Liberty Kernel

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Liberty Kernel

The kernel

API packages provided by this feature

com.ibm.websphere.logging.hpel.reader
com.ibm.websphere.logging.hpel.reader.filters
com.ibm.websphere.logging.hpel.writer

SPI packages provided by this feature

com.ibm.websphere.crypto
com.ibm.websphere.ras
com.ibm.websphere.ras
com.ibm.websphere.ras.annotation
com.ibm.websphere.ras.annotation
com.ibm.ws.ffdc
com.ibm.ws.ffdc
com.ibm.wsspi.config
com.ibm.wsspi.kernel.filemonitor
com.ibm.wsspi.kernel.service.location
com.ibm.wsspi.kernel.service.utils
com.ibm.wsspi.logging
com.ibm.wsspi.logging
com.ibm.wsspi.threading
org.eclipse.equinox.log
org.eclipse.osgi.framework.console
org.eclipse.osgi.framework.eventmgr
org.eclipse.osgi.framework.log
org.eclipse.osgi.service.datalocation
org.eclipse.osgi.service.debug
org.eclipse.osgi.service.environment
org.eclipse.osgi.service.localization
org.eclipse.osgi.service.resolver
org.eclipse.osgi.service.runnable
org.eclipse.osgi.service.security
org.eclipse.osgi.service.urlconversion
org.eclipse.osgi.signedcontent
org.eclipse.osgi.storagemanager
org.eclipse.osgi.util
org.osgi.service.cm
org.osgi.service.component
org.osgi.service.coordinator
org.osgi.service.event
org.osgi.service.log
org.osgi.service.metatype

Feature configuration elements

We can use the following elements in the server.xml file to configure the Liberty Kernel feature:

config
executor
featureManager

feature

fileset
logging
zosLogging

config

Defines how the server processes configuration information.

Attribute name Data type Default Description
monitorInterval A period of time with millisecond precision 500ms Rate at which the server checks for configuration updates. Specify a positive integer followed by a unit of time, which can be hours (h), minutes (m), seconds (s), or milliseconds (ms). For example, specify 500 milliseconds as 500ms. We can include multiple values in a single entry. For example, 1s500ms is equivalent to 1.5 seconds.
onError

IGNORE
FAIL
WARN

WARN Action to take after a incurring a configuration error.

IGNORE

Server will not issue any warning and error messages when it incurs a configuration error.

FAIL

Server will issue a warning or error message on the first error occurrence and then stop the server.

WARN

Server will issue warning and error messages when it incurs a configuration error.

updateTrigger

mbean
polled
disabled

polled Configuration update method or trigger.

mbean

Server will only update the configuration when prompted by an MBean called by an external program such as an integrated development environment or a management application.

polled

Server will scan for changes at the polling interval on all the configuration files and update the runtime configuration with the changes detected.

disabled

Disables all update monitoring. Configuration changes will not be applied while the server is running.

executor

Defines settings for the Liberty kernel default executor. Note that there is always one and exactly one default executor, for use by the Liberty runtime only and not directly accessible by applications. Applications that need to configure and use executors should instead use Managed Executors.

Attribute name Data type Default Description
coreThreads int -1 Steady-state or core number of threads to associate with the executor. The number of threads associated with the executor will quickly grow to this number. If this value is less than 0, a default value is used. This default value is calculated based on the number of hardware threads on the system.
keepAlive A period of time with millisecond precision 60s Amount of time to keep an idle thread in the pool before allowing it to terminate. Specify a positive integer followed by a unit of time, which can be hours (h), minutes (m), seconds (s), or milliseconds (ms). For example, specify 500 milliseconds as 500ms. We can include multiple values in a single entry. For example, 1s500ms is equivalent to 1.5 seconds.
maxThreads int -1 Maximum number of threads that can be associated with the executor. If greater than 0, this value must be greater than or equal to the value of coreThreads. If the value of maxThreads is less than or equal to 0, the maximum number of threads is unbounded. Note that the actual number of threads associated with the executor is determined dynamically by the Liberty kernel, so leaving the maximum threads unbounded does not imply that the runtime will actively create large amounts of threads; it simply lets the Liberty kernel decide how many threads to associate with the executor without having a defined upper boundary.
name string Default Executor The name of the Liberty kernel default executor.
rejectedWorkPolicy

CALLER_RUNS
ABORT

ABORT Policy to employ when the executor is unable to stage work for execution.

CALLER_RUNS

Execute the work immediately on the caller's thread.

ABORT

Raise an exception.

stealPolicy

STRICT
NEVER
LOCAL

LOCAL The work-stealing policy to employ. The options for this policy determine how work is queued, and how threads obtain queued work.

STRICT

All threads that generate work own a local work pile. Threads that are associated with the executor take work from other threads when the local work pile is exhausted.

