From /var/log/hhvm/error.log, found this on mw1280 (API server) when looking for an unrelated change:
Aug 21 11:16:53 mw1280 hhvm: #012Fatal error: unknown exception Aug 21 11:16:53 mw1280 hhvm[21493]: [Mon Aug 21 11:16:53 2017] [hphp] [21493:7f2ff6fff700:6208:000001] [] \nFatal error: unknown exception
Come in spikes, but generally occurs more often in July:
for i in `ls error.log-2017*`; do echo -n $i ":" ; grep "Fatal error: unknown exception" $i | wc -l ; done error.log-20170523 :2 error.log-20170524 :2 error.log-20170525 :10 error.log-20170526 :2 error.log-20170527 :6 error.log-20170528 :2 error.log-20170529 :2 error.log-20170530 :2 error.log-20170531 :12 error.log-20170601 :6 error.log-20170602 :0 error.log-20170603 :14 error.log-20170604 :4 error.log-20170605 :6 error.log-20170606 :2 error.log-20170607 :0 error.log-20170608 :0 error.log-20170609 :4 error.log-20170610 :4 error.log-20170611 :0 error.log-20170612 :0 error.log-20170613 :2 error.log-20170614 :76 error.log-20170615 :8 error.log-20170616 :4 error.log-20170617 :2 error.log-20170618 :0 error.log-20170619 :6 error.log-20170620 :8 error.log-20170621 :6 error.log-20170622 :12 error.log-20170623 :4 error.log-20170624 :12 error.log-20170625 :0 error.log-20170626 :12 error.log-20170627 :8 error.log-20170628 :8 error.log-20170629 :8 error.log-20170630 :24 error.log-20170701 :14 error.log-20170702 :8 error.log-20170703 :24 error.log-20170704 :18 error.log-20170705 :18 error.log-20170706 :76 error.log-20170707 :126 error.log-20170708 :192 error.log-20170709 :182 error.log-20170710 :108 error.log-20170711 :104 error.log-20170712 :104 error.log-20170713 :210 error.log-20170714 :88 error.log-20170715 :194 error.log-20170716 :218 error.log-20170717 :208 error.log-20170718 :114 error.log-20170719 :186 error.log-20170720 :178 error.log-20170721 :102 error.log-20170722 :162 error.log-20170723 :286 error.log-20170724 :164 error.log-20170725 :188 error.log-20170726 :186 error.log-20170727 :264 error.log-20170728 :200 error.log-20170729 :320 error.log-20170730 :40 error.log-20170731 :108 error.log-20170801 :98 error.log-20170802 :120 error.log-20170803 :90 error.log-20170804 :68 error.log-20170805 :42 error.log-20170806 :46 error.log-20170807 :28 error.log-20170808 :30 error.log-20170809 :60 error.log-20170810 :42 error.log-20170811 :44 error.log-20170812 :42 error.log-20170813 :66 error.log-20170814 :44 error.log-20170815 :120 error.log-20170816 :180 error.log-20170817 :228 error.log-20170818 :242 error.log-20170819 :280 error.log-20170820 :278
On a standard app server is occurs less often (e.g. mw1269):
error.log-20170523 :4 error.log-20170524 :2 error.log-20170525 :2 error.log-20170526 :0 error.log-20170527 :2 error.log-20170528 :0 error.log-20170529 :0 error.log-20170530 :0 error.log-20170531 :0 error.log-20170601 :0 error.log-20170602 :2 error.log-20170603 :0 error.log-20170604 :0 error.log-20170605 :2 error.log-20170606 :0 error.log-20170607 :0 error.log-20170608 :6 error.log-20170609 :6 error.log-20170610 :0 error.log-20170611 :2 error.log-20170612 :0 error.log-20170613 :2 error.log-20170614 :42 error.log-20170615 :2 error.log-20170616 :2 error.log-20170617 :4 error.log-20170618 :0 error.log-20170619 :2 error.log-20170620 :2 error.log-20170621 :2 error.log-20170622 :0 error.log-20170623 :4 error.log-20170624 :4 error.log-20170625 :10 error.log-20170626 :10 error.log-20170627 :8 error.log-20170628 :4 error.log-20170629 :4 error.log-20170630 :8 error.log-20170701 :6 error.log-20170702 :2 error.log-20170703 :8 error.log-20170704 :6 error.log-20170705 :10 error.log-20170706 :18 error.log-20170707 :22 error.log-20170708 :40 error.log-20170709 :42 error.log-20170710 :52 error.log-20170711 :36 error.log-20170712 :50 error.log-20170713 :52 error.log-20170714 :34 error.log-20170715 :64 error.log-20170716 :66 error.log-20170717 :66 error.log-20170718 :54 error.log-20170719 :74 error.log-20170720 :60 error.log-20170721 :42 error.log-20170722 :54 error.log-20170723 :68 error.log-20170724 :56 error.log-20170725 :62 error.log-20170726 :64 error.log-20170727 :50 error.log-20170728 :82 error.log-20170729 :42 error.log-20170730 :14 error.log-20170731 :14 error.log-20170801 :30 error.log-20170802 :20 error.log-20170803 :6 error.log-20170804 :28 error.log-20170805 :12 error.log-20170806 :12 error.log-20170807 :20 error.log-20170808 :14 error.log-20170809 :10 error.log-20170810 :10 error.log-20170811 :12 error.log-20170812 :10 error.log-20170813 :12 error.log-20170814 :20 error.log-20170815 :20 error.log-20170816 :24 error.log-20170817 :22 error.log-20170818 :22 error.log-20170819 :26 error.log-20170820 :18