private OperationTracker getOperationTracker(RouterConfig routerConfig, PartitionId partitionId,
      RouterOperation operation) {
    return new AdaptiveOperationTracker(routerConfig, routerMetrics, operation, partitionId, null, time);
  }
Instantiate an adaptive operation tracker.
@param routerConfig the {@link RouterConfig} to use in adaptive tracker.
@param partitionId the {@link PartitionId} to use in adaptive tracker.
@param operation the {@link RouterOperation} to use in the adaptive tracker.
@return an instance of {@link AdaptiveOperationTracker} with the given parameters.
ambry-router/src/test/java/com/github/ambry/router/AdaptiveOperationTrackerTest.java