tryJson drops logs when JSON object has a field with null value

[nbardiuk]

Describe the bug
tryJson drops logs when JSON object has a field with a null value

To Reproduce
Steps to reproduce the behavior:

1. Use this logback.xml configuration...

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
            <providers>
                <pattern>
                    <pattern>
            {
              "event":"#tryJson{%message}"
            }
          </pattern></pattern>
            </providers>
        </encoder>
    </appender>

2. Execute this logger statement

logger.debug("{\"field\":null}");

3. See error, or unexpected output
   the log is empty

Expected behavior
The log output should contain

"event":{"field":null}

Additional context
This used to work with logstash-logback-encoder 6.6

• logstash-logback-encoder 7.0
• logback version 1.2.7
• jackson version 2.13.0
• java version OpenJDK 64-Bit Server VM 11.0.11+9

[brenuart]

Hi @nbardiuk ,

Thanks for the report. I can confirm this is a bug (a regression) introduced in 7.0
If you register a status listener and print logback statuses on the console (see here) you will notice an exception is thrown while trying to serialise the JSON object. The problem occurs when trying to serialise a complex JsonNode (Object, Map or Array) with one its children elements being null.

I'm sorry but there is no workaround for this issue. We are working on it. Stay tuned...

PS: how urgent is it for you to get this solved? Are you just giving 7.0 a try or do you want to roll it into production?

[nbardiuk]

We tried to use the new version and have noticed the issue.
As a workaround, we can use the previous version, which works great for us.
Thank you for looking into it.