how to migrate mysql data to ElasticSearch realtime

The best open source solution would be this. You can run this as a command line and give the incremental logic too in the command.

GO through this session to get a complete idea.

There is an existing project which takes your binlog, transforms it and ships it to Elasticsearch, You can check it out at: https://github.com/siddontang/go-mysql-elasticsearch

Another one would be this one: https://github.com/noplay/python-mysql-replication.

Note, however, that whichever you pick, it's a good practice to pre-create your index and mappings before indexing your binlog. That gives you more control over your data.

UPDATE:

Here is another interesting blog article on the subject: How to keep Elasticsearch synchronized with a relational database using Logstash