Package org.apache.hadoop.mapred

A system for scalable, fault-tolerant, distributed computation over large data collections.

See:
Description

Interface Summary

InputFormat	An input data format.
InputSplit	The description of the data for a single map task.
JobConfigurable	That what may be configured.
JobHistory.Listener	Callback interface for reading back log events from JobHistory.
JobSubmissionProtocol	Protocol that a JobClient and the central JobTracker use to communicate.
Mapper	Maps input key/value pairs to a set of intermediate key/value pairs.
MapRunnable	Expert: Permits greater control of map processing.
OutputCollector	Passed to Mapper and Reducer implementations to collect output data.
OutputFormat	An output data format.
Partitioner	Partitions the key space.
RecordReader	Reads key/value pairs from an input file FileSplit.
RecordWriter	Writes key/value pairs to an output file.
Reducer	Reduces a set of intermediate values which share a key to a smaller set of values.
Reporter	Passed to application code to permit alteration of status.
RunningJob	Includes details on a running MapReduce job.
SequenceFileInputFilter.Filter	filter interface

Class Summary

ClusterStatus	Summarizes the size and current state of the cluster.
Counters	A set of named counters.
Counters.Group	Represents a group of counters, comprising the counters from a particular counter enum class.
DefaultJobHistoryParser	Default parser for job history files.
FileInputFormat	A base class for InputFormat.
FileSplit	A section of an input file.
InputFormatBase	Deprecated. replaced by FileInputFormat
IsolationRunner
JobClient	JobClient interacts with the JobTracker network interface.
JobConf	A map/reduce job configuration.
JobEndNotifier
JobHistory	Provides methods for writing to and reading from job history.
JobHistory.HistoryCleaner	Delete history files older than one month.
JobHistory.JobInfo	Helper class for logging or reading back events related to job start, finish or failure.
JobHistory.MapAttempt	Helper class for logging or reading back events related to start, finish or failure of a Map Attempt on a node.
JobHistory.ReduceAttempt	Helper class for logging or reading back events related to start, finish or failure of a Map Attempt on a node.
JobHistory.Task	Helper class for logging or reading back events related to Task's start, finish or failure.
JobHistory.TaskAttempt	Base class for Map and Reduce TaskAttempts.
JobProfile	A JobProfile is a MapReduce primitive.
JobStatus	Describes the current status of a job.
JobTracker	JobTracker is the central location for submitting and tracking MR jobs in a network environment.
KeyValueLineRecordReader	This class treats a line in the input as a key/value pair separated by a separator character.
KeyValueTextInputFormat	An InputFormat for plain text files.
LineRecordReader	Treats keys as offset in file and value as line.
MapFileOutputFormat	An OutputFormat that writes MapFiles.
MapReduceBase	Base class for Mapper and Reducer implementations.
MapRunner	Default MapRunnable implementation.
OutputFormatBase	A base class for OutputFormat.
PhasedFileSystem	Deprecated. PhasedFileSystem is no longer used during speculative execution of tasks.
SequenceFileAsTextInputFormat	This class is similar to SequenceFileInputFormat, except it generates SequenceFileAsTextRecordReader which converts the input keys and values to their String forms by calling toString() method.
SequenceFileAsTextRecordReader	This class converts the input keys and values to their String forms by calling toString() method.
SequenceFileInputFilter	A class that allows a map/red job to work on a sample of sequence files.
SequenceFileInputFilter.FilterBase	base calss for Filters
SequenceFileInputFilter.MD5Filter	This class returns a set of records by examing the MD5 digest of its key against a filtering frequency f.
SequenceFileInputFilter.PercentFilter	This class returns a percentage of records The percentage is determined by a filtering frequency f using the criteria record# % f == 0.
SequenceFileInputFilter.RegexFilter	Records filter by matching key to regex
SequenceFileInputFormat	An InputFormat for SequenceFiles.
SequenceFileOutputFormat	An OutputFormat that writes SequenceFiles.
SequenceFileRecordReader	An RecordReader for SequenceFiles.
StatusHttpServer	Create a Jetty embedded server to answer http requests.
StatusHttpServer.StackServlet	A very simple servlet to serve up a text representation of the current stack traces.
TaskCompletionEvent	This is used to track task completion events on job tracker.
TaskLogAppender	A simple log4j-appender for the task child's map-reduce system logs.
TaskReport	A report on the state of a task.
TaskTracker	TaskTracker is a process that starts and tracks MR Tasks in a networked environment.
TaskTracker.Child	The main() for child processes.
TaskTracker.MapOutputServlet	This class is used in TaskTracker's Jetty to serve the map outputs to other nodes.
TextInputFormat	An InputFormat for plain text files.
TextOutputFormat	An OutputFormat that writes plain text files.
TextOutputFormat.LineRecordWriter

Enum Summary

JobClient.TaskStatusFilter
JobHistory.Keys	Job history files contain key="value" pairs, where keys belong to this enum.
JobHistory.RecordTypes	Record types are identifiers for each line of log in history files.
JobHistory.Values	This enum contains some of the values commonly used by history log events.
TaskCompletionEvent.Status

Exception Summary

FileAlreadyExistsException	Used when target file already exists for any operation and is not configured to be overwritten.
InvalidFileTypeException	Used when file type differs from the desired file type.
InvalidInputException	This class wraps a list of problems with the input, so that the user can get a list of problems together instead of finding and fixing them one by one.
InvalidJobConfException	This exception is thrown when jobconf misses some mendatory attributes or value of some attributes is invalid.

Package org.apache.hadoop.mapred Description

A system for scalable, fault-tolerant, distributed computation over large data collections.

Applications implement Mapper and Reducer interfaces. These are submitted as a JobConf and are applied to data stored in a FileSystem.

See Google's original Map/Reduce paper for background information.