NEVER

A global work queue is used to feed work to threads that are associated with the executor. No stealing will occur.

LOCAL

A global work queue is used for work generated by threads that are not associated with the executor. Work generated by threads associated with the executor is placed on a local work pile. This work pile is owned by the generating thread, unless another thread steals it. Threads that are associated with the executor take work associated with other threads if the local work pile is empty and there is no work on the global work queue.

featureManager

Defines how the server loads features.

Attribute name Data type Default Description
onError

IGNORE
FAIL
WARN

WARN Action to take after a failure to load a feature.

IGNORE

Server will not issue any warning and error messages when it incurs a configuration error.

FAIL

Server will issue a warning or error message on the first error occurrence and then stop the server.

WARN

Server will issue warning and error messages when it incurs a configuration error.

featureManager > feature

Description: Specifies a feature to be used when the server runs.

Required: false

Data type: string

fileset

Specifies a set of files starting from a base directory and matching a set of patterns.

Attribute name Data type Default Description
caseSensitive boolean true Boolean to indicate whether or not the search should be case sensitive (default: true).
dir Path to a directory ${server.config.dir} The base directory to search for files.
excludes string The comma or space separated list of file name patterns to exclude from the search results, by default no files are excluded.
id string A unique configuration ID.
includes string * The comma or space separated list of file name patterns to include in the search results (default: *).
scanInterval A period of time with millisecond precision 0 Scanning interval to check the fileset for changes as a long with a time unit suffix h-hour, m-minute, s-second, ms-millisecond (e.g. 2ms or 5s). Disabled (scanInterval=0) by default. Specify a positive integer followed by a unit of time, which can be hours (h), minutes (m), seconds (s), or milliseconds (ms). For example, specify 500 milliseconds as 500ms. We can include multiple values in a single entry. For example, 1s500ms is equivalent to 1.5 seconds.

logging

Controls the capture and output of log and trace messages.

Attribute name Data type Default Description
consoleLogLevel

ERROR
WARNING
AUDIT
OFF
INFO

AUDIT The logging level used to filter messages written to system streams. The default value is audit.

ERROR

Error messages will be written to the system error stream.

WARNING

Warning messages will be written to the system output stream. Error messages will be written to the system error stream.

AUDIT

Audit and warning messages will be written to the system output stream. Error messages will be written to the system error stream.

OFF

No server output will be written to system streams. Only JVM output will be written to system streams.

INFO

Info, audit, and warning messages will be written to the system output stream. Error messages will be written to the system error stream.

copySystemStreams boolean true If true, write System.out to the system output stream and System.err to the system error stream. If false, System.out and System.err will write to configured logs like messages.log or trace.log, but not to the system streams. The default value is true.
hideMessage string The list of messages, separated by a comma, configured to be hidden from the console.log and message.log files. If the messages are configured to be hidden, then they are redirected to the trace.log file.
logDirectory Path to a directory ${server.output.dir}/logs Location of the directory for log files. The default value is ${server.output.dir}/logs.
maxFileSize int
Minimum: 0
20 Maximum size of a log file, in megabytes, before being rolled over; a value of 0 means no limit.
maxFiles int
Minimum: 0
2 Maximum number of log files that will be kept, before the oldest file is removed; a value of 0 means no limit.
messageFileName string messages.log Name of the file to which message output will be written relative to the configured log directory. The default value is messages.log.
suppressSensitiveTrace boolean false The server trace can expose sensitive data when tracing untyped data, such as bytes received over a network connection. If true, prevent potentially sensitive information from being exposed in log and trace files. The default value is false.
traceFileName string trace.log Name of the file to which trace output will be written relative to the configured log directory. The default value is trace.log.
traceFormat

ENHANCED
BASIC
ADVANCED

ENHANCED This format is used for the trace log.

ENHANCED

Use the enhanced basic trace format.

BASIC

Use the basic trace format.

ADVANCED

Use the advanced trace format.

traceSpecification string *=info A trace specification that conforms to the trace specification grammar and specifies the initial state for various trace components. An empty value is allowed and treated as 'disable all trace'. Any component that is not specified is initialized to a default state of *=info.

zosLogging

Configuration properties for logging on z/OS.

Attribute name Data type Default Description
enableLogToMVS boolean false Enable routing of USS-started server messages to the MVS console.

