Collector is a service with a single purpose - form and return MetricSource In some cases collector can hold source directly, in other cases it can combine, merge, adopt other source in order to create final source. Also collector can create source by itself.
So general collector sample would be:
<?php
$metric = new \Lamoda\Metric\Common\Metric('sample', 1.0, ['tag' => 'value']);
// You can construct your own source from within your collector implementation
// But for simplicity of the example we just use precreated source
$source = new \Lamoda\Metric\Common\Source\IterableMetricSource([$metric]);
$collector = new \Lamoda\Metric\Collector\SingleSourceCollector($source);
$collectedSource = $collector->collect();This collector is simple and just holds the preconfigured source to collect it on demand.
More complex example is MergingCollector which will combine metrics from different sources into one.
Utility example is TaggingCollectorDecorator which will add default tag values
for each metric collected by delegate.
Collector is a kind of source wrapper in order to stabilize source definition and configuration for further purposes.
You can also use a Storage as hold source
CollectorRegistry can be used to hold named collectors