# CounterEx
**High-performance counter library with pluggable backends and namespace support.**
[](https://github.com/nyo16/CounterEx/actions)
[](https://hex.pm/packages/counter_ex)
[](https://github.com/nyo16/CounterEx/blob/master/LICENSE.md)
CounterEx provides atomic counter operations with three backend options:
- **ETS** (default): Dynamic counters, unlimited capacity
- **Atomics**: Fixed capacity, ultra-fast operations
- **Counters**: Fixed capacity, write-optimized
## Features
- ✨ **Pluggable Backends**: Choose between ETS, Erlang Atomics, or Counters
- 🏷️ **Namespace Support**: Organize counters into logical groups
- ⚡ **High Performance**: Up to 291K operations/second (4 parallel workers)
- 🔒 **Atomic Operations**: Thread-safe increment, set, compare-and-swap
- 📊 **Observability**: Built-in Telemetry integration
- 🎯 **Simple API**: Clean, intuitive function interface
- 🧪 **Well Tested**: Comprehensive test suite with >90% coverage
## Installation
Add `counter_ex` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:counter_ex, "~> 0.2.0"}
]
end
```
## Quick Start
```elixir
# Add to your supervision tree
def start(_type, _args) do
children = [
{CounterEx, []} # Uses ETS backend by default
]
Supervisor.start_link(children, strategy: :one_for_one)
end
# Basic operations
{:ok, 1} = CounterEx.inc(:my_counter)
{:ok, 2} = CounterEx.inc(:my_counter)
{:ok, 2} = CounterEx.get(:my_counter)
# Use namespaces to organize counters
{:ok, 1} = CounterEx.inc(:http, :requests)
{:ok, 1} = CounterEx.inc(:http, :errors)
{:ok, 1} = CounterEx.inc(:db, :queries)
# Get all counters in a namespace
{:ok, counters} = CounterEx.all(:http)
# => %{requests: 1, errors: 1}
```
## Backend Selection
### ETS (Default) - Best for Dynamic Counters
```elixir
{CounterEx, backend: CounterEx.Backend.ETS}
```
**Use when:**
- You don't know how many counters you'll need
- Counter names/keys are dynamic
- You want the simplest solution
**Performance:** ~256K inc/s, ~270K get/s (4 workers on M4 Max)
### Atomics - Best for Maximum Performance
```elixir
{CounterEx,
backend: CounterEx.Backend.Atomics,
backend_opts: [capacity: 10_000]
}
```
**Use when:**
- You have a known, bounded set of counters
- You need maximum performance
- You can estimate capacity upfront
**Performance:** ~253K inc/s, ~291K get/s (4 workers on M4 Max)
### Counters - Best for Write-Heavy Workloads
```elixir
{CounterEx,
backend: CounterEx.Backend.Counters,
backend_opts: [capacity: 5_000]
}
```
**Use when:**
- You have write-heavy workloads
- Many concurrent processes incrementing counters
- Write performance is more critical than read performance
**Performance:** ~248K inc/s, ~269K get/s (4 workers on M4 Max)
See the [Backend Comparison Guide](guides/backends.md) for detailed comparison.
## API Overview
### Basic Operations
```elixir
# Increment
{:ok, 1} = CounterEx.inc(:counter)
{:ok, 11} = CounterEx.inc(:counter, 10)
{:ok, 105} = CounterEx.inc(:counter, 5, 100) # with default value
# Get
{:ok, 105} = CounterEx.get(:counter)
{:ok, nil} = CounterEx.get(:nonexistent)
# Set
{:ok, 42} = CounterEx.set(:counter, 42)
# Reset
{:ok, 0} = CounterEx.reset(:counter)
{:ok, 10} = CounterEx.reset(:counter, 10)
# Delete
:ok = CounterEx.delete(:counter)
```
### Namespace Operations
```elixir
# Increment in namespace
{:ok, 1} = CounterEx.inc(:metrics, :requests, 1, 0)
# Get from namespace
{:ok, 1} = CounterEx.get(:metrics, :requests)
# Get all counters in namespace
{:ok, %{requests: 1, errors: 0}} = CounterEx.all(:metrics)
# Delete entire namespace
:ok = CounterEx.delete_namespace(:metrics)
```
### Advanced Operations
```elixir
# Compare-and-swap
{:ok, 10} = CounterEx.set(:counter, 10)
{:ok, 20} = CounterEx.compare_and_swap(:counter, 10, 20) # succeeds
{:error, :mismatch, 20} = CounterEx.compare_and_swap(:counter, 10, 30) # fails
# Get backend info
{:ok, info} = CounterEx.info()
