DFSInputStream open ( String src , int buffersize , boolean verifyChecksum , FileSystem . Statistics stats , boolean clearOsBuffer , ReadOptions options ) throws IOException { checkOpen ( ) ; incFileReadToStats ( ) ; // Get block info from namenode DFSInputStream stream = new DFSInputStream ( this , src , buffersize , verifyChecksum , clearOsBuffer , options ) ; if ( blockLocationRenewal != null ) { blockLocationRenewal . add ( stream ) ; } return stream ; }
Create an input stream that obtains a nodelist from the namenode and then reads from all the right places . Creates inner subclass of InputStream that does the right out - of - band work .