My apache is serving about 300 request/sec (2 megabytes/s) constantly with server load of 0.05.
After such short traffic jump, apache becomes unresponsive (connection reset after about 30 seconds in firefox) without logging anything. Apache is freezed until apache2 restart procedure.
When freezed, it cannot serve even simple HTML file without PHP or SQL connection (but apache2 processes exists)
I tried different prefork settings from 50 to almost 1000 idle workers and max clients limits of 10000, but nothing helps.
Another symptome apart from not logging anything, is that moments before freeze, apache status module shows (that last time before it gets unresponsive also) that almost every process wait for connection:
__R_R_______R__RR______R___R________________RR_______R______R___ _________R__________R_________________________R________CR___R___ ___________R__________________________C__WR__R________________R_
But in normal, less-laoded work it shows:
C___R___K_C___C___C_____KK______R___C_C_R______C__K___C________K ____C__KR_RR__C___K___KK_C__R__K__C_CK__RC___CR___R__K__C__R____ ___KR____C_____R______R______K__R_______KC__C_K__R____C_______R_
syslog also gives nothing. My machine has 64GB RAM and never exceeds load of 0.1