Method sendRpcToRegion

src/HBaseClient.java:2418–2469

Sends an RPC targeted at a particular region to the right RegionServer. This method is package-private so that the low-level RegionClient can retry RPCs when handling a NotServingRegionException. @param request The RPC to send. This RPC must specify a single specific tabl

(final HBaseRpc request)

   * de-serialized back from the network).
   */
  Deferred<Object> sendRpcToRegion(final HBaseRpc request) {
    if (cannotRetryRequest(request)) {
      return tooManyAttempts(request, null);
    }
    request.attempt++;
    final byte[] table = request.table;
    final byte[] key = request.key;
    final RegionInfo region = getRegion(table, key);

    final class RetryRpc implements Callback<Deferred<Object>, Object> {
      public Deferred<Object> call(final Object arg) {
        if (arg instanceof NonRecoverableException) {
          // No point in retrying here, so fail the RPC.
          HBaseException e = (NonRecoverableException) arg;
          if (e instanceof HasFailedRpcException
              && ((HasFailedRpcException) e).getFailedRpc() != request) {
            // If we get here it's because a dependent RPC (such as a META
            // lookup) has failed.  Therefore the exception we're getting
            // indicates that the META lookup failed, but we need to return
            // to our caller here that it's their RPC that failed.  Here we
            // re-create the exception but with the correct RPC in argument.
            e = e.make(e, request);  // e is likely a PleaseThrottleException.
          }
          request.callback(e);
          return Deferred.fromError(e);
        }
        return sendRpcToRegion(request);  // Retry the RPC.
      }
      public String toString() {
        return "retry RPC";
      }
    }

    if (region != null) {
      if (knownToBeNSREd(region)) {
        final NotServingRegionException nsre =
          new NotServingRegionException("Region known to be unavailable",
                                        request);
        final Deferred<Object> d = request.getDeferred();
        handleNSRE(request, region.name(), nsre);
        return d;
      }
      final RegionClient client = clientFor(region);
      if (client != null && client.isAlive()) {
        request.setRegion(region);
        final Deferred<Object> d = request.getDeferred();
        client.sendRpc(request);
        return d;
      }
    }
    return locateRegion(request, table, key).addBothDeferring(new RetryRpc());
  }

  /**
   * Returns how many lookups in {@code -ROOT-} were performed.