Class LoggingHandler (3.19.0) 

public class LoggingHandler extends Handler

A logging handler that outputs logs generated with java.util.logging.Logger to Cloud Logging.

Java logging levels (see java.util.logging.Level) are mapped to the following Google Cloud Logging severities:

Mapping of Java logging level to Cloud Logging severities
Java Level Cloud Logging Severity
SEVERE ERROR
WARNING WARNING
INFO INFO
CONFIG INFO
FINE DEBUG
FINER DEBUG
FINEST DEBUG

Original Java logging levels are added as labels (with levelName and levelValue keys, respectively) to the corresponding Cloud Logging LogEntry. You can read entry labels using LogEntry#getLabels(). To use logging levels that correspond to Cloud Logging severities you can use LoggingLevel.

Configuration: By default each LoggingHandler is initialized using the following LogManager configuration properties (that you can set in the logging.properties file). If properties are not defined (or have invalid values) then the specified default values are used.

  • com.google.cloud.logging.LoggingHandler.log the log name (defaults to java.log).
  • com.google.cloud.logging.LoggingHandler.level specifies the default level for the handler (defaults to Level.INFO).
  • com.google.cloud.logging.LoggingHandler.filter specifies the name of a Filter class to use (defaults to no filter).
  • com.google.cloud.logging.LoggingHandler.formatter specifies the name of a Formatter class to use (defaults to SimpleFormatter).
  • com.google.cloud.logging.LoggingHandler.flushLevel specifies the flush log level. When a log with this level is published, logs are transmitted to the Cloud Logging service (defaults to LoggingLevel#ERROR).
  • com.google.cloud.logging.LoggingHandler.enhancers specifies a comma separated list of LoggingEnhancer classes. This handler will call each enhancer list whenever it builds a LogEntry instance (defaults to empty list).
  • com.google.cloud.logging.LoggingHandler.resourceType the type name to use when creating the default MonitoredResource (defaults to auto-detected resource type, else "global").
  • com.google.cloud.logging.Synchronicity the synchronicity of the write method to use to write logs to the Cloud Logging service (defaults to Synchronicity#ASYNC).
  • com.google.cloud.logging.LoggingHandler.autoPopulateMetadata is a boolean flag that opts-out the population of the log entries metadata before the logs are sent to Cloud Logging (defaults to true).
  • com.google.cloud.logging.LoggingHandler.redirectToStdout is a boolean flag that opts-in redirecting the output of the handler to STDOUT instead of ingesting logs to Cloud Logging using Logging API (defaults to false). Redirecting logs can be used in Google Cloud environments with installed logging agent to delegate log ingestions to the agent. Redirected logs are formatted as one line Json string following the structured logging guidelines. This flag is deprecated; use com.google.cloud.logging.LoggingHandler.logTarget instead.
  • com.google.cloud.logging.LoggingHandler.logTarget is an enumeration controlling log routing (defaults to CLOUD_LOGGING). If set to STDOUT or STDERR, logs will be printed to the corresponding stream in the Json format that can be parsed by the logging agent. If set to CLOUD_LOGGING, logs will be sent directly to the Google Cloud Logging API.

To add a LoggingHandler to an existing Logger and be sure to avoid infinite recursion when logging, use the #addHandler(Logger, LoggingHandler) method. Alternatively you can add the handler via logging.properties. For example using the following line:

 com.example.mypackage.handlers=com.google.cloud.logging.LoggingHandler

See Also: Structured logging

Inheritance

java.lang.Object > Handler > LoggingHandler

Static Methods

addHandler(Logger logger, LoggingHandler handler)

public static void addHandler(Logger logger, LoggingHandler handler)

Adds the provided LoggingHandler to logger. Use this method to register Cloud Logging handlers instead of Logger#addHandler(Handler) to avoid infinite recursion when logging.

Parameters
Name Description
logger Logger
handler LoggingHandler

Constructors

LoggingHandler()

public LoggingHandler()

Creates a handler that publishes messages to Cloud Logging.

LoggingHandler(String log)

public LoggingHandler(String log)

Creates a handler that publishes messages to Cloud Logging.

Parameter
Name Description
log String

the name of the log to which log entries are written

LoggingHandler(String log, LoggingOptions options)

public LoggingHandler(String log, LoggingOptions options)

Creates a handler that publishes messages to Cloud Logging.

Parameters
Name Description
log String

the name of the log to which log entries are written
options LoggingOptions

options for the Cloud Logging service

LoggingHandler(String log, LoggingOptions options, MonitoredResource monitoredResource)

public LoggingHandler(String log, LoggingOptions options, MonitoredResource monitoredResource)

Creates a handler that publishes messages to Cloud Logging.

