how to install more than one instance DSpace the in same tomcat server?

Question

I want to create another instance of dspace to work on different projects. however I do not know how or if it will conflict with this running.

Answer 1

1) Obviously each instance should be installed to a different set of directories.

2a) Create a separate Context for each instance. That will give them different paths: http://legion.example.com/one/, http://legion.example.com/two/.... I do this on my development workstation all the time.

2b) You can also create separate domains and IP addresses, bind them to multiple Host objects in a single Tomcat configuration: http://one.example.com/, http://two.example.com/.... I have four low-volume production DSpace instances running in one Tomcat instance on a midsized host.

Each DSpace instance needs its own database, but PostgreSQL can host dozens. You should consider creating separate database user accounts for each.

You'll also need separate Handle resolvers for each DSpace, just the same as if each instance was on its own host. When configured for DSpace, the Handle resolver uses the DSpace database instead of its own, so it's specific to a single instance.

Solr ought to be able to serve several sets of cores for several DSpaces, but you'll have to do a fair amount of configuration to keep them distinct and ensure that each DSpace is using its own set. You'll learn a lot more about Solr than you need to know for the captive Solr instance that gets installed with a single DSpace.

But then, you'll also learn a lot more about Tomcat than you need to know for a single DSpace....

If you declare your Contexts in external files ([Tomcat]/config/Catalina/localhost/one.xml etc.) and you have automatic deployment set up right, you can just 'touch' one of the Contexts to restart it without restarting a whole Tomcat. Otherwise you can use the Tomcat Manager webapp to do this. Consider well whether you want to have the Manager running, though, because it is quite powerful and it is exposed on the network. I run such applications on yet another, non-routable address so they can't be reached from Outside.

DSpace is not small, so you will need to ensure that you have enough memory to run several instances and that Tomcat's memory limits are adjusted accordingly. I would suggest also installing a resource monitor such as Psi Probe and glancing at it regularly. The above comments on performance are spot-on.

Learning to make all this work was loads of fun, and took quite some time. On the other hand, for development you may prefer something like https://github.com/DSpace/vagrant-dspace, a packaged virtual machine with DSpace and friends inside.

Answer 2

While it's technically possible, I would advise against this for the following 3 key reasons:

1. Quite a few configuration aspects of DSpace still count on a Tomcat restart to take effect. If you have two instances running in the same Tomcat, it means you have to bring both of them down when you want to update one of them.

2. Performance related issues are already far from trivial to debug in DSpace, even if you have only one instance running in one Tomcat. If you run two instances, it is very likely that you will only make this more difficult.

3. This kind of setup is non-standard. As with all non-standard setups, you will find it much harder to get community support, as very few other people will be in the same boat.

So ... either run two VMs, or just two Tomcat processes on one VM.

If after these warnings, you still want to do it, the basics would be to run all of the webapps you want twice in the tomcat, on different ports. The minimum you would need are 2x XMLUI OR JSPUI and 2x SOLR. It could be possible to run one solr webapp, and keep 2 search, statistics, authority and oai indexes in this one SOLR webapp, but I don't know what the side effects could be.