Retry Logic

Handle transient failures with automatic retries.

Default Behavior

Retries are enabled by default:

var config = downloader.Config.default();
// max_retries = 3
// retry_delay_ms = 1000
// exponential_backoff = true

Configuration

var config = downloader.Config.default();

// Maximum retry attempts
config.max_retries = 5;

// Base delay between retries
config.retry_delay_ms = 500;

// Maximum delay cap
config.max_retry_delay_ms = 30000;

// Use exponential backoff
config.exponential_backoff = true;

Exponential Backoff

With exponential backoff enabled, delays increase:

Attempt	Delay
1	~500ms
2	~1000ms
3	~2000ms
4	~4000ms
5	~8000ms

Jitter (±25%) is applied to prevent thundering herd.

Constant Delay

Disable exponential backoff for constant delays:

config.exponential_backoff = false;
config.retry_delay_ms = 2000;  // Always 2 seconds

Retryable Errors

These errors trigger retries:

• ConnectionFailed
• ConnectionTimeout
• DownloadInterrupted
• ConnectionResetByPeer
• BrokenPipe
• NetworkUnreachable
• HostUnreachable

Non-Retryable Errors

These errors fail immediately:

• InvalidUrl
• UnsupportedProtocol
• FileOpenError
• Cancelled

Disabling Retries

var config = downloader.Config.noRetries();
// Sets max_retries = 0

Example

var config = downloader.Config.default();
config.max_retries = 5;
config.retry_delay_ms = 1000;
config.max_retry_delay_ms = 30000;
config.exponential_backoff = true;

var client = try downloader.Client.init(allocator, config);
defer client.deinit();

// Will retry up to 5 times on transient failures
const bytes = try client.download(url, output, callback);

Error After Retries

When all retries are exhausted:

client.download(url, output, null) catch |err| {
    if (err == error.RetriesExhausted) {
        std.debug.print("Download failed after all retries\n", .{});
    }
};

Next Steps

• Error Handling - Handle all error types
• Configuration - All options