Programmer Think

1, Introduction to SecondaryNameNode When analyzing the edits log files just now, we have introduced the SecondaryNameNode. Here is a summary to show our attention. The secondary namenode is mainly responsible for regularly merging the contents of the edits file into the fsimage This merge operation is called checkpoint. When merging, the co ...

1. Why do you need to use design patterns? Using design patterns to reconstruct the whole code can improve the reusability and scalability of the code and reduce code redundancy. 2. Talk about the six principles of design mode? Open Close Principle: the Open Close Principle is open to extensions and closed to modifications. When the prog ...

job submission process - supplemental map task returns the processing result to MRAPPmaster reduce task combines the map processing results, processes the operations, and then outputs them 1. Steps to realize Zoning: 1.1 First analyze the specific business logic to determine how many partitions there are 1.2 First write a class that inher ...