Terbium is still on HHVM 3.6.5. Upgrade was probably delayed to let long running script finish their job. I am unsure of how we can find a window to upgrade this host, but it would make sense to align it.
Currently, a number of WARNING are raised by CirrusSearch which expect HHVM >= 3.9.0, while not blocking, this is noise...
HHVM on terbium has been upgraded to 3.12.1. But it has a bunch of maintenance script runs by people or via a cron.
Some jobs refers to php5 which is the Zend flavor, that is the case for the updateSuggestedIndex.php script and that triggers the error message.
There was an ongoing extensions/CirrusSearch/maintenance/updateSuggesterIndex.php job that is run via mwscript and that script hardcodes php5:
if [ "`whoami`" != "$MEDIAWIKI_WEB_USER" ] ; then sudo -u "$MEDIAWIKI_WEB_USER" php5 "$MEDIAWIKI_DEPLOYMENT_DIR_DIR_USE/multiversion/MWScript.php" "$@" else php5 "$MEDIAWIKI_DEPLOYMENT_DIR_DIR_USE/multiversion/MWScript.php" "$@" fi
From Logstash the messages are currently emitted for uzwiki and uzwikitionary. And on terbium there are extensions/CirrusSearch/maintenance/updateSuggesterIndex.php runs under php5 for both wikis.
Was due to some code not being compatible with HHVM a couple months ago that prevent deployment.