Method getLastPoint

src/meta/TSUIDQuery.java:161–217

Attempts to fetch the last data point for the given metric or TSUID. If back_scan == 0 and meta is enabled via "tsd.core.meta.enable_tsuid_tracking" or "tsd.core.meta.enable_tsuid_incrementing" then we will look up the metric or TSUID in the meta table first and use the counter there to get the last

(final boolean resolve_names, 
      final int back_scan)

   * went pear shaped.
   */
  public Deferred<IncomingDataPoint> getLastPoint(final boolean resolve_names, 
      final int back_scan) {
    if (back_scan < 0) {
      throw new IllegalArgumentException(
          "Backscan must be zero or a positive number");
    }
    
    this.resolve_names = resolve_names;
    this.back_scan = back_scan;
    
    final boolean meta_enabled = tsdb.getConfig().enable_tsuid_tracking() ||
        tsdb.getConfig().enable_tsuid_incrementing();
    
    class TSUIDCB implements Callback<Deferred<IncomingDataPoint>, byte[]> {
      @Override
      public Deferred<IncomingDataPoint> call(final byte[] incoming_tsuid) 
          throws Exception {
        if (tsuid == null && incoming_tsuid == null) {
          return Deferred.fromError(new RuntimeException("Both incoming and "
              + "supplied TSUIDs were null for " + TSUIDQuery.this));
        } else if (incoming_tsuid != null) {
          setTSUID(incoming_tsuid);
        }
        if (back_scan < 1 && meta_enabled) {
          final GetRequest get = new GetRequest(tsdb.metaTable(), tsuid);
          get.family(TSMeta.FAMILY());
          get.qualifier(TSMeta.COUNTER_QUALIFIER());
          return tsdb.getClient().get(get).addCallbackDeferring(new MetaCB());
        }
        
        if (last_timestamp > 0) {
          last_timestamp = Internal.baseTime(last_timestamp);
        } else {
          last_timestamp = Internal.baseTime(DateTime.currentTimeMillis());
        }
        final byte[] key = RowKey.rowKeyFromTSUID(tsdb, tsuid, last_timestamp);
        final GetRequest get = new GetRequest(tsdb.dataTable(), key);
        get.family(TSDB.FAMILY());
        return tsdb.getClient().get(get).addCallbackDeferring(new LastPointCB());
      }
      @Override
      public String toString() {
        return "TSUID callback";
      }
    }
    
    if (tsuid == null) {
      return tsuidFromMetric(tsdb, metric, tags)
          .addCallbackDeferring(new TSUIDCB());
    }
    try {
      // damn typed exceptions....
      return new TSUIDCB().call(null);
    } catch (Exception e) {
      return Deferred.fromError(e);
    }
  }