Bdtyktl

Running Ubuntu 18.04.1 LTS on a custom built home server (i5-6500, 16GB RAM).

I have been struggling with determining the source of periodic Apache crashes at frequencies ranging from hourly to daily. Apache has run well since the server was built about 2 years ago, until this issue began to occur several months ago. When it crashes, it must be manually restarted using systemctl restart apache2.

The contents of /var/log/apache2/error.log several seconds prior to the SIGTERM:

[Fri Jan 18 04:19:20.651049 2019] [fcgid:info] [pid 29012] mod_fcgid: Process manager 29012 stopped

[Fri Jan 18 04:19:20.675851 2019] [fcgid:info] [pid 29109] mod_fcgid: Process manager 29109 started

[Fri Jan 18 04:19:20.678539 2019] [:notice] [pid 29108] FastCGI: process manager initialized (pid 29108)

[Fri Jan 18 04:19:20.767449 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(401): AH00821: shmcb_init allocated 512000 bytes of shared memory

[Fri Jan 18 04:19:20.767461 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(417): AH00822: for 511912 bytes (512000 including header), recommending 32 subcaches, 88 indexes each

[Fri Jan 18 04:19:20.767463 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(450): AH00824: shmcb_init_memory choices follow

[Fri Jan 18 04:19:20.767466 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(452): AH00825: subcache_num = 32

[Fri Jan 18 04:19:20.767468 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(454): AH00826: subcache_size = 15992

[Fri Jan 18 04:19:20.767469 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(456): AH00827: subcache_data_offset = 2128

[Fri Jan 18 04:19:20.767471 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(458): AH00828: subcache_data_size = 13864

[Fri Jan 18 04:19:20.767473 2019] [socache_shmcb:debug] [pid 28514] mod_socache_shmcb.c(460): AH00829: index_num = 88

[Fri Jan 18 04:19:20.767519 2019] [socache_shmcb:info] [pid 28514] AH00830: Shared memory socache initialised

[Fri Jan 18 04:19:20.767522 2019] [ssl:info] [pid 28514] AH01887: Init: Initializing (virtual) servers for SSL

[Fri Jan 18 04:19:20.771807 2019] [ssl:info] [pid 28514] AH01914: Configuring server cloud.MY_DOMAIN.net:443 for SSL protocol

[Fri Jan 18 04:19:20.771812 2019] [ssl:debug] [pid 28514] ssl_engine_init.c(1658): AH: Init: (cloud.MY_DOMAIN.net:443) mod_md support is unavailable.

[Fri Jan 18 04:19:20.771931 2019] [ssl:debug] [pid 28514] ssl_engine_init.c(492): AH01893: Configuring TLS extension handling

[Fri Jan 18 04:19:20.772076 2019] [ssl:debug] [pid 28514] ssl_util_ssl.c(470): AH02412: [cloud.MY_DOMAIN.net:443] Cert matches for name 'cloud.MY_DOMAIN.net' [subject: CN=MY_DOMAIN.net / issuer: CN=Let's Encrypt Authority X3,O=Let's Encrypt,C=US / serial: ################################ / notbefore: Dec  1 07:03:19 2018 GMT / notafter: Mar  1 07:03:19 2019 GMT]

[Fri Jan 18 04:19:20.772080 2019] [ssl:info] [pid 28514] AH02568: Certificate and private key cloud.MY_DOMAIN.net:443:0 configured from /etc/letsencrypt/live/MY_DOMAIN.net-0009/fullchain.pem and /etc/letsencrypt/live/MY_DOMAIN.net-0009/privkey.pem

[Fri Jan 18 04:19:20.772436 2019] [ssl:info] [pid 28514] AH01914: Configuring server www.MY_DOMAIN.net:443 for SSL protocol

[Fri Jan 18 04:19:20.772439 2019] [ssl:debug] [pid 28514] ssl_engine_init.c(1658): AH: Init: (www.MY_DOMAIN.net:443) mod_md support is unavailable.

