That's interesting.
The way I do the start.sh in my Catalina base is:
BASEDIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )/..
export CATALINA_BASE=$(realpath ${BASEDIR})
/opt/tomcat/tomcat-9/tomcat-9-latest/bin/startup.sh
I could just say $(realpath /opt/tomcat/tomcat-9/tomcat-9-latest)
The old version is we get rid off after 7 days just in case a rollback is
needed.
As for Windows, I was under the impression that they are not big fans of
symlinks anyway so maybe that's ok? :-D
Thank you Mark and Chris!
-----Original Message-----
From: Christopher Schultz <ch...@christopherschultz.net>
Sent: Wednesday, October 18, 2023 7:32 PM
To: users@tomcat.apache.org
Subject: Re: Tomcat minor update
Mark and Aditya,
On 10/18/23 04:21, Mark Thomas wrote:
> On 17/10/2023 22:47, Aditya Shastri wrote:
>> Hello,
>>
>> We have several tomcat instances that use a single CATALINA_HOME which
>> is a symlink for a specific version. The Tomcat instance we use is
>> very barebones and doesn't have any of the apps that come with it.
>>
>> For example,
>> The CATALINA_HOME points to a symlink
>> /opt/tomcat/tomcat-9/tomcat-9-latest ->
>> /opt/tomcat/tomcat-9/apache-tomcat-9.0.80.
>>
>> Now, if I want to upgrade to apache-tomcat-9.0.82, I normally do the
>> following steps:
>> 1. Stop all the running instances of tomcat in the various
>> 'CATALINA_BASE'.
>> 2. Update the symlink /opt/tomcat/tomcat-9/tomcat-9-latest from
>> /opt/tomcat/tomcat-9/apache-tomcat-9.0.80 to
>> /opt/tomcat/tomcat-9/apache-tomcat-9.0.82.
>> 3. Start all the instances.
>>
>> This method appears to work, and I read it as the most appropriate
>> method.
>>
>> My question is, can I change the symlink,
>> '/opt/tomcat/tomcat-9/tomcat-9-latest', while all the instances are
>> running and restart the instances when I have downtime?
>
> Probably not. You might get away with it sometimes but sometimes you are
> going to see errors.
>
>> Does Tomcat load all the CATALINA_HOME jar(s) (not including the
>> webapps folder) and config to memory thereby not caring if the
>> libraries have changed or does it realize that something has changed?
>
> No. The JVM loads classes when they are first referenced.
>
> The issue will be if you update the symlink, then Tomcat tries to load
> another class and the class from the new version is not compatible with
> the classes from the old version. A failure is unlikely but not
> impossible. I wouldn't risk it.
I wonder if we could solve this, at least on *NIX, by resolving
CATALINA_HOME by using `readlink -f`. This would allow you to use a
symlink to point to Tomcat but after catalina.sh is invoked,
CATALINA_HOME could be replaced with a canonicalized one which does not
contain a symlink anymore. Maybe there is a similar
utility/command/path-mangling-magic available on Windows?
That would allow you to change the symlink and not disturb any
currently-running Tomcat instances. You would obviously not want to
remove the old version from the disk before shutting-down those
instances, of course.
-chris
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