E.g. in https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2016.11.22/mediawiki/?id=AViJ_E2IPSU6VDGXPCmC
(which is created by something like $logger->warning( 'foo', [ 'exception' => new Exception( 'bar' ) ] );) th field is exception.trace
/srv/mediawiki/php-1.29.0-wmf.3/includes/user/User.php:5123, /srv/mediawiki/php-1.29.0-wmf.3/includes/user/User.php:2766, /srv/mediawiki/php-1.29.0-wmf.3/includes/context/RequestContext.php:364, /srv/mediawiki/php-1.29.0-wmf.3/includes/StubObject.php:207, /srv/mediawiki/php-1.29.0-wmf.3/includes/StubObject.php:169, /srv/mediawiki/php-1.29.0-wmf.3/includes/StubObject.php:112, /srv/mediawiki/php-1.29.0-wmf.3/includes/StubObject.php:139, /srv/mediawiki/php-1.29.0-wmf.3/includes/parser/Parser.php:2110, /srv/mediawiki/php-1.29.0-wmf.3/includes/parser/Parser.php:2075, /srv/mediawiki/php-1.29.0-wmf.3/includes/parser/Parser.php:1290, /srv/mediawiki/php-1.29.0-wmf.3/includes/parser/Parser.php:441, /srv/mediawiki/php-1.29.0-wmf.3/includes/OutputPage.php:1872, /srv/mediawiki/php-1.29.0-wmf.3/includes/OutputPage.php:1895, /srv/mediawiki/php-1.29.0-wmf.3/extensions/AbuseFilter/AbuseFilter.class.php:759, /srv/mediawiki/php-1.29.0-wmf.3/extensions/AbuseFilter/AbuseFilter.class.php:947, /srv/mediawiki/php-1.29.0-wmf.3/extensions/AbuseFilter/AbuseFilterPreAuthenticationProvider.php:41, /srv/mediawiki/php-1.29.0-wmf.3/extensions/AbuseFilter/AbuseFilterPreAuthenticationProvider.php:13, /srv/mediawiki/php-1.29.0-wmf.3/includes/auth/AuthManager.php:1648, /srv/mediawiki/php-1.29.0-wmf.3/includes/Setup.php:866, /srv/mediawiki/php-1.29.0-wmf.3/includes/WebStart.php:137, /srv/mediawiki/php-1.29.0-wmf.3/index.php:40, /srv/mediawiki/w/index.php:3
which is not exactly user-friendly. It should look more like this:
#0 [internal function]: MWExceptionHandler::handleError(integer, string, string, integer, array) #1 /vagrant/mediawiki/includes/WebResponse.php(45): header(string, boolean) #2 /vagrant/mediawiki/extensions/XAnalytics/XAnalytics.class.php(67): WebResponse->header(string, boolean)
The behavior seems to be coming from NormalizerFormatter::normalizeException (which LogstashFormatter inherits).