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michael-grunder merged 1 commit into from
Jul 28, 2021
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Merged

Add documentation for backoff algorithms #1993

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36 changes: 36 additions & 0 deletions README.markdown
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ You can also make a one-time contribution with one of the links below.
1. [Classes and methods](#classes-and-methods)
* [Usage](#usage)
* [Connection](#connection)
* [Retry and backoff](#retry-and-backoff)
* [Server](#server)
* [Keys and strings](#keys-and-strings)
* [Hashes](#hashes)
Expand Down Expand Up @@ -428,6 +429,41 @@ _**Description**_: Sends a string to Redis, which replies with the same string

*STRING*: the same message.

## Retry and backoff

1. [Maximum retries](#maximum-retries)
1. [Backoff algorithms](#backoff-algorithms)

### Maximum retries
You can set and get the maximum retries upon connection issues using the `OPT_MAX_RETRIES` option. Note that this is the number of _retries_, meaning if you set this option to _n_, there will be a maximum _n+1_ attemps overall. Defaults to 10.

##### *Example*

~~~php
$redis->setOption(Redis::OPT_MAX_RETRIES, 5);
$redis->getOption(Redis::OPT_MAX_RETRIES);
~~~

### Backoff algorithms
You can set the backoff algorithm using the `Redis::OPT_BACKOFF_ALGORITHM` option and choose among the following algorithms described in this blog post by Marc Brooker from AWS: [Exponential Backoff And Jitter](https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter):

* Default: `Redis::BACKOFF_ALGORITHM_DEFAULT`
* Decorrelated jitter: `Redis::BACKOFF_ALGORITHM_DECORRELATED_JITTER`
* Full jitter: `Redis::BACKOFF_ALGORITHM_FULL_JITTER`
* Equal jitter: `Redis::BACKOFF_ALGORITHM_EQUAL_JITTER`
* Exponential: `Redis::BACKOFF_ALGORITHM_EXPONENTIAL`
* Uniform: `Redis::BACKOFF_ALGORITHM_UNIFORM`
* Constant: `Redis::BACKOFF_ALGORITHM_CONSTANT`

These algorithms depend on the _base_ and _cap_ parameters, both in milliseconds, which you can set using the `Redis::OPT_BACKOFF_BASE` and `Redis::OPT_BACKOFF_CAP` options, respectively.

##### *Example*

~~~php
$redis->setOption(Redis::OPT_BACKOFF_ALGORITHM, Redis::BACKOFF_ALGORITHM_DECORRELATED_JITTER);
$redis->setOption(Redis::OPT_BACKOFF_BASE, 500); // base for backoff computation: 500ms
$redis->setOption(Redis::OPT_BACKOFF_CAP, 750); // backoff time capped at 750ms
~~~

## Server

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6 changes: 3 additions & 3 deletions tests/RedisTest.php
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Expand Up @@ -5406,9 +5406,6 @@ public function testMaxRetriesOption() {
}

public function testBackoffOptions() {
$this->redis->setOption(Redis::OPT_MAX_RETRIES, 5);
$this->assertEquals($this->redis->getOption(Redis::OPT_MAX_RETRIES), 5);

$this->redis->setOption(Redis::OPT_BACKOFF_ALGORITHM, Redis::BACKOFF_ALGORITHM_DEFAULT);
$this->assertEquals($this->redis->getOption(Redis::OPT_BACKOFF_ALGORITHM), Redis::BACKOFF_ALGORITHM_DEFAULT);

Expand All @@ -5421,6 +5418,9 @@ public function testBackoffOptions() {
$this->redis -> setOption(Redis::OPT_BACKOFF_ALGORITHM, Redis::BACKOFF_ALGORITHM_EXPONENTIAL);
$this->assertEquals($this->redis->getOption(Redis::OPT_BACKOFF_ALGORITHM), Redis::BACKOFF_ALGORITHM_EXPONENTIAL);

$this->redis->setOption(Redis::OPT_BACKOFF_ALGORITHM, Redis::BACKOFF_ALGORITHM_EQUAL_JITTER);
$this->assertEquals($this->redis->getOption(Redis::OPT_BACKOFF_ALGORITHM), Redis::BACKOFF_ALGORITHM_EQUAL_JITTER);

$this->redis->setOption(Redis::OPT_BACKOFF_ALGORITHM, Redis::BACKOFF_ALGORITHM_FULL_JITTER);
$this->assertEquals($this->redis->getOption(Redis::OPT_BACKOFF_ALGORITHM), Redis::BACKOFF_ALGORITHM_FULL_JITTER);

Expand Down