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# Retries with backoff

> Learn how to configure automatic retries with exponential backoff in Fern SDKs. Control retry limits and customize retryable status codes.

Fern SDKs will automatically retry failed requests with exponential backoff. A request will be retried as
long as the request is deemed retryable and the number of retry attempts has
not grown larger than the configured retry limit.

### Retryable status codes

A request is deemed retryable when any of the following HTTP status codes is returned:

* [408](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/408) (Timeout)
* [429](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/429) (Too Many Requests)
* [5XX](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/500) (Internal Server Errors)

Note that you can configure the list of retryable status codes as well. For example,
if you want to remove the `429` status code from the list of retryable status codes, you can do so.

### Overriding the retry limit

By default, the SDK will retry a failed request up to 2 times. SDK users can override the global
default retry limit when instantiating the client.

#### TypeScript

```ts {4}
import { ImdbClient } from "imdb";

const client = new ImdbClient({
  maxRetries: 1 // overrides the default retry limit to 1
});
```

#### Python

```python {4, 8}
from imdb.client import Imdb, AsyncImdb

client = Imdb({
  max_retries: 1 # overrides the default retry limit to 1
})

async_client = AsyncImdb({
  max_retries: 1 # overrides the default retry limit to 1
})
```

#### Java

```java {4}
import com.imdb.ImdbClient;

ImdbClient client = new ImdbClient.Builder()
  .maxRetries(1) // overrides the default retry limit to 1
  .build();
```

#### Go

```go {7}
  import (
    imdbclient "github.com/fern-workos/workos-go/client"
    "github.com/fern-workos/workos-go/option"
  )

  client := imdbclient.NewClient(
    option.WithMaxAttempts(1), // overrides the default retry limit to 1
  )
```

#### C\#

```csharp {4}
using Imdb;

var client = new ImdbClient(new ClientOptions {
  MaxRetries = 1 // overrides the default retry limit to 1
});
```

#### Swift

```swift {5}
import Imdb

let client = ImdbClient(
  baseURL: "https://api.imdb.com",
  maxRetries: 1 // overrides the default retry limit to 1
)
```

#### PHP

```php {4}
use Imdb\ImdbClient;

$client = new ImdbClient([
  "maxRetries" => 1 // overrides the default retry limit to 1
]);
```

It's also possible to override the retry limit on a per-request basis.

#### TypeScript

```ts {2}
  client.movie.get("tt0111161", {
    maxRetries: 3 // overrides the default retry limit to 3
  });
```

#### Python

```python {2}
  client.movie.get("tt0111161", {
    max_retries: 3 // overrides the default retry limit to 3
  })
```

#### Java

```java {2}
  client.movie().get("tt0111161", RequestOptions.builder()
    .maxRetries(3) // overrides the default retry limit to 3
    .build());
```

#### Go

```go {4}
  response, err := client.Movies.Get(
    ctx,
    "tt0111161",
    option.WithMaxAttempts(1),
  )
```

#### C\#

```csharp {2}
  var movie = await client.Movie.GetAsync("tt0111161", new RequestOptions {
    MaxRetries = 3 // overrides the default retry limit to 3
  });
```

#### Swift

```swift {2}
  let movie = try await client.movie.get("tt0111161", requestOptions: RequestOptions(
    maxRetries: 3 // overrides the default retry limit to 3
  ))
```

#### PHP

```php {2}
  $movie = $client->movie->get("tt0111161", [
    "maxRetries" => 3 // overrides the default retry limit to 3
  ]);
```

### Customizing the backoff schedule

The Java SDK exposes client builder options to tune the exponential backoff applied between retries, alongside `maxRetries`.

#### Java

```java {5-7}
import com.imdb.ImdbClient;

ImdbClient client = new ImdbClient.Builder()
  .maxRetries(3)
  .initialRetryDelayMillis(500)
  .maxRetryDelayMillis(30000)
  .retryJitterFactor(0.1)
  .build();
```

| Option                    | Description                                                 | Default |
| ------------------------- | ----------------------------------------------------------- | ------- |
| `initialRetryDelayMillis` | Initial delay in milliseconds used for exponential backoff. | `1000`  |
| `maxRetryDelayMillis`     | Maximum delay in milliseconds between retries.              | `60000` |
| `retryJitterFactor`       | Jitter factor between 0 and 1 applied to retry delays.      | `0.2`   |

> Learn how to configure automatic retries with exponential backoff in Fern SDKs. Control retry limits and customize retryable status codes.