using the Fuddle CLI

Use Cases

Fuddle may be preferred to server side service discovery when you require application specific routing, instead of load balancing among a set of stateless service nodes.

Such as if you are using consistent hashing to partition work across multiple nodes, you can use Fuddle to lookup nodes based on service, locality or application defined metadata, and subscribe to updates to the matching set of nodes to trigger a rebalance.

Or you may want a custom load balancing policy and retry strategy based on the state of the nodes in the cluster. Such as routing based on node metadata, like routing to the node with the lowest CPU.

Getting Started

Start by installing the Fuddle server using go install github.com/fuddle-io/fuddle.

Demos

Once installed the quickest way to start playing around with Fuddle is to run one of the demo clusters with fuddle demo:

• Counter service: An example of using Fuddle to implement consistent hashing, where each node is responsible for a set of IDs, and counts the number of users with the same ID. Run with fuddle demo counter

After a demo is running, it can be inspected using fuddle status cluster for a cluster overview, or fuddle status node {id} to inspect a specific node in detail.

Server

To start using Fuddle in your own application, you can start the server with fuddle start.

Note since this is an early version Fuddle only supports a single node so is not recommended to be used in production (see details below).

SDK

Use a Fuddle SDK to integrate Fuddle into your application, which lets nodes register themselves, discover other nodes in the cluster and subscribe to updates.

Only a Go SDK is supported so far.

⚠ Limitations

Fuddle is still in early stages of development so has a number of limitations:

No Fault Tolerance

Although the Fuddle API is defined, Fuddle can currently only run on a single node. This means there is no fault tolerance of horizontal scaling, so is not suitable for production use.

Also the Go SDK does not support reconnecting to the Fuddle node if the connection drops without potentially missing updates.

Health Checks

Fuddle requires nodes to explicitly unregister when they are shutdown, so will not detect nodes that have failed. This will be implemented using health checks.