org.apache.hadoop.hdfs.server.datanode.fsdataset
Interface RollingLogs

public interface RollingLogs

Rolling logs consist of a current log and a set of previous logs. The implementation should support a single appender and multiple readers.

Nested Class Summary

static interface	RollingLogs.Appender To append text to the logs.
static interface	RollingLogs.LineIterator To iterate the lines of the logs.

Method Summary

RollingLogs.Appender	appender()
RollingLogs.LineIterator	iterator(boolean skipPrevious) Create an iterator to iterate the lines in the logs.
boolean	roll() Roll current to previous.

Method Detail

iterator

RollingLogs.LineIterator iterator(boolean skipPrevious)
                                  throws IOException

Create an iterator to iterate the lines in the logs.

Parameters:

skipPrevious - Should it skip reading the previous log?

Returns:

a new iterator.

Throws:

IOException

appender

RollingLogs.Appender appender()

Returns:

the only appender to append text to the logs. The same object is returned if it is invoked multiple times.

roll

boolean roll()
             throws IOException

Roll current to previous.

Returns:

true if the rolling succeeded. When it returns false, it is not equivalent to an error. It means that the rolling cannot be performed at the moment, e.g. the logs are being read.

Throws:

IOException