'zipkin' => [
   'class' => TracerAlias::class,
   'serviceName' => 'yii2',
   'endpointUrl' => 'http://127.0.0.1:9411/api/v2/spans',
   'sampleRate' => 1,
   'apiPrefix' => '/'
],

Add zipkin sampler

For single controller

//Add Lxj\Yii2\Zipkin\Filter to behaviors mathod.
public function behaviors()
{
    return [
        'zipkin' => [
            'class' => Filter::class,
        ],
    ];
}

For module

//Define your module extended 'Lxj\Yii2\Zipkin\Module'
class MyModule extends Lxj\Yii2\Zipkin\Module

Demo is here.