Support for multiple listener with different ORACLE_HOMEs

[Rendanic]

I need the ability to create multiple listeneres in different ORACLE_HOMEs. Any idea how we can add this?

I could create a /etc/sysconfig/oracle with ansible for all listeners but I need a structure for it.

[andreasdijkman]

I was thinking about using multiple ENV-variables for the LISTENER, but a reload would reload these changes. I tend towards defining a kind of listener-tab-file with similar format for multiple ORACLE_HOME's and LISTENER-names. The only listener that can be started is LISTENER. But if you have multiple listeners in one ORACLE_HOME, there is no way to start these now.

A listener-tab with something like:

<ORACLE_HOME_1>:<LISTENER_NAME>
<ORACLE_HOME_2>:<LISTENER_NAME>

The LISTENER_NAME could even be optional. A reload of the service would reload this file and would stop the extra listeners, but more importantly would start them at boot.

[Rendanic]

Could we change it to:

<LISTENER_NAME>:<ORACLE_HOME_1>

That fits better to the oratab. LISTENER_NAME = LISTENER when column is empty.

[andreasdijkman]

Yes, that would be more inline with the listener. But on the other hand, this file is totally different and leaving the first column empty would start the line with a :. That looks kind of ugly.

Or just make the listener-name mandatory. I want to make the listener-tab optional anyway. If it's not there, just leave it with that and use LISTENER_ORACLE_HOME, to keep everything backwards compatible.

[Rendanic]

Looks fine for me:

• use LISTENER_ORACLE_HOME Variablen when Listener-tab is missing
• use Listener-tab when existing with :

We should not use LISTENER_ORACLE_HOME and Listener-tab together, because that could create strange mixed configurations with possible problems at a later time.

That offers the needed flexibility and it is easy to use in simple environments.

[ibre5041]

I created PR #10 , it contains antlr3 based library for parsing listener.ora files. So /etc/sysconfig/oracle can contain:

LISTENER_NAME=LISTENER

The script oracle-systemd-service.py iterates over all OHs, until it finds the one where specified listener is configured, read-only OHs are supported too. The format could be even simpler:

LISTENER_NAME=LISTENER,LISTENER_DG,LISTENER_THREE

Matching OH can be deduced by parsing all listener.ora files.

[andreasdijkman]

@ibre5041 thanks for the PR!

How do you start 2 listeners in this case with the same LISTENER_NAME (LISTENER for instance) but from a different ORACLE_HOME?

And if it finds 2 LISTENER's with the same name in 2 ORACLE_HOME's, which LISTENER does it start?

[ibre5041]

It is not bullet proof. At this moment is does not support multiple listeners. Such a change would require changes in internal structures, and I did not have courage to do that(yet).

So some future change can introduce a format like:

 LISTENER_NAME=LISTENER,LISTENER_DG,LISTENER_THREE

or

 LISTENER_NAME=LISTENER:/u01/oracle/product/12.2.0:LISTENER_DG:@LATEST@

In mine installations I do not use multiples listeners so often, and I never use multiple LISTENERs having same name. Also I did not implement any code which would deduce a patch level for each ORACLE_HOME, it would by quite hard. So I just sort ORACLE_HOMEs alphabetically(desc) and I do search for LISTENER_NAME in each ORACLE_HOME until I find it.

For 90% of mine installations the 2nd feature I implemented is just suitable:

LISTENER_ORACLE_HOME=@LATEST@

This will start default listener named ("LISTENER") using alphabetically last ORACLE_HOME. This also simplifies Ansible installations. There is no need to specify particular ORACLE_HOME, when the script can parse oratab and it is good practice to use listener from most recent OH.