adding a convenience base class for various Cloud implementations.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@29689 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/slaves/AbstractCloudImpl.java

+package hudson.slaves;
+
+/**
+ * Additional convenience implementation on top of {@link Cloud} that are likely useful to
+ * typical {@link Cloud} implementations.
+ *
+ * <p>
+ * Whereas {@link Cloud} is the contract between the rest of Hudson and a cloud implementation,
+ * this class focuses on providing a convenience to minimize the effort it takes to integrate
+ * a new cloud to Hudson.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+public abstract class AbstractCloudImpl extends Cloud {
+    /**
+     * Upper bound on how many instances we may provision.
+     */
+    private int instanceCap;
+
+    protected AbstractCloudImpl(String name, String instanceCapStr) {
+        super(name);
+
+        setInstanceCapStr(instanceCapStr);
+    }
+
+    protected void setInstanceCapStr(String value) {
+        if(value==null || value.equals(""))
+            this.instanceCap = Integer.MAX_VALUE;
+        else
+            this.instanceCap = Integer.parseInt(value);
+    }
+
+    /**
+     * Gets the instance cap as string. Used primarily for form binding.
+     */
+    public String getInstanceCapStr() {
+        if(instanceCap==Integer.MAX_VALUE)
+            return "";
+        else
+            return String.valueOf(instanceCap);
+    }
+
+    /**
+     * Gets the instance cap as int, where the capless is represented as {@link Integer#MAX_VALUE}
+     */
+    public int getInstanceCap() {
+        return instanceCap;
+    }
+
+    protected void setInstanceCap(int v) {
+        this.instanceCap = v;
+    }
+}

core/src/main/java/hudson/slaves/Cloud.java

@@ -49,6 +49,7 @@ import java.util.Collection;
  *
  * @author Kohsuke Kawaguchi
  * @see NodeProvisioner
+ * @see AbstractCloudImpl
  */
 public abstract class Cloud extends AbstractModelObject implements ExtensionPoint, Describable<Cloud>, AccessControlled {
 

core/src/main/resources/hudson/slaves/AbstractCloudImpl/help-instanceCapStr.html

+<div>
+    You can place the upward limit to the number of slaves that Hudson may launch from this cloud.
+    This is useful for avoiding surprises in the billing statement.
+
+    <P>
+    For example, if this field is 3, Hudson will only launch a new instance
+    as long as total number of instances you run on this cloud doesn't exceed this number. In this way,
+    even in the worst case of Hudson starting instances and forgetting about them,
+    you have an upper bound in the number of instances that are concurrently executed.
+
+    <p>
+    Leave this field empty to remove a cap.
+</div>
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