appending attribute to EOL with ansible according to prefix - regex

Question

I want to append to the EOL of a log4j.propertis file a string, by using ansible. The problem is that the file has new lines and when trying to use the "backrefs" of the ansible's lineinfile module it adds the string under the line instead of appending to EOL.
The file is log4j properties file which have a line I want to edit. The line start with 'log4j.rootLogger' and I want to append to the EOL a string 'bla'
This is how the line looks like now: log4j.rootLogger=WARN, memory, servlet
Expected after the change: log4j.rootLogger=WARN, memory, servlet, bla
The ansible code I used where rootLoggerAppender is the attribute:
lineinfile:
path: "{{ tomcat_path }}/webapps/ROOT/WEB-INF/config/log4j.properties"
regexp: '^(log4j.rootLogger=\.*)'
line: '\1, {{ rootLoggerAppender }}'
backrefs: yes
update:
when I cat log4j.properties the output as follows:
# servlet appender - logs in memory only, allowing remote read of logs
log4j.rootLogger=DEBUG, memory, servlet
When I have update the ansible code to match the exact line the output was as expected.
lineinfile:
path: "{{ tomcat_path }}/webapps/ROOT/WEB-INF/config/log4j.properties"
regexp: '^(log4j\.rootLogger=DEBUG, memory, servlet)'
line: '\1, {{ rootLoggerAppender }}'
backrefs: yes
I have also noticed the file is a windows file, and when converting it to a linux it worked as expected

Answer 1

Correct regexp is below. Escaped dot match a dot only. The first dot should be escaped, but not the second one. This should match any character.
regexp: '^(log4j\.rootLogger=.*)$'
But this solution is not idempotent. Running this task will add the appender repeatedly
$ cat log4j.properties
log4j.rootLogger=WARN, memory, servlet, bla, bla
The regexp below makes the task idempotent
regexp: '^(log4j\.rootLogger=.*?)(, {{ rootLoggerAppender }})?$'
make the first group non-gready
the second group match 0 or 1 delimited appender
Given the file
$ cat log4j.properties
log4j.rootLogger=WARN, memory, servlet
The idempotent playbook
- hosts: localhost
vars:
rootLoggerAppender: bla
tasks:
- lineinfile:
path: log4j.properties
regexp: '^(log4j\.rootLogger=.*?)(, {{ rootLoggerAppender }})?$'
line: '\1, {{ rootLoggerAppender }}'
backrefs: true
gives
$ cat log4j.properties
log4j.rootLogger=WARN, memory, servlet, bla
The non-idempotent version of the playbook
- hosts: localhost
vars:
rootLoggerAppender: bla
tasks:
- lineinfile:
path: log4j.properties
regexp: '^(log4j\.rootLogger=.*)$'
line: '\1, {{ rootLoggerAppender }}'
backrefs: true
gives the same result
$ cat log4j.properties
log4j.rootLogger=WARN, memory, servlet, bla
, but when running repeatedly it keeps adding the delimited appender
$ cat log4j.properties
log4j.rootLogger=WARN, memory, servlet, bla, bla