org.apache.druid.java.util.common.logger

Class Logger

java.lang.Object

org.apache.druid.java.util.common.logger.Logger

Direct Known Subclasses:

EmittingLogger

public class Logger
extends Object

A Logger for usage inside of Druid. Provides a layer that allows for simple changes to the logging framework with minimal changes to the Druid code. Log levels are used as an indication of urgency around the behavior that is being logged. The intended generic rubric for when to use the different logging levels is as follows. DEBUG: something that a developer wants to look at while actively debugging, but should not be included by default. INFO: a message that is useful to have when trying to retro-actively understand what happened in a running system. There is often a fine line between INFO and DEBUG. We want information from INFO logs but do not want to spam log files either. One rubric to use to help determine if something should be INFO or DEBUG is how often we expect the line to be logged. If there is clarity that it will happen in a controlled manner such that it does not spam the logs, then INFO is fine. Additionally, it can be okay to log at INFO level even if there is a risk of spamming the log file in the case that the log line only happens in specific "error-oriented" situations, this is because such error-oriented situations are more likely to necessitate reading and understanding the logs to eliminate the error. Additionally, it is perfectly acceptable and reasonable to log an exception at INFO level. WARN: a message that indicates something bad has happened in the system that a human should potentially investigate. While it is bad and deserves investigation, it is of a nature that it should be able to wait until the next "business day" for investigation instead of needing immediate attention. ERROR: a message that indicates that something bad has happened such that a human operator should take immediate intervention to triage and resolve the issue as it runs a risk to the smooth operations of the system. Logs at the ERROR level should generally be severe enough to warrant paging someone in the middle of the night. Even though this is the intended rubric, it is very difficult to ensure that, e.g. all ERROR log lines are pageable offenses. As such, it is questionable whether an operator should actually ALWAYS page on every ERROR log line, but as a directional target of when and how to log things, the above rubric should be used to evaluate if a log line is at the correct level.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	Logger.LogFunction

Constructor Summary

Constructors

Modifier	Constructor and Description
	Logger(Class clazz)
protected	Logger(org.slf4j.Logger log, boolean stackTraces)
	Logger(String name)

Method Summary

Modifier and Type	Method and Description
void	assertionError(String message, Object... formatArgs)
void	debug(org.slf4j.Marker marker, String message, Object... formatArgs)
void	debug(String message, Object... formatArgs)
void	debug(Throwable t, String message, Object... formatArgs)
void	debugSegments(Collection<DataSegment> segments, String preamble)
void	error(org.slf4j.Marker marker, String message, Object... formatArgs)
void	error(String message, Object... formatArgs)
void	error(String message, Throwable t) Deprecated.
void	error(Throwable t, String message, Object... formatArgs)
void	errorSegments(Collection<DataSegment> segments, String preamble)
String	getName()
protected org.slf4j.Logger	getSlf4jLogger()
void	info(org.slf4j.Marker marker, String message, Object... formatArgs)
void	info(String message, Object... formatArgs)
void	info(Throwable t, String message, Object... formatArgs)
void	infoSegmentIds(Stream<SegmentId> segments, String preamble)
void	infoSegments(Collection<DataSegment> segments, String preamble)
boolean	isDebugEnabled()
boolean	isInfoEnabled()
boolean	isTraceEnabled()
Logger	noStackTrace() Returns a copy of this Logger that does not log exception stack traces, unless the log level is DEBUG or lower.
String	toString()
void	trace(org.slf4j.Marker marker, String message, Object... formatArgs)
void	trace(String message, Object... formatArgs)
void	warn(org.slf4j.Marker marker, String message, Object... formatArgs)
void	warn(String message, Object... formatArgs)
void	warn(String message, Throwable t) Deprecated.
void	warn(Throwable t, String message, Object... formatArgs)
void	warnSegments(Collection<DataSegment> segments, String preamble)

Methods inherited from class java.lang.Object

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

Constructor Detail

Logger

public Logger(String name)

Logger

public Logger(Class clazz)

Logger

protected Logger(org.slf4j.Logger log,
                 boolean stackTraces)

Method Detail

getSlf4jLogger

protected org.slf4j.Logger getSlf4jLogger()

toString

public String toString()

Overrides:

toString in class Object

noStackTrace

public Logger noStackTrace()

Returns a copy of this Logger that does not log exception stack traces, unless the log level is DEBUG or lower. Useful for writing code like: log.noStackTrace().warn(e, "Something happened.");

trace

public void trace(String message,
                  Object... formatArgs)

trace

public void trace(org.slf4j.Marker marker,
                  String message,
                  Object... formatArgs)

debug

public void debug(String message,
                  Object... formatArgs)

debug

public void debug(org.slf4j.Marker marker,
                  String message,
                  Object... formatArgs)

debug

public void debug(Throwable t,
                  String message,
                  Object... formatArgs)

info

public void info(String message,
                 Object... formatArgs)

info

public void info(org.slf4j.Marker marker,
                 String message,
                 Object... formatArgs)

info

public void info(Throwable t,
                 String message,
                 Object... formatArgs)

warn

@Deprecated
public void warn(String message,
                             Throwable t)

Deprecated.

Protect against assuming slf4j convention. use `warn(Throwable t, String message, Object... formatArgs)` instead

Parameters:

message - The string message

t - The Throwable to log

warn

public void warn(String message,
                 Object... formatArgs)

warn

public void warn(org.slf4j.Marker marker,
                 String message,
                 Object... formatArgs)

warn

public void warn(Throwable t,
                 String message,
                 Object... formatArgs)

error

public void error(String message,
                  Object... formatArgs)

error

public void error(org.slf4j.Marker marker,
                  String message,
                  Object... formatArgs)

error

@Deprecated
public void error(String message,
                              Throwable t)

Deprecated.

Protect against assuming slf4j convention. use `error(Throwable t, String message, Object... formatArgs)` instead

Parameters:

message - The string message

t - The Throwable to log

error

public void error(Throwable t,
                  String message,
                  Object... formatArgs)

assertionError

public void assertionError(String message,
                           Object... formatArgs)

debugSegments

public void debugSegments(@Nullable
                          Collection<DataSegment> segments,
                          @Nullable
                          String preamble)

infoSegments

public void infoSegments(@Nullable
                         Collection<DataSegment> segments,
                         @Nullable
                         String preamble)

infoSegmentIds

public void infoSegmentIds(@Nullable
                           Stream<SegmentId> segments,
                           @Nullable
                           String preamble)

warnSegments

public void warnSegments(@Nullable
                         Collection<DataSegment> segments,
                         @Nullable
                         String preamble)

errorSegments

public void errorSegments(@Nullable
                          Collection<DataSegment> segments,
                          @Nullable
                          String preamble)

isTraceEnabled

public boolean isTraceEnabled()

isDebugEnabled

public boolean isDebugEnabled()

isInfoEnabled

public boolean isInfoEnabled()

getName

public String getName()