DEVELOPER.md in logstash-input-mongodb-0.3.3 vs DEVELOPER.md in logstash-input-mongodb-0.4.0

@@ -1,2 +1,46 @@
 # logstash-input-example
 Example input plugin. This should help bootstrap your effort to write your own input plugin!
+
+## Build new gem
+
+Change version in logstash-input-mongodb.gemspec
+
+And build new gem:
+
+```bash
+$ gem build logstash-input-mongodb.gemspec
+```
+
+## Developing
+
+### Use rvm on Ubuntu
+
+1. Install rvm https://rvm.io/
+
+2. Install jruby
+
+```bash
+$ rvm install jruby 1.7.25
+```
+
+3. Use jruby from rvm
+
+```bash
+$ rvm alias create default jruby-1.7.25
+$ rvm use default
+$ /bin/bash --login
+$ gem install bundler
+$ bundle install
+```
+
+4. Run tests
+
+* Unit
+```bash
+$ ruby test/*
+```
+
+* Rspec (but it needs mongo on localhost, it would be nice to have it is not depended on local mongo)
+```bash
+$ ./bin/rspec
+```