README

Clustering support for PHP-LRPM, including different sharding strategies.

Usage

You should extend the abstract PHPLRPM\Cluster\ShardingConfigurationSource class and implement a nullary (zero-argument) constructor which will be initializing instances of PHPLRPM\ConfigurationSource, PHPLRPM\Cluster\Providers\ClusterConfigurationProvider and PHPLRPM\Cluster\Filters\ShardingConfigurationFilter:

namespace MyNamespace;
use PHPLRPM\Cluster\ShardingConfigurationSource;

class MyLRPMWorkerShardingConfiguration extends ShardingConfigurationSource
{
    public function __construct()
    {
        //instance of PHPLRPM\ConfigurationSource
        $this->confSource = new MyLRPMWorkerConfiguration()
        //instance of PHPLRPM\Cluster\Providers\ClusterConfigurationProvider
        $this->clusterConfProvider = new EnvironmentBasedClusterConfigurationProvider();
        //instance of PHPLRPM\Cluster\Filters\ShardingConfigurationFilter
        $this->configurationFilter = new BalancedShardingConfigurationFilter();
    }
}

Then you may provide MyLRPMWorkerShardingConfiguration as a regular ConfigurationSource for PHP-LRPM, e.g.

lrpm '\MyNamespace\MyLRPMWorkerShardingConfiguration'

See https://github.com/vrza/php-lrpm#usage for more details.

Sharding Strategies

You can either write your own ShardingConfigurationFilter or use one of the built-in filters.

Balanced

Use the BalancedShardingConfigurationFilter when either:

scaling involves restarting the entire cluster
perfect load balancing is necessary

Pros	Cons
Perfect load balancing	Potentially large number of disrupted processes when rescaling

Rendezvous Hashing

Use the RendezvousHashingShardingConfigurationFilter when both:

minimal worker process disruption is highly desirable
load balancing biased towards certain nodes is tolerable

Pros	Cons
Minimal disruption when rescaling	Biased load balancing

Simple hashing

Use the HashingShardingConfigurationFilter to achieve:

decent (but not perfect) load balancing
some (but not complete) worker process disruption when cluster is rescaled

Pros	Cons
Strikes a balance between load balancing and disruption	Guarantees neither perfect load balancing nor minimal disruption

Cluster Configuration and Providers

Cluster configuration parameters are

total number of nodes in the cluster
zero-based index of current node

You can either write your own ClusterConfigurationProvider or use one of the built-in providers.

Environment-based Cluster Configuration Provider

Use the EnvironmentBasedClusterConfigurationProvider to load cluster configuration from environment variables PHP_LRPM_NUMBER_OF_INSTANCES and PHP_LRPM_INSTANCE_NUMBER. Default variable names can be overridden.

File-based Cluster Configuration Provider

Use the FileBasedClusterConfigurationProvider to load cluster configuration from a JSON configuration file, e.g.:

{
    "numberOfInstances": 3,
    "instanceNumber" : 2
}

Installation

Assuming you have PHP Composer installed, and that the composer executable is in your $PATH:

composer require php-lrpm/php-lrpm-cluster

php-lrpm / php-lrpm-cluster

Maintainers

Details