My apache2, running on a debian stretch server, often shows instabilities that make the apache's processes number grow, as in this image:
When the processes number reaches the maximum processes number allowed, the apache server reaches a saturation point and stops responding.
Apache is helped by a varnish cache, while https handshake is made by pound.
The server hosts a mediawiki site; mediawiki is known to be quite resource hungry, but mediawiki is configure to use a memcached server, not only on varnish. Anyway, this site's traffic is quite low.
Another site is hosted, and it has many accesses, but its code is quite optimized.
My question is: why does the apache's processes number start growing? what could be the reason? is there any apache parameter which I could change? any help is appreciated.
UPDATE:
apache's server-status shows something like this:
Current Time: Thursday, 22-Nov-2018 22:11:32 CET
Restart Time: Thursday, 22-Nov-2018 17:01:50 CET
Parent Server Config. Generation: 6
Parent Server MPM Generation: 5
Server uptime: 5 hours 9 minutes 42 seconds
Server load: 1.56 1.62 1.60
Total accesses: 290978 - Total Traffic: 13.0 GB
CPU Usage: u3035.84 s853.12 cu95.02 cs23.17 - 21.6% CPU load
15.7 requests/sec - 0.7 MB/second - 46.8 kB/request
211 requests currently being processed, 29 idle workers
WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW
WWWWWWWWWWWWWWWW_WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW_WWWWWWWWW
WWWWWWWWWWWWW_WWWWWWWWWWWWWWWWW_WWWWWWK_WW_WWWWWWWWWW__WW_WWWWWW
_WWWW_WWWW__WWWW__WWWWWKWW_W__WW_WW_W____W_K____................
Scoreboard Key:
"_" Waiting for Connection, "S" Starting up, "R" Reading Request,
"W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup,
"C" Closing connection, "L" Logging, "G" Gracefully finishing,
"I" Idle cleanup of worker, "." Open slot with no current process
Srv PID Acc M CPU SS Req Conn Child Slot Client Protocol VHost Request
0-5 7078 39/1894/7033 W 51.62 2474 0 1212.2 76.84 291.35 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
1-5 7079 26/1754/6210 W 46.84 2617 0 325.6 69.37 232.28 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
2-5 6992 45/2272/7227 W 65.72 2063 0 967.3 135.68 323.88 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
3-5 7115 34/1956/6752 W 51.85 2276 0 550.6 75.82 255.04 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
4-5 7116 13/2177/7569 W 55.30 1474 0 95.5 97.34 363.31 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
5-5 24741 38/38/2319 W 0.81 2303 0 470.6 0.46 78.81 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
6-5 7164 8/1820/3582 W 55.88 2273 0 2053.8 88.03 152.63 localhost http/1.1 www.myserver.net:8080 GET /indice.php?id=95&includisottoaree=1&parole=dieci+comandame
7-5 6991 41/2284/4871 W 61.35 2411 0 1672.6 101.89 225.53 localhost http/1.1 www.myserver.net:8080 GET /indice.php?id=151&area=video&includisottoaree=1&parole=die
8-5 7177 13/1905/5509 W 54.31 2513 0 110.7 65.53 242.78 localhost http/1.1 www.myserver.net:8080 GET /indice.php?id=95&includisottoaree=1&parole=dieci+comandame
9-5 7178 19/1685/3773 W 57.13 2311 0 230.0 85.37 198.94 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
10-5 6993 10/1730/6138 W 58.98 2153 0 279.8 77.14 269.71 localhost http/1.1 www.myserver.net:8080 GET /indice.php?id=95&includisottoaree=1&parole=dieci+comandame
11-5 7203 24/1800/7684 W 64.24 2497 0 410.8 94.65 378.47 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
12-5 24767 25/322/4734 W 8.75 1703 0 949.1 8.59 193.58 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
13-5 7274 26/2444/4303 W 62.34 1077 0 265.0 84.95 165.15 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
14-5 6994 27/1825/3191 W 51.14 2257 0 200.5 116.68 183.87 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
15-5 7275 11/1920/5549 W 47.93 2234 0 229.7 81.32 239.53 127.0.0.1 http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
16-5 7296 38/1966/5571 W 54.47 2516 0 872.8 80.50 309.33 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
17-5 24768 12/28/1781 W 0.36 2249 0 135.1 0.22 67.21 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
18-5 7351 10/2297/5512 W 75.49 1529 0 74.7 120.55 275.52 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
19-5 7352 13/2282/3062 W 65.76 2157 0 347.7 86.21 125.06 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
20-5 7381 23/2084/2791 W 57.86 2017 0 1473.5 180.55 242.64 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
21-5 7382 6/2094/4607 W 55.89 2571 0 33.0 78.08 188.96 127.0.0.1 http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
22-5 7407 24/2039/4816 W 54.73 2393 0 518.9 81.25 208.01 localhost http/1.1 www.myserver.net:8080 GET /indice.php?id=95&includisottoaree=1&parole=dieci+comandame
23-5 6990 6/1881/3829 W 52.14 2369 0 80.3 85.97 185.38 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
24-5 7408 41/2789/4877 W 81.54 1050 0 1052.5 139.01 231.51 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
25-5 7441 45/2442/4354 W 82.24 1014 0 4094.1 123.39 238.31 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
26-5 7442 9/1853/3907 W 40.79 2489 0 117.7 66.26 166.42 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
27-5 23874 4/1412/3792 W 34.98 2551 0 557.1 58.33 164.30 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
28-5 23926 3/1636/4245 W 49.36 2594 0 31.9 125.24 236.27 127.0.0.1 http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
29-5 23927 47/2030/3795 W 58.84 1437 0 1151.4 95.04 168.33 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=19354&anchor=documento_6&rito
30-5 7477 33/2402/4309 W 62.78 2423 0 5086.6 146.04 252.14 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=46711&anchor=documento_8&rito
31-5 24786 26/36/1660 W 1.07 2129 0 819.7 0.84 94.21 localhost http/1.1 www.myserver.net:8080 GET /materiale/anteprima.php?file=35212&anchor=documento_7&rito
etc...
Why are most child still sending reply after a long time?
Does the high value of SS mean that the child servers are kept without reusing them and without killing them? KeepAliveTimeout is 5 sec....
