Log4j – Log4j Filters - Apache Log4j 2

Filters

Filters allow Log Events to be evaluated to determine if or how they should be published. A Filter will be called on one of its filter methods and will return a Result, which is an Enum that has one of 3 values - ACCEPT, DENY or NEUTRAL.

Filters may be configured in one of four locations:

Context-wide Filters are configured directly in the configuration. Events that are rejected by these filters will not be passed to loggers for further processing. Once an event has been accepted by a Context-wide filter it will not be evaluated by any other Context-wide Filters nor will the Logger's Level be used to filter the event. The event will be evaluated by Logger and Appender Filters however.
Logger Filters are configured on a specified Logger. These are evaluated after the Context-wide Filters and the Log Level for the Logger. Events that are rejected by these filters will be discarded and the event will not be passed to a parent Logger regardless of the additivity setting.
Appender Filters are used to determine if a specific Appender should handle the formatting and publication of the event.
Appender Reference Filters are used to determine if a Logger should route the event to an appender.

BurstFilter

The BurstFilter provides a mechanism to control the rate at which LogEvents are processed by silently discarding events after the maximum limit has been reached.

Burst Filter Parameters
Parameter Name	Type	Description
level	String	Level of messages to be filtered. Anything at or below this level will be filtered out if `maxBurst` has been exceeded. The default is WARN meaning any messages that are higher than warn will be logged regardless of the size of a burst.
rate	float	The average number of events per second to allow.
maxBurst	integer	The maximum number of events that can occur before events are filtered for exceeding the average rate. The default is 10 times the rate.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

A configuration containing the BurstFilter might look like:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

CompositeFilter

The CompositeFilter provides a way to specify more than one filter. It is added to the configuration as a filters element and contains other filters to be evaluated. The filters element accepts no parameters.

A configuration containing the CompositeFilter might look like:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Filters>
    <Marker marker="EVENT" onMatch="ACCEPT" onMismatch="NEUTRAL"/>
    <DynamicThresholdFilter key="loginId" defaultThreshold="ERROR"
                            onMatch="ACCEPT" onMismatch="NEUTRAL">
      <KeyValuePair key="User1" value="DEBUG"/>
    </DynamicThresholdFilter>
  </Filters>
  <Appenders>
    <File name="Audit" fileName="logs/audit.log">
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
    </File>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Logger name="EventLogger" level="info">
      <AppenderRef ref="Audit"/>
    </Logger>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

DynamicThresholdFilter

The DynamicThresholdFilter allows filtering by log level based on specific attributes. For example, if the user's loginId is being captured in the ThreadContext Map then it is possible to enable debug logging for only that user.

Dynamic Threshold Filter Parameters
Parameter Name	Type	Description
defaultThreshold	String	Level of messages to be filtered. If there is no matching key in the key/value pairs then this level will be compared against the event's level.
keyValuePair	KeyValuePair[]	One or more KeyValuePair elements that define the matching value for the key and the Level to evaluate when the key matches.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

Here is a sample configuration containing the DynamicThresholdFilter:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <DynamicThresholdFilter key="loginId" defaultThreshold="ERROR"
                          onMatch="ACCEPT" onMismatch="NEUTRAL">
    <KeyValuePair key="User1" value="DEBUG"/>
  </DynamicThresholdFilter>
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

MapFilter

The MapFilter allows filtering against data elements that are in a MapMessage.

Map Filter Parameters
Parameter Name	Type	Description
keyValuePair	KeyValuePair[]	One or more KeyValuePair elements that define the key in the map and the value to match on. If the same key is specified more than once then the check for that key will automatically be an "or" since a Map can only contain a single value.
operator	String	If the operator is "or" then a match by any one of the key/value pairs will be considered to be a match, otherwise all the key/value pairs must match.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

As in this configuration, the MapFilter can be used to log particular events:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <MapFilter onMatch="ACCEPT" onMismatch="NEUTRAL" operator="or">
    <KeyValuePair key="eventId" value="Login"/>
    <KeyValuePair key="eventId" value="Logout"/>
  </MapFilter>
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

This sample configuration will exhibit the same behavior as the preceding example since the only logger configured is the root.

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <MapFilter onMatch="ACCEPT" onMismatch="NEUTRAL" operator="or">
        <KeyValuePair key="eventId" value="Login"/>
        <KeyValuePair key="eventId" value="Logout"/>
      </MapFilter>
      <AppenderRef ref="RollingFile">
      </AppenderRef>
    </Root>
  </Loggers>
</Configuration>

This third sample configuration will exhibit the same behavior as the preceding examples since the only logger configured is the root and the root is only configured with a single appender reference.

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile">
        <MapFilter onMatch="ACCEPT" onMismatch="NEUTRAL" operator="or">
          <KeyValuePair key="eventId" value="Login"/>
          <KeyValuePair key="eventId" value="Logout"/>
        </MapFilter>
      </AppenderRef>
    </Root>
  </Loggers>
</Configuration>

MarkerFilter

The MarkerFilter compares the configured Marker value against the Marker that is included in the LogEvent. A match occurs when the Marker name matches either the Log Event's Marker or one of its parents.

