Upgrading LogStash Log4j configuration to Log4j2

Question

I am trying to migrate my Spring Boot app from Log4j to Log4j 2. I understand the Log4j 2 changed the syntax of .properties configurations from the original Log4j.

Here is a snippet of my original Log4j configuration:

log4j.appender.logstash=org.apache.log4j.net.SocketAppender
log4j.appender.logstash.layout=org.apache.log4j.PatternLayout
log4j.appender.logstash.layout.ConversionPattern=%d{HH:mm:ss.SSS} %-5p %c {2} %x - %m%n
log4j.appender.logstash.Port=4560
log4j.appender.logstash.RemoteHost=logs.example.com
log4j.appender.logstash.ReconnectionDelay=10000

and here is what I updated it to, for Log4j 2:

appender.logstash.type=SocketAppender # Or 'Socket'
appender.logstash.name=logStash
appender.logstash.layout.type=PatternLayout
appender.logstash.layout.pattern=%d{HH:mm:ss.SSS} %-5p %c {2} %x - %m%n
appender.logstash.host=logs.example.com
appender.logstash.port=4560
appender.logstash.reconnectionDelayMillis=10000

However, when I do this, my console and file appenders work just fine, but the LogStash appender throws a Broken pipe error.

I've looked into this an it seems that I may need to wrap the SocketAppender in an AsyncAppender and pointing the ref towards my logStash SocketAppender (as in this documentation), but then I get exceptions that the properties do not exist: appender.async.type=Async appender.async.ref=logStash # Or 'refs', 'appender-ref', etc.

Is a .properties file not the way to go for Async Socket Appenders? I could use some help in migrating from Log4j 1 to 2 via this properties file.

Answer 1

There is a problem in older releases of logstash-log4j2. It was fixed in release 3.2. The newer release may be taken from this link.

Besides, the appender name is not SocketAppender but Socket - that is according to the documentation example, which uses the name Socket in log4j2.xml:

<Appenders>
    <Socket name="socket" host="localhost" port="9500">
      <SerializedLayout />
    </Socket>
</Appenders>

I suppose you should change you log4j2.properties accordingly:

appender.logstash.type=Socket
appender.logstash.name=logStash
appender.logstash.layout.type=PatternLayout
...

I know that this is the matter of habit and "do-not-change-the-working-code" approach but may be it worth to move to xml configuration format while migrating to log4j2, since vast of the examples in the documentation are using it.