Am 18.10.2016 um 10:10 schrieb Kozak, Milos:
Hi,

I am debugging a mod_jk load-balancing configuration which has been used a lot, 
but for two nodes only. Currently, we made a change for more nodes, and we are 
facing problem.

Original idea was to have one PROD and DR servers such that all requests are 
handled by PROD and if PROD goes down DR takes over. In order to do that we 
used activation=disabled for DR worker, such that:


worker.list=jkstatus,lbhierarchy
worker.jkstatus.type=status
worker.lbhierarchy.type=lb
worker.lbhierarchy.balance_workers=hierarchy-1,hierarchy-2

worker.hierarchy-1.type=ajp13
worker.hierarchy-1.host=host1
worker.hierarchy-1.port=8009
worker.hierarchy-1.socket_timeout=0
worker.hierarchy-1.socket_keepalive=False
worker.hierarchy-1.retries=2
worker.hierarchy-1.connection_pool_timeout=0
worker.hierarchy-1.lbfactor=1
worker.hierarchy-1.redirect=hierarchy-2

worker.hierarchy-2.type=ajp13
worker.hierarchy-2.host=host2
worker.hierarchy-2.port=8009
worker.hierarchy-2.socket_timeout=0
worker.hierarchy-2.socket_keepalive=False
worker.hierarchy-2.retries=2
worker.hierarchy-2.connection_pool_timeout=0
worker.hierarchy-2.lbfactor=1
worker.hierarchy-2.activation=disabled


However, the current demand is to have four servers which are chained. 
Basically, we try to have one PROD and 3 DR servers. Each DR is activated when 
the previous worker goes down. Therefore, we prepared configuration like this:



worker.list=jkstatus,lbhierarchy,lb2hierarchy
worker.jkstatus.type=status
worker.lbhierarchy.type=lb
worker.lbhierarchy.balance_workers=hierarchy-1,hierarchy-2,hierarchy-3,hierarchy-4

worker.hierarchy-1.type=ajp13
worker.hierarchy-1.host=host
worker.hierarchy-1.port=8009
worker.hierarchy-1.socket_timeout=0
worker.hierarchy-1.socket_keepalive=False
worker.hierarchy-1.retries=2
worker.hierarchy-1.connection_pool_timeout=0
worker.hierarchy-1.lbfactor=1
worker.hierarchy-1.redirect=hierarchy-2

worker.hierarchy-2.type=ajp13
worker.hierarchy-2.host=host
worker.hierarchy-2.port=8010
worker.hierarchy-2.socket_timeout=0
worker.hierarchy-2.socket_keepalive=False
worker.hierarchy-2.retries=2
worker.hierarchy-2.connection_pool_timeout=0
worker.hierarchy-2.lbfactor=1
worker.hierarchy-2.activation=disabled
worker.hierarchy-2.redirect=hierarchy-3

worker.hierarchy-3.type=ajp13
worker.hierarchy-3.host=host
worker.hierarchy-3.port=8011
worker.hierarchy-3.socket_timeout=0
worker.hierarchy-3.socket_keepalive=False
worker.hierarchy-3.retries=2
worker.hierarchy-3.connection_pool_timeout=0
worker.hierarchy-3.lbfactor=1
worker.hierarchy-3.activation=disabled
worker.hierarchy-3.redirect=hierarchy-4

worker.hierarchy-4.type=ajp13
worker.hierarchy-4.host=host12
worker.hierarchy-4.port=10603
worker.hierarchy-4.socket_timeout=0
worker.hierarchy-4.socket_keepalive=False
worker.hierarchy-4.retries=2
worker.hierarchy-4.connection_pool_timeout=0
worker.hierarchy-4.lbfactor=1
worker.hierarchy-4.activation=disabled
worker.hierarchy-4.redirect=hierarchy-1

Initially, 3 servers are disabled and redirect is specified.

Problem occurs when hierarchy-3 worker goes down because hierarchy-4 never gets 
initiated and mod_jk log says that:
All tomcat instances failed, no more workers left

However, workers list is like this:
worker.lbhierarchy.balance_workers=hierarchy-1,hierarchy-2,hierarchy-3,hierarchy-4

Which means we have got more than 3 workers hence we have more workers left... 
Here is log where I tried to take down workers one by one:

