How are partitions located in HBase?
In HBase, partitions are located using regions. The HBase data table is divided into multiple regions, with each region responsible for storing a portion of the data. Each region has a range (startKey and endKey) that indicates the data range it is responsible for storing.
HBase utilizes the consistent hashing algorithm to determine the partitioning and location of each Region. The specific steps are as follows:
- When creating a new table, HBase will automatically partition a certain number of initial regions based on the table’s pre-partitioning strategy. If no pre-partitioning strategy is specified, HBase will default to creating one region.
- HBase will assign these initial Regions to RegionServers in the HBase cluster based on the range information of the Regions.
- When a client requests access to a specific row, the HBase client will calculate a HashCode based on the RowKey of that row.
- The HBase client uses consistent hashing algorithm to map the HashCode to a position on a virtual ring.
- HBase determines the corresponding Region based on this location, and then sends the request to the RegionServer responsible for that Region.
- Upon receiving the request, the RegionServer locates the specific data based on the RowKey and internal data index of the region, and then returns it to the client.
In this way, HBase can efficiently locate and access data through the mapping of consistent hashing algorithm and the range information of Regions. Additionally, when needing to scale the cluster, load balancing and automatic data migration can be achieved by adding RegionServers and redistributing Regions.