# `PhoenixMicro.Utils.Backoff`
[🔗](https://github.com/iamkanishka/phoenix_micro/blob/v1.0.0/lib/phoenix_micro/utils/backoff.ex#L1)

Shared exponential backoff with optional full jitter.

Used by `Consumer.RetryScheduler`, `Transport.RabbitMQ`, `Transport.Kafka`,
`Transport.NATS`, and `Transport.RedisStreams` for reconnect delays.

## Algorithm

Full jitter (default, recommended for distributed systems):

    delay = random_between(0, min(cap, base * 2^attempt))

Decorrelated jitter (alternative — avoids thundering herd even better):

    delay = random_between(base, min(cap, last_delay * 3))

No jitter (deterministic — useful in tests):

    delay = min(cap, base * 2^attempt)

## Usage

    iex> PhoenixMicro.Utils.Backoff.next_delay(3, base: 500, cap: 30_000)
    # returns something between 0 and 4000ms (full jitter)

    iex> PhoenixMicro.Utils.Backoff.sequence(5, base: 100, cap: 5_000, jitter: false)
    [100, 200, 400, 800, 1600]

# `opts`

```elixir
@type opts() :: [
  base: pos_integer(),
  cap: pos_integer(),
  jitter: boolean() | :decorrelated,
  multiplier: number()
]
```

# `next_delay`

```elixir
@spec next_delay(pos_integer(), opts()) :: non_neg_integer()
```

Returns the next backoff delay in milliseconds for the given attempt number.

`attempt` is 1-indexed (first retry = 1).

## Options

- `:base` — base delay in ms (default: 500)
- `:cap` — maximum delay in ms (default: 30_000)
- `:jitter` — `true` for full jitter, `false` for none (default: `true`)
- `:multiplier` — exponential factor (default: 2)

# `sequence`

```elixir
@spec sequence(non_neg_integer(), opts()) :: [non_neg_integer()]
```

Returns a list of `count` delay values — useful for testing retry sequences.

## Example

    iex> PhoenixMicro.Utils.Backoff.sequence(4, base: 100, cap: 1_000, jitter: false)
    [100, 200, 400, 800]

# `sleep`

```elixir
@spec sleep(pos_integer(), opts()) :: non_neg_integer()
```

Sleeps for the calculated backoff delay.
Returns the delay used (useful for logging).

---

*Consult [api-reference.md](api-reference.md) for complete listing*