Logstash Ruby filter error

Hi All,

I have written a ruby filter to check if a pattern present in a message and drop the event if pattern is not present.

I'm getting below mentioned error after updating the logstash configuration,

[2018-07-17T23:27:55,117][ERROR][logstash.filters.ruby ] Could not process event: no implicit conversion of LogStash::Event into String {:script_path=>"/etc/logstash/conf.d/extra/scripts/avips.rb", :class=>"TypeError", :backtrace=>["org/jruby/RubyRegexp.java:1107:inmatch'", "/etc/logstash/conf.d/extra/scripts/avips.rb:5:in filter'", "/usr/share/logstash/vendor/bundle/jruby/2.3.0/gems/logstash-filter-ruby-3.1.4/lib/logstash/filters/ruby/script/context.rb:55:inexecute_filter'", "/usr/share/logstash/vendor/bundle/jruby/2.3.0/gems/logstash-filter-ruby-3.1.4/lib/logstash/filters/ruby/script.rb:30:in execute'", "/usr/share/logstash/vendor/bundle/jruby/2.3.0/gems/logstash-filter-ruby-3.1.4/lib/logstash/filters/ruby.rb:98:infile_script'", "/usr/share/logstash/vendor/bundle/jruby/2.3.0/gems/logstash-filter-ruby-3.1.4/lib/logstash/filters/ruby.rb:84:in filter'", "/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:145:indo_filter'", "/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:164:in block in multi_filter'", "org/jruby/RubyArray.java:1734:ineach'", "/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:161:in multi_filter'", "/usr/share/logstash/logstash-core/lib/logstash/filter_delegator.rb:47:inmulti_filter'", "(eval):8476:in block in initialize'", "org/jruby/RubyArray.java:1734:ineach'", "(eval):8473:in block in initialize'", "(eval):1519:inblock in filter_func'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:445:in filter_batch'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:424:inworker_loop'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:386:in block in start_workers'"]}

Below is the code written in ruby file.
def register(params)

def filter(event)
if /^.([sid:\s\d+]).$/.match(event)
return event
return nil

Below is the logstash filter code
filter { if "av" in [tags] and "test" in [tags] { ruby { path => "/etc/logstash/conf.d/extra/scripts/avips.rb" add_tag => ["ips"] } } }

if /^.([sid:\s\d+]).$/.match(event.get("message"))
    return [event]
    return []

The add_tag appears not to work, which feels like a bug to me.

I believe your pattern may need a little tweaking: brackets and parens ([, ], (, and )) have special meaning and need escaping to match literal characters, so your pattern becomes:


However, what you're looking to do can be achieved in normal Logstash flow control using the Drop Filter Plugin:

filter {
  if [message] !~ /^\(\[sid:\s\d+\]\)/ {
    drop { }

Logstash is throwing a ruby exception. That I guess is a reason that add_tag is not working

I want to use regex to match a message and then add a tag accordingly. using if statement seems to be solving the problem. However, I'm still not sure, if ruby filter is returning a Logstash::Event object or array, how to convert that to a string so that logstash can process it further.

No, sir. Even if you fix the exception it still ignores the add_tag.

In general, decoration only occurs in Logstash filter plugins on success, by design. It is up to each plugin to respect this, so there may be a few that behave incorrectly, but generally that is the rule.

The Event is the base unit in a Logstash pipeline -- it has fields and metadata that are manipulated by the filters and used by the outputs. The Ruby filter should return an array of zero or more Events.

It does not decorate. Even when it succeeds.

:thinking: confirmed:

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