org.apache.hadoop.mapred
Class Counters

java.lang.Object
  org.apache.hadoop.mapred.Counters

All Implemented Interfaces:

Iterable<Counters.Group>, Writable

public class Counters
extends Object
implements Writable, Iterable<Counters.Group>

A set of named counters.

Counters represent global counters, defined either by the Map-Reduce framework or applications. Each Counter can be of any Enum type.

Counters are bunched into Counters.Groups, each comprising of counters from a particular Enum class.

Nested Class Summary

static class	Counters.Counter A counter record, comprising its name and value.
static class	Counters.Group Group of counters, comprising of counters from a particular counter Enum class.

Constructor Summary

Counters()

Method Summary

Counters.Counter	findCounter(Enum key) Find the counter for the given enum.
Counters.Counter	findCounter(String group, int id, String name) Find a counter by using strings
long	getCounter(Enum key) Returns current value of the specified counter, or 0 if the counter does not exist.
Counters.Group	getGroup(String groupName) Returns the named counter group, or an empty group if there is none with the specified name.
Collection<String>	getGroupNames() Returns the names of all counter classes.
void	incrAllCounters(Counters other) Increments multiple counters by their amounts in another Counters instance.
void	incrCounter(Enum key, long amount) Increments the specified counter by the specified amount, creating it if it didn't already exist.
Iterator<Counters.Group>	iterator()
void	log(org.apache.commons.logging.Log log) Logs the current counter values.
String	makeCompactString() Convert a counters object into a single line that is easy to parse.
void	readFields(DataInput in) Read a set of groups.
int	size() Returns the total number of counters, by summing the number of counters in each group.
static Counters	sum(Counters a, Counters b) Convenience method for computing the sum of two sets of counters.
String	toString() Return textual representation of the counter values.
void	write(DataOutput out) Write the set of groups.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Counters

public Counters()

Method Detail

getGroupNames

public Collection<String> getGroupNames()

Returns the names of all counter classes.

Returns:

Set of counter names.

iterator

public Iterator<Counters.Group> iterator()

Specified by:

iterator in interface Iterable<Counters.Group>

getGroup

public Counters.Group getGroup(String groupName)

Returns the named counter group, or an empty group if there is none with the specified name.

findCounter

public Counters.Counter findCounter(Enum key)

Find the counter for the given enum. The same enum will always return the same counter.

Parameters:

key - the counter key

Returns:

the matching counter object

findCounter

public Counters.Counter findCounter(String group,
                                    int id,
                                    String name)

Find a counter by using strings

Parameters:

group - the name of the group

id - the id of the counter within the group (0 to N-1)

name - the internal name of the counter

Returns:

the counter for that name

incrCounter

public void incrCounter(Enum key,
                        long amount)

Increments the specified counter by the specified amount, creating it if it didn't already exist.

Parameters:

key - identifies a counter

amount - amount by which counter is to be incremented

getCounter

public long getCounter(Enum key)

Returns current value of the specified counter, or 0 if the counter does not exist.

incrAllCounters

public void incrAllCounters(Counters other)

Increments multiple counters by their amounts in another Counters instance.

Parameters:

other - the other Counters instance

sum

public static Counters sum(Counters a,
                           Counters b)

Convenience method for computing the sum of two sets of counters.

size

public int size()

Returns the total number of counters, by summing the number of counters in each group.

write

public void write(DataOutput out)
           throws IOException

Write the set of groups. The external format is: #groups (groupName group)* i.e. the number of groups followed by 0 or more groups, where each group is of the form: groupDisplayName #counters (false | true counter)* where each counter is of the form: name value

Specified by:

write in interface Writable

Parameters:

out - DataOuput to serialize this object into.

Throws:

IOException

readFields

public void readFields(DataInput in)
                throws IOException

Read a set of groups.

Specified by:

readFields in interface Writable

Parameters:

in - DataInput to deseriablize this object from.

Throws:

IOException

log

public void log(org.apache.commons.logging.Log log)

Logs the current counter values.

Parameters:

log - The log to use.

toString

public String toString()

Return textual representation of the counter values.

Overrides:

toString in class Object

makeCompactString

public String makeCompactString()

Convert a counters object into a single line that is easy to parse.

Returns:

the string with "name=value" for each counter and separated by ","