Dataverse uses timers to automatically run scheduled Harvest and Metadata export jobs.
When running a Dataverse cluster - i.e. multiple Dataverse application servers talking to the same database - only one of them must act as the dedicated timer server. This is to avoid starting conflicting batch jobs on multiple nodes at the same time.
This does not affect a single-server installation. So you can safely skip this section unless you are running a multi-server cluster.
The following JVM option instructs the application to act as the dedicated timer server:
IMPORTANT: Note that this option is automatically set by the Dataverse installer script. That means that when configuring a multi-server cluster, it will be the responsibility of the installer to remove the option from the domain.xml of every node except the one intended to be the timer server. We also recommend that the following entry in the domain.xml:
<ejb-timer-service timer-datasource="jdbc/VDCNetDS"> is changed back to
<ejb-timer-service> on all the non-timer server nodes. Similarly, this option is automatically set by the installer script. Changing it back to the default setting on a server that doesn’t need to run the timer will prevent a potential race condition, where multiple servers try to get a lock on the timer database.
These timers are created when scheduled harvesting is enabled by a local admin user (via the “Manage Harvesting Clients” page).
In a multi-node cluster, all these timers will be created on the dedicated timer node (and not necessarily on the node where the harvesting clients was created and/or saved).
A timer will be automatically removed, when a harvesting client with an active schedule is deleted, or if the schedule is turned off for an existing client.
This timer is created automatically whenever the application is deployed or restarted. There is no admin user-accessible configuration for this timer.
This timer runs a daily job that tries to export all the local, published datasets that haven’t been exported yet, in all the supported metdata formats, and cache the results on the filesystem. (Note that, normally, an export will happen automatically whenever a dataset is published. So this scheduled job is there to catch any datasets for which that export did not succeed, for one reason or another). Also, since this functionality has been added in version 4.5: if you are upgrading from a previous version, none of your datasets are exported yet. So the first time this job runs, it will attempt to export them all.
This daily job will also update all the harvestable OAI sets configured on your server, adding new and/or newly published datasets or marking deaccessioned datasets as “deleted” in the corresponding sets as needed.
This job is automatically scheduled to run at 2AM local time every night. If really necessary, it is possible (for an advanced user) to change that time by directly editing the EJB timer application table in the database.