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Description:

RequestsStampede 0.9.1

Overview
The Requests Stampede library is a wrapper around the Requests library
that provides request retry logic and backoff delays. The goal of the project
is to improve upstream service stability and time to recovery following an
outage and influx of retry requests. The library provides various default
configurations with sane parameters; however, behavior is configurable via both
programmatic declarations and configuration files.
Inspiration
The Request Stampede library was largely inspired by the 2021-01-15 Signal
messaging service outage
wherein a service disruption was worsened by their mobile app retry-logic
inflicting a self-induced DDoS attack
on their systems. The project implementes many of the recommendations outlined
in Google Cloud's blog post on the subject.
Usage
Basic
import RequestsStampede.horde

horde = RequestsStampede.horde.RetryRequest()

response = horde.get("https://www.example.com/")
print(response)

import RequestsStampede.horde

session = RequestsStampede.horde.RetrySession()

response = session.post(
"https://www.example.com/login",
data={
'username': 'johndoe',
'password': 'hunter2'
}
)
print(response)

response = session.get("https://www.example.com/profile")
print(response)

Intermediate
import requests.session
import RequestsStampede.horde

session = RequestsStampede.horde.RetrySession(
session=requests.session.Session(
headers={
"Authorization": "Bearer <TOKEN>"
}
)
)

response = session.post("https://www.example.com/resource")
print(response)

response = session.get("https://www.example.com/resource")
print(response)

Advanced
Configuration
stampede.yml
retry_config:
retry_enabled: True
retry_policy:
type: infinite

backoff_enabled: True
backoff_policy:
type: fibonacci
initial_delay: 0.0
maximum_delay: 144.0

import requests.session
import RequestsStampede.horde

session = RequestsStampede.horde.RetrySession(
session=requests.session.Session(
headers={
"Authorization": "Bearer <TOKEN>"
}
)
)

response = session.post("https://www.example.com/resource")
print(response)

response = session.get("https://www.example.com/resource")
print(response)

Features
HTTP Methods
The Requests Stampede library supports all HTTP methods currently supported by
the Requests library:

GET
OPTIONS
HEAD
POST
PUT
PATCH
DELETE

Retry Configuration
When an HTTP request is unsuccessful, that request may be retried depending on
the configured retry policy. Following an unsuccessful request or retry
attempt, a backoff delay may be introduced in an effort to reduce congestion
and system load on the upstream resource.
Retry Policies
Fixed
The fixed retry policy will attempt to retransmit a request until the maximum
number of attempts has been reached. Upon exhaustion of all retry attempts, the
request will be discarded.
Infinite
The infinite retry policy will indefinitely retransmit a request until a
successful response is received.
Backoff Policies
Fixed
Following a failed request, a fixed backoff policy will introduce a constant
delay between the next attempted transmission. For example, a delay of 5
seconds may be introduced between request attempts.
Random
Following a failed request, a random backoff policy will introduce a random,
normally distributed, delay between two configurable bounds prior to the next
attempted transmission. For example, a random delay between 5 and 15 seconds
may be introduced between request attempts.
Fibonacci
Following a failed request, a series of fibonacci
delays will be introduced in between subsequent transmission attempts. For
example, a retry attempt sequence may follow the pattern below:
No | Event
---|------
0 | Initial Request, Failure
1 | Backoff, 0 sec
2 | Retry Request, Failure
3 | Backoff, 1 sec
4 | Retry Request, Failure
5 | Backoff, 1 sec
6 | Retry Request, Failure
7 | Backoff, 2 sec
8 | Retry Request, Failure
9 | Backoff, 3 sec
...

Configuration Methods
Programatic
The RetryRequest and RetrySession classes accept parameters to configure
both the desired retry configuration and request session object.
Configuration File
If configuration parameters are not provided to RetryRequest or
RetrySession, RequestsStampede will traverse the file-system for a
configuration file, stampede.yml. For example, given an application running
in /etc/application, RequestsStampede will traverse the following paths and
select the first configuration file encountered:

/etc/application/stampede.yml
/etc/stampede.yml
/stampede.yml
$HOME/stampede.yml

If no configuration file is located, a default retry configuration will be
utilized.
Request Interfaces
Requests Stampede exposes two interfaces within the RequestsStampede.horde
sub-module, whether you choose RetryRequest or RetrySession is entirely
dependent on whether or not you require session persistence across multiple
requests.
Non-Persistent Session
For basic applications, such as unauthenticated web scraping, RetryRequest is
likely suffient. The interface does not offer session persistence across
multiple requests by default.
Persistent Session
For more complex use-cases, your application may require session persistence to
properly authenticate with an upstream resource. The RetrySession interface
is best suited for this use case as it will use one session for all requests.
Logging
The logging module is used for all logging interfaces within the
RequestsStampede module. Logs may be exposed by raising the logging level (i.e.
logging.basicConfig(level=logging.DEBUG)).
Development
Virtual Environment
virtualenv --python=python3 venv
source venv/bin/activate

Local Installation
pip3 install .

Development Dependencies
pip3 install -r dev-requirements.txt

Code Formatting & Linting
black .
pylint RequestsStampede
pylint tests

Tests
pytest

Contributors

Patrick Murray
Zachary Barden

Attribution

The Requests Stampede icon and banner graphics use content created by
Game-icons.net which was licensed under a
Creative Commons 3.0 license.
Minor modifications were made to the content for use by the Requests
Stampede project.