Reimplement Lock API using Lock objects

Modified PolicyResourceLockManager to just return a feature, deferring
the lock() call/method to the feature, itself.  The manager was also
modified so that, if it can't find an enabled provider, it will return
a default provider, whose lock() methods always fail.  Once a feature
has been identified, the manager will cache it for use thereafter.

Modified the feature API to return lock objects and simplified the
interface to remove the beforeXxx and afterXxx methods.
Moved the unlock and refresh methods from the feature API into the
lock class, renaming them to free and extend, respectively.
Added a separate, feature-simple-locking project, which implements
a simple version of the locking feature, over a single JVM.
Extensively revised the distributed locking feature to fit in with
the new API.

Added support for persistence so that the various LockImpl classes
can be serialized and still function correctly when they are
deserialized back into new feature instances
Added default implementations of free & extend to LockImpl.
Modified API to take the ownerKey string, instead of the owner object.
Removed Extractor as unneeded - may add via another review, if still useful.

Updates per review comments:
- Updated licenses in feature-simple-locking
- Added beforeCreateLock & afterCreateLock to feature API
- Moved SimpleLockingFeature into policy-management so that it's
  always available
- Moved the executor service, "exsvc", into PolicyEngine
- Moved Extrator into policy-utils
- Changed Extractor logging level for exceptions
- Fixed feature sequence numbers
- Fixed mixing of seconds and milliseconds
- Renamed exsvc
- Modified to use property method with default value
- Configured scheduled executor
- Added suffix to Extractor.register()
- Eliminated Feature Api and tied lock manager into engine
- Added non-null checks to LockImpl parameters
- Added non-null checks to createLock() parameters
- Checked that lockManager is initialized

Change-Id: Iddba38157ddc5f7277656979c0e679e5489eb7b1
Issue-ID: POLICY-2113
Signed-off-by: Jim Hahn <jrh3@att.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/policy-management/src/main/java/org/onap/policy/drools/system/PolicyEngine.java b/policy-management/src/main/java/org/onap/policy/drools/system/PolicyEngine.java
index 653ff72e..cb0749d9 100644
--- a/policy-management/src/main/java/org/onap/policy/drools/system/PolicyEngine.java
+++ b/policy-management/src/main/java/org/onap/policy/drools/system/PolicyEngine.java
@@ -22,6 +22,7 @@ package org.onap.policy.drools.system;
 
 import java.util.List;
 import java.util.Properties;
+import java.util.concurrent.ScheduledExecutorService;
 import org.onap.policy.common.capabilities.Lockable;
 import org.onap.policy.common.capabilities.Startable;
 import org.onap.policy.common.endpoints.event.comm.Topic.CommInfrastructure;
@@ -29,6 +30,8 @@ import org.onap.policy.common.endpoints.event.comm.TopicListener;
 import org.onap.policy.common.endpoints.event.comm.TopicSink;
 import org.onap.policy.common.endpoints.event.comm.TopicSource;
 import org.onap.policy.common.endpoints.http.server.HttpServletServer;
+import org.onap.policy.drools.core.lock.Lock;
+import org.onap.policy.drools.core.lock.LockCallback;
 import org.onap.policy.drools.features.PolicyEngineFeatureApi;
 import org.onap.policy.drools.protocol.configuration.ControllerConfiguration;
 import org.onap.policy.drools.protocol.configuration.PdpdConfiguration;
@@ -198,6 +201,11 @@ public interface PolicyEngine extends Startable, Lockable, TopicListener {
     List<HttpServletServer> getHttpServers();
 
     /**
+     * Gets a thread pool that can be used to execute background tasks.
+     */
+    ScheduledExecutorService getExecutorService();
+
+    /**
      * get properties configuration.
      *
      * @return properties objects
@@ -280,6 +288,31 @@ public interface PolicyEngine extends Startable, Lockable, TopicListener {
     boolean deliver(CommInfrastructure busType, String topic, String event);
 
     /**
+     * Requests a lock on a resource. Typically, the lock is not immediately granted,
+     * though a "lock" object is always returned. Once the lock has been granted (or
+     * denied), the callback will be invoked to indicate the result.
+     *
+     * <p/>
+     * Notes:
+     * <dl>
+     * <li>The callback may be invoked <i>before</i> this method returns</li>
+     * <li>The implementation need not honor waitForLock={@code true}</li>
+     * </dl>
+     *
+     * @param resourceId identifier of the resource to be locked
+     * @param ownerKey information identifying the owner requesting the lock
+     * @param holdSec amount of time, in seconds, for which the lock should be held once
+     *        it has been granted, after which it will automatically be released
+     * @param callback callback to be invoked once the lock is granted, or subsequently
+     *        lost; must not be {@code null}
+     * @param waitForLock {@code true} to wait for the lock, if it is currently locked,
+     *        {@code false} otherwise
+     * @return a new lock
+     */
+    public Lock createLock(String resourceId, String ownerKey, int holdSec, LockCallback callback,
+                    boolean waitForLock);
+
+    /**
      * Invoked when the host goes into the active state.
      */
     void activate();