fostam/retry

With Retry, you can repeat the execution of any callable until it either succeeds, or the maximum number of attempts has been reached. Several delay policies are available for determining the sleep time between the attempts.

Features

• Simple usage
• Different delay strategies
• Works with any PHP Callable
• No dependencies

Install

The easiest way to install Retry is by using composer:

$> composer require fostam/retry

Usage

try {
    // sleep 1 second between attempts
    $funcResult = Retry::onFailure('myfunc', 3, new ConstantDelayPolicy(1000));
}
catch (RetryLimitException $e) {
    // failed after maximum number of attempts
}

// success before maximum number of attempts have been exceeded

Payload Callables

Payload callables can be functions, class/object methods or closures, as listed in the PHP documentation.

Failure Condition

Payload callables are considered to have failed if they either throw an Exception or return false. If false is a legitimate result of your callable, use onException() instead of onFailure(), in which case the return value of the callable will be ignored.

The original exception that was thrown in the payload callable is chained to the RetryLimitException and can be retrieved via $e->getPrevious().

You can also use the onCondition() method and pass a validation callable that takes the result of the payload callable as argument and returns true or false to indicate whether the original callable failed or not:

$password = 'secret';
Retry::onCondition('getInput', function($result) use ($password) {
    return $result === $password;
}, 3);

Passing Parameters

If you use a function or a class/object method as callable and need to pass parameters, you can wrap the call with a closure:

private function multiply($a, $b) {
    return $a * $b;
}

...

$x = 3;
$y = 4;
Retry::onFailure(function() use ($x, $y) {
    return $this->multiply($x, $y);
}, 3);

Delay Policies

Retry sleeps between two payload calls. There are multiple policies available to determine the time period of the delay. All numerical values for delay policies are interpreted as milliseconds (ms).

Constant Sleep Value

// sleep 2000 milliseconds (i.e. 2 seconds) between attempts
$policy = new ConstantDelayPolicy(2000);

Linear Sleep Value Increase

// sleep 1 second after the first, 2 after the second, 3 after the third...
$policy = new LinearDelayPolicy(1000);

Exponential Sleep Value Increase

// sleep 1, 2, 4, 8, 16, ...
$policy = new ExponentialDelayPolicy(1000);

// sleep 1, 3, 9, 27, ...
$policy = new ExponentialDelayPolicy(1000, 3);

Fixed Series of Sleep Values

// sleep 2, 2, 4, 20, 20, 20, 20 ... (stick to last value after series has ended)
$policy = new SeriesDelayPolicy([2000, 2000, 4000, 20000]);

// sleep 2, 2, 4, 20, 2, 2, 4, 20, 2, 2, 4, ... (repeat series after it has ended)
$policy = new SeriesDelayPolicy([2000, 2000, 4000, 20000], true);

Sleep with Random Jitter

// sleep a random amount between 1900 and 2100 milliseconds
$policy = new JitterDelayPolicy(2000, 100);

No Sleep

// don't sleep at all
$policy = new NoneDelayPolicy();

Advanced Features

Omitting Delay Policy

In case you do not want any delay between the attempts, you can either use the NoneDelayPolicy as described above, pass NULL as Delay Policy, or omit the Delay Policy argument at all:

// retry without delay
Retry::onFailure('myfunc', 3);

Getting the Number of Attempts

If you need to get the number of attempts that were necessary for a successful payload call, e.g. for logging purposes, you can pass a variable by reference to the onFailure(), onException() and onCondition()methods:

Retry::onFailure('myfunc', 3, null, $tries);
print "success after {$tries} attempts";

Abort the Retry Loop

To abort the retry loop without signalling "success", an AbortException can be thrown from inside the payload function.