# %{
# type: :ets,
# counters_count: 42,
# namespaces: [:default, :http, :db],
# ...
# }
```
## Use Cases
### HTTP Request Tracking
```elixir
defmodule MyApp.Metrics do
def track_request(status) do
CounterEx.inc(:http, :total_requests)
case status do
s when s in 200..299 -> CounterEx.inc(:http, :success)
s when s in 400..499 -> CounterEx.inc(:http, :client_errors)
s when s in 500..599 -> CounterEx.inc(:http, :server_errors)
end
end
def get_metrics do
CounterEx.all(:http)
end
end
```
### Rate Limiting
```elixir
defmodule MyApp.RateLimiter do
@max_requests 100
def check_rate_limit(user_id) do
key = :"user_#{user_id}"
case CounterEx.get(:rate_limits, key) do
{:ok, count} when count >= @max_requests ->
{:error, :rate_limit_exceeded}
{:ok, _count} ->
{:ok, _} = CounterEx.inc(:rate_limits, key)
:ok
{:ok, nil} ->
{:ok, _} = CounterEx.inc(:rate_limits, key, 1, 0)
:ok
end
end
end
```
## Configuration
### Periodic Sweep
Clear all counters periodically:
```elixir
{CounterEx, interval: 60_000} # Clear every 60 seconds
```
### Multiple Counter Instances
Run multiple instances with different backends:
```elixir
children = [
# Fast metrics with Atomics
{CounterEx, name: :metrics, backend: CounterEx.Backend.Atomics, backend_opts: [capacity: 1000]},
# Dynamic user counters with ETS
{CounterEx, name: :users, backend: CounterEx.Backend.ETS}
]
```
## Performance
Benchmarks on Apple M4 Max (16 cores, 64GB RAM) with 4 parallel workers:
| Backend | Operation | Throughput | Notes |
|---------|-----------|------------|-------|
| **Atomics** | get() | **291K ops/s** | Fastest reads |
| **Atomics** | inc() | **253K ops/s** | Best overall |
| **Atomics** | set() | **257K ops/s** | |
| **ETS** | get() | **270K ops/s** | |
| **ETS** | inc() | **256K ops/s** | Most flexible |
| **ETS** | set() | **262K ops/s** | |
| **Counters** | get() | **269K ops/s** | |
| **Counters** | inc() | **248K ops/s** | Write-optimized |
| **Counters** | set() | **256K ops/s** | |
**System Configuration:**
- **CPU**: Apple M4 Max (12 performance + 4 efficiency cores)
- **Memory**: 64 GB
- **OS**: macOS 26.1
- **Elixir**: 1.18.4
- **Erlang/OTP**: 28.0.1 (JIT enabled)
Run your own benchmarks:
```elixir
CounterEx.benchmark(parallel: 4)
```
## Telemetry
CounterEx emits telemetry events for observability:
```elixir
:telemetry.attach(
"counter-handler",
[:counter_ex, :backend, :ets, :inc],
&handle_event/4,
nil
)
def handle_event([:counter_ex, :backend, :ets, :inc], measurements, metadata, _config) do
# measurements: %{count: 1}
# metadata: %{namespace: :http, key: :requests, step: 1}
end
```
Events emitted:
- `[:counter_ex, :backend, :ets, :inc]`
- `[:counter_ex, :backend, :ets, :set]`
- `[:counter_ex, :backend, :ets, :delete]`
- `[:counter_ex, :backend, :ets, :cas]`
- ... (similar for atomics and counters backends)
## Migration from 0.1.x
See the [Migration Guide](guides/migration.md) for upgrading from version 0.1.x.
**Key Changes:**
- Return values now use `{:ok, value}` tuples
- `all/0` now returns a map instead of list
- New namespace support
- Pluggable backend architecture
## Documentation
- [API Documentation](https://hexdocs.pm/counter_ex)
- [Backend Comparison Guide](guides/backends.md)
- [Migration Guide](guides/migration.md)
## Contributing
Contributions are welcome! Please feel free to submit a Pull Request.
## License
Copyright 2025 © nyo16
Licensed under the Apache License, Version 2.0. See [LICENSE.md](LICENSE.md) for details.
