Method syncToStorage

src/meta/UIDMeta.java:174–277

Attempts a CompareAndSet storage call, loading the object from storage, synchronizing changes, and attempting a put. Note: If the local object didn't have any fields set by the caller then the data will not be written. @param tsdb The TSDB to use for storage access @param overwrite When the R

(final TSDB tsdb, 
      final boolean overwrite)

   * @throws JSONException if the object could not be serialized
   */
  public Deferred<Boolean> syncToStorage(final TSDB tsdb, 
      final boolean overwrite) {
    if (uid == null || uid.isEmpty()) {
      throw new IllegalArgumentException("Missing UID");
    }
    if (type == null) {
      throw new IllegalArgumentException("Missing type");
    }

    boolean has_changes = false;
    for (Map.Entry<String, Boolean> entry : changed.entrySet()) {
      if (entry.getValue()) {
        has_changes = true;
        break;
      }
    }
    if (!has_changes) {
      LOG.debug(this + " does not have changes, skipping sync to storage");
      throw new IllegalStateException("No changes detected in UID meta data");
    }
    
    /**
     * Callback used to verify that the UID to name mapping exists. Uses the TSD
     * for verification so the name may be cached. If the name does not exist
     * it will throw a NoSuchUniqueId and the meta data will not be saved to
     * storage
     */
    final class NameCB implements Callback<Deferred<Boolean>, String> {
      private final UIDMeta local_meta;
      
      public NameCB(final UIDMeta meta) {
        local_meta = meta;
      }
      
      /**
       *  Nested callback used to merge and store the meta data after verifying
       *  that the UID mapping exists. It has to access the {@code local_meta} 
       *  object so that's why it's nested within the NameCB class
       */
      final class StoreUIDMeta implements Callback<Deferred<Boolean>, 
        ArrayList<KeyValue>> {

        /**
         * Executes the CompareAndSet after merging changes
         * @return True if the CAS was successful, false if the stored data
         * was modified during flight.
         */
        @Override
        public Deferred<Boolean> call(final ArrayList<KeyValue> row) 
          throws Exception {
          
          final UIDMeta stored_meta;
          if (row == null || row.isEmpty()) {
            stored_meta = null;
          } else {
            stored_meta = JSON.parseToObject(row.get(0).value(), UIDMeta.class);
            stored_meta.initializeChangedMap();
          }