configuring STREAM_SELECT_USEC

[rbro]

Hello,

I am making an async request, and while waiting for the response, I want to do other work. In my case, it's calling a check heartbeat function in rabbitmq, so I don't lose the connection while my request is processing - related to what I wrote at the bottom of #6. I am using a pattern like:

while (true)
{
	if ($client->hasResponse($requestId))
	{
		$client->handleResponse($requestId);
		break;
	}

	// do other work here
}

What I noticed is that in hasResponse, Socket::STREAM_SELECT_USEC is 20000 microseconds, which is a little quick for what I need. I would prefer to wait a little longer each iteration as the check heartbeat function doesn't need to run that often.

Would it be possible to allow the user to change STREAM_SELECT_USEC to be another value? Right now it's a constant, so it can't be changed.

Thanks again for your help.

[hollodotme]

@rbro Thanks for the issue.

First of all: Congratulations, you spotted a bug. 🎉

The value of STREAM_SELECT_USEC should be 200000, not 20000. (See http://php.net/stream_select, red box)

Can you please open another issue for that and provide a simple PR which changes that value? That would be great and much appreciated!

---

I quickly looked where I could add a custom value for STREAM_SELECT_USEC best. Currently I see three options:

Option 1

Configure it via ConfiguresSocketConnection interface (UnixDomainSocket or NetworkSocket) and at the 200000 as a constant to the SocketConnections/Defaults.php.
That means the configured value applies to ALL requests/checks on that connection. I don't know if that is a good idea.

Option 2

Introduce a new optional parameter to the following methods:

• Client->hasResponse()
• Client->waitForResponse()
• Client->waitForResponses()
• Client->getRequestIdsHavingResponse()
• Client->readReadyResponses()
• Client->handleReadyResponses()

This would introduce quite a lot of complexity and harms the readability of the current lib API, IMO. Even though this is a more flexible approach when you want to have wait-times that differ for each request. And that sentence leads to...

Option 3

Introduce a new getter/setter in the request classes for the wait-time and add it to the internal socket instance, so each socket can have a custom wait-time for stream_select.

But that means that it just applies to Client->hasResponse() and Client->waitForResponse(), because those methods use the stream_select call inside of Socket.php which checks only one socket. All other Client methods above use a stream_select call for multiple sockets in Client-> getRequestIdsHavingResponse() to reduce the amount of stream_select calls. So in most cases (multi-request-checks) the custom value wouldn't be applied.

Long story short:

None of the 3 options is a good / flexible solution in my opinion. Furthermore they add complexity and maybe even a BC break for a use-case which can be solved by one line of user-land code:

<?php

while (true)
{
	if ($client->hasResponse($requestId))
	{
		$client->handleResponse($requestId);
		break;
	}

        usleep(500000); # Wait half a second

	// do other work here
}

If no one else has strong arguments against it or better solutions, I'd close and label this issue as wontfix. 😬

[rbro]

@hollodotme - thanks, I'll submit a PR soon. I'll think through possible options too, but I'm doing now what you wrote at the end with usleep, but it has a side effect and is why I noticed the issue above. My message queue processing times were a lot slower than what they should have been when processing say 1,000's of messages. I was losing up to half a second for each message I was processing from rabbitmq because if the fastcgi server returned while usleep was running, the script would have to wait for usleep to finish before calling stream_select again. It would be much more efficient to have that waiting be done in the call to stream_select because then the response from the fastcgi server will be processed as soon as it comes in rather than waiting for usleep to finish.

[hollodotme]

@rbro Well, that is a valid point. 👍

I am currently in the middle of organizing a PHP conference which happens next weekend, so I have little time to do some prototyping and testing during the next 2 weeks. But I'll surely try to wrap my head around it and find a proper solution. Any input is welcome in the meanwhile. 😄