limiter

# limiter

Rate limiter for Crystal. Memory and Redis based. Redis limiter is shared (unlike Memory limiter which is local for process), so it can be used across multiple processes.

## Installation


Add this to your application's `shard.yml`:

```yaml
dependencies:
  limiter:
    github: kostya/limiter
```

## Basic Limiter Usage

```crystal
require "limiter"
limiter = Limiter::Memory.new
limiter.add_limit(2.seconds, 10) # allow 10 requests per 2.seconds
limiter.add_limit(1.hour, 1000)  # allow 1000 requests per 1.hour

res = limiter.request? { some_high_cost_action } # => return value of block or nil
res = limiter.request! { some_high_cost_action } # => return value of block or raise Limiter::Error

```

## Example Memory Limiter


```crystal
require "limiter"

limiter = Limiter::Memory.new
limiter.add_limit(2.seconds, 10) # allow 10 requests per 2.seconds
limiter.add_limit(1.hour, 1000)  # allow 1000 requests per 1.hour

record Result, val : Float64

def some_high_cost_action : Result
  # ...
  sleep 0.1
  # ...
  return Result.new(rand)
end

res = [] of Result
limited_count = 0

1000.times do
  if val = limiter.request? { some_high_cost_action }
    res << val
  else
    limited_count += 1
  end
end

p res.size
p limited_count
```

## Example Redis Limiter

```crystal
require "redis"
require "limiter"

redis_client = Redis::PooledClient.new

limiter = Limiter::Redis(Redis::PooledClient).new(redis_client, "my_limiter1")
limiter.add_limit(2.seconds, 10) # allow 10 requests per 2.seconds
limiter.add_limit(1.hour, 1000)  # allow 1000 requests per 1.hour

record Result, val : Float64

def some_high_cost_action : Result
  # ...
  sleep 0.1
  # ...
  return Result.new(rand)
end

res = [] of Result

50.times do
  if val = limiter.request? { some_high_cost_action }
    res << val
  else
    x = limiter.next_usage_after
    puts "processed: #{res.size}, next usage after #{x} seconds"
    sleep(x)
  end
end

puts "processed #{res.size}"
```