log4j2 - Syslog appender and PatternLayout

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I need to log events into the syslog. I use lo4j2 and the syslog appender. My appenders block in log4j2.xml looks like this:

        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        <Syslog name="syslog" host="localhost" port="514" protocol="UDP" charset="ISO-8859-1">
        <RollingFile name="AppLog" fileName="/var/log/app.log"
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>

As you can see I have a Console appender and RollingFile appender with a specific PatternLayout. I want to use the same PatternLayout for the Syslog appender. However, the log messages in the syslog seem to always use a predefined layout. I tried to do the following:

<Syslog name="syslog" host="localhost" port="514" protocol="UDP" charset="ISO-8859-1">
    <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>

But this does not have any effect. the syslog messages still have the same predfined format.

How can I determine the format of my log messages that go into the syslog?

As mentioned in this log4j2 bug report, the developers of log4j2 coded the SyslogAppender as a SocketAppender hardwired to a SyslogLayout

because it is intended to conform to either the original syslog format or RFC 5424. No other Layout should be permitted.

They unfortunately did not realize that the RFC 5424 specifications do not enforce any particular format for the message contained in the log, that in the Log4j2 implementation is only the %m portion of the log.

To solve this issue, a solution (suggested in the same bug report) is to reproduce the syslog format using a PatternLayout inside a SocketAppender, like so

<Socket name="SYSLOG" host="localhost" port="514" protocol="UDP">
    pattern="&lt;1&gt;%d{MMM dd HH:mm:ss} ${hostName} appName: {

This will write well-formatted RFC5424 logs to local 514 port through UDP. Following is a sample log output:

Sep 14 10:40:50 app-hostname app-name: { "host":"host-name-01", "thread":"http-nio-8080-exec-4", "level":"DEBUG", "logger":"ExecuteTimeInterceptor", "line":52, "message":"GET &#x2F;health 200 served in 3", "exception":"" }

Log4j – Log4j 2 Appenders, Every Appender must implement the Appender interface. Each column can specify either a StringLayout (e.g., a PatternLayout) along with an optional conversion This attribute only applies to RFC 5424 syslog records. Log4j2 - Syslog appender and PatternLayout I need to write events to syslog. I am using lo4j2 and syslog appender. The appender append block in log

I don't believe you can use a pattern on the basic Syslog appender.

From the docs it states that

"SyslogAppender is a SocketAppender that writes its output to a remote destination specified by a host and port in a format that conforms with either the BSD Syslog format or the RFC 5424" http://logging.apache.org/log4j/2.x/manual/appenders.html#SyslogAppender

However, it does allow you to specify "format = RFC 5424"

If you use RFC 5424

Then you can put a PatterLayout in the loggerFields parameter. See http://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout

Hope that helps!

Log4j – Log4j 2 Layouts, An Appender uses a Layout to format a LogEvent into a form that meets the needs of See PatternLayout for information on the pattern strings. An Appender uses a Layout to format a LogEvent into a form that meets the needs of whatever will be consuming the log event. In Log4j 1.x and Logback Layouts were expected to transform an event into a String. In Log4j 2 Layouts return a byte array. This allows the result of the Layout to be useful in many more types of Appenders.

You can use SocketAppender and PatternLayout to format syslog (syslog-ng) messages. To support dynamic Severities with a fixed Facility (e.g.: 'user-level messages' - see RFC5424) the pattern should look like this:

<Socket name="SYSLOG" host="${env:INTERFACE}" port="514" protocol="UDP">
   <PatternLayout pattern="&lt;%level{TRACE=15, DEBUG=15, INFO=14, WARN=12, ERROR=11, Fatal=11,&gt;%replace{${env:APPLICATION_NAME}}{\r}{}[%X{PID}] %t(%T) %c{10} - %m%n"/>

To calculate the Priority value (PRIVAL) for Facility 'user-level message' and Severity 'informational messages' - see RFC5424) the following example might help:

Syslog:          Facility  | Severity
Numerical Code:      1          6
Bin:             0 0 0 0 1 |  1 1 0
Dec:                 8     +    6    =  14


Intro to Log4j2, In Log4J2, an appender is simply a destination for log events; it can be as But there exists many more variables and formatting in the PatternLayout. For example, if the Syslog appender fails to send events to the remote  Log4j 2 is a new and improved version of the classic Log4j framework. In this article, we'll introduce the most common appenders, layouts, and filters via practical examples. In Log4J2, an appender is simply a destination for log events; it can be as simple as a console and can be complex like any RDBMS.

