org.apache.hadoop.fs.statistics

Class IOStatisticsLogging

java.lang.Object

org.apache.hadoop.fs.statistics.IOStatisticsLogging

@InterfaceAudience.Public
 @InterfaceStability.Unstable
public final class IOStatisticsLogging
extends Object

Utility operations convert IO Statistics sources/instances to strings, especially for robustly logging.

Method Summary

Modifier and Type	Method and Description
static Object	demandStringifyIOStatistics(IOStatistics statistics) On demand stringifier of an IOStatistics instance.
static Object	demandStringifyIOStatisticsSource(org.apache.hadoop.fs.statistics.IOStatisticsSource source) On demand stringifier of an IOStatisticsSource instance.
static String	ioStatisticsSourceToString(Object source) Extract the statistics from a source object -or "" if it is not an instance of IOStatistics, IOStatisticsSource or the retrieved statistics are null.
static String	ioStatisticsToPrettyString(IOStatistics statistics) Convert IOStatistics to a string form, with all the metrics sorted and empty value stripped.
static String	ioStatisticsToString(IOStatistics statistics) Convert IOStatistics to a string form.
static void	logIOStatisticsAtDebug(org.slf4j.Logger log, String message, Object source) Extract any statistics from the source and log at debug, if the log is set to log at debug.
static void	logIOStatisticsAtDebug(String message, Object source) Extract any statistics from the source and log to this class's log at debug, if the log is set to log at debug.

Methods inherited from class java.lang.Object

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

Method Detail

ioStatisticsSourceToString

public static String ioStatisticsSourceToString(@Nullable
                                                Object source)

Extract the statistics from a source object -or "" if it is not an instance of IOStatistics, IOStatisticsSource or the retrieved statistics are null.

Exceptions are caught and downgraded to debug logging.

Parameters:

source - source of statistics.

Returns:

a string for logging.

ioStatisticsToString

public static String ioStatisticsToString(@Nullable
                                          IOStatistics statistics)

Convert IOStatistics to a string form.

Parameters:

statistics - A statistics instance.

Returns:

string value or the empty string if null

ioStatisticsToPrettyString

public static String ioStatisticsToPrettyString(@Nullable
                                                IOStatistics statistics)

Convert IOStatistics to a string form, with all the metrics sorted and empty value stripped. This is more expensive than the simple conversion, so should only be used for logging/output where it's known/highly likely that the caller wants to see the values. Not for debug logging.

Parameters:

statistics - A statistics instance.

Returns:

string value or the empty string if null

demandStringifyIOStatisticsSource

public static Object demandStringifyIOStatisticsSource(@Nullable
                                                       org.apache.hadoop.fs.statistics.IOStatisticsSource source)

On demand stringifier of an IOStatisticsSource instance.

Whenever this object's toString() method is called, it evaluates the statistics.

This is designed to affordable to use in log statements.

Parameters:

source - source of statistics -may be null.

Returns:

an object whose toString() operation returns the current values.

demandStringifyIOStatistics

public static Object demandStringifyIOStatistics(@Nullable
                                                 IOStatistics statistics)

On demand stringifier of an IOStatistics instance.

Whenever this object's toString() method is called, it evaluates the statistics.

This is for use in log statements where for the cost of creation of this entry is low; it is affordable to use in log statements.

Parameters:

statistics - statistics to stringify -may be null.

Returns:

an object whose toString() operation returns the current values.

logIOStatisticsAtDebug

public static void logIOStatisticsAtDebug(org.slf4j.Logger log,
                                          String message,
                                          Object source)

Extract any statistics from the source and log at debug, if the log is set to log at debug. No-op if logging is not at debug or the source is null/of the wrong type/doesn't provide statistics.

Parameters:

log - log to log to

message - message for log -this must contain "{}" for the statistics report to actually get logged.

source - source object

logIOStatisticsAtDebug

public static void logIOStatisticsAtDebug(String message,
                                          Object source)

Extract any statistics from the source and log to this class's log at debug, if the log is set to log at debug. No-op if logging is not at debug or the source is null/of the wrong type/doesn't provide statistics.

Parameters:

message - message for log -this must contain "{}" for the statistics report to actually get logged.

source - source object