Update README.md

README.md

@@ -83,6 +83,13 @@ Since LNEx relies on OSM gazetteers for extraction, the performance of the tool
    - "build_hash" : "929b9739cae115e73c346cb5f9a6f24ba735a743",
    - "build_timestamp" : "2015-07-16T14:31:07Z"
 
+## Debugging ##
+
+There are a few things you need to make sure of before you get Photon to work well with LNEx.
+- You should have the latest photon jar file (see above).
+- Your elasticsearch-dsl in python should be compatible with the Photon version you downloaded. You should first check the version of elasticsearch by running `curl -XGET 'http://localhost:9200'`, you will find the version number under `version/number`.
+- The current version of elasticsearch using by Photon is `5.5.0`, so we should get the compatible elasticsearch-dsl to use it in our Python code. You can do that by visiting [this page](https://elasticsearch-dsl.readthedocs.io/en/latest/). You will find the compatible version under `The recommended way to set your requirements ...`. In the case of `5.5.0`, the compatible version is `elasticsearch-dsl-5.4.0`, so we install it as so `pip install "elasticsearch-dsl>=5.0.0,<6.0.0"`.
+
 ## Licenses ##
 
 This work is licensed under AGPL-3.0 and CreativesForGood licenses. A copy of the first license can be found in this repository. The other license can be found over this link [C4G License](https://github.com/halolimat/CreativesForGoodLicense).