, (*1)
Summary
Exponential back-offs prevent overloading an unavailable service by doubling the timeout each iteration. This class uses
an exponential back-off algorithm to calculate the timeout for the next request., (*2)
This library allows doing exponential backoff in non-blocking mode in Swoole., (*3)
Installation
composer require crowdstar/exponential-backoff:~3.0.0
Sample Usage
In following code pieces, we assume that you want to store return value of method MyClass::fetchData() in variable
$result, and you want to do exponential backoff on that because something unexpected could happen when running method
MyClass::fetchData()., (*4)
1. Retry When Return Value Is Empty
Following code is to try to fetch some non-empty data back with method MyClass::fetchData(). This piece of code will
try a few more times (by default 4) until either we get some non-empty data back, or we have reached maximum numbers
of retries., (*5)
run(
function () {
return MyClass::fetchData();
}
);
?>
2. Retry When Certain Exceptions Thrown Out
Following code is to try to fetch some data back with method MyClass::fetchData(), which may throw out exceptions.
This piece of code will try a few more times (by default 4) until either we get some data back, or we have reached
maximum numbers of retries., (*6)
NOTE: Internal PHP errors (class Error) won't trigger exponential backoff. They should be
fixed manually., (*7)
run(
function () {
return MyClass::fetchData();
}
);
} catch (Throwable $t) {
// Handle the errors here.
}
?>
Don't Throw Out an Exception When Finally Failed
When method call MyClass::fetchData() finally fails with an exception caught, we can silence the exception without
throwing it out by overriding method AbstractRetryCondition::throwable():, (*8)
run(
function () {
return MyClass::fetchData();
}
);
?>
If needed, you can have more complex logic defined when overriding method AbstractRetryCondition::throwable()., (*9)
3. Retry When Customized Condition Met
Following code is to try to fetch some non-empty data back with method MyClass::fetchData(). This piece of code works
the same as the first example, except that here it's implemented with a customized condition class instead of class
\CrowdStar\Backoff\EmptyValueCondition., (*10)
run(
function () {
return MyClass::fetchData();
}
);
?>
4. More Options When Doing Exponential Backoff
Following code is to try to fetch some data back with method MyClass::fetchData(). This piece of code works the
same as the second example, except that here it's implemented with a customized condition class instead of class
\CrowdStar\Backoff\ExceptionBasedCondition., (*11)
In this piece of code, we also show what options are available when doing exponential backoff with the package., (*12)
setType(ExponentialBackoff::TYPE_SECONDS)
->setType(ExponentialBackoff::TYPE_MICROSECONDS)
->setMaxAttempts(3)
->setMaxAttempts(4);
$result = $backoff->run(
function () {
return MyClass::fetchData();
}
);
?>
5. To Disable Exponential Backoff Temporarily
There are two ways to disable exponential backoff temporarily for code piece like following:, (*13)
<?php
$result = MyClass::fetchData();
?>
First, you may disable exponential backoff temporarily by calling method \CrowdStar\Backoff\ExponentialBackoff::disable(). For example:, (*14)
disable();
$result = $backoff->run(function () {return MyClass::fetchData();});
?>
You may also disable exponential backoff temporarily by using class \CrowdStar\Backoff\NullCondition:, (*15)
setRetryCondition(new NullCondition()) // The method here is for demonstration purpose.
->run(function () {return MyClass::fetchData();});
?>
All these 3 code piece work the same, having return value of method call MyClass::fetchData() assigned to variable $result., (*16)
Sample Scripts
Sample scripts can be found under folder examples/. Before running them under CLI, please do a composer update first:, (*17)
composer update -n
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