Hi Marcin,
Thank you for your careful analysis.
Your connectionTimeout on the tomcat side is way too low. This timeout
is meant for cutting connections after a longer idle time. It should
coincide with the connection_pool_timeout of mod_jk (although tomcat
uses milliseconds and mod_jk seconds). Normal values are 10 minutes or
maybe 1 minute.
Concerning your question, what could be blocking between forwarding the
headers and the body: reading the request body from the browser sits in
between. If you increase the JklogLevel to trace, you will find an
"enter" and an "exit" message for the nested functions
ajp_read_into_msg_buff() and ajp_read_fully_from_server() which read the
POST body from the browser (via apache methods). Most likely you will
find out, that the time passes by between enter and exit of
ajp_read_fully_from_server().
Hope that helps?
Regards,
Rainer
Marcin Zajączkowski wrote:
Hi,
I observe in mod_jk's log errors:
[error] ajp_get_reply::jk_ajp_common.c (1566): (ajp13w) Tomcat is down
or refused connection. No response has been sent to the client (yet)
In the rush hours (20-30 requests/second) up to several entries per hour.
Sometimes it's followed by:
[error] ajp_service::jk_ajp_common.c (1928): (ajp13w) Connecting to
tomcat failed. Tomcat is probably not started or is listening on the
wrong port
or
[error] ajp_connection_tcp_get_message::jk_ajp_common.c (948): (ajp13w)
can't receive the response message from tomcat, network problems or
tomcat is down (127.0.0.1:8009), err=-104
but usually it is covered by another retries. It's corresponding to
exception in tomcat:
ERROR [org.apache.jk.common.HandlerRequest] Error decoding request
java.net.SocketTimeoutException: Read timed out
*Note* Post is quite long because of info from logs. To get know what it
is about it is enough to read descriptions next to numbers.
I increased logs granularity (mod_jk and tomcat + tcpdump) and in a few
checked issues it looks like:
*1*. mod_jk talks with tomcat and some request is serviced.
(...)
[11:10:30] [debug] ajp_process_callback::jk_ajp_common.c (1491): AJP13
protocol: Reuse is OK
[debug] ajp_done::jk_ajp_common.c (2258): recycling connection pool
slot=0 for worker ajp13w
[debug] jk_handler::mod_jk.c (2126): Service finished with status=200
for worker=wlb
*2*. A few seconds later thread is used again by an another request.
[11:10:32] [debug] wc_get_worker_for_name::jk_worker.c (114): found a
worker wlb
[debug] wc_get_name_for_type::jk_worker.c (290): Found worker type 'lb'
[debug] init_ws_service::mod_jk.c (584): Service protocol=HTTP/1.1
method=POST (...)
[debug] service::jk_lb_worker.c (840): service sticky_session=1
id='8A49C0D934C8A115342BA5CBFC79C434'
[debug] service::jk_lb_worker.c (860): service worker=ajp13w route=ajp13w
[debug] ajp_get_endpoint::jk_ajp_common.c (2315): acquired connection
pool slot=0
[debug] ajp_marshal_into_msgb::jk_ajp_common.c (548): ajp marshaling done
[debug] ajp_service::jk_ajp_common.c (1771): processing ajp13w with 2
retries
[debug] ajp_connection_tcp_send_message::jk_ajp_common.c (893): sending
to ajp13 pos=4 len=307 max=8192
(...) [header is sent and it is received by tomcat]
*3*.
a) mod_jk tries to send body:
[11:10:32] [debug] ajp_send_request::jk_ajp_common.c (1273): request
body to send 646 - request body to resend 0
b) tomcat is waiting for it:
DEBUG [org.apache.jk.common.ChannelSocket] Call next 0
[EMAIL PROTECTED]
DEBUG [org.apache.jk.common.HandlerRequest] Handling 2
DEBUG [org.apache.jk.common.ChannelSocket] receive()
*4*. 5 seconds later (connector timeout is 5000ms) tomcat throws exception:
[11:10:37] ERROR [org.apache.jk.common.HandlerRequest] Error decoding
request
java.net.SocketTimeoutException: Read timed out
and resets connection (regarding to tcpdump log)
*5*. A few more seconds later (e.g. 8 from point 3) mod_jk starts
sending a body:
[11:10:40] [debug] ajp_connection_tcp_send_message::jk_ajp_common.c
(893): sending to ajp13 pos=4 len=652 max=8192
[debug] ajp_connection_tcp_send_message::jk_ajp_common.c (893): 0000 12
34 02 88 02 86 3C 3F (...) [body's dump]
*6*. Unfortunately connection was already reseted by tomcat and mod_jk
got info about that:
[11:10:40] [info] ajp_connection_tcp_get_message::jk_ajp_common.c
(942): (ajp13w) Tomcat has forced a connection close for socket 28
[error] ajp_get_reply::jk_ajp_common.c (1566): (ajp13w) Tomcat is down
or refused connection. No response has been sent to the client (yet)
[info] ajp_service::jk_ajp_common.c (1877): (ajp13w) receiving from
tomcat failed, recoverable operation attempt=0
*7*. mod_jk tries to do send request again to tomcat:
[11:10:40] [info] ajp_service::jk_ajp_common.c (1916): (ajp13w) sending
request to tomcat failed, recoverable operation attempt=1
[debug] jk_open_socket::jk_connect.c (335): socket TCP_NODELAY set to On
[debug] jk_open_socket::jk_connect.c (433): trying to connect socket 28
to 127.0.0.1:8009
[debug] jk_open_socket::jk_connect.c (459): socket 28 connected to
127.0.0.1:8009
[debug] ajp_connect_to_endpoint::jk_ajp_common.c (847): Connected socket
28 to (127.0.0.1:8009)
[debug] ajp_connection_tcp_send_message::jk_ajp_common.c (893): sending
to ajp13 pos=4 len=307 max=8192
Usually (but not always) it is able to do that without errors.
I sniffed into mod_jk source code, but I haven't found a place where it
can stuck.
*Question*
What can be delay (about 8 seconds) in mod_jk between sending HTTP
header and HTTP content caused by?
I use Apache 2.0.52 (with MPM prefork), mod_jk 1.2.20, JBoss 3.2.5 with
Tomcat 5.0 (probably 5.0.27) and Red Hat Enterprise Linux ES 4.
mod_jk configuration is quite simple, without load balancing (and wasn't
changed for years).
<workers.properties>
workers.tomcat_home=/jboss/deploy/jbossweb-tomcat50.sar
workers.java_home=/jboss/java
ps=/
worker.list=wlb,jkstatus
worker.ajp13w.type=ajp13
worker.ajp13w.host=localhost
worker.ajp13w.port=8009
worker.wlb.type=lb
worker.wlb.balance_workers=ajp13w
</workers.properties>
The only change in mod_jk config was:
JkShmSize 1024k
<servel.xml>
<Connector port="8009" address="127.0.0.1"
minProcessors="5" maxProcessors="100"
enableLookups="false" acceptCount="100" debug="0"
connectionTimeout="5000" useURIValidationHack="false"
protocol="AJP/1.3"/>
</servel.xml>
Thanks for your advice
Marcin
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