make cleanup and pre-creation recurrence period configurable

README.md

@@ -226,6 +226,7 @@ credentials:
 -   On every agent provisioned by the plugin, there is an environment
     variable `OPENSTACK_PUBLIC_IP` declared with the public IP address
     allocated for the machine.
+-   Default recurrence period for thread cleaning up agents is 10 minutes, for thread pre-creating node it is 2 minutes. These values can be modified by setting new values in milliseconds in system properties `jenkins.openstack.cleanupPeriod` and `jenkins.openstack.preCreationPeriod`. This is particularly useful in combinations with single-use agents (agents with 1 executor and retention time set to `0`) for Jenkins installation with quick and often executed jobs.
 
 ### Troubleshooting
 

plugin/src/main/java/jenkins/plugins/openstack/compute/JCloudsCleanupThread.java

@@ -26,6 +26,8 @@
 import org.openstack4j.api.exceptions.ClientResponseException;
 import org.openstack4j.api.exceptions.StatusCode;
 import org.openstack4j.model.compute.Server;
+import java.util.concurrent.TimeUnit;
+
 
 import javax.annotation.Nonnull;
 
@@ -41,14 +43,17 @@
 @Extension @Restricted(NoExternalUse.class)
 public final class JCloudsCleanupThread extends AsyncPeriodicWork {
     private static final Logger LOGGER = Logger.getLogger(JCloudsCleanupThread.class.getName());
+    private final Long recurrencePeriod;
 
     public JCloudsCleanupThread() {
         super("OpenStack slave cleanup");
+        recurrencePeriod = Long.getLong("jenkins.openstack.cleanupPeriod", TimeUnit.MINUTES.toMillis(10));
+        LOGGER.log(Level.FINE, "OpenStack cleanup recurrence period is {0}ms", recurrencePeriod);
     }
 
     @Override
     public long getRecurrencePeriod() {
-        return MIN * 10;
+        return recurrencePeriod;
     }
 
     @Override

plugin/src/main/java/jenkins/plugins/openstack/compute/JCloudsPreCreationThread.java

@@ -13,6 +13,8 @@
 import hudson.Functions;
 import hudson.model.TaskListener;
 import hudson.model.AsyncPeriodicWork;
+import java.util.concurrent.TimeUnit;
+
 
 /**
  * Periodically ensure enough slaves are created.
@@ -37,14 +39,17 @@
 @Extension @Restricted(NoExternalUse.class)
 public final class JCloudsPreCreationThread extends AsyncPeriodicWork {
     private static final Logger LOGGER = Logger.getLogger(JCloudsPreCreationThread.class.getName());
+    private final Long recurrencePeriod;
 
     public JCloudsPreCreationThread() {
         super("OpenStack slave pre-creation");
+        recurrencePeriod = Functions.getIsUnitTest() ? Long.MAX_VALUE : Long.getLong("jenkins.openstack.preCreationPeriod", TimeUnit.MINUTES.toMillis(2));
+        LOGGER.log(Level.FINE, "OpenStack pre-creation recurrence period is {0}ms", recurrencePeriod);
     }
 
     @Override
     public long getRecurrencePeriod() {
-        return Functions.getIsUnitTest() ? Long.MAX_VALUE : MIN * 2;
+        return recurrencePeriod;
     }
 
     @Override