etouches/phplumber

Pipelining library which allows a mix of asynchronous and synchronous processes.

Phplumber

Phplumber is a very simple pipelining library for PHP which allows a mix of asynchronous and synchronous processes. Use it to break a large process into multiple steps using a queue and multi-processing. Phplumber contains no hard-coded dependencies and can be backed by any queue setup and any storage mechanism., _(*1)

Requirements

• PHP 5.3+
• A queue, such as RabbitMQ or Redis
• Storage, such as a relational database table or Redis

Example

Let's take creating and filling a database as an example. It takes multiple steps and some can be done concurrently., _(*2)

1. Create database (one process)
2. Create and populate tables (one process per table)
3. Create views dependent on multiple tables (one process, dependent on all tables existing)

                         Create table 1
                       /                \
    Create database ->   Create table 2   -> Create views
                       \                /
                         Create table 3

First we would define our processes. Sequential steps extend Process. A step that can run multiple times with different data extends MultiProcess., _(*3)

class CreateDatabase extends Process
{
    public function invoke($payload)
    {
        $database_name = $payload['database_name'];
        echo "Drop database $database_name if it exists...\n";
        echo "Creating database $database_name...\n";
    }
}

```php class CreateTable extends MultiProcess { // Determine the data we need to queue for async processes public function getAsyncPayloads($payload) { $database_name = $payload['database_name']; $table_names = array('first_table', 'second_table', 'third_table');, <sub>(*4)</sub>

    $payloads = array();
    foreach ($table_names as $table) {
        $payloads[] = array('database_name' => $database_name, 'table_name' => $table);
    }
    return $payloads;
}

public function invoke($payload)
{
    $database_name = $payload['database_name'];
    $table_name = $payload['table'];
    echo "Connecting to database $database_name...\n";
    echo "Creating and populating $table_name...\n";

    switch ($payload['table']) {
        case 'first_table':
            // Create table and insert rows...
            break;
        // ...
    }
}

}, <sub>(*5)</sub>

Then we define the sequence of processes.

```php
class CreateAndFillDatabase extends ProcessList
{
    protected function setup()
    {
        $this
            ->add('CreateDatabase')
            ->add('CreateTable')
            ->add('CreateViews');
    }
}

We can now kick off the process sequence., <sub>(*6)</sub>

$equation = new CreateAndFillDatabase();
$equation->process(array('database_name' => 'test_db'));

See the examples directory for complete, working demos., <sub>(*7)</sub>

Getting Started

1. Implement StorageInterface. This will hold semaphore data. Appropriate storage engines include any relational database, nosql, or key-value stores such as Redis.
2. Extend the Queue class to integrate with a queue system. Appropriate queue engines include Redis and RabbitMQ.
3. Write each process as a class that extends Process (for synchronous) or MultiProcess (for asynchronous).
4. Implement ProcessFactoryInterface. This will create each instance of ProcessInterface, allowing you to set up your processes with any prerequisites, such as a database connection or configuration options.
5. Put the processes together by extending ProcessList.
6. Implement a worker daemon which instantiates your Queue implementation and calls consume() to listen for incoming messages. Each message is to invoke a single part of a multi-process. Run multiple workers to execute processes concurrently.
7. Choose a place in your system to start the entire workflow, instantiate your ProcessList, and call process(), passing it the initial payload.