Attribute name	Data type	Default	Description
coreThreads	int	-1	Steady-state or core number of threads to associate with the executor. The number of threads associated with the executor will quickly grow to this number. If this value is less than 0, a default value is used. This default value is calculated based on the number of hardware threads on the system.
keepAlive	A period of time with millisecond precision	60s	Amount of time to keep an idle thread in the pool before allowing it to terminate. Specify a positive integer followed by a unit of time, which can be hours (h), minutes (m), seconds (s), or milliseconds (ms). For example, specify 500 milliseconds as 500ms. We can include multiple values in a single entry. For example, 1s500ms is equivalent to 1.5 seconds.
maxThreads	int	-1	Maximum number of threads that can be associated with the executor. If greater than 0, this value must be greater than or equal to the value of coreThreads. If the value of maxThreads is less than or equal to 0, the maximum number of threads is unbounded. Note that the actual number of threads associated with the executor is determined dynamically by the Liberty kernel, so leaving the maximum threads unbounded does not imply that the runtime will actively create large amounts of threads; it simply lets the Liberty kernel decide how many threads to associate with the executor without having a defined upper boundary.
name	string	Default Executor	The name of the Liberty kernel default executor.
rejectedWorkPolicy	CALLER_RUNS ABORT	ABORT	Policy to employ when the executor is unable to stage work for execution. CALLER_RUNS Execute the work immediately on the caller's thread. ABORT Raise an exception.
stealPolicy	STRICT NEVER LOCAL	LOCAL	The work-stealing policy to employ. The options for this policy determine how work is queued, and how threads obtain queued work. STRICT All threads that generate work own a local work pile. Threads that are associated with the executor take work from other threads when the local work pile is exhausted. NEVER A global work queue is used to feed work to threads that are associated with the executor. No stealing will occur. LOCAL A global work queue is used for work generated by threads that are not associated with the executor. Work generated by threads associated with the executor is placed on a local work pile. This work pile is owned by the generating thread, unless another thread steals it. Threads that are associated with the executor take work associated with other threads if the local work pile is empty and there is no work on the global work queue.

Attribute name	Data type	Default	Description
caseSensitive	boolean	true	Boolean to indicate whether or not the search should be case sensitive (default: true).
dir	Path to a directory	${server.config.dir}	The base directory to search for files.
excludes	string		The comma or space separated list of file name patterns to exclude from the search results, by default no files are excluded.
id	string		A unique configuration ID.
includes	string	*	The comma or space separated list of file name patterns to include in the search results (default: *).
scanInterval	A period of time with millisecond precision	0	Scanning interval to check the fileset for changes as a long with a time unit suffix h-hour, m-minute, s-second, ms-millisecond (e.g. 2ms or 5s). Disabled (scanInterval=0) by default. Specify a positive integer followed by a unit of time, which can be hours (h), minutes (m), seconds (s), or milliseconds (ms). For example, specify 500 milliseconds as 500ms. We can include multiple values in a single entry. For example, 1s500ms is equivalent to 1.5 seconds.

Attribute name	Data type	Default	Description
consoleLogLevel	ERROR WARNING AUDIT OFF INFO	AUDIT	The logging level used to filter messages written to system streams. The default value is audit. ERROR Error messages will be written to the system error stream. WARNING Warning messages will be written to the system output stream. Error messages will be written to the system error stream. AUDIT Audit and warning messages will be written to the system output stream. Error messages will be written to the system error stream. OFF No server output will be written to system streams. Only JVM output will be written to system streams. INFO Info, audit, and warning messages will be written to the system output stream. Error messages will be written to the system error stream.
copySystemStreams	boolean	true	If true, write System.out to the system output stream and System.err to the system error stream. If false, System.out and System.err will write to configured logs like messages.log or trace.log, but not to the system streams. The default value is true.
hideMessage	string		The list of messages, separated by a comma, configured to be hidden from the console.log and message.log files. If the messages are configured to be hidden, then they are redirected to the trace.log file.
logDirectory	Path to a directory	${server.output.dir}/logs	Location of the directory for log files. The default value is ${server.output.dir}/logs.
maxFileSize	int Minimum: 0	20	Maximum size of a log file, in megabytes, before being rolled over; a value of 0 means no limit.
maxFiles	int Minimum: 0	2	Maximum number of log files that will be kept, before the oldest file is removed; a value of 0 means no limit.
messageFileName	string	messages.log	Name of the file to which message output will be written relative to the configured log directory. The default value is messages.log.
suppressSensitiveTrace	boolean	false	The server trace can expose sensitive data when tracing untyped data, such as bytes received over a network connection. If true, prevent potentially sensitive information from being exposed in log and trace files. The default value is false.
traceFileName	string	trace.log	Name of the file to which trace output will be written relative to the configured log directory. The default value is trace.log.
traceFormat	ENHANCED BASIC ADVANCED	ENHANCED	This format is used for the trace log. ENHANCED Use the enhanced basic trace format. BASIC Use the basic trace format. ADVANCED Use the advanced trace format.
traceSpecification	string	*=info	A trace specification that conforms to the trace specification grammar and specifies the initial state for various trace components. An empty value is allowed and treated as 'disable all trace'. Any component that is not specified is initialized to a default state of *=info.