private OperationTracker getOperationTrackerForDelete(boolean crossColoEnabled, int successTargetForDelete,
      int parallelism, RouterOperation routerOperation, boolean includeDownReplicas, boolean enableOfflineRepair) {
    Properties props = new Properties();
    props.setProperty(RouterConfig.ROUTER_DELETE_SUCCESS_TARGET, Integer.toString(successTargetForDelete));
    props.setProperty(RouterConfig.ROUTER_DELETE_REQUEST_PARALLELISM, Integer.toString(parallelism));
    props.setProperty(RouterConfig.ROUTER_GET_REQUEST_PARALLELISM, Integer.toString(parallelism));
    if (enableOfflineRepair) {
      props.setProperty(RouterConfig.ROUTER_REPAIR_REQUESTS_DB_FACTORY,
          "com.github.ambry.repair.MysqlRepairRequestsDbFactory");
      props.setProperty(RouterConfig.ROUTER_DELETE_OFFLINE_REPAIR_ENABLED, "true");
    }
    return getOperationTracker(props, crossColoEnabled, parallelism, routerOperation, includeDownReplicas, true);
  }
Returns the right {@link OperationTracker} for Delete requests.
@param crossColoEnabled {@code true} if cross colo needs to be enabled. {@code false} otherwise.
@param successTargetForDelete the number of successful responses required for Ttl operation to succeed.
@param parallelism the number of parallel requests that can be in flight.
@param routerOperation the {@link RouterOperation} associate with this request.
@param includeDownReplicas whether to include down replicas in operation tracker.
@return the right {@link OperationTracker} based on {@link #operationTrackerType}.
ambry-router/src/test/java/com/github/ambry/router/OperationTrackerTest.java