Apache 500 on parallels plesk + mod_jk: Could not find a worker for worker name

For a long time I had 3 Java web apps running on box with Parallels Plesk panel. Everything was fine until yesterday.
Without any reason I started to get 500 on all apps running throe mod_jk – php apps are fine.

I tuned log level to debug for both apache and mod_jk – nothing beside this in mod_jk log is suspicious:

[Wed Jan 25 19:57:49 2012][5147:0000] [debug] map_uri_to_worker::jk_uri_worker_map.c (449): Attempting to map URI '/' from 2 maps
[Wed Jan 25 19:57:49 2012][5147:0000] [debug] map_uri_to_worker::jk_uri_worker_map.c (461): Attempting to map context URI '/*'
[Wed Jan 25 19:57:49 2012][5147:0000] [debug] map_uri_to_worker::jk_uri_worker_map.c (475): Found a wildchar match seomanagonode -> /*
[Wed Jan 25 19:57:49 2012][5147:0000] [debug] jk_handler::mod_jk.c (1839): Into handler jakarta-servlet worker=seomanagonode r->proxyreq=0
[Wed Jan 25 19:57:49 2012][5147:0000] [debug] wc_get_worker_for_name::jk_worker.c (111): did not find a worker seomanagonode
[Wed Jan 25 19:57:49 2012][5147:0000] [info]  jk_handler::mod_jk.c (1993): Could not find a worker for worker name=seomanagonode

and in access log I found:

195.150.128.28 - - [25/Jan/2012:08:45:58 +0100] "GET / HTTP/1.1" 500 806 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.1 (KHTML, like Gecko) Ubuntu/11.04 Chromium/14.0.835.202 Chrome/14.0.835.202 Safari/535.1"

I am running:

• Plesk 9.5.4
• Apache 2.2
• Tomcat 6.x

worker configuration is as follows:

# seomanago.pl
worker.seomanagonode.port=8009
worker.seomanagonode.host=seomanago.pl
worker.seomanagonode.type=ajp13
worker.seomanagonode.ping_mode=A
worker.seomanagonode.socket_timeout=60
worker.seomanagonode.prepost_timeout=10000
worker.seomanagonode.connect_timeout=10000
worker.seomanagonode.connection_pool_size=200
worker.seomanagonode.connection_pool_timeout=300
worker.seomanagonode.retries=20

Any ideas? I hate Plesk – but it was not my choice – I just need to survive with it until we will be able to move to other hosting provider.

In Tomcat I see line indicating JK startup:

INFO: JK: ajp13 listening on /188.165.22.102:8009

In mod_jk.log there is information about creating worker:

[Wed Jan 25 18:45:52 2012][12306:0000] [debug] build_worker_map::jk_worker.c (236): creating worker seomanagonode
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] wc_create_worker::jk_worker.c (141): about to create instance seomanagonode of ajp13
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] wc_create_worker::jk_worker.c (154): about to validate and init seomanagonode
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_validate::jk_ajp_common.c (1806): worker seomanagonode contact is 'seomanago.pl:8009'
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1895): setting socket keepalive to 0
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1934): setting socket timeout to 60
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1938): setting socket buffer size to 0
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1942): setting connection recycle timeout to 0
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1946): setting cache timeout to 0
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1950): setting connect timeout to 10000
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1954): setting reply timeout to 0
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1958): setting prepost timeout to 10000
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1962): setting recovery opts to 0
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_init::jk_ajp_common.c (1966): setting number of retries to 20
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] ajp_create_endpoint_cache::jk_ajp_common.c (1843): setting connection cache size to 200
[Wed Jan 25 18:45:52 2012][12306:0000] [debug] build_worker_map::jk_worker.c (248): removing old seomanagonode worker

Any ideas where to look for more info on such thing?