org.apache.ignite.igfs.mapreduce

Interface IgfsJob

All Known Implementing Classes:

IgfsInputStreamJobAdapter, IgfsJobAdapter

public interface IgfsJob

Defines executable unit for IgfsTask. Before this job is executed, it is assigned one of the ranges provided by the IgfsRecordResolver passed to one of the IgniteFs.execute(...) methods.

execute(org.apache.ignite.IgniteFileSystem, IgfsFileRange, org.apache.ignite.igfs.IgfsInputStream) method is given IgfsFileRange this job is expected to operate on, and already opened IgfsInputStream for the file this range belongs to.

Note that provided input stream has position already adjusted to range start. However, it will not automatically stop on range end. This is done to provide capability in some cases to look beyond the range end or seek position before the reange start.

In majority of the cases, when you want to process only provided range, you should explicitly control amount of returned data and stop at range end. You can also use IgfsInputStreamJobAdapter, which operates on IgfsRangeInputStream bounded to range start and end, or manually wrap provided input stream with IgfsRangeInputStream.

You can inject any resources in concrete implementation, just as with regular ComputeJob implementations.

Method Summary

Modifier and Type	Method and Description
void	cancel() This method is called when system detects that completion of this job can no longer alter the overall outcome (for example, when parent task has already reduced the results).
Object	execute(IgniteFileSystem igfs, IgfsFileRange range, IgfsInputStream in) Executes this job.

Method Detail

execute

Object execute(IgniteFileSystem igfs,
               IgfsFileRange range,
               IgfsInputStream in)
        throws IgniteException,
               IOException

Executes this job.

Parameters:

igfs - IGFS instance.

range - File range aligned to record boundaries.

in - Input stream for split file. This input stream is not aligned to range and points to file start by default.

Returns:

Execution result.

Throws:

IgniteException - If execution failed.

IOException - If file system operation resulted in IO exception.

cancel

void cancel()

This method is called when system detects that completion of this job can no longer alter the overall outcome (for example, when parent task has already reduced the results). Job is also cancelled when IgniteFuture.cancel() is called.

Note that job cancellation is only a hint, and just like with Thread.interrupt() method, it is really up to the actual job instance to gracefully finish execution and exit.