Call to a member function resolve on null
mmenozzi opened this issue · 4 comments
Hi,
I use the AMP's beanstalk client with https://github.com/webgriffe/esb.
Sometimes (but I never found the cause) the ESB application crashes with the following error:
PHP Fatal error: Uncaught Error: Call to a member function resolve() on null in vendor/amphp/beanstalk/src/BeanstalkClient.php:38
That resolve is the one inside the response event callback of the client:
$this->connection->addEventHandler("response", function ($response) {
/** @var Deferred $deferred */
$deferred = array_shift($this->deferreds);
if ($response instanceof Throwable) {
$deferred->fail($response);
} else {
$deferred->resolve($response);
}
});And this is strange because only Deferred instances are added to the BeanstalkClient::$deferreds array.
beanstalk/src/BeanstalkClient.php
Line 55 in 9973d81
beanstalk/src/BeanstalkClient.php
Line 68 in 9973d81
So it seems that, sometimes, the response event is fired when the BeanstalkClient::$deferreds array is empty. Indeed, array_shift returns null if the array is empty (http://php.net/manual/en/function.array-shift.php).
I don't know how this could happen but happens...
Maybe we can prevent such error with a simple check:
$this->connection->addEventHandler("response", function ($response) {
if (empty($this->deferreds)) {
return;
}
/** @var Deferred $deferred */
$deferred = array_shift($this->deferreds);
if ($response instanceof Throwable) {
$deferred->fail($response);
} else {
$deferred->resolve($response);
}
});But I don't know if the right thing to do.
@kelunik what do you think?
No, the check just hides the error. We have to find the cause.
My initial guess would be that it might happen on connection closes?
I don't think so. I did some other investigation and what can I say is that it happens during the execution of this method (but only sometimes, I think it depends on what is in the tube):
Do you see any unexpected usage in this method?