[Fri Jan 18 04:19:20.772541 2019] [ssl:debug] [pid 28514] ssl_engine_init.c(492): AH01893: Configuring TLS extension handling

[Fri Jan 18 04:19:20.772687 2019] [ssl:debug] [pid 28514] ssl_util_ssl.c(470): AH02412: [www.MY_DOMAIN.net:443] Cert matches for name 'www.MY_DOMAIN.net' [subject: CN=MY_DOMAIN.net / issuer: CN=Let's Encrypt Authority X3,O=Let's Encrypt,C=US / serial: ################################ / notbefore: Dec  1 07:03:19 2018 GMT / notafter: Mar  1 07:03:19 2019 GMT]

[Fri Jan 18 04:19:20.772691 2019] [ssl:info] [pid 28514] AH02568: Certificate and private key www.MY_DOMAIN.net:443:0 configured from /etc/letsencrypt/live/MY_DOMAIN.net-0009/fullchain.pem and /etc/letsencrypt/live/MY_DOMAIN.net-0009/privkey.pem

[Fri Jan 18 04:19:20.772785 2019] [ssl:info] [pid 28514] AH01876: mod_ssl/2.4.29 compiled against Server: Apache/2.4.29, Library: OpenSSL/1.1.0g

[Fri Jan 18 04:19:20.772807 2019] [watchdog:debug] [pid 28514] mod_watchdog.c(454): AH010033: Watchdog: Running with WatchdogInterval 1000ms

[Fri Jan 18 04:19:20.772811 2019] [watchdog:debug] [pid 28514] mod_watchdog.c(462): AH02974: Watchdog: found parent providers.

[Fri Jan 18 04:19:20.772813 2019] [watchdog:debug] [pid 28514] mod_watchdog.c(508): AH02977: Watchdog: found child providers.

[Fri Jan 18 04:19:20.772816 2019] [watchdog:debug] [pid 28514] mod_watchdog.c(516): AH02978: Watchdog: Looking for child (_singleton_).

[Fri Jan 18 04:19:20.772818 2019] [watchdog:debug] [pid 28514] mod_watchdog.c(516): AH02978: Watchdog: Looking for child (_default_).

[Fri Jan 18 04:19:20.773834 2019] [mpm_prefork:notice] [pid 28514] AH00163: Apache/2.4.29 (Ubuntu) mod_fastcgi/mod_fastcgi-SNAP-0910052141 mod_fcgid/2.3.9 OpenSSL/1.1.0g configured -- resuming normal operations

[Fri Jan 18 04:19:20.773842 2019] [mpm_prefork:info] [pid 28514] AH00164: Server built: 2018-10-10T18:59:25

[Fri Jan 18 04:19:20.773849 2019] [core:notice] [pid 28514] AH00094: Command line: '/usr/sbin/apache2'

[Fri Jan 18 04:19:20.773851 2019] [core:debug] [pid 28514] log.c(1570): AH02639: Using SO_REUSEPORT: yes (1)

[Fri Jan 18 04:19:20.773867 2019] [mpm_prefork:debug] [pid 28514] prefork.c(923): AH00165: Accept mutex: fcntl (default: sysvsem)

[Fri Jan 18 04:19:20.777421 2019] [watchdog:debug] [pid 29114] mod_watchdog.c(565): AH02980: Watchdog: nothing configured?

[Fri Jan 18 04:19:20.777503 2019] [proxy:debug] [pid 29114] proxy_util.c(1785): AH00925: initializing worker proxy:reverse shared

[Fri Jan 18 04:19:20.777510 2019] [proxy:debug] [pid 29114] proxy_util.c(1827): AH00927: initializing worker proxy:reverse local

[Fri Jan 18 04:19:20.777525 2019] [proxy:debug] [pid 29114] proxy_util.c(1878): AH00931: initialized single connection worker in child 29114 for (*)

[Fri Jan 18 04:19:20.778007 2019] [ssl:info] [pid 29114] [client 192.168.1.1:47184] AH01964: Connection to child 1 established (server www.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:20.778241 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(2139): [client 192.168.1.1:47184] AH02043: SSL virtual host for servername cloud.MY_DOMAIN.net found

[Fri Jan 18 04:19:20.778267 2019] [core:debug] [pid 29114] protocol.c(2257): [client 192.168.1.1:47184] AH03155: select protocol from , choices=h2,http/1.1 for server cloud.MY_DOMAIN.net

[Fri Jan 18 04:19:20.781857 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(2067): [client 192.168.1.1:47184] AH02041: Protocol: TLSv1.2, Cipher: ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)

[Fri Jan 18 04:19:20.782763 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Initial (No.1) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:20.783793 2019] [watchdog:debug] [pid 29115] mod_watchdog.c(565): AH02980: Watchdog: nothing configured?

[Fri Jan 18 04:19:20.783874 2019] [proxy:debug] [pid 29115] proxy_util.c(1785): AH00925: initializing worker proxy:reverse shared

[Fri Jan 18 04:19:20.783881 2019] [proxy:debug] [pid 29115] proxy_util.c(1827): AH00927: initializing worker proxy:reverse local

[Fri Jan 18 04:19:20.783898 2019] [proxy:debug] [pid 29115] proxy_util.c(1878): AH00931: initialized single connection worker in child 29115 for (*)

[Fri Jan 18 04:19:21.779826 2019] [watchdog:debug] [pid 29120] mod_watchdog.c(565): AH02980: Watchdog: nothing configured?

