rpc_load_balancer

## 0.3.0

### Features
- Wrap `RpcLoadBalancer.call/5` and `RpcLoadBalancer.cast/5` in `:telemetry.span/3` under the prefix `[:rpc_load_balancer, :rpc]`. Emits `:start`, `:stop` (with `:duration` measurement), and `:exception` events. Metadata: `:type` (`:call` or `:cast`), `:node`, `:module` (`inspect/1`'d), `:function`, `:load_balancer` (nullable), and on `:stop` a `:status` derived from the result tuple (`:ok`, `ErrorMessage.code`, or `:error`).
- Add `RpcLoadBalancer.Metrics` with `metrics/0` returning ready-to-register `Telemetry.Metrics` definitions for `rpc_load_balancer.rpc.request.start.count`, `rpc_load_balancer.rpc.request.stop.count`, and `rpc_load_balancer.rpc.duration.milliseconds`. Drop into any `PrometheusTelemetry` supervisor.
- Declare `:telemetry` and `:telemetry_metrics` as direct dependencies (previously transitive via `:elixir_cache`).

## 0.2.2

### Features
- Add `LeastCpu` selection algorithm that routes calls to the node with the lowest CPU utilization, sampled via `:cpu_sup` and cached in `:persistent_term`
- Add optional `child_specs/2` callback to the `SelectionAlgorithm` behaviour so algorithms can contribute their own supervised children

### Fixes
- Ensure the configured selection algorithm module is loaded before checking for `child_specs/2`, preventing startup races
- Use `Cache.PersistentTerm` for `NodeCpuCache` and fix the `:cpu_sup` apply call to stabilize CPU sampling

## 0.2.1

### Features
- Add `CallDirect` selection algorithm for local-node execution without `:erpc` overhead
- Add `Drainer` module for graceful connection draining with in-flight call tracking
- Add `IndexRegistry` for lock-free index allocation using `:atomics` and `:persistent_term`
- Add `Retry` module with configurable retry logic for RPC operations
- Add `Config` module for centralized application configuration defaults
- Add `ValueCache` backed by `Cache.PersistentTerm`
- Add `call_directly?` option to `call/5`, `cast/5`, `call_on_random_node/5`, and `cast_on_random_node/5`
- Add `select_node/2` to the public API

### Refactors
- Consolidate cache initialization into `RpcLoadBalancer` supervisor
- Extract retry logic from `LoadBalancer` into dedicated `Retry` module
- Simplify selection algorithms (`LeastConnections`, `PowerOfTwo`, `RoundRobin`, `WeightedRoundRobin`) by leveraging shared caches
- Promote `RpcLoadBalancer` to a `Supervisor` managing caches and the load balancer GenServer

### Docs
- Add `testing-with-call-direct` how-to guide
- Update architecture docs, reference docs, and getting started tutorial for new API

## 0.1.0
- Initial Release