[Tue Oct 18 09:51:30.623 2016] [31890:139909801125856] [info] 
ajp_service::jk_ajp_common.c (2773): (hierarchy-1) sending request to tomcat 
failed (recoverable), because of error during request sending (attempt=1)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [info] 
jk_open_socket::jk_connect.c (817): connect to HOST:8009 failed (errno=111)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [info] 
ajp_connect_to_endpoint::jk_ajp_common.c (1068): (hierarchy-1) Failed opening 
socket to (HOST:8009) (errno=111)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [error] 
ajp_send_request::jk_ajp_common.c (1728): (hierarchy-1) connecting to backend 
failed. Tomcat is probably not started or is listening on the wrong port 
(errno=111)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [info] 
ajp_service::jk_ajp_common.c (2773): (hierarchy-1) sending request to tomcat 
failed (recoverable), because of error during request sending (attempt=2)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [error] 
ajp_service::jk_ajp_common.c (2794): (hierarchy-1) connecting to tomcat failed 
(rc=-3, errors=5, client_errors=0).
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1595): service failed, worker hierarchy-1 is in error 
state
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [info] 
jk_open_socket::jk_connect.c (817): connect to HOST:8010 failed (errno=111)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [info] 
ajp_connect_to_endpoint::jk_ajp_common.c (1068): (hierarchy-2) Failed opening 
socket to (HOST:8010) (errno=111)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [error] 
ajp_send_request::jk_ajp_common.c (1728): (hierarchy-2) connecting to backend 
failed. Tomcat is probably not started or is listening on the wrong port 
(errno=111)
[Tue Oct 18 09:51:30.724 2016] [31890:139909801125856] [info] 
ajp_service::jk_ajp_common.c (2773): (hierarchy-2) sending request to tomcat 
failed (recoverable), because of error during request sending (attempt=1)
[Tue Oct 18 09:51:30.824 2016] [31890:139909801125856] [info] 
jk_open_socket::jk_connect.c (817): connect to HOST:8010 failed (errno=111)
[Tue Oct 18 09:51:30.824 2016] [31890:139909801125856] [info] 
ajp_connect_to_endpoint::jk_ajp_common.c (1068): (hierarchy-2) Failed opening 
socket to (HOST:8010) (errno=111)
[Tue Oct 18 09:51:30.824 2016] [31890:139909801125856] [error] 
ajp_send_request::jk_ajp_common.c (1728): (hierarchy-2) connecting to backend 
failed. Tomcat is probably not started or is listening on the wrong port 
(errno=111)
[Tue Oct 18 09:51:30.824 2016] [31890:139909801125856] [info] 
ajp_service::jk_ajp_common.c (2773): (hierarchy-2) sending request to tomcat 
failed (recoverable), because of error during request sending (attempt=2)
[Tue Oct 18 09:51:30.824 2016] [31890:139909801125856] [error] 
ajp_service::jk_ajp_common.c (2794): (hierarchy-2) connecting to tomcat failed 
(rc=-3, errors=5, client_errors=0).
[Tue Oct 18 09:51:30.825 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1595): service failed, worker hierarchy-2 is in error 
state
[Tue Oct 18 09:51:30.825 2016] [31890:139909801125856] [info] 
jk_open_socket::jk_connect.c (817): connect to HOST:8011 failed (errno=111)
[Tue Oct 18 09:51:30.825 2016] [31890:139909801125856] [info] 
ajp_connect_to_endpoint::jk_ajp_common.c (1068): (hierarchy-3) Failed opening 
socket to (HOST:8011) (errno=111)
[Tue Oct 18 09:51:30.825 2016] [31890:139909801125856] [error] 
ajp_send_request::jk_ajp_common.c (1728): (hierarchy-3) connecting to backend 
failed. Tomcat is probably not started or is listening on the wrong port 
(errno=111)
[Tue Oct 18 09:51:30.825 2016] [31890:139909801125856] [info] 
ajp_service::jk_ajp_common.c (2773): (hierarchy-3) sending request to tomcat 
failed (recoverable), because of error during request sending (attempt=1)
[Tue Oct 18 09:51:30.925 2016] [31890:139909801125856] [info] 
jk_open_socket::jk_connect.c (817): connect to HOST:8011 failed (errno=111)
[Tue Oct 18 09:51:30.925 2016] [31890:139909801125856] [info] 
ajp_connect_to_endpoint::jk_ajp_common.c (1068): (hierarchy-3) Failed opening 
socket to (HOST:8011) (errno=111)
[Tue Oct 18 09:51:30.925 2016] [31890:139909801125856] [error] 
ajp_send_request::jk_ajp_common.c (1728): (hierarchy-3) connecting to backend 
failed. Tomcat is probably not started or is listening on the wrong port 
(errno=111)
[Tue Oct 18 09:51:30.925 2016] [31890:139909801125856] [info] 
ajp_service::jk_ajp_common.c (2773): (hierarchy-3) sending request to tomcat 
failed (recoverable), because of error during request sending (attempt=2)
[Tue Oct 18 09:51:30.925 2016] [31890:139909801125856] [error] 
ajp_service::jk_ajp_common.c (2794): (hierarchy-3) connecting to tomcat failed 
(rc=-3, errors=5, client_errors=0).
[Tue Oct 18 09:51:30.925 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1595): service failed, worker hierarchy-3 is in error 
state
[Tue Oct 18 09:51:31.026 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1664): All tomcat instances failed, no more workers 
left (attempt=0, retry=1)
[Tue Oct 18 09:51:31.026 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1664): All tomcat instances failed, no more workers 
left (attempt=1, retry=1)
[Tue Oct 18 09:51:31.026 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1664): All tomcat instances failed, no more workers 
left (attempt=2, retry=1)
[Tue Oct 18 09:51:31.026 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1664): All tomcat instances failed, no more workers 
left (attempt=3, retry=1)
[Tue Oct 18 09:51:31.026 2016] [31890:139909801125856] [info] 
service::jk_lb_worker.c (1675): All tomcat instances are busy or in error state
[Tue Oct 18 09:51:31.026 2016] [31890:139909801125856] [error] 
service::jk_lb_worker.c (1680): All tomcat instances failed, no more workers 
left
[Tue Oct 18 09:51:31.026 2016] [31890:139909801125856] [info] 
jk_handler::mod_jk.c (2991): Service error=0 for worker=lbhierarchy


I tested similar configuration for 5 workers, and I never got over worker 3..


We are using :
Server Version: Apache/2.2.15 (Unix) mod_jk/1.2.41
JK Version: mod_jk/1.2.41


I don't know whether is this a bug or did I miss something in documentation? 
Thanks for a help!

Look at "distance" instead of activation. Set all workers active and use distance values, e.g. "0" for all "normal workers", "1" for the first DR group, "2" etc.

See:

http://tomcat.apache.org/connectors-doc/reference/workers.html

Regards,

Rainer


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