[Fri Jan 18 04:19:21.779935 2019] [proxy:debug] [pid 29120] proxy_util.c(1785): AH00925: initializing worker proxy:reverse shared

[Fri Jan 18 04:19:21.779942 2019] [proxy:debug] [pid 29120] proxy_util.c(1827): AH00927: initializing worker proxy:reverse local

[Fri Jan 18 04:19:21.779971 2019] [proxy:debug] [pid 29120] proxy_util.c(1878): AH00931: initialized single connection worker in child 29120 for (*)

[Fri Jan 18 04:19:23.304175 2019] [ssl:info] [pid 29115] [client 192.168.1.1:47190] AH01964: Connection to child 2 established (server www.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:23.304484 2019] [ssl:debug] [pid 29115] ssl_engine_kernel.c(2139): [client 192.168.1.1:47190] AH02043: SSL virtual host for servername cloud.MY_DOMAIN.net found

[Fri Jan 18 04:19:23.304499 2019] [core:debug] [pid 29115] protocol.c(2257): [client 192.168.1.1:47190] AH03155: select protocol from , choices=h2,http/1.1 for server cloud.MY_DOMAIN.net

[Fri Jan 18 04:19:23.305841 2019] [ssl:debug] [pid 29115] ssl_engine_kernel.c(2067): [client 192.168.1.1:47190] AH02041: Protocol: TLSv1.2, Cipher: ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)

[Fri Jan 18 04:19:23.305954 2019] [ssl:debug] [pid 29115] ssl_engine_kernel.c(377): [client 192.168.1.1:47190] AH02034: Initial (No.1) HTTPS request received for child 2 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:23.782768 2019] [watchdog:debug] [pid 29134] mod_watchdog.c(565): AH02980: Watchdog: nothing configured?

[Fri Jan 18 04:19:23.782860 2019] [proxy:debug] [pid 29134] proxy_util.c(1785): AH00925: initializing worker proxy:reverse shared

[Fri Jan 18 04:19:23.782866 2019] [proxy:debug] [pid 29134] proxy_util.c(1827): AH00927: initializing worker proxy:reverse local

[Fri Jan 18 04:19:23.782881 2019] [proxy:debug] [pid 29134] proxy_util.c(1878): AH00931: initialized single connection worker in child 29134 for (*)

[Fri Jan 18 04:19:23.795902 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.2) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:23.860810 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.3) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:23.955395 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.4) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:24.092544 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.5) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:24.237533 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.6) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:25.200469 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.7) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:25.237710 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.8) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:25.338693 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.9) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:25.642150 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.10) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:25.869587 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.11) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:25.974026 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.12) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:26.118787 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.13) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:26.229663 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.14) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:26.340689 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.15) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:26.681396 2019] [ssl:debug] [pid 28656] ssl_engine_kernel.c(377): [client 192.168.1.1:63023] AH02034: Subsequent (No.4) HTTPS request received for child 3 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:26.823089 2019] [ssl:debug] [pid 28656] ssl_engine_io.c(1103): [client 192.168.1.1:63023] AH02001: Connection closed to child 3 with standard shutdown (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:26.856368 2019] [ssl:info] [pid 29120] [client 192.168.1.1:63039] AH01964: Connection to child 6 established (server www.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:26.856817 2019] [ssl:debug] [pid 29120] ssl_engine_kernel.c(2139): [client 192.168.1.1:63039] AH02043: SSL virtual host for servername cloud.MY_DOMAIN.net found

[Fri Jan 18 04:19:26.863787 2019] [ssl:debug] [pid 29120] ssl_engine_kernel.c(2067): [client 192.168.1.1:63039] AH02041: Protocol: TLSv1.2, Cipher: ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)

[Fri Jan 18 04:19:26.865493 2019] [ssl:debug] [pid 29120] ssl_engine_kernel.c(377): [client 192.168.1.1:63039] AH02034: Initial (No.1) HTTPS request received for child 6 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:27.153860 2019] [ssl:debug] [pid 29120] ssl_engine_kernel.c(377): [client 192.168.1.1:63039] AH02034: Subsequent (No.2) HTTPS request received for child 6 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:27.297174 2019] [ssl:debug] [pid 29120] ssl_engine_kernel.c(377): [client 192.168.1.1:63039] AH02034: Subsequent (No.3) HTTPS request received for child 6 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:27.436015 2019] [ssl:info] [pid 29134] [client 192.168.1.1:63040] AH01964: Connection to child 7 established (server www.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:27.436301 2019] [ssl:debug] [pid 29134] ssl_engine_kernel.c(2139): [client 192.168.1.1:63040] AH02043: SSL virtual host for servername tautulli.MY_DOMAIN.net found

