Output Format

Owned by Prudence Au
Last updated: Oct 14, 2019
1 min read

Several considerations:

  1. Logs should be human-readable (within reason). 

  2. Shipper and indexing performance and durability depends on logs that can be parsed quickly and reliably.

  3. Consistency means fewer shipping and indexing rules are required.

Text Output

TODO: 20190115 - do not take the example in this section until I reverify it in terms of the reworked spec example in 

https://gerrit.onap.org/r/#/c/62405/20/reference/logging-kubernetes/logdemonode/charts/logdemonode/resources/config/logback.xml

LOG-630: Single logback.xml in OOM onap parent chartClosed

ONAP needs to strike a balance between human-readable and machine-readable logs. This means:

  • The use of PIPE (|) as a delimiter. (Previously tab, and before that ... pipe).

  • Escaping all messages, exceptions, MDC values, Markers, etc. to replace tabs and pipes in their content.

  • Escaping all newlines with \n so that each entry is on one line. 

In logback, this looks like:

<property name="defaultPattern" value="%nopexception%logger |%date{yyyy-MM-dd'T'HH:mm:ss.SSSXXX,UTC} |%level |%replace(%replace(%replace(%message){'\t','\\\\t'}){'\n','\\\\n'}){'|','\\\\|'} |%replace(%replace(%replace(%mdc){'\t','\\\\t'}){'\n','\\\\n'}){'|','\\\\|'} |%replace(%replace(%replace(%rootException){'\t','\\\\t'}){'\n','\\\\n'}){'|','\\\\|'} |%replace(%replace(%replace(%marker){'\t','\\\\t'}){'\n','\\\\n'}){'|','\\\\|'} |%thread |%n"/>

The output of which, with MDCs, a Marker and a nested exception, with newlines added for readability, looks like:

org.onap.example.component1.subcomponent1.LogbackTest |2017-08-06T16:09:03.594Z |ERROR |Here's an error, that's usually bad |key1=value1, key2=value2 with space, key5=value5"with"quotes, key3=value3\nwith\nnewlines, key4=value4\twith\ttabs |java.lang.RuntimeException: Here's Johnny \n\tat org.onap.example.component1.subcomponent1.LogbackTest.main(LogbackTest.java:24) \nWrapped by: java.lang.RuntimeException: Little pigs, little pigs, let me come in \n\tat org.onap.example.component1.subcomponent1.LogbackTest.main(LogbackTest.java:27) |AMarker1 |main

Default Logstash indexing rules understand output in this format.

XML Output

For Log4j 1.X output, since escaping is not supported, the best alternative is to emit logs in XML format, we will expand on JSON support

There may be other instances where XML (or JSON) output may be desirable. Default indexing rules support 

Default Logstash indexing rules understand the XML output of Log4J's XMLLayout.

Note that we're hoping that support for indexing of XML output can be deprecated during Beijing. This relies on the adoption of ODL Carbon, which should eliminate any remnant of Log4J1.X.