Retry Logic

Automatic retry with exponential backoff and jitter for transient failures like network timeouts and connection drops.

Configuration

Session.configure do |config|
  config.enable_retry = true
  config.retry_config = Session::RetryConfig.new(
    max_attempts: 3,
    base_delay: 100.milliseconds,
    max_delay: 5.seconds,
    backoff_multiplier: 2.0,
    jitter: 0.1
  )
end

Properties

Property	Type	Default	Description
max_attempts	Int32	3	Total attempts (including first)
base_delay	Time::Span	100.milliseconds	Initial delay between retries
max_delay	Time::Span	5.seconds	Maximum delay cap
backoff_multiplier	Float64	2.0	Delay multiplier per attempt
jitter	Float64	0.1	Random variation (0.1 = +/-10%)

How Backoff Works

Delay formula: base_delay * (backoff_multiplier ^ attempt) * jitter_factor, capped at max_delay.

With defaults, approximate delays:

• Attempt 1 fails: ~100ms wait

• Attempt 2 fails: ~200ms wait

• Attempt 3: final attempt, no retry

Jitter adds random variation to prevent multiple clients from retrying in lockstep (thundering herd).

Store Integration

When enable_retry is true, RedisStore automatically wraps all operations with retry logic using the retryable_connection_error? predicate. No manual retry code is needed.

Direct Usage

For custom retry logic outside the store:

# Retry any exception
Session::Retry.with_retry(Session.config.retry_config) do
  some_operation
end

# Retry only specific exceptions
Session::Retry.with_retry_if(
  ->(ex : Exception) { Session::Retry.retryable_connection_error?(ex) },
  Session.config.retry_config
) do
  some_operation
end

Retry Predicates

Predicate	Retries On
retryable_connection_error?	IO::Error, Redis::ConnectionError, Redis::CommandTimeoutError
retryable_timeout_error?	IO::TimeoutError, Redis::CommandTimeoutError
retryable_network_error?	IO::Error, Redis::ConnectionError, Redis::CommandTimeoutError

See Also

• Circuit Breaker

• Error Handling