This occurs when the following happens:
1. Consider a client that invokes HBaseAdmin.checkHBaseAvailable(config) before doing anything. Although this method copies the HBaseConfiguration object and sets hbase.client.retries.number to 1 (see HBaseAdmin, line 751), it creates an HBaseAdmin object, which invokes HConnectionManager.getConnection(conf). Please notice that this conf is that with hbase.client.retries.number equals to 1.
2. HConnectionManager.getConnection then creates a HConnection using this conf and puts it into a static map (see HConnectionManager, line 93) indexed by hbase.rootdir.
3. Then, if the same client now creates a HTable object (using, for instance, a HBaseConfiguration with hbase.client.retries.number equals to 10 but the same hbase.rootdir), it will invoke HConnectionManager.getConnection(conf) again (see HTable, line 109). However, when it checks the static map for a HConnection it finds one - the one previously created by the HBaseAdmin object and using hbase.client.retries.number 1 - and returns it without creating a new one with the correct HBaseConfiguration.
However, the expected behavior is: HConnectionManager must return different HConnections for different HBaseConfigurations.