$wgEventStreams = [
    [
        'stream' => 'analytics.link_hover',
        'schema_title' => 'analytics/link_hover',
    ],
    [
        'stream' => 'pageview',
        'schema_title' => 'analytics/pageview',
        'sampling' => [
        	'rate' => 0.5,
        	'identifier' => 'pageview'
        ],
    ],
    [
        'stream' => 'mobile_apps.session',
        'schema_title' => 'analytics/mobile_apps/session',
        'sampling' => [
        	'identifier' => 'device'
        ],
    ],
];

$wgEventLoggingStreamNames = [
	'analytics.link_hover',
	'pageview',
	'edit',
	'edit.growth',
	'mobile_apps.session',
];

( function() {
  $( document ).ready( function() {
    var pageEvent = {
      $schema: '/analytics/pageview/1.0.0',
      page_token: mw.user.getPageviewToken(),
      session_id: mw.user.sessionId()
    };
    mw.eventLog.submit( 'pageview', pageEvent ); // will be sent approx. half the time
    mw.eventLog.submit( 'mobile_apps.session', { $schema: '/analytics/mobile_apps/session/1.0.0' } ); // will not be sent
  });
  // From https://wikitech.wikimedia.org/wiki/Event_Platform/Instrumentation_How_To:
  $( '#content' ).on( 'mouseover', 'a.extiw', function ( jqEvent ) {
    var link = jqEvent.target;
    var linkHoverEvent = {
      // $schema is required and must be set to the exact value of $id that you set in your schema.
      $schema: '/analytics/link_hover/1.0.0',
      link_href: link.href,
      link_title: link.title,
    };
    var streamName = 'analytics.interwiki_link_hover';
    console.log("logging event with data " + JSON.stringify(linkHoverEvent) + " to stream '" + streamName + "'");
    mw.eventLog.submit( streamName, linkHoverEvent );
  } );
}() );