rolling back my 9366 to bring Stephen's slave related changes to the main line

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@9382 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/SlaveAvailabilityStrategy.java

+package hudson.model;
+
+import hudson.util.DescriptorList;
+import hudson.ExtensionPoint;
+import org.kohsuke.stapler.StaplerRequest;
+import net.sf.json.JSONObject;
+
+/**
+ * Slave availability strategy
+ */
+public abstract class SlaveAvailabilityStrategy implements Describable<SlaveAvailabilityStrategy>, ExtensionPoint {
+
+    /**
+     * This method will be called periodically to allow this strategy to decide what to do with it's owning slave.
+     * The default implementation takes the slave on-line every time it's off-line.
+     *
+     * @param slave The slave that owns this strategy, i.e. {@code slave.getAvailabilityStrategy() == this}
+     * @param state Some state information that may be useful in deciding what to do.
+     * @return The number of minutes after which the strategy would like to be checked again. The strategy may be
+     *         rechecked earlier or later that this!
+     */
+    public long check(Slave slave, State state) {
+        Slave.ComputerImpl c = slave.getComputer();
+        if (c != null && c.isOffline() && c.isStartSupported())
+            c.tryReconnect();  
+        return 5;
+    }
+
+    /**
+     * All registered {@link SlaveAvailabilityStrategy} implementations.
+     */
+    public static final DescriptorList<SlaveAvailabilityStrategy> LIST = new DescriptorList<SlaveAvailabilityStrategy>(
+            Always.DESCRIPTOR
+    );
+
+    public static class State {
+        private final boolean jobWaiting;
+        private final boolean jobRunning;
+
+        public State(boolean jobWaiting, boolean jobRunning) {
+            this.jobWaiting = jobWaiting;
+            this.jobRunning = jobRunning;
+        }
+
+        public boolean isJobWaiting() {
+            return jobWaiting;
+        }
+
+        public boolean isJobRunning() {
+            return jobRunning;
+        }
+    }
+
+    public static class Always extends SlaveAvailabilityStrategy {
+
+        public Descriptor<SlaveAvailabilityStrategy> getDescriptor() {
+            return DESCRIPTOR;
+        }
+
+        public static final Descriptor<SlaveAvailabilityStrategy> DESCRIPTOR =
+                new DescriptorImpl();
+
+        private static class DescriptorImpl extends Descriptor<SlaveAvailabilityStrategy> {
+            public DescriptorImpl() {
+                super(Always.class);
+            }
+
+            public String getDisplayName() {
+                return "Keep this slave on-line as much as possible";
+            }
+
+            public SlaveAvailabilityStrategy newInstance(StaplerRequest req, JSONObject formData) throws FormException {
+                return new Always();
+            }
+
+
+        }
+    }
+}

war/resources/help/system-config/master-slave/availability.html

+<div>
+    Controls when Hudson starts and stops the slave.
+
+    <dl>
+        <dt><b>
+            Keep this slave on-line as much as possible
+        </b></dt>
+        <dd>
+            This is the default and normal setting.
+            In this mode, Hudson uses tries to keep the slave on-line.
+            If Hudson can start the slave without user assistance, it will periodically
+            attempt to restart the slave if it is unavailable.
+            Hudson will not take the slave off-line.
+        </dd>
+
+        <dt><b>
+            Take this slave on-line and off-line at specific times
+        </b></dt>
+        <dd>
+            In this mode, Hudson will keep the slave on-line according to the configured schedule.
+            If Hudson can start the slave without user assistance, it will periodically
+            attempt to start the slave if it is unavailable during an on-line window.
+
+            During an off-line window, the slave will only be taken off-line if there are no active
+            jobs running on the slave.
+        </dd>
+
+        <dt><b>
+            Take this slave on-line and off-line as needed
+        </b></dt>
+        <dd>
+            In this mode, if Hudson can start the slave without user assistance, it will periodically
+            attempt to start the slave while there are unexecuted jobs which meet the following criteria:
+            <ul>
+                <li>They have been in the queue for at least the specified startup demand period</li>
+                <li>They can execute on this slave</li>
+            </ul>
+
+            The slave will be taken off-line if:
+            <ul>
+                <li>There are no active jobs running on the slave</li>
+                <li>The slave has been idle for at least the specified idle period</li>
+            </ul>
+        </dd>
+    </dl>
+</div>
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war/resources/help/system-config/master-slave/startMethod.html

+<div>
+    Controls how Hudson starts the slave.
+</div>
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