Parameters
Name Description
log String

the name of the log to which log entries are written
options LoggingOptions

options for the Cloud Logging service
monitoredResource com.google.cloud.MonitoredResource

the monitored resource to which log entries refer. If it is null then a default resource is created based on the project ID and deployment environment.

LoggingHandler(String log, LoggingOptions options, MonitoredResource monitoredResource, List<LoggingEnhancer> enhancers)

public LoggingHandler(String log, LoggingOptions options, MonitoredResource monitoredResource, List<LoggingEnhancer> enhancers)

Creates a handler that publishes messages to Cloud Logging.

Parameters
Name Description
log String

the name of the log to which log entries are written
options LoggingOptions

options for the Cloud Logging service
monitoredResource com.google.cloud.MonitoredResource

the monitored resource to which log entries refer. If it is null then a default resource is created based on the project ID and deployment environment.
enhancers List<LoggingEnhancer>

List of LoggingEnhancer instances used to enhance anyLogEntry instances built by this handler.

LoggingHandler(String log, LoggingOptions options, MonitoredResource monitoredResource, List<LoggingEnhancer> enhancers, LogDestinationName destination)

public LoggingHandler(String log, LoggingOptions options, MonitoredResource monitoredResource, List<LoggingEnhancer> enhancers, LogDestinationName destination)

Creates a handler that publishes messages to Cloud Logging. Auto-population of the logs metadata can be opted-out in options argument or in the configuration file. At least one flag LoggingOptions or LoggingConfig has to be explicitly set to false in order to opt out the metadata auto-population.

Parameters
Name Description
log String

the name of the log to which log entries are written
options LoggingOptions

options for the Cloud Logging service
monitoredResource com.google.cloud.MonitoredResource

the monitored resource to which log entries refer. If it is null then a default resource is created based on the project ID and deployment environment.
enhancers List<LoggingEnhancer>

List of LoggingEnhancer instances used to enhance anyLogEntry instances built by this handler.
destination LogDestinationName

the log destination LogDestinationName (see 'logName' parameter in https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry)

Methods

close()

public synchronized void close()

Closes the handler and the associated Logging object.

Overrides

flush()

public void flush()
Overrides

getAutoPopulateMetadata()

public Boolean getAutoPopulateMetadata()

Gets the metadata auto population flag.

Returns
Type Description
Boolean

getFlushLevel()

public Level getFlushLevel()

Get the flush log level.

Returns
Type Description
Level

getLogTarget()

public LoggingHandler.LogTarget getLogTarget()
Returns
Type Description
LoggingHandler.LogTarget

getRedirectToStdout() (deprecated)

public Boolean getRedirectToStdout()
Returns
Type Description
Boolean

getSynchronicity()

public Synchronicity getSynchronicity()

Get the flush log level.

Returns
Type Description
Synchronicity

logEntryFor(LogRecord record)

protected LogEntry.Builder logEntryFor(LogRecord record)
Parameter
Name Description
record LogRecord
Returns
Type Description
LogEntry.Builder

publish(LogRecord record)

public void publish(LogRecord record)
Parameter
Name Description
record LogRecord
Overrides

setAutoPopulateMetadata(boolean value)

public void setAutoPopulateMetadata(boolean value)

Sets the metadata auto population flag.

Parameter
Name Description
value boolean

setFlushLevel(Level flushLevel)

public void setFlushLevel(Level flushLevel)

Sets minimum logging level to log immediately and flush any pending writes.

Parameter
Name Description
flushLevel Level

minimum log level to trigger flush

setLogTarget(LoggingHandler.LogTarget value)

public void setLogTarget(LoggingHandler.LogTarget value)

Configure the destination for ingested logs. If set to STDOUT or STDERR, logs will be printed to the corresponding stream in the Json format that can be parsed by the logging agent. If set to CLOUD_LOGGING, logs will be sent directly to the Google Cloud Logging API.

This method is mutually exclusive with #setRedirectToStdout(boolean).

Parameter
Name Description
value LoggingHandler.LogTarget

setRedirectToStdout(boolean value) (deprecated)

public void setRedirectToStdout(boolean value)

Deprecated. Use #setLogTarget(LogTarget).

Enable/disable redirection to STDOUT. If set to true, logs will be printed to STDOUT in the Json format that can be parsed by the logging agent. If set to false, logs will be ingested to Cloud Logging by calling Logging API.

This method is mutually exclusive with #setLogTarget(LogTarget).

Parameter
Name Description
value boolean

setSynchronicity(Synchronicity synchronicity)

public void setSynchronicity(Synchronicity synchronicity)

Sets synchronicity of logging writes. By default, writes are asynchronous.

Parameter
Name Description
synchronicity Synchronicity
Synchronicity