[Fri Jan 18 04:19:27.436335 2019] [core:debug] [pid 29134] protocol.c(2257): [client 192.168.1.1:63040] AH03155: select protocol from , choices=h2,http/1.1 for server tautulli.MY_DOMAIN.net

[Fri Jan 18 04:19:27.439472 2019] [ssl:debug] [pid 29134] ssl_engine_kernel.c(2067): [client 192.168.1.1:63040] AH02041: Protocol: TLSv1.2, Cipher: ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)

[Fri Jan 18 04:19:27.786856 2019] [watchdog:debug] [pid 29183] mod_watchdog.c(565): AH02980: Watchdog: nothing configured?

[Fri Jan 18 04:19:27.786966 2019] [proxy:debug] [pid 29183] proxy_util.c(1785): AH00925: initializing worker proxy:reverse shared

[Fri Jan 18 04:19:27.786973 2019] [proxy:debug] [pid 29183] proxy_util.c(1827): AH00927: initializing worker proxy:reverse local

[Fri Jan 18 04:19:27.786988 2019] [proxy:debug] [pid 29183] proxy_util.c(1878): AH00931: initialized single connection worker in child 29183 for (*)

[Fri Jan 18 04:19:28.787927 2019] [watchdog:debug] [pid 29186] mod_watchdog.c(565): AH02980: Watchdog: nothing configured?

[Fri Jan 18 04:19:28.788027 2019] [proxy:debug] [pid 29186] proxy_util.c(1785): AH00925: initializing worker proxy:reverse shared

[Fri Jan 18 04:19:28.788035 2019] [proxy:debug] [pid 29186] proxy_util.c(1827): AH00927: initializing worker proxy:reverse local

[Fri Jan 18 04:19:28.788053 2019] [proxy:debug] [pid 29186] proxy_util.c(1878): AH00931: initialized single connection worker in child 29186 for (*)

[Fri Jan 18 04:19:30.941966 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.16) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:30.983215 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.17) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:31.326812 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.18) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:31.372147 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.19) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:31.462389 2019] [ssl:debug] [pid 29120] ssl_engine_kernel.c(377): [client 192.168.1.1:63039] AH02034: Subsequent (No.4) HTTPS request received for child 6 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:33.877610 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.20) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:33.915044 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.21) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:34.368821 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.22) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:34.608589 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.23) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:34.660253 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.24) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:35.206134 2019] [ssl:debug] [pid 28735] ssl_engine_io.c(1103): [client 192.168.1.1:49536] AH02001: Connection closed to child 0 with standard shutdown (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:35.206771 2019] [ssl:debug] [pid 28658] ssl_engine_io.c(1103): [client 192.168.1.1:38116] AH02001: Connection closed to child 4 with standard shutdown (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:35.213859 2019] [ssl:debug] [pid 28807] ssl_engine_io.c(1103): [client 192.168.1.1:46554] AH02001: Connection closed to child 5 with standard shutdown (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:35.491299 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.25) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:35.567105 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.26) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:38.535059 2019] [ssl:debug] [pid 29115] ssl_engine_io.c(1103): [client 192.168.1.1:47190] AH02001: Connection closed to child 2 with standard shutdown (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:39.299918 2019] [ssl:debug] [pid 29114] ssl_engine_kernel.c(377): [client 192.168.1.1:47184] AH02034: Subsequent (No.27) HTTPS request received for child 1 (server cloud.MY_DOMAIN.net:443)

[Fri Jan 18 04:19:40.777331 2019] [core:info] [pid 28514] AH00096: removed PID file /var/run/apache2/apache2.pid (pid=28514)

[Fri Jan 18 04:19:40.777360 2019] [mpm_prefork:notice] [pid 28514] AH00169: caught SIGTERM, shutting down

Clearly, mpm_prefork sends Apache a SIGTERM, triggering the shut down. But I don't understand what is causing this to occur. Is there another log file that I should be examining?

The contents of mpm_prefork.conf was originally set to default values. The server is never under a heavy load and I don't see anything indicating that MaxClients is reached or anything of the sort. Despite this, I thought that perhaps the default settings were still to restrictive, so I have tried adjusting them to improve performance:

<IfModule mpm_prefork_module>

  StartServers 2

  MinSpareServers 2

  MaxSpareServers 5

  MaxClients 50

  ServerLimit 50

  MaxRequestsPerChild 100

</IfModule>

Am I overlooking something? Any help or pointers are appreciated, thanks!