A return value of -1 indicates that an estimate could not be produced, and should be ignored. The value returned by this method is really only useful when compared to previous or subsequent returned values.]]> A distributed implementation of {@link org.apache.hadoop.fs.FileSystem}. This is loosely modelled after Google's GFS.

The most important difference is that unlike GFS, Hadoop DFS files have strictly one writer at any one time. Bytes are always appended to the end of the writer's stream. There is no notion of "record appends" or "mutations" that are then checked or reordered. Writers simply emit a byte stream. That byte stream is guaranteed to be stored in the order written.

]]> Since the list is fetched in batches, it does not represent a consistent snapshot of the entire list of encryption zones.

This method can only be called by HDFS superusers.]]> Inotify users may want to tune the following HDFS parameters to ensure that enough extra HDFS edits are saved to support inotify clients that fall behind the current state of the namespace while reading events. The default parameter values should generally be reasonable. If edits are deleted before their corresponding events can be read, clients will see a {@link org.apache.hadoop.hdfs.inotify.MissingEventsException} on {@link org.apache.hadoop.hdfs.DFSInotifyEventInputStream} method calls. It should generally be sufficient to tune these parameters: dfs.namenode.num.extra.edits.retained dfs.namenode.max.extra.edits.segments.retained Parameters that affect the number of created segments and the number of edits that are considered necessary, i.e. do not count towards the dfs.namenode.num.extra.edits.retained quota): dfs.namenode.checkpoint.period dfs.namenode.checkpoint.txns dfs.namenode.num.checkpoints.retained dfs.ha.log-roll.period

It is recommended that local journaling be configured (dfs.namenode.edits.dir) for inotify (in addition to a shared journal) so that edit transfers from the shared journal can be avoided. @throws IOException If there was an error obtaining the stream.]]> This method must return as quickly as possible, since it's called in a critical section of the NameNode's operation. @param succeeded Whether authorization succeeded. @param userName Name of the user executing the request. @param addr Remote address of the request. @param cmd The requested command. @param src Path of affected source file. @param dst Path of affected destination file (if any). @param stat File information for operations that change the file's metadata (permissions, owner, times, etc).]]>