On 15/02/2023 12:24, Patkar Omkar Anant wrote:
Hi All,
We are facing an issue with Apache Tomcat 9. I had posted this issue in
Bugzilla forum, and from there I was re-directed here.
The link to the bug is = https://bz.apache.org/bugzilla/show_bug.cgi?id=66476
I will elaborate the details here: -
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ERROR: -
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10-Feb-2023 02:16:19.618 SEVERE [http-nio-80-Acceptor]
org.apache.tomcat.util.net.Acceptor.run Socket accept failed
java.io.IOException: Duplicate accept detected. This is a known OS
bug. Please consider reporting that you are affected:
The only result of that error message is that the duplicate accept is
ignored. It should be transparent to the client as request processing
will continue on the original connection.
If you see this message as a result of a false positive then the client
connection will be dropped. That is obviously more problematic.
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We are using Camunda 7.16 BPMN tool which comes with inbuilt Apache Tomcat
9.0.58. This is deployed on our Linux VM (CentOS). The VM is within our company
network, and ... via company's firewall another trusted application on Azure
cloud (outside company network)...is only allowed to make REST API calls to
Camunda (hosted on Tomcat). When Tomcat is started all works fine, requests
placed from trusted application on Azure Cloud are able to reach our Tomcat and
our application works on it, until out of the blue and randomly above error
occurs and tomcat no longer serves request coming from external application on
cloud.
To be clear, no further requests can be served from the external
application but internal clients can continue?
What has been tried so far ?: -
From several posts after google search it was found that Linux Kernel version
could help. Previously it was 3.x and now it is upgraded to 6.0.9-1 and Apache
Tomcat version is 9.0.58... still we face the above error.
That suggests you are seeing false positives rather than the Linux bug.
To avoid the false positives, you need to upgrade as the detection got a
lot better in 9.0.59 onwards.
1) Why it behaves strangely with external requests and not with internal ones ?
Do internal and external requests go to the same connector?
It would be worth running Wireshark or equivalent to look at the
external traffic that is being received. In particular, look at the
source port for the requests once the problem starts.
2) How can we consistently reproduce the issue ?
If you want to test the original Linux bug, steps to reproduce are in
the Ubuntu issue referenced in the error message.
If you want to recreate the issue you are seeing (which I suspect is
specific to your environment) you'll need to figure out what is
happening first.
3) What could be the possible cause and how to fix it ?
Assuming you are seeing false positives with the Linux bug detection,
the client using the same port for multiple requests. If the Linux bug
error message is a red herring, then an Acceptor crash might explain
what you are seeing.
Mark
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