stamina: Production-grade Retries Made Easy

Transient failures are common in distributed systems. To make your systems resilient, you need to retry failed operations. But bad retries can make things much worse.

stamina is an opinionated wrapper around the great-but-unopinionated Tenacity package. Our goal is to be as ergonomic as possible, while doing the right thing by default, and minimizing the potential for misuse. It is the result of years of copy-pasting the same configuration over and over again:

Retry only on certain exceptions – or even a subset of them by introspecting them first using a backoff hook.
Exponential backoff with jitter between retries.
Limit the number of retries and total time.
Automatic async support – including Trio.
Preserve type hints of the decorated callable.
Flexible instrumentation with Prometheus, structlog, and standard library's logging support out-of-the-box.
Dedicated support for testing that allows to globally deactivate retries, or to limit the number of retries and to remove backoffs.

For example:

import httpx

import stamina


@stamina.retry(on=httpx.HTTPError, attempts=3)
def do_it(code: int) -> httpx.Response:
    resp = httpx.get(f"https://httpbin.org/status/{code}")
    resp.raise_for_status()

    return resp

Async callables work use the same API and it's possible to retry arbitrary blocks, too. Check out our tutorial for more examples!

Or, if you prefer video, here's a brief introduction into retries and stamina:

Release Information

Removed

Support for Python 3.8 and 3.9.

Added

The type hints for our public API are now also verified using Pyrefly and ty. #124
stamina.retry() now retries wrapped generator functions and async generator functions.

Warning: Being able to asend and athrow into wrapped async generators introduced nontrivial complexity in the implementation and is therefore provisional. If supporting these features causes problems, they may be removed again in a future version. #123
An on hook can now return a float or a datetime.timedelta to specify a custom backoff that overrides the default backoff. #103 #125

Fixed

Prevent unbounded stop condition when both attempts and timeout are non-None falsy values. #109
Default wait_exp_base parameter is now an integer to prevent an OverflowError after the 1023th retry. #104
Attempt.next_wait now returns the correct value. #115

Full Changelog →

Credits

stamina is written by Hynek Schlawack and distributed under the terms of the MIT license.

The development is kindly supported by my employer Variomedia AG and all my amazing GitHub Sponsors.

This project would not be possible without the years of incredible work that went into Tenacity.

stamina for Enterprise

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stamina

Description