RE: Core Dump File generating Issue

["Chaudhary, Mohit" <mo...@dxc.com>]

Hello Team,

Onto our tomcat production environment we are having two server clustered .where we have only one tomcat app running.
We are facing some issue in production system and observed there are core dump files getting generated inside the tomcat-install/bin folder. The core is getting generated along with pid eg. core.21539.
Some times,core dump file keeps up growing in larger size amount like 18GB to 19GB which is making full the allocated disk for tomcat-install/bin file system. This intern causes to get tomcat application on hung state and result an instance down for production server. Some time it is highly impacting to one node of cluster and some time both the node were down.
For tomcat side, we have not configured/enabled anything related to generate the core dump  file at tomcat-install/bin location. We are not aware from where and how this core file is getting generated.
The client is asking for an evidence from where the core file is getting generated and also application details etc.
We require your support how shall to proceed to analyze core file and provide evidence to client. Currently ,we do not have any analyzer tool install on system.

Thanks & Regards,
Mohit Chaudhary



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Re: Core Dump File generating Issue

[Suvendu Sekhar Mondal <su...@gmail.com>]

Hello Mohit,

On Tue, Jun 6, 2023 at 4:48 AM Chaudhary, Mohit <mo...@dxc.com> wrote:
>
> Hello Team,
>
> Onto our tomcat production environment we are having two server clustered .where we have only one tomcat app running.
> We are facing some issue in production system and observed there are core dump files getting generated inside the tomcat-install/bin folder. The core is getting generated along with pid eg. core.21539.
> Some times,core dump file keeps up growing in larger size amount like 18GB to 19GB which is making full the allocated disk for tomcat-install/bin file system. This intern causes to get tomcat application on hung state and result an instance down for production server. Some time it is highly impacting to one node of cluster and some time both the node were down.
> For tomcat side, we have not configured/enabled anything related to generate the core dump  file at tomcat-install/bin location. We are not aware from where and how this core file is getting generated.

Tomcat does not generate core dumps. Your JVM is producing it as it's
crashing due to some issue. Normally when JVM crashes due to fatal
error, apart from generating core dumps it also generate one crash log
file(e.g. hs_err_pidXXXX.log). It has some human readable information
about why the crash occurred. Are you getting it?

> The client is asking for an evidence from where the core file is getting generated and also application details etc.
> We require your support how shall to proceed to analyze core file and provide evidence to client. Currently ,we do not have any analyzer tool install on system.

You have not provided any environment information. So, it'll be hard
to tell what tools you can use.

There are a couple of ways to extract information out of a core dump.
To extract thread details I generally use jstack. Command will be
something like this:
 jstack -J-d64 path_to_java/bin/java path_of_your_core_dump/core.21539

You can also use jmap to create a heap dump out of a java core. Sample
command: jmap -J-d64 path_to_java/bin/java
path_of_your_core_dump/core.21539

Please note that path_to_java should be the Java binary location which
produced the core dump, otherwise it throws errors and data extraction
fails. That means, you have to use those JDK tools in your production
system. Also note, since you'll be processing a 18GB core dump, those
tools can consume a good amount of CPU and memory.

>
> Thanks & Regards,
> Mohit Chaudhary
>
>
>
> DXC Technology Company -- This message is transmitted to you by or on behalf of DXC Technology Company or one of its affiliates. It is intended exclusively for the addressee. The substance of this message, along with any attachments, may contain proprietary, confidential or privileged information or information that is otherwise legally exempt from disclosure. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient of this message, you are not authorized to read, print, retain, copy or disseminate any part of this message. If you have received this message in error, please destroy and delete all copies and notify the sender by return e-mail. Regardless of content, this e-mail shall not operate to bind DXC Technology Company or any of its affiliates to any order or other contract unless pursuant to explicit written agreement or government initiative expressly permitting the use of e-mail for such purpose.

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