Added support for custom hooks in the VoldemortBuildAndPushJob. Heart…

…beat hooks run in a daemon thread.

contrib/hadoop-store-builder/src/java/voldemort/store/readonly/mr/azkaban/BuildAndPushHook.java

@@ -0,0 +1,49 @@
+package voldemort.store.readonly.mr.azkaban;
+
+import java.util.Properties;
+
+/**
+ * This can be implemented in order to act on certain stages of the Build and Push job.
+ *
+ * Implementations of this interface must have a no-arguments constructor.
+ *
+ * All hooks registered via the job's config will be instantiated by reflection, and
+ * then provided the job's properties via the {@link #init(java.util.Properties)}
+ * function. Afterward, the {@link #invoke(BuildAndPushStatus, String)} function will
+ * be called at various stages of the job, within a try/catch (i.e.: the hooks are
+ * executed on a best effort basis and are not meant to be allowed to fail the job).
+ */
+public interface BuildAndPushHook {
+  /**
+   * A hook name, for logging purposes.
+   *
+   * @return a human-readable name for the hook.
+   */
+  String getName();
+
+  /**
+   * Hooks can inspect the job's regular config params as well as look for config params
+   * that they need for their own operation. It is strongly recommended to name-space
+   * config params that are hook-specific, in order to avoid name-clashes, according to
+   * the following convention: "hooks." followed by the hook's FQCN, followed by a config
+   * name, for example:
+   *
+   * hooks.com.company.fully.qualified.class.name.of.TheHook.some-config-name=some-config-value
+   *
+   * If this function throws an exception, its {@link #invoke(BuildAndPushStatus, String)}
+   * function will not be called during the job.
+   *
+   * @param properties of the Build and Push job.
+   */
+  void init(Properties properties) throws Exception;
+
+  /**
+   * This is called by the Build and Push job at various stages during the life-cycle of the job.
+   *
+   * It is called within a try/catch and will not allow the job to fail even if it throws.
+   *
+   * @param status an instance of the BuildAndPushStatus enum
+   * @param details Can be null. Not all stages have details associated with them.
+   */
+  void invoke(BuildAndPushStatus status, String details);
+}

contrib/hadoop-store-builder/src/java/voldemort/store/readonly/mr/azkaban/BuildAndPushStatus.java

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+package voldemort.store.readonly.mr.azkaban;
+
+/**
+ * This enum describes the various stages a Build and Push can be in.
+ */
+public enum BuildAndPushStatus {
+  // The "happy path" status:
+  STARTING,
+  BUILDING,
+  PUSHING,
+  FINISHED,
+  HEARTBEAT, // N.B.: The heartbeat is emitted periodically during any of the stages...
+  // The "not-so-happy path" status:
+  CANCELLED,
+  FAILED;
+}