Installing and Getting Started with Gearman

In my last post on Gearman, I have discussed why I love this tool. In this post, I am going to share some commands and codes to get you started with Gearman.

Install Gearman:

sudo apt-get install gearman

1	sudo apt-get install gearman

Install Gearman PHP Extension:

# Enable PEAR and PECL
sudo apt-get install php-pear

1 2	# Enable PEAR and PECL sudo apt-get install php-pear

Now, let’s install gearman pecl extension:

sudo pecl install gearman

1	sudo pecl install gearman

Did that work? NO! Why? Because Gearman PECL extension is still in beta mode. Unless a PECL package is “stable”, you have to mention the full channel name to force the beta installation:

sudo pecl install channel://pecl.php.net/gearman-0.8.0

1	sudo pecl install channel://pecl.php.net/gearman-0.8.0

Did it work? NO! Why? It asks for “libgearman”. Hell no! I can’t find that package! 🙁

Ok, don’t panick! It happens that libgearman was initially released as libgearman1 and afterwards came libgearman2 and libgearman3.

Are you on Ubuntu? Use this:

sudo apt-get install libgearman-dev

1	sudo apt-get install libgearman-dev

No, I am on Debian! Okay, try this:

sudo apt-get install libgearman2

1	sudo apt-get install libgearman2

Still no results? Use aptitude to find libgearman.

Now run the command again:

sudo pecl install channel://pecl.php.net/gearman-0.8.0

1	sudo pecl install channel://pecl.php.net/gearman-0.8.0

Works, right? If you get an error message regarding “autoconf” or something, Google is your best friend. If everything is okay, go ahead!

Run Gearman Daemon:
Gearman Daemon runs in the background. It matches the client request to the specific worker process. It registers worker processes and distributes the workload among them. To run it:

sudo gearmand -d -u root

1	sudo gearmand -d -u root

If you want the daemon to go verbose and help you in debugging with detailed data, use the “-vvv” switch like this:

sudo gearmand -d -vvv -u root

1	sudo gearmand -d -vvv -u root

You can change the startup parameters by editing the file: /etc/default/gearman-job-server. Don’t forget to play with the configuration a bit 🙂

Get a PHP Worker:
Let’s code a handy string processor:

<?php
// Create a GearmanWorker object
$worker= new GearmanWorker();
// Add the default server
$worker->addServer();
// Register the processing function
$worker->addFunction("process_string", "processString");
// Trigger the infinite loop
while ($worker->work());

// The main function that processes the job
function processString($job)
{
  // get the workload - it's a string. use serialization to pass objects
  $param = $job->workload();
  return "You passed the string: {$param} \n It had: ".strlen($param)." chars \n";
}
?>

<?php

// Create a GearmanWorker object

$worker= new GearmanWorker();

// Add the default server

$worker->addServer();

// Register the processing function

$worker->addFunction("process_string", "processString");

// Trigger the infinite loop

while ($worker->work());

// The main function that processes the job

function processString($job)

{

// get the workload - it's a string. use serialization to pass objects

$param = $job->workload();

return "You passed the string: {$param} \n It had: ".strlen($param)." chars \n";

}

So you see, I built a super useful string processor. With it’s high level of intelligence, it can echo back the string and tell you how many characters were there. When invoked, Gearman shall call the function with the $job parameter as a gearman job. The workload() method will extract parameter passed from the client.

We just defined a function, created a GearmanWorker object, connected to the default server and registered the function.

Now, how do we invoke the job? With a client:

<?php
// construct a client object
$client= new GearmanClient();
// add the default server
$client->addServer();
// print the output of the job. first parameter is the job name, second one is the parameter
print $client->do("process_string", "Hello Gearman!");
?>

<?php

// construct a client object

$client= new GearmanClient();

// add the default server

$client->addServer();

// print the output of the job. first parameter is the job name, second one is the parameter

print $client->do("process_string", "Hello Gearman!");

So, what are the output? I had three terminal tabs open. One for the main gearmand with verbose mode, another for worker.php and other one for the client output. Here’s the output sequentially:

masnun@lighthouse:~$ sudo gearmand -d -vvv -u root
 INFO Starting up
masnun@lighthouse:~$  INFO Listening on 0.0.0.0:4730 (7)
 INFO Creating wakeup pipe
 INFO Creating IO thread wakeup pipe
 INFO Adding event for listening socket (7)
 INFO Adding event for wakeup pipe
 INFO Entering main event loop
 INFO Accepted connection from 127.0.0.1:45305
 INFO [   0]       127.0.0.1:45305 Connected
 INFO Accepted connection from 127.0.0.1:45306
 INFO [   0]       127.0.0.1:45306 Connected
 INFO [   0]       127.0.0.1:45306 Disconnected

masnun@lighthouse:~$ sudo gearmand -d -vvv -u root

INFO Starting up

masnun@lighthouse:~$ INFO Listening on 0.0.0.0:4730 (7)

INFO Creating wakeup pipe

INFO Creating IO thread wakeup pipe

INFO Adding event for listening socket (7)

INFO Adding event for wakeup pipe

INFO Entering main event loop

INFO Accepted connection from 127.0.0.1:45305

INFO [ 0] 127.0.0.1:45305 Connected

INFO Accepted connection from 127.0.0.1:45306

INFO [ 0] 127.0.0.1:45306 Connected

INFO [ 0] 127.0.0.1:45306 Disconnected

masnun@lighthouse:~/gearman$ php worker.php

1	masnun@lighthouse:~/gearman$ php worker.php

masnun@lighthouse:~/gearman$ php client.php
You passed the string: Hello Gearman! 
 It had: 14 chars 
masnun@lighthouse:~/gearman$

masnun@lighthouse:~/gearman$ php client.php

You passed the string: Hello Gearman!

It had: 14 chars

masnun@lighthouse:~/gearman$

NOTES:
— For ease of demonstration, I have executed the client from a command line script, in actual live environment, you shall be calling it from a web app.

— On a remote SSH connection, you may not be able to have 3 terminal tabs open. Put an “&” after the commands to send them to background 🙂

— Use the same command to spawn as many workers as you need

Happy Gearing with PHP!

7 replies on “Installing and Getting Started with Gearman”

If you get an error message regarding “autoconf” or something

sudo apt-get install build-essentials 🙂

Nice simple and nifty example 🙂

[…] Reference: You can also read the getting started guide from this page. Or if you want to install it through unix package manager you can also follow this post […]