Marker Filter Parameters
Parameter Name	Type	Description
marker	String	The name of the Marker to compare.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

A sample configuration that only allows the event to be written by the appender if the Marker matches:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <MarkerFilter marker="FLOW" onMatch="ACCEPT" onMismatch="DENY"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

RegexFilter

The RegexFilter allows the formatted or unformatted message to be compared against a regular expression.

Regex Filter Parameters
Parameter Name	Type	Description
regex	String	The regular expression.
useRawMsg	boolean	If true the unformatted message will be used, otherwise the formatted message will be used. The default value is false.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

A sample configuration that only allows the event to be written by the appender if it contains the word "test":

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <RegexFilter regex=".* test .*" onMatch="ACCEPT" onMismatch="DENY"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

StructuredDataFilter

The StructuredDataFilter is a MapFilter that also allows filtering on the event id, type and message.

StructuredData Filter Parameters
Parameter Name	Type	Description
keyValuePair	KeyValuePair[]	One or more KeyValuePair elements that define the key in the map and the value to match on. "id", "id.name", "type", and "message" should be used to match on the StructuredDataId, the name portion of the StructuredDataId, the type, and the formatted message respectively. If the same key is specified more than once then the check for that key will automatically be an "or" since a Map can only contain a single value.
operator	String	If the operator is "or" then a match by any one of the key/value pairs will be considered to be a match, otherwise all the key/value pairs must match.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

As in this configuration, the StructuredDataFilter can be used to log particular events:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <StructuredDataFilter onMatch="ACCEPT" onMismatch="NEUTRAL" operator="or">
    <KeyValuePair key="id" value="Login"/>
    <KeyValuePair key="id" value="Logout"/>
  </StructuredDataFilter>
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

ThreadContextMapFilter

The ThreadContextMapFilter allows filtering against data elements that are in the ThreadContext Map.

ThreadContext Map Filter Parameters
Parameter Name	Type	Description
keyValuePair	KeyValuePair[]	One or more KeyValuePair elements that define the key in the map and the value to match on. If the same key is specified more than once then the check for that key will automatically be an "or" since a Map can only contain a single value.
operator	String	If the operator is "or" then a match by any one of the key/value pairs will be considered to be a match, otherwise all the key/value pairs must match.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

A configuration containing the ThreadContextMapFilter might look like:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <ThreadContextMapFilter onMatch="ACCEPT" onMismatch="NEUTRAL" operator="or">
    <KeyValuePair key="User1" value="DEBUG"/>
    <KeyValuePair key="User2" value="WARN"/>
  </ThreadContextMapFilter>
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

The ThreadContextMapFilter can also be applied to a logger for filtering:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <BurstFilter level="INFO" rate="16" maxBurst="100"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
      <ThreadContextMapFilter onMatch="ACCEPT" onMismatch="NEUTRAL" operator="or">
        <KeyValuePair key="foo" value="bar"/>
        <KeyValuePair key="User2" value="WARN"/>
      </ThreadContextMapFilter>
    </Root>
  </Loggers>
</Configuration>

ThresholdFilter

This filter returns the onMatch result if the level in the LogEvent is the same or more specific than the configured level and the onMismatch value otherwise. For example, if the ThresholdFilter is configured with Level ERROR and the LogEvent contains Level DEBUG then the onMismatch value will be returned since ERROR events are more specific than DEBUG.

Threshold Filter Parameters
Parameter Name	Type	Description
level	String	A valid Level name to match on.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

A sample configuration that only allows the event to be written by the appender if the level matches:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <ThresholdFilter level="TRACE" onMatch="ACCEPT" onMismatch="DENY"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>

TimeFilter

The time filter can be used to restrict filter to only a certain portion of the day.

Time Filter Parameters
Parameter Name	Type	Description
start	String	A time in HH:mm:ss format.
end	String	A time in HH:mm:ss format. Specifying an end time less than the start time will result in no log entries being written.
timezone	String	The timezone to use when comparing to the event timestamp.
onMatch	String	Action to take when the filter matches. May be ACCEPT, DENY or NEUTRAL. The default value is NEUTRAL.
onMismatch	String	Action to take when the filter does not match. May be ACCEPT, DENY or NEUTRAL. The default value is DENY.

A sample configuration that only allows the event to be written by the appender from 5:00 to 5:30 am each day using the default timezone:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
  <Appenders>
    <RollingFile name="RollingFile" fileName="logs/app.log"
                 filePattern="logs/app-%d{MM-dd-yyyy}.log.gz">
      <TimeFilter start="05:00:00" end="05:30:00" onMatch="ACCEPT" onMismatch="DENY"/>
      <PatternLayout>
        <pattern>%d %p %c{1.} [%t] %m%n</pattern>
      </PatternLayout>
      <TimeBasedTriggeringPolicy />
    </RollingFile>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="RollingFile"/>
    </Root>
  </Loggers>
</Configuration>