You can use add additional elements to an RFC5424 formatted SyslogAppender message using the LoggerFields tag like this:

  <KeyValuePair key="thread" value="%t"/>
  <KeyValuePair key="priority" value="%p"/>
  <KeyValuePair key="category" value="%c"/>
  <KeyValuePair key="exception" value="%ex"/>

I then pull these out using rsyslog's RFC5424 parsing module, mmpstrucdata, to create json tree. The rsyslog.conf template for accessing them looks like:

template(name="jsondump" type="string" string="'%$!rfc5424-sd!mdc@18060!thread%', '%$!rfc5424-sd!mdc@18060!priority%', '%$!rfc5424-sd!mdc@18060!category%', '%$!rfc5424-sd!mdc@18060!exception%'")

I was just trying to do the same and thought I'd share what worked for me. - Sam

log4j2 - Syslog appender and PatternLayout, Log4j2 - Syslog appender and PatternLayout. As mentioned in this log4j2 error report , log4j2 developers encoded SyslogAppender as a SocketAppender associated with SyslogLayout. You can use SocketAppender and PatternLayout to format syslog messages (syslog-ng). Layouts. An Appender uses a Layout to format a LogEvent into a form that meets the needs of whatever will be consuming the log event. In Log4j 1.x and Logback Layouts were expected to transform an event into a String. In Log4j 2 Layouts return a byte array.

I used the config posted by butcher82, but had to change it a bit to produce the result I needed.

What I got in the end is a message with the correct priority, timestamp (without leading zeros for days), host and a message part. The mapping between syslog and log4J level is used as defined in org.apache.log4j.Level and the facility is set to 1 (user-level messages), to simplify the priority calculation.

This pattern should be compatible with RFC-3164:

<Socket name="SysLogAppender" host="localhost" port="514" protocol="UDP">
    <PatternLayout pattern="&lt;%level{TRACE=7, DEBUG=7, INFO=6, WARN=4, ERROR=3, Fatal=0}&gt;%d{MMM d hh:mm:ss} ${hostName} %m%n"/>

Below is the produced output:

<3>Dec 15 09:59:16 foo.bar.hostname this is a test message

Note: One might add an application name or pid, after the hostname.

Log Appender: What Is It and Why Would You Use It?, is the part of a logging system that's responsible for sending the log messages to some destination or medium. The PatternLayout class extends the abstract org.apache.log4j.Layout class and overrides the format() method to structure the logging information according to a supplied pattern. PatternLayout is also a simple Layout object that provides the following- Bean Property which can be set using the configuration file:

log4j - Configuration, object has different properties associated with it, and these properties indicate the behavior of that object. Java log4j logging Introduction. log4j is “a popular logging package written in Java. One of its distinctive features is the notion of inheritance in loggers. Using a logger hierarchy it is possible to control which log statements are output at arbitrary granularity.”

Log4j2 RollingFileAppender example, is set to true by default, that is children inherit the appenders of their ancestors by default. If this variable is set to false then the appenders found in the ancestors of this logger are not used. Appenders. Appenders are responsible for delivering LogEvents to their destination. Every Appender must implement the Appender interface. Most Appenders will extend AbstractAppender which adds Lifecycle and Filterable support. Lifecycle allows components to finish initialization after configuration has completed and to perform cleanup during

Additivity Property - Apache Logging Services, log4j2 syslog appender example patternlayout log4j2 log4j2 patternlayout replace example log4j2 multiple appenders properties log4j2 additivity log4j highlight  I have set up a java app to send log4j2 logs to syslog on Ubuntu 10.04.4 LTS. I see that log4j2 seems to be ok, I don't see errors in the startup. But I don't see any log messages getting to syslog anywhere. This is more of a log4j2 and syslog setup question than sumo logic, but thought I'd try. Here's the log4j2 config file:

  • This does not allow writing messages to a custom facility, such as local4.
  • This seems like the right direction, but I don't quite understand how to use the <loggerFields> tag in my log4j2.xml. what should I put in the 'key' attribute? An example would be very useful.
  • @conornicol, I believe you misunderstand the PatternLayout part. It's by far not possible to inject a custom PatternLayout into the RFC-5424 Layout. What you're influencing is the part within []. You're not affecting the message part of that layout.
  • Is there way to add these LoggerFields in log4j2.properties files. I want to do it for elasticsearch 5x and it support only log4j.properties no log4j2.xml and I don't see example any where on net and docs for LoggerFields in properties file
  • Adding this to properties files does not work appender.sumo_syslog.loggerFields={'key' : 'priority', 'value' : '%p'}